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Calcium for high blood pressure: Calcium supplements: Do they interfere with blood pressure drugs?

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Mechanisms Involved in the Relationship between Low Calcium Intake and High Blood Pressure

Calcium intake has a role in blood pressure regulation and the parathyroid glands play a role in calcium homeostasis, thus the link between calcium intake, parathyroid function, and blood pressure seems to be intuitively valid. However, few studies have evaluated the pathways linking calcium intake, parathyroid function, and blood pressure altogether. The following section accounts for the physiological bases of this relationship, focusing on the effects of the parathyroid hormone (PTH) and the not completely purified and characterized parathyroid hypertensive factor (PHF).

2.1.1. Mechanisms Mediated by Parathyroid Hormone (PTH)

Several studies have reported that calcium intake is inversely associated with blood pressure, both in humans [3,11,12,21,22,23] and in animals [2,5,6]. The inverse relationship between calcium intake and plasma PTH levels has also been widely studied at different ages and physiological stages in both humans and animals, in acute and long term studies [24,25,26,27]. Similarly, the direct relationship between plasma PTH and blood pressure both in healthy subjects and animals is also well documented [25,28,29,30,31,32,33]. The relationship between the reported parathyroid hormone serum levels and blood pressure measurements in normotensive and hypertensive subjects is shown in . Studies showing a correlation between blood pressure values and quartiles and quintiles of parathyroid hormone levels in human studies are shown in . Some studies in humans have shown low calcium intake, increased PTH levels, and increased blood pressure in the same subjects, although no description of mechanisms involved in this relationship were mentioned [34,35,36] ().

Table 1

Parathyroid hormone (PTH) serum levels and blood pressure (BP) values in normotensive and hypertensive subjects.

Reference
(First Author)
Method Country and Participants PTH (pmol/L) BP (SBP − DBP mmHg)
Young 1990 [28] Cross-sectional USA, 115 subjects, ≈45 years NT = 4. 5 ± 2.2 NT = 120(±11) − 80(±8)
HT = 5.0 ± 2.4 HT = 138(±8) − 95(±5)
Brickman 1990 [29] Cross-sectional USA, 38 men, ≈56 years NT = 20.8 ± 1.1 NT = 123(±2.8) − 78(±1.3)
HT = 28.4 + 3.5 HT = 150(±3.9) − 97(±0.9)
Morfis 1997 [30] Cross-sectional Australia, 123 subjects, 63–88 years NT = 2. 7 ± 1.1 NT = 125(±12) − 71(±7)
HT = 2.9 ± 1.3 HT =135(±14) − 73(±10)
Park 2015 [32] Cross-sectional Korea, 1664 postmenopausal women, >50 years NT = 63.7 ± 23.4 NT = 117.5(±12.4) − 73.3(±8.1)
HT = 68.3 ± 23.6 HT = 149.4(±11.4) − 86.0(±10.1)

Table 2

Blood pressure (BP) values by quartiles or quintiles of parathyroid hormone (PTH) levels in human studies.

Reference
(First Author)
Method Country and Participants PTH (pmol/L) BP (SBP − DBP mmHg)
Snijder 2007 [31] Cross-sectional The Netherlands, 1205 subjects, participants, 55–85 years Q1: <2.45 150.1(±26.1) − 82.5(±13.0)
Q2: 2.45–3. 13 151.7(±24.8) − 82.6(±13.4)
Q3: 3.14–4.25 154.7(±24.6) – 84.3(±13.6)
Q4: >4.25 156.2(±27.6) − 83.9(±13.0)
Chan 2011 [25] Cross-sectional China, 939 men, >65 years Q1: <3.1 135.8(±1.7) − 76.5(±0.8)
Q2: 3.2–4.1 139.9(±1.6) − 76. 5(±0.8)
Q3: 4.2–5.5 141.4(±1.7) − 76.5(±0.8)
Q4: >5.5 143.6(±1.8) − 79.9(±0.8)
Yao 2016 [33] Cohort study USA, 7504 subjects, 45–64 years Q1: 3.2–28.8 112(±13) − 68.0(±8.2)
Q2: 28.9–34.9 113(±12) − 68.4(±8.3)
Q3: 35.0–41. 5 114(±12) − 69.4(±8.5)
Q4: 41.6–50.1 115(±12) − 69.9(±8.1)
Q5: 50.2–162.6 115(±12) − 70.5(±8.2)

Table 3

Parathyroid hormone (PTH) and blood pressure (BP) and dietary calcium intake in human studies.

Reference
(First Author)
Method Country and Participants Ca Intake (mg/day) PTH (pmol/L) BP (SBP − DBP mmHg)
Takagi 1991 [34] Clinical trial Japan, 9 HT, 65–86 years, CaSup (1 g) vs. diet Ca 500 mg, 8 weeks 1 g/day (CaSup) 27 −13.6 mmHg to −5.0 mmHg
500 mg/day (diet) 33 −1.5 mmHg to +1.0 mmHg
Jorde 2000 [36] Cohort study Norway, 1113 subjects, 30–79 years 592.1(±459.6) 4.5(±1.2) 143.4(±19.9) − 84.3(±10.4)
400. 3(±227.3) 9.1(±2.4) 153.9(±27.1) − 89.7(±14.1)
Kamycheva 2004 [35] Cross-sectional Norway, 3570 subjects, >24 years 499(±259) Q1 <1.9 136.9(±17.7)
476(±257) Q2 1.9–2.6 140.1(±19.6)
443(±233) Q3 2. 61–3.5 142.0(±20.3)
430(±243) Q4 >3.5 145.2(±20.3)
478(±277) Q1 <1.8 133.2(±18.5)
428(±227) Q2 1.8–2.4 135.5(±21.5)
431(±226) Q3 2.41–3.3 141. 9(±22.4)
408(±217) Q4 >3.3 146.5(±23.2)

Several studies have shown that PTH levels can independently predict cardiovascular disease and mortality [35,37,38,39]. The prospective and multicenter Osteoporotic Fractures in Men (MrOS) study, including 1490 men older than 65 years and followed up for 7.3 years, shows that concentrations of PTH were associated with an increased risk of cardiovascular mortality (adjusted hazard ratio SD = 1.21, 95% CI = 1.00–1.45) and from all causes (adjusted HR per SD = 1.15, 95% CI = 1.03–1.29) [37]. The Multi-Ethnic Study of Atherosclerosis (MESA) cohort study in which 3002 men and women, aged 59 ± 9.7 years, without cardiovascular antecedents were followed up for 9.0 years found that higher PTH serum concentrations were associated with a greater risk of hypertension, even after adjusting for potential confounders (HR = 1. 27, 95% CI = 1.01–1.59) [39]. The population-based, cross-sectional Tromsø study including 3570 men and women aged 25–79 years found a positive relationship between serum PTH and SBP with the highest quartile of serum PTH found to be an independent predictor of coronary heart disease in both sexes (OR = 1.70, 95% CI = 1.08–2.70 for males, OR = 1.73, 95% CI = 1.04–2.88 for females, p < 0.05).

PTH is an 84-amino-acid polypeptide (≈9.5 kilodalton (kDa)) secreted by the chief cells of the parathyroid gland. PTH acts on the cell membrane of its target tissues through a G-protein-coupled receptor, the parathyroid hormone receptor type 1 (PTHr-1). Expression of PTH receptors has been reported in many tissues, including vascular smooth muscle and endothelial cells [40]. The PTHr-1 couples to several signaling pathways, namely: the Gαs/adenylate cyclase (AC)/cAMP/protein kinase A (PKA), the Gαq/phospholipase C (PLC)β/inositol trisphosphate (IP3)/intracellular Ca/protein kinase C (PKC), the Gα12/13 phospholipase D/RhoA pathway, and the mitogen-activated protein kinase (extracellular signal regulated kinase [ERK1/2]) signaling cascade [41,42].

Several mechanisms have been proposed to explain the effect of PTH on blood pressure: (a) an increase in cytosolic free calcium concentration ([Ca2+]i) through the PTH receptor (PTHr-1) in vascular smooth muscle, (b) increase calcitriol concentration, and (c) a cross-talk with the renin–angiotensin–aldosterone system (RAAS). The last two will be described in its corresponding sections.

High [Ca2+]i increases vascular reactivity, and therefore peripheral vascular resistance and responsiveness to the sympathetic and the RAAS, which all elevate blood pressure. Calcium channel blockers, such as nifedipine and verapamil, are valuable antihypertensive drugs as they inhibit Ca2+ entry to the cell and reduce [Ca2+]i. In the same way, calcium supplementation in subjects with low calcium intake has been described to decrease [Ca2+]i [43,44], hence diminishing blood pressure. It has been shown that PTH increases calcium entry into a variety of mammalian tissues and cell lines, such as cardiomyocytes [45], enterocytes [46], kidney [47], liver [48], peripheral nerves [49], osteosarcoma cells [50], and osteoblastlike cells [51]. Significantly higher [Ca2+]i was also found in human platelets and lymphocytes of hypertensive patients [29,52]. The activation of PTHr-1/Gq/PLC/IP3, PTHr-1/Gα12-13/phospholipase D/RhoA cascades, and of calcium channels are the signaling pathways by which PTH increases [Ca2+]i and blood pressure [47].

A controversial effect is the vasodilator effect of acute PTH infusion, both in vivo and in vitro. In vascular smooth muscle cells, PTHr-1 couples primarily to Gαs, which increases cAMP and decreases [Ca2+]i [53]. Nonetheless, the sustained activation of this cascade shows desensitization to PTH in a time- and concentration-dependent fashion [54,55,56]. The chronic infusion of PTH has been associated with arterial hypertension [57]. Long-standing high levels of PTH, such as in hyperparathyroidism, are frequently related to hypertension, whereas parathyroidectomy is associated with a decrease in [Ca2+]i and blood pressure [58]. A rise of [Ca2+]i through PTHr-1/Gαs/AC/cAMP via opening calcium channels in a cell line derived from fetal rat aorta was also described [59]. Therefore, the desensitization of the cAMP pathway to PTH, as well as the stimulation of other blood pressure mediators considered below, like the RAAS and calcitriol, may explain the long-term pressor effects of PTH.

2.1.2. Parathyroid Hypertensive Factor (PHF)

In the early 1990s, Lewanczuk et al. described that the infusion of plasma from hypertensive rats and from hypertensive subjects on normotensive rats increased the mean arterial pressure of those rats [60,61]. They attributed this effect to the presence of a novel hypertensive factor in the plasma of the hypertensive donors. The same group also reported the parathyroid origin of this factor by transplanting parathyroid glands from hypertensive rats into parathyroidectomized normotensive rats. An increase in blood pressure was shown in the rats after transplantation [60,62,63]. Due to this, the non-isolated substance was called parathyroid hypertensive factor (PHF) [60].

In spontaneously hypertensive rat strains, low calcium intake increases blood pressure that the authors explained was due to an increase of PFH [64]. These authors also proposed that PHF regulates blood pressure by modifying the concentration of [Ca2+]i in vascular smooth muscle [60,65,66]. In isolated vascular smooth muscle cells from rat tail arteries, Shan et al. found that the infusion of semi-purified plasma from hypertensive rats enhanced the opening of the L-type calcium channel, an effect antagonized by the dihydropyridine calcium channel blocker nifedipine [67].

Although the effect of plasma from hypertensive rats has been well-documented, the purification and characterization of PHF is uncomplete. Benishin et al. showed the correlation of a UV spectrum of dialyzed plasma from hypertensive rats with a small (≈3 kDa), trypsin-inactivated and boiled-resistant peptide [68]. Years later, the same group proposed that the PHF structure has both peptide and lysophospholid motifs, critical for its biological activity [69]. Schlüter et al. also isolated a peptide-like vasopressor of low molecular weight (0.6–2.5 kDa) from parathyroid tissue of patients with tertiary hyperparathyroidism. The eluent was shown to be polar, hydrophilic, and protease-sensitive, but not heat-resistant. Schlüter’s group also suggested that further purifications were needed as several substances were shown on the mass spectrometry [70].

Although the existence of PHF may explain the blood pressure changes induced by alterations in a calcium diet, there is still much to know about this mediator. First, the published results have been poorly replicated outside the group that described PHF [71]. On the other hand, after 30 years of being described, the definitive chemical structure of this mediator is still unknown and there have not been reports of new attempts to purify it. Nonetheless, the function of the parathyroid gland seems to play a key role in blood pressure regulation, as was reported both in humans and in normotensive and hypertensive animals.

In summary, the bulk of information of this section orients towards an increase of the parathyroid gland activity by low calcium intake leading to an increase of [Ca2+]i in vascular smooth muscle cells and consequently a rise in blood pressure (). In addition to the direct effect of PTH (or PHF) in smooth muscle, we will later discuss the effects of PTH mediated by calcitriol and RAAS. A demonstration of the effect of parathyroid activity in the regulation of blood pressure related to calcium intake is shown in a study of parathyroidectomized rats in comparison with sham operation rats. After 10 weeks on a calcium-free diet, the sham operation rats showed an increase in SBP of 3.44 (SE = 1.95) mmHg, while the parathyroidectomized rats showed a decrease in SBP of −9.67 (SE = 2.05) mmHg. A highly statistical significant difference of 13.11 mmHg was found between the two groups [2].

Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Nutr Res Pract. 2012 Oct; 6(5): 421–428.

,1,2 and 3

Mi-Hyun Kim

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

So Young Bu

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

Mi-Kyeong Choi

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

Corresponding author.

Received 2012 May 24; Revised 2012 Jun 29; Accepted 2012 Jul 16.

Copyright ©2012 The Korean Nutrition Society and the Korean Society of Community NutritionThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been cited by other articles in PMC.

Abstract

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.

Keywords: Dietary calcium intake, hypertension, oxidative stress indices, plant calcium

Introduction

The relationship between calcium intake and cardiovascular diseases (CVD) has been explored through numerous molecular, animal, and human studies for several decades. An epidemiological study showed that residents who consumed hard water which was rich in calcium and magnesium had a lower mortality rate caused by circulatory diseases than those who had consumed soft water [1]. This finding suggested that the intake of calcium might be related to cardiovascular diseases. Also, several systematic reviews revealed that calcium supplementation reduced systolic blood pressure (SBP), particularly among hypertensive subjects but not among normotensive subjects [2-6]. A reduction of serum total cholesterol has been reported in hypercholesterolemic subjects given 1 g of calcium per day for 8 weeks [7,8]. More recent studies showed that 1 g/day of calcium supplementation for one year increased the level of HDL-cholesterol and decreased the level of LDL-cholesterol [9,10].

In addition, some observational studies reported that low calcium intake was associated with increased risk of CVD. The Iowa Women Health Study found that Caucasian women aged 55-69 years with low calcium intake (< 696 mg/day) had a high mortality rate due to cardiovascular heart disease (RR 1. 58, 95% CI 1.02-2.50) compared to those with high calcium intake (> 1,425 mg/day) [11]. Also, Wang et al. [12] found a higher rate of hypertension (RR 1.12, 95% CI 1.05-1.20) among women aged over 45 years consuming low calcium (< 558 mg/day) compared to those with high calcium consumption (1,679 mg/day). Other cohort studies reported the association between low calcium intake and increased risk of hypertension [13,14]. Meanwhile, several studies reported that calcium intake had an association with oxidative stress and suggested that calcium supplementation might increase the lipid oxidation [15,16]. As the pathogenesis of hypertension is often associated with oxidative stress, the relationships among calcium intake, blood pressure, and oxidative stress status should be investigated.

Traditionally, the Korean diet has been highly dependent on plant based foods, such as cereals, pulses, roots and various vegetables, now known for having many healthy benefits. Despite many healthy benefits of plant oriented foods, limited consumption in dairy and animal foods in Korean diet relative to western diet has been concerned for insufficient calcium. According to the recent Korean National Health and Nutrition Examination Survey (KNHANES) 2010, the mean daily calcium intake of Korean adults aged 19 and older was 535.2 mg, which was 75.6% of the Korean recommended level. Also, 64.5% of these adults consumed calcium under estimated average requirement (EAR) [17]. This national data indicate that the average calcium intake of Korean adults is within the range of high CVD related mortality risk or high prevalence of hypertension as reported by the previous researches [11,12].

Furthermore, the prevalence of hypertension in Korean adults (≥ 20 years) is 28.9% (30.1% for males, 27.7% for females) [17]. This is slightly lower than the prevalence of hypertension for Americans (31.4%-32.1% for males, 32.8% for females) [18]. But considering the significant difference in the prevalence of overweight and obesity between US adults (BMI ≥ 25; males 72.8%, females 63.0%) and Korean adults (BMI ≥ 25; males 36.5%, females 26.4%), the prevalence of hypertension in Korea seems to be very high. Based on these concerns, a study to investigate the calcium intake status among Korean adults with or without hypertension and its relation to blood pressure and CVD risk-related parameters is needed.

Therefore, this study was carried out for the following two aims: first, to evaluate the calcium intake status between the hypertension and normotension groups; and second, to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices in the hypertension and normotension groups.

Subjects and Methods

Participants

Initially, Korean adults were recruited for this study. Study participants agreed to provide their personal information regarding the purpose and the procedures of the project. Blood pressure was measured twice in seated posture by using a mercury sphygmomanometer, and the two measurements were averaged for systolic and diastolic pressures. Eighty-three subjects with 140 mmHg or higher in SBP or 90 mmHg or higher in diastolic blood pressure (DBP) were assigned to a hypertension group according to JNC-VII guidelines [19]. Participants with 120 mmHg or less SBP and 80 mmHg or less DBP were assigned to a normotension group. Each group was consisted of a similar percentage of subjects in age and gender (42 hypertensive men vs. 41 normotensive men). This study was approved by the College of Medicine, Chung-Ang University Institutional Review Board (IRB), and written informed consent was obtained from each subjects.

Anthropometric measurements

Height was measured using a standard stadiometer following study protocols, and weight in kilograms was measured on a calibrated Inbody (Biospace, Seoul, Korea) system. Measurements were repeated at least two times for each subject and BMI was calculated as weight in kilograms divided by height in meters, squared.

Dietary intake survey

The dietary intake survey was conducted by a 24-hour recall method for 3 days. Study subjects in each group were interviewed by trained research staff to examine the types and amounts of all foods that the subjects had consumed in the previous 3 days. Food models and photographs were used to assist in estimating serving sizes of foods. Dietary intake of calcium and other nutrients were analyzed by using Can-Pro 3.0 (The Korean Nutrition Society, Seoul, Korea).

Collection of blood and urine samples

The subjects fasted overnight after the dietary intake survey, and then 15 ml of venous blood was collected – half volume in an evacuated blood collection tube and the other half in an EDTA-coated blood collection tube. In the evacuated blood collection tube, serum was separated by centrifugation at × 400 g for 15 minutes. Blood samples collected in the EDTA-coated blood collection tube were stored at -20℃ until a test was performed. Spot urine samples were collected and aliquoted for analysis of multiple indices and kept in a freezer at -20℃.

Analysis of biochemical indices

Serum triglyceride, total cholesterol, glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were analyzed by using a commercial kit based on enzymatic principles, and the content of HDL-cholesterol was analyzed by the colorimetric method after separating LDL and VLDL by using a dextran sulfate-Mg2+ sedimentation [20]. Serum LDL-cholesterol was calculated by the Friedewald formula [21] by utilizing triglyceride, total cholesterol, and HDL-cholesterol values.

Glutathione (GSH) in red blood cells was analyzed by using a modification of van Klaveren’s method [22]. After centrifugation of the blood samples at × 2,500 g and 4℃, red blood cells were hemolyzed by adding Millipore grade water. Tricholoroacetic acid (TCA) was added to the hemolyzed sample, and centrifuged at × 10,000 g for 5 minutes. Supernatants were subjected to reaction buffer (0.248 mg/ml NADPH in 143 mM sodium phosphate, 6.3 mM Na4-EDTA at pH 7.5, 6 mM DTNB) with glutathione disulfide reductase (5 U/ml) for 20 minutes at 35℃ and the absorbance was measured in 412 nm by spectrophotometer (UVIKON, Kontron Inc., Milan, Italy). The amount of GSH in red blood cells was indicated as µmol/g hemoglobin (Hb). Glutathione peroxidase (GPx) activity in the red blood cells was analyzed by using methods by Aydin et al. [23]. Regarding GPx, absorbance was measured in 340 nm for 3 minutes using a spectrophotometer (UVIKON, Kontron Inc. , Milan, Italy) by adding 8.8 mmol/l H2O2 after 50 mM Tris buffer (pH 7.6), 1 mM Na2EDTA, 2 mM NADPH, 4 mM sodium azide, and 1 unit/ml glutathione reductase, which were reacted with the 20 ul hemolyzed sample at 37℃ for 5 minutes. GPx activity in red blood cells was indicated as U/g Hb.

Urinary lipid peroxidation was analyzed according to the manual of Tagesson et al. [24]. Briefly, 50 µl urine samples were mixed with 23 mM thiobarbituric acid reagent, 0.5 M phosphoric acid 300 µl and then heated at 95℃ for one hour and then cooled down. After adding 100 µl methanol, samples were subjected to HPLC (501 Waters, Messachusetts, USA) for thiobarbituric acid reactive substance (TBARS) analysis. Urinary malondialdehyde (MDA) concentration in urine aliquot was indicated as µmol/g creatinine (Cr).

Statistical analysis

Statistical analyses including the mean and standard deviation values of all results were performed using the SAS program (version 9. 1; SAS Institute Inc, Cary, NC, USA). Student’s unpaired t-test was used to analyze the differences between the hypertension group and the normotension group and between men and women. Pearson’s partial correlation coefficient was used to determine an association between variables and to verify significance. All statistical tests were two-sided, and value of P < 0.05 was considered statistically significant.

Results

General characteristics

The general characteristics of the hypertension group and the normotension group are presented in . There were no significant differences in age, height, and weight between the hypertension and normotension groups; however, the hypertension group had significantly higher BMI (P < 0.001), SBP (P < 0.001), and DBP (P < 0.001) than the normotension group.

Table 1

Anthropometric measurements of the subjects

Energy, selective nutrients, and calcium intakes

Energy and selective nutrient intake of the subjects is shown in . The average daily energy intake was 1,493.7 kcal for the hypertension group and 1,602.0 kcal for the normotension group without showing a significant difference between two groups. The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg), but there was no significant difference. The percentage of people who consumed calcium less than EAR for Koreans was higher in the hypertension group (85.5%) compared with that in the normotension group (79.5%) but with no statistical difference between the two groups. Also, the mean daily intake of animal calcium and plant calcium, the calcium intake per 1,000 kcal, and the calcium percentage for Recommended Intake (RI) tended to be lower in the hypertension group ().

Table 2

Daily energy and nutrient intakes of the subjects

Table 3

Daily calcium intake status of the subjects

Food group intake status

Food intake from different food groups is shown in . The total daily food intake was 993.0 g for the hypertension group and 1,117.2 g for the normotension group, not showing a significant difference. The intakes of sugar/sweeteners and seasonings were significantly higher in the normotension group, while the intake of mushrooms was higher in the hypertension group. Except for these three food groups, no significant difference was found in consumption of the other food groups between the hypertension and normotension groups.

Table 4

Daily food intakes from each food group of the subjects

Biochemical indices in blood and urine

Biochemical indices in blood and urine of the subjects are described in . No significant difference was found in blood and urine biochemical indices between the hypertension and normotension groups.

Table 5

Biochemical indices in blood and urine of the subjects

Correlation between calcium intake, and blood pressure and biochemical indices

shows the correlation between blood pressure and nutrient intake in both groups after adjusting for age, gender, BMI, and energy intake. In the hypertension group, DBP had a significant negative correlation with plant fat (P < 0.05) and plant calcium (P < 0.01). In the normotension group, however, no significant correlation was found between blood pressure and nutrient intake.

Table 6

Correlations between blood pressure and nutrient intakes adjusted for age, sex, BMI, and energy intake of the subjects

The correlations between biochemical indices and nutrient intake after adjusting for age, gender, BMI, and energy intake are shown in . No significant difference was found between biochemical indices and nutrient intake in the hypertension group, but in the normotension group, serum triglyceride was significantly and positively correlated with total calcium intake and animal calcium intake.

Table 7

Correlations between calcium intake and blood parameters adjusted for age, sex, BMI, and energy intake of the subjects

Discussion

The present study examined the calcium intake status and the relation between dietary calcium intake and blood pressure, blood lipid profiles, and blood/urine oxidative stress indices in Korean adults with or without hypertension. The major finding was that the calcium intake of both groups was low and was mainly derived from plant foods. Also, the plant food-derived calcium intake was significantly and negatively correlated with DBP in the hypertension group but not in the normotension group.

Dietary calcium intake of the hypertension group tended to be lower than that of the normotension group, and the calcium intake level of both groups is considered quite insufficient. There are two possible reasons for the low calcium intake of the subjects. First, the overall food intake was low, which means a low daily energy intake. The amount of energy intake in both the hypertension and normotension groups was just 1,493.7 kcal and 1,602.0 kcal, respectively. Additionally, calcium intake relative to energy intake of 1,000 kcal within both hypertension and normotension groups was still below the recommended intake [25]. The second possible reason for low calcium intake in study subjects was the low intake of main food sources for calcium, particularly milk and dairy products. According to the KNHANES [17], even though the top ranked food source for calcium intake in Koreans was milk, the average amount of milk consumed by Korean adults was 74.0 g per day, which corresponds to only one third of a small carton (~200 ml) of milk. In the current study, the milk consumption of the study subjects was even less, showing 40.9 g for the hypertension group and 51.4 g for the normotension group. Considering the fact that 100 g of milk contains about 100 mg of calcium, the subjects consumed only 50 mg of calcium from their daily milk consumption. In addition to milk, small bony fishes such as anchovies are an important food source for supplying calcium in the average Korean diet, but the portion size is very small in relative to other side-dishes typically found in the Korean diet and therefore may not play a significant role in increasing calcium consumption. Also, the low intake of calcium derived from animal-based foods, such as milk and small bony fish, compared with relatively high intake of calcium derived from plant foods, which have low bioavailability, in both the hypertension and normotension groups may be indicative of the overall poor calcium status in these study subjects.

Many epidemiological studies have reported results showing the relationship between calcium intake and blood pressure [2,26,27]. For instance, the amount of calcium intake was negatively correlated with high blood pressure, many hypertension patients had a low calcium intake in their diet [2,27], and the supplementation of calcium-rich foods decreased blood pressure [26]. These findings indicate that calcium consumption is beneficial for prevention and treatment of hypertension. In the present study, diastolic blood pressure was significantly and negatively correlated with plant calcium consumption in the hypertension subjects but not in the normotension subjects. Some possible explanations for the association of calcium intake with reducing the risk of hypertension have been suggested by several experimental studies [28-34]. Calcium is involved in regulating blood pressure by controlling vascular smooth muscle cell contractility and thus modulating peripheral vascular resistance [28-31]. In addition, extracellular ionized calcium inhibits renin secretion by interacting with the calcium-sensing receptor [32-34]. Another possible explanation offered by the current study is that calcium intake of the study subjects was more highly dependent on the consumption of plant-based foods than animal-based foods. So far, many studies have mainly focused on the consumption of dairy products for investigating the relationship between calcium and blood pressure [35], but for the subjects whose frequent food source is plant-based, studies may need a different approach to investigate the relationship between the consumption of calcium derived from plant-based food and blood pressure. Based on the reports that lowering diastolic blood pressure by 2 mmHg is associated with 17% reduction in the incidence of hypertension, 6% decrease in the risk of cardiac diseases [36], and reduced ventricular function [37], a follow-up study is warranted as our results show a correlation between calcium derived from plant foods and blood pressure. In addition, the plant calcium intake of the normotension group had no association with their blood pressure, showing a difference from the hypertensive group. Therefore, further studies are also needed to investigate the plant calcium’s effect on lowering blood pressure with different blood pressure status.

Calcium consumption is also related to the lipoprotein metabolism and affects the level of blood lipid profiles [38-42]. Two main mechanisms of lowering blood lipids by calcium have been suggested. Dietary calcium engages the formation of intestinal soap with intestinal fatty acids. Particularly saturated fatty acids [40,42] and calcium also increase the excretion of blood lipids through binding with bile acids and consequently lower the synthesis of LDL-cholesterol [41,43]. While such a beneficial effect of calcium is reported in subjects who consumed more than 1,000 mg of calcium, the daily calcium intake of our current study subjects including both the hypertension and normotension groups was very low. In this study the level of total cholesterol and LDL-cholesterol had no significant association with the calcium intake of the hypertension and normotension groups.

Lorenzen et al. [43] reported that calcium intake from dairy products lowers the triglyceride contents in chylomicron and leads to an increase in chylomicron clearance and a decrease in fat absorption. On the other hand, a study of van Meijl et al. [42] argued that the increase in chylomicron clearance was not only from the calcium consumption and that the effect of calcium consumption should be differentiated from the consumption of dairy products. Yu et al. [44] reported that when the average daily calcium intake was above 422 mg, the consumption of dairy products and animal food-based calcium was positively associated with serum LDL cholesterol. In the current study, total calcium consumption and the calcium consumption derived from animal based-foods in the normotensive group were positively associated with blood triglycerides. One possible explanation for the positive relationship between calcium consumption and serum triglycerides is the tendency of the subjects to have high calcium intake from animal-based foods. Our present study identified a significant relationship between calcium and blood pressure and blood lipids in the context of daily calcium intake rather than calcium fortification or high calcium supplements. As this study is one of few studies investigating the role of daily calcium intake in the prevalence of hypertension and other metabolic diseases, further research is needed in a large and diverse population.

In spite of the beneficial effects of calcium, which lowers the blood pressure and the level of blood lipids, several studies raised the concern about calcium over-supplementation [45-46]. Supplementation of high amounts of calcium leads to the increase of cellular calcium ions. These over-produced calcium ions generate free radicals and inflammatory mediators, and continuously cause cellular damage [15]. Also, daily supplementation of 900 mg of calcium as a type of dairy product (3 servings per day) for overweight women for 12 weeks increased the biomarkers of lipids oxidation [16]. In the current study, since the level of calcium intake was very low, this may lead to subtle or no alterations in biomarkers of lipid oxidation in blood and urine samples of the hypertension and normotension groups.

This study has several limitations: 1) the size of study subjects in both the hypertension and normotension groups was not large enough to have statistical power for the results of several serum biomarkers, 2) the level of blood pressure in the hypertension group (152.8/86.2 mmHg, diagnosed as phase I hypertension) was relatively mild, making it difficult to find the differences in several measurements between the hypertension and normotension groups, and 3) limited methodology was used to investigate the calcium intake of subjects as we carried out the 24 hour recall but not food frequency records.

In conclusion, the daily calcium intake of hypertension patients tended to be lower than that of normotensive subjects. Also, relative to animal-based foods, plant-based foods were high contributors to calcium sources for both hypertension and normotension subjects. In the hypertension subjects, the intake of plant food-derived calcium was negatively correlated with the DBP, while animal food-derived calcium was positively correlated with DPB and in the healthy subjects, total calcium intake was positively correlated with serum triglycerides. However, there was no significant finding to show the relationship between calcium and lipid oxidation. Overall, these data suggest the importance of adequate calcium consumption and implicate to reconsider plant based foods as good calcium source for hypertension patients. Further investigation is necessary to identify the role of calcium derived from plant foods in populations with high dependency on plant-based food.

Acknowledgment

We would like to express our appreciation to Glenn Hawes for assistance to manuscript preparation.

References

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Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Nutr Res Pract. 2012 Oct; 6(5): 421–428.

,1,2 and 3

Mi-Hyun Kim

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

So Young Bu

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

Mi-Kyeong Choi

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

Corresponding author.

Received 2012 May 24; Revised 2012 Jun 29; Accepted 2012 Jul 16.

Copyright ©2012 The Korean Nutrition Society and the Korean Society of Community NutritionThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been cited by other articles in PMC.

Abstract

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.

Keywords: Dietary calcium intake, hypertension, oxidative stress indices, plant calcium

Introduction

The relationship between calcium intake and cardiovascular diseases (CVD) has been explored through numerous molecular, animal, and human studies for several decades. An epidemiological study showed that residents who consumed hard water which was rich in calcium and magnesium had a lower mortality rate caused by circulatory diseases than those who had consumed soft water [1]. This finding suggested that the intake of calcium might be related to cardiovascular diseases. Also, several systematic reviews revealed that calcium supplementation reduced systolic blood pressure (SBP), particularly among hypertensive subjects but not among normotensive subjects [2-6]. A reduction of serum total cholesterol has been reported in hypercholesterolemic subjects given 1 g of calcium per day for 8 weeks [7,8]. More recent studies showed that 1 g/day of calcium supplementation for one year increased the level of HDL-cholesterol and decreased the level of LDL-cholesterol [9,10].

In addition, some observational studies reported that low calcium intake was associated with increased risk of CVD. The Iowa Women Health Study found that Caucasian women aged 55-69 years with low calcium intake (< 696 mg/day) had a high mortality rate due to cardiovascular heart disease (RR 1.58, 95% CI 1.02-2.50) compared to those with high calcium intake (> 1,425 mg/day) [11]. Also, Wang et al. [12] found a higher rate of hypertension (RR 1.12, 95% CI 1.05-1.20) among women aged over 45 years consuming low calcium (< 558 mg/day) compared to those with high calcium consumption (1,679 mg/day). Other cohort studies reported the association between low calcium intake and increased risk of hypertension [13,14]. Meanwhile, several studies reported that calcium intake had an association with oxidative stress and suggested that calcium supplementation might increase the lipid oxidation [15,16]. As the pathogenesis of hypertension is often associated with oxidative stress, the relationships among calcium intake, blood pressure, and oxidative stress status should be investigated.

Traditionally, the Korean diet has been highly dependent on plant based foods, such as cereals, pulses, roots and various vegetables, now known for having many healthy benefits. Despite many healthy benefits of plant oriented foods, limited consumption in dairy and animal foods in Korean diet relative to western diet has been concerned for insufficient calcium. According to the recent Korean National Health and Nutrition Examination Survey (KNHANES) 2010, the mean daily calcium intake of Korean adults aged 19 and older was 535.2 mg, which was 75.6% of the Korean recommended level. Also, 64.5% of these adults consumed calcium under estimated average requirement (EAR) [17]. This national data indicate that the average calcium intake of Korean adults is within the range of high CVD related mortality risk or high prevalence of hypertension as reported by the previous researches [11,12].

Furthermore, the prevalence of hypertension in Korean adults (≥ 20 years) is 28.9% (30.1% for males, 27.7% for females) [17]. This is slightly lower than the prevalence of hypertension for Americans (31.4%-32.1% for males, 32.8% for females) [18]. But considering the significant difference in the prevalence of overweight and obesity between US adults (BMI ≥ 25; males 72.8%, females 63.0%) and Korean adults (BMI ≥ 25; males 36.5%, females 26.4%), the prevalence of hypertension in Korea seems to be very high. Based on these concerns, a study to investigate the calcium intake status among Korean adults with or without hypertension and its relation to blood pressure and CVD risk-related parameters is needed.

Therefore, this study was carried out for the following two aims: first, to evaluate the calcium intake status between the hypertension and normotension groups; and second, to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices in the hypertension and normotension groups.

Subjects and Methods

Participants

Initially, Korean adults were recruited for this study. Study participants agreed to provide their personal information regarding the purpose and the procedures of the project. Blood pressure was measured twice in seated posture by using a mercury sphygmomanometer, and the two measurements were averaged for systolic and diastolic pressures. Eighty-three subjects with 140 mmHg or higher in SBP or 90 mmHg or higher in diastolic blood pressure (DBP) were assigned to a hypertension group according to JNC-VII guidelines [19]. Participants with 120 mmHg or less SBP and 80 mmHg or less DBP were assigned to a normotension group. Each group was consisted of a similar percentage of subjects in age and gender (42 hypertensive men vs. 41 normotensive men). This study was approved by the College of Medicine, Chung-Ang University Institutional Review Board (IRB), and written informed consent was obtained from each subjects.

Anthropometric measurements

Height was measured using a standard stadiometer following study protocols, and weight in kilograms was measured on a calibrated Inbody (Biospace, Seoul, Korea) system. Measurements were repeated at least two times for each subject and BMI was calculated as weight in kilograms divided by height in meters, squared.

Dietary intake survey

The dietary intake survey was conducted by a 24-hour recall method for 3 days. Study subjects in each group were interviewed by trained research staff to examine the types and amounts of all foods that the subjects had consumed in the previous 3 days. Food models and photographs were used to assist in estimating serving sizes of foods. Dietary intake of calcium and other nutrients were analyzed by using Can-Pro 3.0 (The Korean Nutrition Society, Seoul, Korea).

Collection of blood and urine samples

The subjects fasted overnight after the dietary intake survey, and then 15 ml of venous blood was collected – half volume in an evacuated blood collection tube and the other half in an EDTA-coated blood collection tube. In the evacuated blood collection tube, serum was separated by centrifugation at × 400 g for 15 minutes. Blood samples collected in the EDTA-coated blood collection tube were stored at -20℃ until a test was performed. Spot urine samples were collected and aliquoted for analysis of multiple indices and kept in a freezer at -20℃.

Analysis of biochemical indices

Serum triglyceride, total cholesterol, glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were analyzed by using a commercial kit based on enzymatic principles, and the content of HDL-cholesterol was analyzed by the colorimetric method after separating LDL and VLDL by using a dextran sulfate-Mg2+ sedimentation [20]. Serum LDL-cholesterol was calculated by the Friedewald formula [21] by utilizing triglyceride, total cholesterol, and HDL-cholesterol values.

Glutathione (GSH) in red blood cells was analyzed by using a modification of van Klaveren’s method [22]. After centrifugation of the blood samples at × 2,500 g and 4℃, red blood cells were hemolyzed by adding Millipore grade water. Tricholoroacetic acid (TCA) was added to the hemolyzed sample, and centrifuged at × 10,000 g for 5 minutes. Supernatants were subjected to reaction buffer (0.248 mg/ml NADPH in 143 mM sodium phosphate, 6.3 mM Na4-EDTA at pH 7.5, 6 mM DTNB) with glutathione disulfide reductase (5 U/ml) for 20 minutes at 35℃ and the absorbance was measured in 412 nm by spectrophotometer (UVIKON, Kontron Inc., Milan, Italy). The amount of GSH in red blood cells was indicated as µmol/g hemoglobin (Hb). Glutathione peroxidase (GPx) activity in the red blood cells was analyzed by using methods by Aydin et al. [23]. Regarding GPx, absorbance was measured in 340 nm for 3 minutes using a spectrophotometer (UVIKON, Kontron Inc., Milan, Italy) by adding 8.8 mmol/l H2O2 after 50 mM Tris buffer (pH 7.6), 1 mM Na2EDTA, 2 mM NADPH, 4 mM sodium azide, and 1 unit/ml glutathione reductase, which were reacted with the 20 ul hemolyzed sample at 37℃ for 5 minutes. GPx activity in red blood cells was indicated as U/g Hb.

Urinary lipid peroxidation was analyzed according to the manual of Tagesson et al. [24]. Briefly, 50 µl urine samples were mixed with 23 mM thiobarbituric acid reagent, 0.5 M phosphoric acid 300 µl and then heated at 95℃ for one hour and then cooled down. After adding 100 µl methanol, samples were subjected to HPLC (501 Waters, Messachusetts, USA) for thiobarbituric acid reactive substance (TBARS) analysis. Urinary malondialdehyde (MDA) concentration in urine aliquot was indicated as µmol/g creatinine (Cr).

Statistical analysis

Statistical analyses including the mean and standard deviation values of all results were performed using the SAS program (version 9.1; SAS Institute Inc, Cary, NC, USA). Student’s unpaired t-test was used to analyze the differences between the hypertension group and the normotension group and between men and women. Pearson’s partial correlation coefficient was used to determine an association between variables and to verify significance. All statistical tests were two-sided, and value of P < 0.05 was considered statistically significant.

Results

General characteristics

The general characteristics of the hypertension group and the normotension group are presented in . There were no significant differences in age, height, and weight between the hypertension and normotension groups; however, the hypertension group had significantly higher BMI (P < 0.001), SBP (P < 0.001), and DBP (P < 0.001) than the normotension group.

Table 1

Anthropometric measurements of the subjects

Energy, selective nutrients, and calcium intakes

Energy and selective nutrient intake of the subjects is shown in . The average daily energy intake was 1,493.7 kcal for the hypertension group and 1,602.0 kcal for the normotension group without showing a significant difference between two groups. The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg), but there was no significant difference. The percentage of people who consumed calcium less than EAR for Koreans was higher in the hypertension group (85.5%) compared with that in the normotension group (79.5%) but with no statistical difference between the two groups. Also, the mean daily intake of animal calcium and plant calcium, the calcium intake per 1,000 kcal, and the calcium percentage for Recommended Intake (RI) tended to be lower in the hypertension group ().

Table 2

Daily energy and nutrient intakes of the subjects

Table 3

Daily calcium intake status of the subjects

Food group intake status

Food intake from different food groups is shown in . The total daily food intake was 993.0 g for the hypertension group and 1,117.2 g for the normotension group, not showing a significant difference. The intakes of sugar/sweeteners and seasonings were significantly higher in the normotension group, while the intake of mushrooms was higher in the hypertension group. Except for these three food groups, no significant difference was found in consumption of the other food groups between the hypertension and normotension groups.

Table 4

Daily food intakes from each food group of the subjects

Biochemical indices in blood and urine

Biochemical indices in blood and urine of the subjects are described in . No significant difference was found in blood and urine biochemical indices between the hypertension and normotension groups.

Table 5

Biochemical indices in blood and urine of the subjects

Correlation between calcium intake, and blood pressure and biochemical indices

shows the correlation between blood pressure and nutrient intake in both groups after adjusting for age, gender, BMI, and energy intake. In the hypertension group, DBP had a significant negative correlation with plant fat (P < 0.05) and plant calcium (P < 0.01). In the normotension group, however, no significant correlation was found between blood pressure and nutrient intake.

Table 6

Correlations between blood pressure and nutrient intakes adjusted for age, sex, BMI, and energy intake of the subjects

The correlations between biochemical indices and nutrient intake after adjusting for age, gender, BMI, and energy intake are shown in . No significant difference was found between biochemical indices and nutrient intake in the hypertension group, but in the normotension group, serum triglyceride was significantly and positively correlated with total calcium intake and animal calcium intake.

Table 7

Correlations between calcium intake and blood parameters adjusted for age, sex, BMI, and energy intake of the subjects

Discussion

The present study examined the calcium intake status and the relation between dietary calcium intake and blood pressure, blood lipid profiles, and blood/urine oxidative stress indices in Korean adults with or without hypertension. The major finding was that the calcium intake of both groups was low and was mainly derived from plant foods. Also, the plant food-derived calcium intake was significantly and negatively correlated with DBP in the hypertension group but not in the normotension group.

Dietary calcium intake of the hypertension group tended to be lower than that of the normotension group, and the calcium intake level of both groups is considered quite insufficient. There are two possible reasons for the low calcium intake of the subjects. First, the overall food intake was low, which means a low daily energy intake. The amount of energy intake in both the hypertension and normotension groups was just 1,493.7 kcal and 1,602.0 kcal, respectively. Additionally, calcium intake relative to energy intake of 1,000 kcal within both hypertension and normotension groups was still below the recommended intake [25]. The second possible reason for low calcium intake in study subjects was the low intake of main food sources for calcium, particularly milk and dairy products. According to the KNHANES [17], even though the top ranked food source for calcium intake in Koreans was milk, the average amount of milk consumed by Korean adults was 74.0 g per day, which corresponds to only one third of a small carton (~200 ml) of milk. In the current study, the milk consumption of the study subjects was even less, showing 40.9 g for the hypertension group and 51.4 g for the normotension group. Considering the fact that 100 g of milk contains about 100 mg of calcium, the subjects consumed only 50 mg of calcium from their daily milk consumption. In addition to milk, small bony fishes such as anchovies are an important food source for supplying calcium in the average Korean diet, but the portion size is very small in relative to other side-dishes typically found in the Korean diet and therefore may not play a significant role in increasing calcium consumption. Also, the low intake of calcium derived from animal-based foods, such as milk and small bony fish, compared with relatively high intake of calcium derived from plant foods, which have low bioavailability, in both the hypertension and normotension groups may be indicative of the overall poor calcium status in these study subjects.

Many epidemiological studies have reported results showing the relationship between calcium intake and blood pressure [2,26,27]. For instance, the amount of calcium intake was negatively correlated with high blood pressure, many hypertension patients had a low calcium intake in their diet [2,27], and the supplementation of calcium-rich foods decreased blood pressure [26]. These findings indicate that calcium consumption is beneficial for prevention and treatment of hypertension. In the present study, diastolic blood pressure was significantly and negatively correlated with plant calcium consumption in the hypertension subjects but not in the normotension subjects. Some possible explanations for the association of calcium intake with reducing the risk of hypertension have been suggested by several experimental studies [28-34]. Calcium is involved in regulating blood pressure by controlling vascular smooth muscle cell contractility and thus modulating peripheral vascular resistance [28-31]. In addition, extracellular ionized calcium inhibits renin secretion by interacting with the calcium-sensing receptor [32-34]. Another possible explanation offered by the current study is that calcium intake of the study subjects was more highly dependent on the consumption of plant-based foods than animal-based foods. So far, many studies have mainly focused on the consumption of dairy products for investigating the relationship between calcium and blood pressure [35], but for the subjects whose frequent food source is plant-based, studies may need a different approach to investigate the relationship between the consumption of calcium derived from plant-based food and blood pressure. Based on the reports that lowering diastolic blood pressure by 2 mmHg is associated with 17% reduction in the incidence of hypertension, 6% decrease in the risk of cardiac diseases [36], and reduced ventricular function [37], a follow-up study is warranted as our results show a correlation between calcium derived from plant foods and blood pressure. In addition, the plant calcium intake of the normotension group had no association with their blood pressure, showing a difference from the hypertensive group. Therefore, further studies are also needed to investigate the plant calcium’s effect on lowering blood pressure with different blood pressure status.

Calcium consumption is also related to the lipoprotein metabolism and affects the level of blood lipid profiles [38-42]. Two main mechanisms of lowering blood lipids by calcium have been suggested. Dietary calcium engages the formation of intestinal soap with intestinal fatty acids. Particularly saturated fatty acids [40,42] and calcium also increase the excretion of blood lipids through binding with bile acids and consequently lower the synthesis of LDL-cholesterol [41,43]. While such a beneficial effect of calcium is reported in subjects who consumed more than 1,000 mg of calcium, the daily calcium intake of our current study subjects including both the hypertension and normotension groups was very low. In this study the level of total cholesterol and LDL-cholesterol had no significant association with the calcium intake of the hypertension and normotension groups.

Lorenzen et al. [43] reported that calcium intake from dairy products lowers the triglyceride contents in chylomicron and leads to an increase in chylomicron clearance and a decrease in fat absorption. On the other hand, a study of van Meijl et al. [42] argued that the increase in chylomicron clearance was not only from the calcium consumption and that the effect of calcium consumption should be differentiated from the consumption of dairy products. Yu et al. [44] reported that when the average daily calcium intake was above 422 mg, the consumption of dairy products and animal food-based calcium was positively associated with serum LDL cholesterol. In the current study, total calcium consumption and the calcium consumption derived from animal based-foods in the normotensive group were positively associated with blood triglycerides. One possible explanation for the positive relationship between calcium consumption and serum triglycerides is the tendency of the subjects to have high calcium intake from animal-based foods. Our present study identified a significant relationship between calcium and blood pressure and blood lipids in the context of daily calcium intake rather than calcium fortification or high calcium supplements. As this study is one of few studies investigating the role of daily calcium intake in the prevalence of hypertension and other metabolic diseases, further research is needed in a large and diverse population.

In spite of the beneficial effects of calcium, which lowers the blood pressure and the level of blood lipids, several studies raised the concern about calcium over-supplementation [45-46]. Supplementation of high amounts of calcium leads to the increase of cellular calcium ions. These over-produced calcium ions generate free radicals and inflammatory mediators, and continuously cause cellular damage [15]. Also, daily supplementation of 900 mg of calcium as a type of dairy product (3 servings per day) for overweight women for 12 weeks increased the biomarkers of lipids oxidation [16]. In the current study, since the level of calcium intake was very low, this may lead to subtle or no alterations in biomarkers of lipid oxidation in blood and urine samples of the hypertension and normotension groups.

This study has several limitations: 1) the size of study subjects in both the hypertension and normotension groups was not large enough to have statistical power for the results of several serum biomarkers, 2) the level of blood pressure in the hypertension group (152.8/86.2 mmHg, diagnosed as phase I hypertension) was relatively mild, making it difficult to find the differences in several measurements between the hypertension and normotension groups, and 3) limited methodology was used to investigate the calcium intake of subjects as we carried out the 24 hour recall but not food frequency records.

In conclusion, the daily calcium intake of hypertension patients tended to be lower than that of normotensive subjects. Also, relative to animal-based foods, plant-based foods were high contributors to calcium sources for both hypertension and normotension subjects. In the hypertension subjects, the intake of plant food-derived calcium was negatively correlated with the DBP, while animal food-derived calcium was positively correlated with DPB and in the healthy subjects, total calcium intake was positively correlated with serum triglycerides. However, there was no significant finding to show the relationship between calcium and lipid oxidation. Overall, these data suggest the importance of adequate calcium consumption and implicate to reconsider plant based foods as good calcium source for hypertension patients. Further investigation is necessary to identify the role of calcium derived from plant foods in populations with high dependency on plant-based food.

Acknowledgment

We would like to express our appreciation to Glenn Hawes for assistance to manuscript preparation.

References

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Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Nutr Res Pract. 2012 Oct; 6(5): 421–428.

,1,2 and 3

Mi-Hyun Kim

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

So Young Bu

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

Mi-Kyeong Choi

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

Corresponding author.

Received 2012 May 24; Revised 2012 Jun 29; Accepted 2012 Jul 16.

Copyright ©2012 The Korean Nutrition Society and the Korean Society of Community NutritionThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been cited by other articles in PMC.

Abstract

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.

Keywords: Dietary calcium intake, hypertension, oxidative stress indices, plant calcium

Introduction

The relationship between calcium intake and cardiovascular diseases (CVD) has been explored through numerous molecular, animal, and human studies for several decades. An epidemiological study showed that residents who consumed hard water which was rich in calcium and magnesium had a lower mortality rate caused by circulatory diseases than those who had consumed soft water [1]. This finding suggested that the intake of calcium might be related to cardiovascular diseases. Also, several systematic reviews revealed that calcium supplementation reduced systolic blood pressure (SBP), particularly among hypertensive subjects but not among normotensive subjects [2-6]. A reduction of serum total cholesterol has been reported in hypercholesterolemic subjects given 1 g of calcium per day for 8 weeks [7,8]. More recent studies showed that 1 g/day of calcium supplementation for one year increased the level of HDL-cholesterol and decreased the level of LDL-cholesterol [9,10].

In addition, some observational studies reported that low calcium intake was associated with increased risk of CVD. The Iowa Women Health Study found that Caucasian women aged 55-69 years with low calcium intake (< 696 mg/day) had a high mortality rate due to cardiovascular heart disease (RR 1.58, 95% CI 1.02-2.50) compared to those with high calcium intake (> 1,425 mg/day) [11]. Also, Wang et al. [12] found a higher rate of hypertension (RR 1.12, 95% CI 1.05-1.20) among women aged over 45 years consuming low calcium (< 558 mg/day) compared to those with high calcium consumption (1,679 mg/day). Other cohort studies reported the association between low calcium intake and increased risk of hypertension [13,14]. Meanwhile, several studies reported that calcium intake had an association with oxidative stress and suggested that calcium supplementation might increase the lipid oxidation [15,16]. As the pathogenesis of hypertension is often associated with oxidative stress, the relationships among calcium intake, blood pressure, and oxidative stress status should be investigated.

Traditionally, the Korean diet has been highly dependent on plant based foods, such as cereals, pulses, roots and various vegetables, now known for having many healthy benefits. Despite many healthy benefits of plant oriented foods, limited consumption in dairy and animal foods in Korean diet relative to western diet has been concerned for insufficient calcium. According to the recent Korean National Health and Nutrition Examination Survey (KNHANES) 2010, the mean daily calcium intake of Korean adults aged 19 and older was 535.2 mg, which was 75.6% of the Korean recommended level. Also, 64.5% of these adults consumed calcium under estimated average requirement (EAR) [17]. This national data indicate that the average calcium intake of Korean adults is within the range of high CVD related mortality risk or high prevalence of hypertension as reported by the previous researches [11,12].

Furthermore, the prevalence of hypertension in Korean adults (≥ 20 years) is 28.9% (30.1% for males, 27.7% for females) [17]. This is slightly lower than the prevalence of hypertension for Americans (31.4%-32.1% for males, 32.8% for females) [18]. But considering the significant difference in the prevalence of overweight and obesity between US adults (BMI ≥ 25; males 72.8%, females 63.0%) and Korean adults (BMI ≥ 25; males 36.5%, females 26.4%), the prevalence of hypertension in Korea seems to be very high. Based on these concerns, a study to investigate the calcium intake status among Korean adults with or without hypertension and its relation to blood pressure and CVD risk-related parameters is needed.

Therefore, this study was carried out for the following two aims: first, to evaluate the calcium intake status between the hypertension and normotension groups; and second, to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices in the hypertension and normotension groups.

Subjects and Methods

Participants

Initially, Korean adults were recruited for this study. Study participants agreed to provide their personal information regarding the purpose and the procedures of the project. Blood pressure was measured twice in seated posture by using a mercury sphygmomanometer, and the two measurements were averaged for systolic and diastolic pressures. Eighty-three subjects with 140 mmHg or higher in SBP or 90 mmHg or higher in diastolic blood pressure (DBP) were assigned to a hypertension group according to JNC-VII guidelines [19]. Participants with 120 mmHg or less SBP and 80 mmHg or less DBP were assigned to a normotension group. Each group was consisted of a similar percentage of subjects in age and gender (42 hypertensive men vs. 41 normotensive men). This study was approved by the College of Medicine, Chung-Ang University Institutional Review Board (IRB), and written informed consent was obtained from each subjects.

Anthropometric measurements

Height was measured using a standard stadiometer following study protocols, and weight in kilograms was measured on a calibrated Inbody (Biospace, Seoul, Korea) system. Measurements were repeated at least two times for each subject and BMI was calculated as weight in kilograms divided by height in meters, squared.

Dietary intake survey

The dietary intake survey was conducted by a 24-hour recall method for 3 days. Study subjects in each group were interviewed by trained research staff to examine the types and amounts of all foods that the subjects had consumed in the previous 3 days. Food models and photographs were used to assist in estimating serving sizes of foods. Dietary intake of calcium and other nutrients were analyzed by using Can-Pro 3.0 (The Korean Nutrition Society, Seoul, Korea).

Collection of blood and urine samples

The subjects fasted overnight after the dietary intake survey, and then 15 ml of venous blood was collected – half volume in an evacuated blood collection tube and the other half in an EDTA-coated blood collection tube. In the evacuated blood collection tube, serum was separated by centrifugation at × 400 g for 15 minutes. Blood samples collected in the EDTA-coated blood collection tube were stored at -20℃ until a test was performed. Spot urine samples were collected and aliquoted for analysis of multiple indices and kept in a freezer at -20℃.

Analysis of biochemical indices

Serum triglyceride, total cholesterol, glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were analyzed by using a commercial kit based on enzymatic principles, and the content of HDL-cholesterol was analyzed by the colorimetric method after separating LDL and VLDL by using a dextran sulfate-Mg2+ sedimentation [20]. Serum LDL-cholesterol was calculated by the Friedewald formula [21] by utilizing triglyceride, total cholesterol, and HDL-cholesterol values.

Glutathione (GSH) in red blood cells was analyzed by using a modification of van Klaveren’s method [22]. After centrifugation of the blood samples at × 2,500 g and 4℃, red blood cells were hemolyzed by adding Millipore grade water. Tricholoroacetic acid (TCA) was added to the hemolyzed sample, and centrifuged at × 10,000 g for 5 minutes. Supernatants were subjected to reaction buffer (0.248 mg/ml NADPH in 143 mM sodium phosphate, 6.3 mM Na4-EDTA at pH 7.5, 6 mM DTNB) with glutathione disulfide reductase (5 U/ml) for 20 minutes at 35℃ and the absorbance was measured in 412 nm by spectrophotometer (UVIKON, Kontron Inc., Milan, Italy). The amount of GSH in red blood cells was indicated as µmol/g hemoglobin (Hb). Glutathione peroxidase (GPx) activity in the red blood cells was analyzed by using methods by Aydin et al. [23]. Regarding GPx, absorbance was measured in 340 nm for 3 minutes using a spectrophotometer (UVIKON, Kontron Inc., Milan, Italy) by adding 8.8 mmol/l H2O2 after 50 mM Tris buffer (pH 7.6), 1 mM Na2EDTA, 2 mM NADPH, 4 mM sodium azide, and 1 unit/ml glutathione reductase, which were reacted with the 20 ul hemolyzed sample at 37℃ for 5 minutes. GPx activity in red blood cells was indicated as U/g Hb.

Urinary lipid peroxidation was analyzed according to the manual of Tagesson et al. [24]. Briefly, 50 µl urine samples were mixed with 23 mM thiobarbituric acid reagent, 0.5 M phosphoric acid 300 µl and then heated at 95℃ for one hour and then cooled down. After adding 100 µl methanol, samples were subjected to HPLC (501 Waters, Messachusetts, USA) for thiobarbituric acid reactive substance (TBARS) analysis. Urinary malondialdehyde (MDA) concentration in urine aliquot was indicated as µmol/g creatinine (Cr).

Statistical analysis

Statistical analyses including the mean and standard deviation values of all results were performed using the SAS program (version 9.1; SAS Institute Inc, Cary, NC, USA). Student’s unpaired t-test was used to analyze the differences between the hypertension group and the normotension group and between men and women. Pearson’s partial correlation coefficient was used to determine an association between variables and to verify significance. All statistical tests were two-sided, and value of P < 0.05 was considered statistically significant.

Results

General characteristics

The general characteristics of the hypertension group and the normotension group are presented in . There were no significant differences in age, height, and weight between the hypertension and normotension groups; however, the hypertension group had significantly higher BMI (P < 0.001), SBP (P < 0.001), and DBP (P < 0.001) than the normotension group.

Table 1

Anthropometric measurements of the subjects

Energy, selective nutrients, and calcium intakes

Energy and selective nutrient intake of the subjects is shown in . The average daily energy intake was 1,493.7 kcal for the hypertension group and 1,602.0 kcal for the normotension group without showing a significant difference between two groups. The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg), but there was no significant difference. The percentage of people who consumed calcium less than EAR for Koreans was higher in the hypertension group (85.5%) compared with that in the normotension group (79.5%) but with no statistical difference between the two groups. Also, the mean daily intake of animal calcium and plant calcium, the calcium intake per 1,000 kcal, and the calcium percentage for Recommended Intake (RI) tended to be lower in the hypertension group ().

Table 2

Daily energy and nutrient intakes of the subjects

Table 3

Daily calcium intake status of the subjects

Food group intake status

Food intake from different food groups is shown in . The total daily food intake was 993.0 g for the hypertension group and 1,117.2 g for the normotension group, not showing a significant difference. The intakes of sugar/sweeteners and seasonings were significantly higher in the normotension group, while the intake of mushrooms was higher in the hypertension group. Except for these three food groups, no significant difference was found in consumption of the other food groups between the hypertension and normotension groups.

Table 4

Daily food intakes from each food group of the subjects

Biochemical indices in blood and urine

Biochemical indices in blood and urine of the subjects are described in . No significant difference was found in blood and urine biochemical indices between the hypertension and normotension groups.

Table 5

Biochemical indices in blood and urine of the subjects

Correlation between calcium intake, and blood pressure and biochemical indices

shows the correlation between blood pressure and nutrient intake in both groups after adjusting for age, gender, BMI, and energy intake. In the hypertension group, DBP had a significant negative correlation with plant fat (P < 0.05) and plant calcium (P < 0.01). In the normotension group, however, no significant correlation was found between blood pressure and nutrient intake.

Table 6

Correlations between blood pressure and nutrient intakes adjusted for age, sex, BMI, and energy intake of the subjects

The correlations between biochemical indices and nutrient intake after adjusting for age, gender, BMI, and energy intake are shown in . No significant difference was found between biochemical indices and nutrient intake in the hypertension group, but in the normotension group, serum triglyceride was significantly and positively correlated with total calcium intake and animal calcium intake.

Table 7

Correlations between calcium intake and blood parameters adjusted for age, sex, BMI, and energy intake of the subjects

Discussion

The present study examined the calcium intake status and the relation between dietary calcium intake and blood pressure, blood lipid profiles, and blood/urine oxidative stress indices in Korean adults with or without hypertension. The major finding was that the calcium intake of both groups was low and was mainly derived from plant foods. Also, the plant food-derived calcium intake was significantly and negatively correlated with DBP in the hypertension group but not in the normotension group.

Dietary calcium intake of the hypertension group tended to be lower than that of the normotension group, and the calcium intake level of both groups is considered quite insufficient. There are two possible reasons for the low calcium intake of the subjects. First, the overall food intake was low, which means a low daily energy intake. The amount of energy intake in both the hypertension and normotension groups was just 1,493.7 kcal and 1,602.0 kcal, respectively. Additionally, calcium intake relative to energy intake of 1,000 kcal within both hypertension and normotension groups was still below the recommended intake [25]. The second possible reason for low calcium intake in study subjects was the low intake of main food sources for calcium, particularly milk and dairy products. According to the KNHANES [17], even though the top ranked food source for calcium intake in Koreans was milk, the average amount of milk consumed by Korean adults was 74.0 g per day, which corresponds to only one third of a small carton (~200 ml) of milk. In the current study, the milk consumption of the study subjects was even less, showing 40.9 g for the hypertension group and 51.4 g for the normotension group. Considering the fact that 100 g of milk contains about 100 mg of calcium, the subjects consumed only 50 mg of calcium from their daily milk consumption. In addition to milk, small bony fishes such as anchovies are an important food source for supplying calcium in the average Korean diet, but the portion size is very small in relative to other side-dishes typically found in the Korean diet and therefore may not play a significant role in increasing calcium consumption. Also, the low intake of calcium derived from animal-based foods, such as milk and small bony fish, compared with relatively high intake of calcium derived from plant foods, which have low bioavailability, in both the hypertension and normotension groups may be indicative of the overall poor calcium status in these study subjects.

Many epidemiological studies have reported results showing the relationship between calcium intake and blood pressure [2,26,27]. For instance, the amount of calcium intake was negatively correlated with high blood pressure, many hypertension patients had a low calcium intake in their diet [2,27], and the supplementation of calcium-rich foods decreased blood pressure [26]. These findings indicate that calcium consumption is beneficial for prevention and treatment of hypertension. In the present study, diastolic blood pressure was significantly and negatively correlated with plant calcium consumption in the hypertension subjects but not in the normotension subjects. Some possible explanations for the association of calcium intake with reducing the risk of hypertension have been suggested by several experimental studies [28-34]. Calcium is involved in regulating blood pressure by controlling vascular smooth muscle cell contractility and thus modulating peripheral vascular resistance [28-31]. In addition, extracellular ionized calcium inhibits renin secretion by interacting with the calcium-sensing receptor [32-34]. Another possible explanation offered by the current study is that calcium intake of the study subjects was more highly dependent on the consumption of plant-based foods than animal-based foods. So far, many studies have mainly focused on the consumption of dairy products for investigating the relationship between calcium and blood pressure [35], but for the subjects whose frequent food source is plant-based, studies may need a different approach to investigate the relationship between the consumption of calcium derived from plant-based food and blood pressure. Based on the reports that lowering diastolic blood pressure by 2 mmHg is associated with 17% reduction in the incidence of hypertension, 6% decrease in the risk of cardiac diseases [36], and reduced ventricular function [37], a follow-up study is warranted as our results show a correlation between calcium derived from plant foods and blood pressure. In addition, the plant calcium intake of the normotension group had no association with their blood pressure, showing a difference from the hypertensive group. Therefore, further studies are also needed to investigate the plant calcium’s effect on lowering blood pressure with different blood pressure status.

Calcium consumption is also related to the lipoprotein metabolism and affects the level of blood lipid profiles [38-42]. Two main mechanisms of lowering blood lipids by calcium have been suggested. Dietary calcium engages the formation of intestinal soap with intestinal fatty acids. Particularly saturated fatty acids [40,42] and calcium also increase the excretion of blood lipids through binding with bile acids and consequently lower the synthesis of LDL-cholesterol [41,43]. While such a beneficial effect of calcium is reported in subjects who consumed more than 1,000 mg of calcium, the daily calcium intake of our current study subjects including both the hypertension and normotension groups was very low. In this study the level of total cholesterol and LDL-cholesterol had no significant association with the calcium intake of the hypertension and normotension groups.

Lorenzen et al. [43] reported that calcium intake from dairy products lowers the triglyceride contents in chylomicron and leads to an increase in chylomicron clearance and a decrease in fat absorption. On the other hand, a study of van Meijl et al. [42] argued that the increase in chylomicron clearance was not only from the calcium consumption and that the effect of calcium consumption should be differentiated from the consumption of dairy products. Yu et al. [44] reported that when the average daily calcium intake was above 422 mg, the consumption of dairy products and animal food-based calcium was positively associated with serum LDL cholesterol. In the current study, total calcium consumption and the calcium consumption derived from animal based-foods in the normotensive group were positively associated with blood triglycerides. One possible explanation for the positive relationship between calcium consumption and serum triglycerides is the tendency of the subjects to have high calcium intake from animal-based foods. Our present study identified a significant relationship between calcium and blood pressure and blood lipids in the context of daily calcium intake rather than calcium fortification or high calcium supplements. As this study is one of few studies investigating the role of daily calcium intake in the prevalence of hypertension and other metabolic diseases, further research is needed in a large and diverse population.

In spite of the beneficial effects of calcium, which lowers the blood pressure and the level of blood lipids, several studies raised the concern about calcium over-supplementation [45-46]. Supplementation of high amounts of calcium leads to the increase of cellular calcium ions. These over-produced calcium ions generate free radicals and inflammatory mediators, and continuously cause cellular damage [15]. Also, daily supplementation of 900 mg of calcium as a type of dairy product (3 servings per day) for overweight women for 12 weeks increased the biomarkers of lipids oxidation [16]. In the current study, since the level of calcium intake was very low, this may lead to subtle or no alterations in biomarkers of lipid oxidation in blood and urine samples of the hypertension and normotension groups.

This study has several limitations: 1) the size of study subjects in both the hypertension and normotension groups was not large enough to have statistical power for the results of several serum biomarkers, 2) the level of blood pressure in the hypertension group (152.8/86.2 mmHg, diagnosed as phase I hypertension) was relatively mild, making it difficult to find the differences in several measurements between the hypertension and normotension groups, and 3) limited methodology was used to investigate the calcium intake of subjects as we carried out the 24 hour recall but not food frequency records.

In conclusion, the daily calcium intake of hypertension patients tended to be lower than that of normotensive subjects. Also, relative to animal-based foods, plant-based foods were high contributors to calcium sources for both hypertension and normotension subjects. In the hypertension subjects, the intake of plant food-derived calcium was negatively correlated with the DBP, while animal food-derived calcium was positively correlated with DPB and in the healthy subjects, total calcium intake was positively correlated with serum triglycerides. However, there was no significant finding to show the relationship between calcium and lipid oxidation. Overall, these data suggest the importance of adequate calcium consumption and implicate to reconsider plant based foods as good calcium source for hypertension patients. Further investigation is necessary to identify the role of calcium derived from plant foods in populations with high dependency on plant-based food.

Acknowledgment

We would like to express our appreciation to Glenn Hawes for assistance to manuscript preparation.

References

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Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Nutr Res Pract. 2012 Oct; 6(5): 421–428.

,1,2 and 3

Mi-Hyun Kim

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

So Young Bu

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

Mi-Kyeong Choi

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

1Department of Food and Nutrition, Kangwon National University, Samcheok 245-711, Korea.

2Division of Food Science, Kyungil University, Gyeongsan 712-701, Korea.

3Division of Food Science, Kongju National University, 54 Daehak-ro, Yesan, Chungnam 340-742, Korea.

Corresponding author.

Received 2012 May 24; Revised 2012 Jun 29; Accepted 2012 Jul 16.

Copyright ©2012 The Korean Nutrition Society and the Korean Society of Community NutritionThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This article has been cited by other articles in PMC.

Abstract

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.

Keywords: Dietary calcium intake, hypertension, oxidative stress indices, plant calcium

Introduction

The relationship between calcium intake and cardiovascular diseases (CVD) has been explored through numerous molecular, animal, and human studies for several decades. An epidemiological study showed that residents who consumed hard water which was rich in calcium and magnesium had a lower mortality rate caused by circulatory diseases than those who had consumed soft water [1]. This finding suggested that the intake of calcium might be related to cardiovascular diseases. Also, several systematic reviews revealed that calcium supplementation reduced systolic blood pressure (SBP), particularly among hypertensive subjects but not among normotensive subjects [2-6]. A reduction of serum total cholesterol has been reported in hypercholesterolemic subjects given 1 g of calcium per day for 8 weeks [7,8]. More recent studies showed that 1 g/day of calcium supplementation for one year increased the level of HDL-cholesterol and decreased the level of LDL-cholesterol [9,10].

In addition, some observational studies reported that low calcium intake was associated with increased risk of CVD. The Iowa Women Health Study found that Caucasian women aged 55-69 years with low calcium intake (< 696 mg/day) had a high mortality rate due to cardiovascular heart disease (RR 1.58, 95% CI 1.02-2.50) compared to those with high calcium intake (> 1,425 mg/day) [11]. Also, Wang et al. [12] found a higher rate of hypertension (RR 1.12, 95% CI 1.05-1.20) among women aged over 45 years consuming low calcium (< 558 mg/day) compared to those with high calcium consumption (1,679 mg/day). Other cohort studies reported the association between low calcium intake and increased risk of hypertension [13,14]. Meanwhile, several studies reported that calcium intake had an association with oxidative stress and suggested that calcium supplementation might increase the lipid oxidation [15,16]. As the pathogenesis of hypertension is often associated with oxidative stress, the relationships among calcium intake, blood pressure, and oxidative stress status should be investigated.

Traditionally, the Korean diet has been highly dependent on plant based foods, such as cereals, pulses, roots and various vegetables, now known for having many healthy benefits. Despite many healthy benefits of plant oriented foods, limited consumption in dairy and animal foods in Korean diet relative to western diet has been concerned for insufficient calcium. According to the recent Korean National Health and Nutrition Examination Survey (KNHANES) 2010, the mean daily calcium intake of Korean adults aged 19 and older was 535.2 mg, which was 75.6% of the Korean recommended level. Also, 64.5% of these adults consumed calcium under estimated average requirement (EAR) [17]. This national data indicate that the average calcium intake of Korean adults is within the range of high CVD related mortality risk or high prevalence of hypertension as reported by the previous researches [11,12].

Furthermore, the prevalence of hypertension in Korean adults (≥ 20 years) is 28.9% (30.1% for males, 27.7% for females) [17]. This is slightly lower than the prevalence of hypertension for Americans (31.4%-32.1% for males, 32.8% for females) [18]. But considering the significant difference in the prevalence of overweight and obesity between US adults (BMI ≥ 25; males 72.8%, females 63.0%) and Korean adults (BMI ≥ 25; males 36.5%, females 26.4%), the prevalence of hypertension in Korea seems to be very high. Based on these concerns, a study to investigate the calcium intake status among Korean adults with or without hypertension and its relation to blood pressure and CVD risk-related parameters is needed.

Therefore, this study was carried out for the following two aims: first, to evaluate the calcium intake status between the hypertension and normotension groups; and second, to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices in the hypertension and normotension groups.

Subjects and Methods

Participants

Initially, Korean adults were recruited for this study. Study participants agreed to provide their personal information regarding the purpose and the procedures of the project. Blood pressure was measured twice in seated posture by using a mercury sphygmomanometer, and the two measurements were averaged for systolic and diastolic pressures. Eighty-three subjects with 140 mmHg or higher in SBP or 90 mmHg or higher in diastolic blood pressure (DBP) were assigned to a hypertension group according to JNC-VII guidelines [19]. Participants with 120 mmHg or less SBP and 80 mmHg or less DBP were assigned to a normotension group. Each group was consisted of a similar percentage of subjects in age and gender (42 hypertensive men vs. 41 normotensive men). This study was approved by the College of Medicine, Chung-Ang University Institutional Review Board (IRB), and written informed consent was obtained from each subjects.

Anthropometric measurements

Height was measured using a standard stadiometer following study protocols, and weight in kilograms was measured on a calibrated Inbody (Biospace, Seoul, Korea) system. Measurements were repeated at least two times for each subject and BMI was calculated as weight in kilograms divided by height in meters, squared.

Dietary intake survey

The dietary intake survey was conducted by a 24-hour recall method for 3 days. Study subjects in each group were interviewed by trained research staff to examine the types and amounts of all foods that the subjects had consumed in the previous 3 days. Food models and photographs were used to assist in estimating serving sizes of foods. Dietary intake of calcium and other nutrients were analyzed by using Can-Pro 3.0 (The Korean Nutrition Society, Seoul, Korea).

Collection of blood and urine samples

The subjects fasted overnight after the dietary intake survey, and then 15 ml of venous blood was collected – half volume in an evacuated blood collection tube and the other half in an EDTA-coated blood collection tube. In the evacuated blood collection tube, serum was separated by centrifugation at × 400 g for 15 minutes. Blood samples collected in the EDTA-coated blood collection tube were stored at -20℃ until a test was performed. Spot urine samples were collected and aliquoted for analysis of multiple indices and kept in a freezer at -20℃.

Analysis of biochemical indices

Serum triglyceride, total cholesterol, glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were analyzed by using a commercial kit based on enzymatic principles, and the content of HDL-cholesterol was analyzed by the colorimetric method after separating LDL and VLDL by using a dextran sulfate-Mg2+ sedimentation [20]. Serum LDL-cholesterol was calculated by the Friedewald formula [21] by utilizing triglyceride, total cholesterol, and HDL-cholesterol values.

Glutathione (GSH) in red blood cells was analyzed by using a modification of van Klaveren’s method [22]. After centrifugation of the blood samples at × 2,500 g and 4℃, red blood cells were hemolyzed by adding Millipore grade water. Tricholoroacetic acid (TCA) was added to the hemolyzed sample, and centrifuged at × 10,000 g for 5 minutes. Supernatants were subjected to reaction buffer (0.248 mg/ml NADPH in 143 mM sodium phosphate, 6.3 mM Na4-EDTA at pH 7.5, 6 mM DTNB) with glutathione disulfide reductase (5 U/ml) for 20 minutes at 35℃ and the absorbance was measured in 412 nm by spectrophotometer (UVIKON, Kontron Inc., Milan, Italy). The amount of GSH in red blood cells was indicated as µmol/g hemoglobin (Hb). Glutathione peroxidase (GPx) activity in the red blood cells was analyzed by using methods by Aydin et al. [23]. Regarding GPx, absorbance was measured in 340 nm for 3 minutes using a spectrophotometer (UVIKON, Kontron Inc., Milan, Italy) by adding 8.8 mmol/l H2O2 after 50 mM Tris buffer (pH 7.6), 1 mM Na2EDTA, 2 mM NADPH, 4 mM sodium azide, and 1 unit/ml glutathione reductase, which were reacted with the 20 ul hemolyzed sample at 37℃ for 5 minutes. GPx activity in red blood cells was indicated as U/g Hb.

Urinary lipid peroxidation was analyzed according to the manual of Tagesson et al. [24]. Briefly, 50 µl urine samples were mixed with 23 mM thiobarbituric acid reagent, 0.5 M phosphoric acid 300 µl and then heated at 95℃ for one hour and then cooled down. After adding 100 µl methanol, samples were subjected to HPLC (501 Waters, Messachusetts, USA) for thiobarbituric acid reactive substance (TBARS) analysis. Urinary malondialdehyde (MDA) concentration in urine aliquot was indicated as µmol/g creatinine (Cr).

Statistical analysis

Statistical analyses including the mean and standard deviation values of all results were performed using the SAS program (version 9.1; SAS Institute Inc, Cary, NC, USA). Student’s unpaired t-test was used to analyze the differences between the hypertension group and the normotension group and between men and women. Pearson’s partial correlation coefficient was used to determine an association between variables and to verify significance. All statistical tests were two-sided, and value of P < 0.05 was considered statistically significant.

Results

General characteristics

The general characteristics of the hypertension group and the normotension group are presented in . There were no significant differences in age, height, and weight between the hypertension and normotension groups; however, the hypertension group had significantly higher BMI (P < 0.001), SBP (P < 0.001), and DBP (P < 0.001) than the normotension group.

Table 1

Anthropometric measurements of the subjects

Energy, selective nutrients, and calcium intakes

Energy and selective nutrient intake of the subjects is shown in . The average daily energy intake was 1,493.7 kcal for the hypertension group and 1,602.0 kcal for the normotension group without showing a significant difference between two groups. The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg), but there was no significant difference. The percentage of people who consumed calcium less than EAR for Koreans was higher in the hypertension group (85.5%) compared with that in the normotension group (79.5%) but with no statistical difference between the two groups. Also, the mean daily intake of animal calcium and plant calcium, the calcium intake per 1,000 kcal, and the calcium percentage for Recommended Intake (RI) tended to be lower in the hypertension group ().

Table 2

Daily energy and nutrient intakes of the subjects

Table 3

Daily calcium intake status of the subjects

Food group intake status

Food intake from different food groups is shown in . The total daily food intake was 993.0 g for the hypertension group and 1,117.2 g for the normotension group, not showing a significant difference. The intakes of sugar/sweeteners and seasonings were significantly higher in the normotension group, while the intake of mushrooms was higher in the hypertension group. Except for these three food groups, no significant difference was found in consumption of the other food groups between the hypertension and normotension groups.

Table 4

Daily food intakes from each food group of the subjects

Biochemical indices in blood and urine

Biochemical indices in blood and urine of the subjects are described in . No significant difference was found in blood and urine biochemical indices between the hypertension and normotension groups.

Table 5

Biochemical indices in blood and urine of the subjects

Correlation between calcium intake, and blood pressure and biochemical indices

shows the correlation between blood pressure and nutrient intake in both groups after adjusting for age, gender, BMI, and energy intake. In the hypertension group, DBP had a significant negative correlation with plant fat (P < 0.05) and plant calcium (P < 0.01). In the normotension group, however, no significant correlation was found between blood pressure and nutrient intake.

Table 6

Correlations between blood pressure and nutrient intakes adjusted for age, sex, BMI, and energy intake of the subjects

The correlations between biochemical indices and nutrient intake after adjusting for age, gender, BMI, and energy intake are shown in . No significant difference was found between biochemical indices and nutrient intake in the hypertension group, but in the normotension group, serum triglyceride was significantly and positively correlated with total calcium intake and animal calcium intake.

Table 7

Correlations between calcium intake and blood parameters adjusted for age, sex, BMI, and energy intake of the subjects

Discussion

The present study examined the calcium intake status and the relation between dietary calcium intake and blood pressure, blood lipid profiles, and blood/urine oxidative stress indices in Korean adults with or without hypertension. The major finding was that the calcium intake of both groups was low and was mainly derived from plant foods. Also, the plant food-derived calcium intake was significantly and negatively correlated with DBP in the hypertension group but not in the normotension group.

Dietary calcium intake of the hypertension group tended to be lower than that of the normotension group, and the calcium intake level of both groups is considered quite insufficient. There are two possible reasons for the low calcium intake of the subjects. First, the overall food intake was low, which means a low daily energy intake. The amount of energy intake in both the hypertension and normotension groups was just 1,493.7 kcal and 1,602.0 kcal, respectively. Additionally, calcium intake relative to energy intake of 1,000 kcal within both hypertension and normotension groups was still below the recommended intake [25]. The second possible reason for low calcium intake in study subjects was the low intake of main food sources for calcium, particularly milk and dairy products. According to the KNHANES [17], even though the top ranked food source for calcium intake in Koreans was milk, the average amount of milk consumed by Korean adults was 74.0 g per day, which corresponds to only one third of a small carton (~200 ml) of milk. In the current study, the milk consumption of the study subjects was even less, showing 40.9 g for the hypertension group and 51.4 g for the normotension group. Considering the fact that 100 g of milk contains about 100 mg of calcium, the subjects consumed only 50 mg of calcium from their daily milk consumption. In addition to milk, small bony fishes such as anchovies are an important food source for supplying calcium in the average Korean diet, but the portion size is very small in relative to other side-dishes typically found in the Korean diet and therefore may not play a significant role in increasing calcium consumption. Also, the low intake of calcium derived from animal-based foods, such as milk and small bony fish, compared with relatively high intake of calcium derived from plant foods, which have low bioavailability, in both the hypertension and normotension groups may be indicative of the overall poor calcium status in these study subjects.

Many epidemiological studies have reported results showing the relationship between calcium intake and blood pressure [2,26,27]. For instance, the amount of calcium intake was negatively correlated with high blood pressure, many hypertension patients had a low calcium intake in their diet [2,27], and the supplementation of calcium-rich foods decreased blood pressure [26]. These findings indicate that calcium consumption is beneficial for prevention and treatment of hypertension. In the present study, diastolic blood pressure was significantly and negatively correlated with plant calcium consumption in the hypertension subjects but not in the normotension subjects. Some possible explanations for the association of calcium intake with reducing the risk of hypertension have been suggested by several experimental studies [28-34]. Calcium is involved in regulating blood pressure by controlling vascular smooth muscle cell contractility and thus modulating peripheral vascular resistance [28-31]. In addition, extracellular ionized calcium inhibits renin secretion by interacting with the calcium-sensing receptor [32-34]. Another possible explanation offered by the current study is that calcium intake of the study subjects was more highly dependent on the consumption of plant-based foods than animal-based foods. So far, many studies have mainly focused on the consumption of dairy products for investigating the relationship between calcium and blood pressure [35], but for the subjects whose frequent food source is plant-based, studies may need a different approach to investigate the relationship between the consumption of calcium derived from plant-based food and blood pressure. Based on the reports that lowering diastolic blood pressure by 2 mmHg is associated with 17% reduction in the incidence of hypertension, 6% decrease in the risk of cardiac diseases [36], and reduced ventricular function [37], a follow-up study is warranted as our results show a correlation between calcium derived from plant foods and blood pressure. In addition, the plant calcium intake of the normotension group had no association with their blood pressure, showing a difference from the hypertensive group. Therefore, further studies are also needed to investigate the plant calcium’s effect on lowering blood pressure with different blood pressure status.

Calcium consumption is also related to the lipoprotein metabolism and affects the level of blood lipid profiles [38-42]. Two main mechanisms of lowering blood lipids by calcium have been suggested. Dietary calcium engages the formation of intestinal soap with intestinal fatty acids. Particularly saturated fatty acids [40,42] and calcium also increase the excretion of blood lipids through binding with bile acids and consequently lower the synthesis of LDL-cholesterol [41,43]. While such a beneficial effect of calcium is reported in subjects who consumed more than 1,000 mg of calcium, the daily calcium intake of our current study subjects including both the hypertension and normotension groups was very low. In this study the level of total cholesterol and LDL-cholesterol had no significant association with the calcium intake of the hypertension and normotension groups.

Lorenzen et al. [43] reported that calcium intake from dairy products lowers the triglyceride contents in chylomicron and leads to an increase in chylomicron clearance and a decrease in fat absorption. On the other hand, a study of van Meijl et al. [42] argued that the increase in chylomicron clearance was not only from the calcium consumption and that the effect of calcium consumption should be differentiated from the consumption of dairy products. Yu et al. [44] reported that when the average daily calcium intake was above 422 mg, the consumption of dairy products and animal food-based calcium was positively associated with serum LDL cholesterol. In the current study, total calcium consumption and the calcium consumption derived from animal based-foods in the normotensive group were positively associated with blood triglycerides. One possible explanation for the positive relationship between calcium consumption and serum triglycerides is the tendency of the subjects to have high calcium intake from animal-based foods. Our present study identified a significant relationship between calcium and blood pressure and blood lipids in the context of daily calcium intake rather than calcium fortification or high calcium supplements. As this study is one of few studies investigating the role of daily calcium intake in the prevalence of hypertension and other metabolic diseases, further research is needed in a large and diverse population.

In spite of the beneficial effects of calcium, which lowers the blood pressure and the level of blood lipids, several studies raised the concern about calcium over-supplementation [45-46]. Supplementation of high amounts of calcium leads to the increase of cellular calcium ions. These over-produced calcium ions generate free radicals and inflammatory mediators, and continuously cause cellular damage [15]. Also, daily supplementation of 900 mg of calcium as a type of dairy product (3 servings per day) for overweight women for 12 weeks increased the biomarkers of lipids oxidation [16]. In the current study, since the level of calcium intake was very low, this may lead to subtle or no alterations in biomarkers of lipid oxidation in blood and urine samples of the hypertension and normotension groups.

This study has several limitations: 1) the size of study subjects in both the hypertension and normotension groups was not large enough to have statistical power for the results of several serum biomarkers, 2) the level of blood pressure in the hypertension group (152.8/86.2 mmHg, diagnosed as phase I hypertension) was relatively mild, making it difficult to find the differences in several measurements between the hypertension and normotension groups, and 3) limited methodology was used to investigate the calcium intake of subjects as we carried out the 24 hour recall but not food frequency records.

In conclusion, the daily calcium intake of hypertension patients tended to be lower than that of normotensive subjects. Also, relative to animal-based foods, plant-based foods were high contributors to calcium sources for both hypertension and normotension subjects. In the hypertension subjects, the intake of plant food-derived calcium was negatively correlated with the DBP, while animal food-derived calcium was positively correlated with DPB and in the healthy subjects, total calcium intake was positively correlated with serum triglycerides. However, there was no significant finding to show the relationship between calcium and lipid oxidation. Overall, these data suggest the importance of adequate calcium consumption and implicate to reconsider plant based foods as good calcium source for hypertension patients. Further investigation is necessary to identify the role of calcium derived from plant foods in populations with high dependency on plant-based food.

Acknowledgment

We would like to express our appreciation to Glenn Hawes for assistance to manuscript preparation.

References

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Calcium Supplements and High Blood Pressure Medications

Calcium supplements are generally safe and are not likely to affect your blood pressure, at least not directly. However, if you are being treated for hypertension, calcium supplements may indirectly cause your blood pressure to rise by interfering with your medication’s effects.

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Calcium supplements can interfere with the action of certain high blood pressure medications, making them less effective at controlling blood pressure. In this case, the calcium isn’t actually causing your blood pressure to rise; rather, it is stopping your medications from exerting their blood-pressure-lowering effects. 

These interactions are uncommon, and only affect a small number of high blood pressure medicines. The two blood pressure-lowering medications that are most likely to interact with calcium supplements are thiazide diuretics and calcium channel blockers. Here is how calcium supplements can interfere with those two types of medication.

Thiazide Diuretics

Thiazide diuretics work to lower your blood pressure by helping your kidneys get rid of excess water and sodium (rather than holding on to it). Lowering the volume of fluid in your bloodstream relieves some of the pressure, making it easier for your heart to pump.

If you take calcium supplements while using a thiazide diuretic, the calcium can disrupt the diuretic’s action on the kidneys, which in turn makes the drug less effective at lowering your blood pressure.

In some cases, taking calcium with a thiazide diuretic can lead to a condition called milk-alkali syndrome in which the body becomes less acidic and blood calcium levels begin to rise. This can lead to hypercalcemia (abnormally high blood calcium), the condition of which increases the risk of heart attack, acute kidney failure, and seizure.

If taking a thiazide diuretic, you should restrict your calcium intake to less than 1,500 milligrams (mg) per day.

Calcium Channel Blockers

Calcium channel blockers help lower blood pressure this way: they stop calcium from interacting with blood vessels, which lowers the blood vessel’s ability to tighten and ultimately leads to looser vessels and lower blood pressure.

It makes sense, then, that calcium channel blockers can also be affected by calcium supplements. However, there’s typically only a risk when you’re getting extremely high levels of supplemented calcium (such as being given high doses of calcium through IV in a hospital).

In this case, the interaction is very straightforward: very high levels of blood calcium can “out-compete” the drug’s ability to block the interaction between calcium and your blood vessels. In essence, there is so much calcium that the drug simply cannot block it all. When this happens, it can be quickly reversed by stopping the IV administration of calcium.

There is no evidence that oral calcium supplements can interfere with calcium channel blockers. However, to be safe, check your blood pressure regularly if taking calcium supplements and calcium channel blockers together.

Other Blood Pressure Medications

Calcium supplements do not interfere with other common blood pressure medications like ACE inhibitors, beta-blockers, or other types of diuretics. Still, you should always consult your doctor before beginning supplementation with any vitamin, mineral, or herbal product.

Many supplements are known to interact with prescription drugs, which is why you should always consult your doctor or pharmacist before taking supplements, including vitamins and herbal remedies.

Can Potassium and Calcium Help Your Hypertension?

Potassium and calcium and are minerals that may be key to preventing hypertension (high blood pressure) or lowering it if your blood pressure is already elevated.

The notion of blood pressure control through supplements was tested in a 1998 study of 300 nurses who didn’t normally consume a lot of calcium or potassium in their diets. They took calcium and potassium supplements for 16 weeks, and at the end of the study, researchers found that potassium helped to lower blood pressure a little bit, but calcium did not at all. The conclusion: Potassium supplements may be somewhat helpful in lowering blood pressure, but getting more nutrients through food may be a better approach.

Another study also found that the hypertension-lowering effects of potassium supplements were somewhat similar to the results seen when people followed the Dietary Approaches to Stop Hypertension, or DASH, diet. The DASH diet is focused on consuming lots of vegetables, fruits, low-fat or fat-free dairy products, whole grains, fish, poultry, beans, nuts, and seeds. Many of these foods are rich sources of potassium. A study that focused just on the DASH diet found that it lowered blood pressure for just

about everybody who tried it, regardless of gender, race, weight, hypertension status, or physical activity level.

A Potassium-Rich Diet

It’s known that potassium-rich foods can help control high blood pressure. But what should you eat? A variety of foods contain potassium, such as fruits, vegetables, dairy products, and fish. Those especially rich in potassium include potatoes, lima beans, bananas, tomato sauce, beet greens, fat-free yogurt or milk, halibut, tuna, and orange juice. Here’s how some of these choices stack up:

  • One cup of orange juice: 496 milligrams (mg) of potassium
  • One baked potato: 1,081 mg
  • One cup of sliced bananas: 594 mg
  • One cup of tomato sauce: 909 mg
  • One cup of cooked spinach: 839 mg

Recommendations are that you eat about 4,700 mg of potassium each day. But don’t go overboard; too much potassium can be especially dangerous for older adults and people with kidney disorders. Ask your doctor about your specific needs.

The Scoop on Calcium and Hypertension

A recent review of research on calcium to treat high blood pressure examined 13 small studies and found little evidence that calcium supplements helped to reduce hypertension, though the authors of the review did point out that the studies may not have been big enough to draw good conclusions and more research is needed.

Even though there is no conclusive evidence that calcium supplements will help to control your hypertension, at least one large study found that a low-fat diet that included dairy products (a rich source of calcium) did decrease the risk of developing hypertension for a study group of almost 30,000 women over the age of 45.

This research showed that women who drank two or more daily servings of skim milk (or consumed other low-fat dairy products) reduced their risk for developing high blood pressure by 10 percent compared with women who didn’t consume dairy products as frequently. It wasn’t clear if it was the calcium or the consumption of dairy products in general that tended to lower a person’s risk for developing high blood pressure. (The study also found that taking calcium as a supplement didn’t have the same benefit.)

While scientists try to tease out the exact effects of potassium and calcium on hypertension, the bottom line when it comes to preventing or treating this disease is to eat a healthy, balanced diet rich in vegetables, fruits, and low-fat or fat-free dairy products.

Hypertension | Federal Center for Risk Management

HYPERTENSION (Greek, hyper- + tonos tension) is an excessive muscle tension, manifested by their increased resistance to stretching. The term is used to denote increased tension of smooth muscles of hollow organs (for example, stomach, bladder, etc.), ducts and vessels, as well as skeletal muscles.
Hypertension of the walls of arterioles is one of the reasons for an increase in blood pressure (blood pressure) – arterial hypertension, incl.hours with hypertension. (Brief Medical Encyclopedia, 1989, M.).

According to WHO statistics, every third person in the world has a disease at the stage of development or already suffers from hypertension. The number of people with this disease increases with age. There are five times more patients between the ages of 50 and 60 years than those between the ages of 20 and 40, which is why hypertension is called “half disease”.

The leading cause of cardiovascular mortality is arterial hypertension.The incidence of arterial hypertension in Russia is about 40%.

Causes and risks

Causes of high blood pressure:
  • Smoking
  • Excess weight
  • Sedentary lifestyle
  • Drinking a lot of salt
  • Excessive alcohol consumption (more than 1-2 glasses per day)
  • Stress
  • Old age
  • Genetics
  • Cases of hypertension in the family
  • Chronic renal failure
  • Diseases of the adrenal gland or thyroid gland
Who is at greater risk for hypertension?
  • People whose family members have (or have suffered) high blood pressure.
  • People who smoke.
  • Pregnant women.
  • Women taking birth control pills.
  • People over 35 years old.
  • People who are overweight.
  • Inactive people.
  • People who abuse alcohol.
  • People who eat a lot of fatty and salty foods.

Diet for hypertension

DASH (Dietary Approaches to Stop Hypertension).

According to numerous clinical studies, developed at the National Institute of Heart, Lung and Circulation (part of the National Institutes of Health, controlled by the US government), a diet plan can lead to a decrease in blood pressure numbers as soon as 2 weeks after starting a DASH diet.

A distinctive feature of the DASH diet is a combination of foods such as fruits, vegetables and low-fat dairy products. This food is able to enrich the body with potassium, calcium and magnesium, which work together to have a powerful normalizing effect on blood pressure.

Increasing the intake of potassium, magnesium and calcium while restricting sodium (salt) intake has a very pronounced effect on blood pressure. This combination of nutrients acts as a diuretic, helping the body eliminate excess salt.

  • Fruits and vegetables, legumes, whole grain products, dairy products are rich in potassium (balances the intracellular sodium content).
  • The normalizing effect of calcium on blood pressure has not been proven, but it is well known that low calcium intake is correlated with elevated blood pressure numbers.Calcium comes from dairy products, green leafy vegetables, fish with edible bones, special calcium-fortified foods.
  • Lack of magnesium in the body leads to an increase in blood pressure. Good sources of magnesium include legumes, green leafy vegetables, nuts and seeds, whole grains, and lean meats.

Source: http://dietadash.ru/

Upper and lower blood pressure. Classification of AD

Systolic pressure (upper) is the pressure that develops during the contraction of the heart muscle.Partly in its creation, large arteries, such as the aorta, are involved, acting as a buffer. After the heart contraction, the aortic valve closes and blood cannot flow back to the heart, at which point it is filled with oxygen-rich blood for the next contraction. At this stage, the blood passively moves through the vessels – this will be the so-called diastolic pressure (lower) .

  • Optimal BP – SBP (systolic blood pressure) <120 / DBP (diastolic blood pressure) <80 mm Hg.Art.
  • Normal BP SBP 120-129 / DBP 80-84 mm Hg. (prehypertension according to JNC-VII)
  • High-normal blood pressure SBP 130-139 / DBP 85-89 mm Hg. (prehypertension according to JNC-VII)
  • Grade 1 AH – SBP 140-159 / DBP 90-99.
  • Grade 2 AH – SBP 160-179 / DBP 100-109.
  • Grade 3 AH – SBP 180 and above / DBP 110 and above.
  • Isolated systolic hypertension – SBP above or equal to 140 / DBP below 90.

How to measure pressure correctly.

Measurement conditions:

  • Rest for at least 5 minutes before taking blood pressure measurements.
  • At least 30 minutes before measuring blood pressure, you must refrain from smoking and drinking caffeine (coffee, cola, tea).
  • During the measurement, one should sit, leaning against the back of a chair, and the motionless arm should lie comfortably on the table.
  • Do not talk during measurement.
  • The cuff should be wrapped around the forearm with the center of the inflatable bag just above the brachial artery, and the bottom edge of the cuff should be about 2–3 cm above the elbow.
  • The cuff inflatable bag must be at heart level during measurement.
  • Legs should not be crossed during measurement.
  • Feet should be on the floor.
  • The bladder must be emptied before measuring blood pressure.
  • The shoulder should not be squeezed by clothing (all the more, measurement through clothing is unacceptable).

Failure to comply with these conditions may lead to high blood pressure:

  • after taking coffee – by 11/5 mm Hg.Art.
  • alcohol at – 8/8 mm Hg. Art.
  • 90,015 smoking per – 6/5 mm Hg. Art.

  • with an overflowing bladder – by 15/10 mm Hg. Art.
  • in the absence of back support – systolic at 6-10 mm Hg. Art.
  • with no hand support – by 7/11 mm Hg. Art.

Tonometers

Which blood pressure monitors are better to use?

For home blood pressure measurement, there are several types of devices available on the market:

  • Auscultatory method: Mercury, aneroid (“dial”) and electronic (“hybrid”) blood pressure monitors are used in conjunction with a stethoscope.
  • Electronic automated devices for measuring blood pressure at shoulder, wrist and fingers.
  • Electronic shoulder-level blood pressure monitors, whether semi-automatic (manual cuffs inflate by squeezing a bulb) or automatic (battery or mains powered) are preferred for self-monitoring at home.

Preferred are tonometers with memory, which automatically store each measurement (with date and time) and the average of all measurements prior to the doctor’s visit.
Wrist devices are less accurate and not recommended unless shoulder blood pressure measurement is impossible or very difficult.
Finger devices are not recommended.

Mercury blood pressure monitors require extensive training and have been banned in some countries for environmental reasons. Aneroid devices also require preparation and regular calibration. The use of these devices should be limited to patients in whom automatic measurements are impossible or inaccurate.

Selecting the correct cuff and the size of the patient’s arm is essential for accurate measurement. The cuff inflatable bag should cover 80-100% of the shoulder circumference. The use of small cuffs can lead to an overestimation of blood pressure, while the use of large cuffs can lead to an underestimation of blood pressure. Therefore, if your arm has a circumference of <24 cm or> 32 cm, make sure that the device is equipped with a small or large cuff, respectively.

Source: Cardiologist – site about diseases of the heart and blood vessels.http://www.cardiolog.org/

What German experts advise for hypertensive patients | Culture and Lifestyle in Germany and Europe | DW

Do you smoke, suffer from excess weight, exercise a little, like to drink a glass or two? It is not surprising that you have hypertension. You urgently need to do something to stabilize your blood pressure.

Avoid salt

Of course, you can take medication. There are many of them, they are well known. But we are not talking about them.And not even that it would be good to quit smoking and try to avoid stressful situations. These are, as they say, commonplaces. But German doctors consider less radical things to be no less important. For example, eliminate salt from the diet – or at least reduce its use to a minimum. It has been scientifically proven that, in at least one third of hypertensive patients, it is the excess of salt in the body that was the main cause of the disease.

Therefore, as German experts strongly advise, it is necessary to give up nuts, chips, meat fried in a pan.Do not add salt to food while eating. Use salt substitutes (they contain less sodium, which is harmful to the body, contained in salt). And believe me: if you replace salt with other seasonings, the taste of your food will not deteriorate.

Instead of a sofa – sports

Are you tired or, on the contrary, you feel cheerful and think that you don’t have to move anymore? It’s a delusion! To lower blood pressure, you need to exercise regularly. Not necessarily, of course, a marathon run: it is just dangerous.But swimming, brisk walking, cycling, or even light exercise on a stationary bike can do wonders. Of course, accustoming yourself to regular sports is not a matter of one day, here you need to show patience and perseverance. The main thing is that these classes are regular.

And one more thing: sports will help you lose a couple of extra pounds. Physicians agree that being overweight contributes to hypertension. And with her, as you know, jokes are bad: the risk of heart attack and stroke increases.In addition, exercising can relieve stress and improve emotional well-being.

Everything is good in moderation

Nobody forces you to neglect a glass of wine or a glass of beer. But it is important that everything is in moderation. An excess of sugar, caffeine, nicotine, alcohol is a poison for the body. This is what often becomes the cause of cardiovascular diseases.

Not only fast food should be excluded from the diet, but also fatty pork, French fries with ketchup and mayonnaise, and other things containing a lot of fat and sugar.Everyone knows how healthy vegetables and fruits are. Then why not replace the cake with an apple or a pear? Buckwheat also helps lower blood pressure. Or maybe switch to Mediterranean cuisine that uses garlic? Scientists have proven that garlic improves blood circulation and dilates blood vessels.

Buy a tonometer and keep records

For those with high blood pressure, a tonometer in the house is a must. Measure your blood pressure at the same time every day.It is advisable to write down the measurement results in a special notebook. In addition, it is worth writing down what you ate and drank that day, how much time you did sports, and so on. And you will soon see how your food and your lifestyle can help lower or stabilize your blood pressure. Be patient: good work takes time. And most importantly, start dealing with your pressure now.

See also:

  • Hazardous and wholesome food

    Which food to eat?

    For the 60th time in most countries on May 29, World Healthy Digestion Day is celebrated, established by the World Organization of Gastroenterology (WOG) and the World Health Organization (WHO).It is held to draw public attention to the problems of digestive disorders and to find effective ways to combat them. So which foods are good for us and which should be avoided?

  • Dangerous and wholesome food

    Sweets

    Say no to chocolates, gummy bears, lemonade, Coca-Cola, Fanta, other sweets and tonic soft drinks! All of them contain simple carbohydrates, which, when processed, take fluid from the body and dehydrate it.Simple carbohydrates also have a detrimental effect on the state of collagen fibers, on which the elasticity of the skin depends: wrinkles appear, the oval of the face sags.

  • Dangerous and wholesome food

    Fast food

    The main disadvantage of fast food is the trans fats it contains, obtained from vegetable oils during the hydrogenation process: liquid vegetable oils are saturated with hydrogen bubbles at high temperatures. As a result, trans-isomers with a distorted molecular structure are formed.Once in the body, such molecules disrupt metabolic processes in cells, which can lead to chronic inflammation.

  • Dangerous and healthy food

    Alcohol

    It is known that red wine can be good for the body – but only if you drink one glass. Consuming more is only harmful. And even more so when it comes to stronger alcoholic beverages. Alcohol abuse is strongly reflected on the face: it turns red and swells.In addition, alcohol contains a lot of sugar that breaks down collagen fibers.

  • Dangerous and healthy food

    Salty

    Anyone who is addicted to chips and foods similar to them consumes not only too many unhealthy trans fats, but also salt. And its main component – sodium – has the ability to retain water in the body. As a result, blood pressure can jump. Excess salt disrupts metabolism, causes heart problems, and worsens complexion.

  • Dangerous and wholesome food

    Carbohydrates

    Permanently exclude white bread and pasta from your diet! The fact is that they contain too many carbohydrates, which are nothing more than sugar molecules. Overuse of white flour baked goods leads to glycation – the sugaring of collagen fibers, sticking them together and breaking them down. As a result, our skin loses its elasticity and ages quickly. Not to mention digestive disorders.

  • Dangerous and wholesome food

    Coffee

    Coffee speeds up metabolism, which means it stimulates weight loss.On the other hand, research shows that as early as two to three cups of coffee a day can cause sudden changes in blood pressure, which can lead to heart problems. Drinking coffee on an empty stomach increases the acidity of the stomach, and this is a direct path to the development of ulcers and gastritis. And coffee also has a diuretic effect, which causes dehydration of the body, kidneys suffer.

  • Dangerous and wholesome food

    Coconut oil

    Coconut oil is one of the richest foods in saturated fatty acids.It contains 90 percent of these healthy fats. Among them is lauric acid, which has a pronounced antimicrobial effect, which helps to strengthen the body’s immunity in the fight against viruses, fungi, infections, inflammations. Coconut oil also contains vitamin E, which is effective against wrinkles.

  • Dangerous and wholesome food

    Green tea

    Green tea is a storehouse of antioxidants, including polyphenols and flavonoids, which prevent skin aging and the appearance of wrinkles, as well as protect us from cancer and other diseases.The composition of its leaves also includes a unique amino acid – L-theanine, which has a relaxing effect and protects a person from the effects of stress on his body.

  • Dangerous and wholesome food

    Bitter chocolate

    Cocoa, which is 80 percent dark chocolate, is a real source of powerful antioxidants, saturated fatty acids and flavonoids, which help to improve the elasticity of blood vessels, blood circulation, and the normalization of arterial pressure.Not to mention, this product evens out the complexion and protects the skin from the harmful effects of the sun.

  • Dangerous and wholesome food

    Papaya

    The fruits of this tropical plant are a valuable dietary product, because they have a very low calorie content: there are only 39 calories per 100 grams of pulp. The low fructose content of papaya promotes proper digestion, while its beta-carotene, vitamins C and E improve complexion and protect the skin from sunburn.

  • Dangerous and wholesome food

    Carrots

    In addition to improving eyesight, carrots also have a wonderful effect on the skin. The fact is that this product is rich in beta-carotene, which is synthesized in the body into vitamin A, and it helps prevent the overproduction of cells in the epidermis, where excess sebum, combined with dead cells, clogs the pores. Carrots are also good for improving bowel function and strengthening the immune system.

  • Dangerous and wholesome food

    Seeds

    Seeds of sunflower, pumpkin, flax, chia (Spanish sage) are truly the elixir of youth.Due to their content of selenium, vitamin E, magnesium, protein, omega-3-unsaturated fatty acids, other vitamins and minerals, they are very useful for moisturizing the skin, smoothing out folds on it and preventing the appearance of wrinkles on the face.

  • Dangerous and wholesome food

    Spinach

    What is not in this green herb! It is rich in iron, folic acid, chlorophyll, fiber, vitamins E, C and A, magnesium, proteins, and these are the guarantors of good health, since they help to improve the functioning of the intestines, cleanse the body of harmful substances, and are an effective means of combating skin aging.

  • Dangerous and healthy food

    Salmon

    This fish is a valuable source of beauty and superfood for those who often deal with stress. Salmon is rich in vitamin D, the role of which is both in strengthening bones and protecting the body from skin diseases, heart and brain diseases, cancer, and depression. And the presence of omega-3-unsaturated fatty acids in it makes it a product that helps to eliminate wrinkles.

    Author: Nataliya Koroleva

90,000 10 foods that lower blood pressure as an alternative to medication

Your doctor may have told you to avoid certain foods that increase blood pressure, but you should know that there are 90,087 foods that also lower blood pressure .And if it is important for you to lower blood pressure, then, by all means, you should add these foods to your diet.

What are you doing to lower your blood pressure?

  • Do you give your salaries to doctors and pharmacists?
  • Do you sacrifice the flavors of your favorite foods?
  • Are you missing some of your favorite activities?

If you have high blood pressure or have recently been diagnosed with it, your life will never be the same.

High blood pressure is a serious health problem that requires major lifestyle changes and treatments to control pressure.

High blood pressure is not something you can or want to ignore, and it certainly should not be taken lightly.

But while doctors and medications can help you lower your blood pressure, ultimately you must make changes in your health that will keep your blood pressure under control.

Proper diet is better than drug dependence

While many people are amazed at the wonders of modern medicine, you should know that no drug is completely safe in terms of health risks.

Many drugs used to lower blood pressure often cause some unpleasant side effects such as diarrhea, constipation, erectile dysfunction, lack of energy, dizziness, coughing, vomiting, headache, weight loss or gain.

Each of these side effects may require additional treatment, which means more doctor visits, possibly more drugs, and of course more money.

If you are faced with high blood pressure, you should know that there are alternatives to the expensive medical treatment – products that lower blood pressure.

You may already know to avoid certain foods that can increase your blood pressure, such as salty foods, alcohol, processed meat or coffee .

But adding the right foods to your diet, such as foods rich in potassium, calcium and magnesium, can help you lower your blood pressure naturally without the harsh side effects of blood pressure medications.

How do foods lower our blood pressure?

  • Potassium-rich foods help our kidneys cleanse excess sodium, one of the main culprits of high blood pressure.
  • Calcium helps blood vessels contract and dilate, and not enough calcium can constrict the walls of the arteries.Calcium also helps balance the body’s supply of sodium.
  • Magnesium helps calcium and potassium pass through the cell walls. Studies show that low magnesium levels can increase the likelihood of a heart attack by 60% [1]

10 Foods That Lower Blood Pressure

This does not mean that you should not take medications prescribed by your doctor.

But adding foods that lower blood pressure to your diet will give you additional control over your health, which will give you faster results than taking medication alone.

Below are 10 foods that can help lower blood pressure.

  1. Flax seeds

    Studies have shown that flax seeds can successfully lower blood pressure.

    Flaxseed does not have a strong taste, which allows it to be added anywhere: from salads to soups and sandwiches, and much more [2] .

  2. Fresh green leaves

    Foods such as fresh cabbage, arugula, turnip greens, romaine lettuce and spinach are naturally high in potassium.

    Avoid canned greens such as spinach and turnip greens because they usually add salt.

  3. Red beet

    Having high levels of nitric oxide, red beets help open blood vessels to lower blood pressure.

    In addition, studies have shown that nitrates in beet juice successfully reduced blood pressure in study participants in just 24 hours [3] .


    Read also



  4. White beans

    Just one cup of white beans, such as cannellini or navy beans, can give you 13% calcium, 30% magnesium, and 24% potassium every day.

    Make sure you choose uncanned food if you don’t want to cook dry beans.

  5. Yogurt

    Yogurt is packed with calcium – you can get almost half of your daily serving in just one cup!

    It also contains 12% magnesium and 18% potassium, which the body needs.

  6. Bananas

    Bananas have long been known as a source of potassium, but they also contain significant amounts of magnesium and calcium.


    Read also



  7. Quinoa

    This whole grain contains 15% magnesium daily, plus the 1.5% calcium and 4.5% potassium you need.

    It is also gluten free.

  8. Broccoli

    Broccoli has a potassium-calcium-magnesium trifecta in each stem.

    There are many great recipes with this product.

  9. Skim milk

    You can lower your blood pressure with this product, as it is loaded with calcium.

    1-2 glasses of milk are enough per day.

    Vitamin D and calcium work together to lower blood pressure by 3-10% [4] .

  10. Sunflower seeds

    These small seeds provide an excellent source of magnesium.

    Just do not buy salted seeds, as you need to minimize salt intake with high blood pressure.


Adding these 10 foods that lower blood pressure to your diet can be additional steps to improving your health that will help your body resist high blood pressure.

Notes

  1. ↑ https: //www.rodalewellness.com/health/lower-blood-pressure-minerals
  2. ↑ http: //www.naturalmedicinejournal.com/journal/2014-02/flaxseed-reduces-high-blood-pressure
  3. ↑ http: //www.qmul.ac.uk/media/news/items/smd/31048.html
  4. ↑ http: //www.joybauer.com/high-blood-pressure/

Arterial hypertension: what is the role of potassium and magnesium?

The prevalence of arterial hypertension in Ukraine and the world is constantly increasing.Recently, electrolyte imbalances, in particular magnesium and potassium, have been assigned an important role in the development and progression of cardiovascular diseases (Shilov A.M. et al., 2010). It has been proven that the duet of potassium and magnesium is relevant both for prevention and for effective control of blood pressure in patients with arterial hypertension who take these macronutrients in complex treatment (Tkachenko V.I., Bagro T.O., 2016). Moreover, it is the “duet” that is important for the organism, and not the “solo” of one of them.In this regard, PANANGIN, containing potassium and magnesium in an active, easily digestible form, from the Gedeon Richter company, has acquired particular relevance.

Potassium and magnesium are some of the most abundant cations in the body. Potassium ions are involved in the transmission of nerve impulses, contraction of cardiomyocytes, skeletal and smooth muscle fibers, regulate and support the functions of the urinary system. Magnesium is a regulator of vascular tone, blood pressure and peripheral circulation. It is an important cofactor for both absorption and maintenance of optimal levels of intracellular potassium.Magnesium itself can have a positive effect on lowering blood pressure, acting as a natural calcium channel blocker (Ukholkina G.B., 2011; Kosarev V.V., Babanov S.A., 2012).

The consequence of potassium-magnesium deficiency is quite often a violation of the rhythm of cardiac activity (atrial fibrillation). Arterial hypertension is detected in 60% of such persons. Among other things, neurological (fatigue, depression, sleep disturbance, migraine) and muscle (calf muscle cramps) symptoms are also considered a manifestation of magnesium and potassium deficiency (Shilov A.M. et al., 2010; Yankovskaya L.V., 2015).

Due to the available evidence of the effect of potassium intake on blood pressure reduction, the clinical guidelines of the WHO, the American Heart Association, the Canadian, European and International Hypertension Societies along with the use of traditional antihypertensive drugs, recommendations for reducing salt intake and other non-pharmacological methods have included a prescription to increase potassium intake to reduce the incidence of hypertension and prevent cardiovascular complications.These recommendations are especially important to take into account when taking diuretics (Tkachenko V.I., Bagro T.O., 2016).

A common misconception is the position of doctors, according to which the use of ACE inhibitors and angiotensin II receptor blockers eliminates the need for taking potassium preparations due to their potassium-sparing properties. In most cases, the doses of ACE inhibitors prescribed by doctors in the treatment of patients with heart failure are insufficient to replenish the loss of potassium (Berezin A.E., 2015).

Correct the imbalance of potassium and magnesium in the body under the power of PANANGIN. The drug is capable of providing a whole range of effects that have a beneficial effect on the state of the cardiovascular system:

  • to help reduce the level of blood pressure in patients with arterial hypertension;
  • to maintain the elasticity of the vessel walls;
  • reduce the risk of developing arrhythmias;
  • improve myocardial contractile function and prevent the development of heart failure;
  • Improve vascular endothelial function, reduce the risk and rate of development of atherosclerosis;
  • reduce blood viscosity and thrombus formation (Lyashenko E.A., 2012).

The use of potassium and magnesium preparations (PANANGIN) in the complex treatment of arterial hypertension can enhance the effect of antihypertensive therapy, reduce the risk of its side effects, as well as cardiovascular events. Adequate intake of potassium and magnesium is a measure of prevention of arterial hypertension and cardiovascular diseases. Therefore, PANANGIN can be recommended as an addition to the diet of healthy individuals in order to increase the levels of potassium and magnesium in the body (V.I., Bagro T.O., 2016).

Press service of “Weekly Apteka”

Information for you:

90,000 10 products that help with hypertension – Rossiyskaya Gazeta

Pressure jumps? Tortured by hypertension? Do not limit treatment to pills.

Proper nutrition also helps to stabilize blood pressure.

Drug treatment and diet complement each other well in the fight against hypertension, which, if insufficient attention is paid to it, will lead to heart attack or stroke.Medicines should be selected by a doctor, and you can provide yourself with suitable nutrition.

Do not gas

For high blood pressure, a diet low in fat and cholesterol, rich in grains, fruits and vegetables, is recommended.

Replace animal fats with vegetable fats. Avoid butter, sour cream, pork, beef, sodas, and caffeinated drinks. It is better to exclude spicy foods, seasonings, pickles, canned foods, flour and confectionery products.

Of the cooking methods, it is better to give preference to boiling, steaming, baking. Focus on vegetables, fish, dairy products. Moreover, it is important to make the principle of healthy eating the norm: if today you replace a sandwich with sausage with a vegetable salad, and tomorrow you will again reach for uncooked smoked, such a “diet” will not help stabilize the pressure.

This is elementary

If you are hypertensive, eat more potassium-rich foods.Potassium helps to reduce the negative effect on blood pressure of another mineral element – sodium.

Remember that natural foods are the best source of potassium, not drugs. For example, plain rice is an excellent product in this regard. Have a rice fasting day 1-2 times a week. Take a glass of dry rice, rinse it several times, fill it with water, leave it overnight, and in the morning cook it without salt. Divide the rice into 8 pieces and eat all day. The potassium in rice will displace sodium, the amount of water in your body will decrease, and your blood pressure will drop without any medication.

Potassium is also rich in many fruits (bananas, oranges, tangerines), dried fruits (raisins, dried apricots), vegetables (especially potatoes, beans), seaweed, squid, fish (cod, hake), oat and wheat groats, milk, yogurt.

Another important element that is useful for stabilizing blood pressure is magnesium, its presence in the body helps to expand blood vessels and strengthen their walls. In addition, the lack of magnesium “pulls” the leaching of potassium and an increase in the content of sodium inside the cells, which also leads to an increase in pressure.

Legumes contain magnesium in sufficient quantity – beans, peas, lentils. Plus, they’re high in fiber, which keeps you full and prevents you from gaining excess fat.

What is the salt

Vitamins C (cauliflower, black currant, rosehip), A (carrot, liver, egg yolk), group B (bran, cabbage, yeast) are important for hypertension.

But the consumption of salt should be limited to 2.5 g (a teaspoon without top) per day.Try not to add salt to food, use spices. As a last resort, use low sodium salt. It also contains the ions of potassium, magnesium, iodine necessary for health. Processed foods contain significantly more salt than natural ones, for example, sausage and cheese contain 15 times more salt than natural meat and milk.

Be careful with alcohol!

In very small amounts, alcohol helps to dilate the arteries of the heart and lower blood pressure.But with higher doses of alcohol, blood pressure can rise significantly. In addition, alcohol reduces the effectiveness of drugs that the patient takes to treat hypertension.

By the way

What you need to know about hypertension?

Normal blood pressure at any age is 120/80 mm Hg. Art.

The main harm from hypertension is that it sharply accelerates the development of atherosclerosis, heart failure and heart rhythm disturbances.

Hypertension is one of the main causes of heart attacks and strokes at a young working age.

Tips

10 products, especially useful for hypertensive patients

1 Curd is a source of calcium, potassium and magnesium. Potassium strengthens heart health, magnesium promotes vasodilation. It is advisable to consume at least 3-5 tablespoons of cottage cheese per day.

2 Pumpkin seeds are an excellent source of zinc.According to the WHO, zinc deficiency in the body increases the risk of heart attack. Eat 20 grams of pumpkin seeds a day.

3 Red bell pepper – champion in vitamin C. People who consume a lot of foods with vitamin C, hypertension develops less often. Eat 2 fresh peppers a day, you can add them to your salad.

4 Cocoa is rich in flavonoids that improve vascular health and lower blood pressure. You can not drink it every day, just 1-2 glasses of cocoa per week.

5 Salmon is rich in omega-3 fatty acids. This substance, among other useful properties, helps to reduce pressure. We recommend eating salmon 3 times a week for 150-200 g.

6 Oats are a source of selenium. Several studies have shown that adding oatmeal to your diet helps regulate both systolic and diastolic blood pressure. Oats contain both soluble and insoluble fiber. Often people with hypertension also suffer from diabetes.A cup of oatmeal with skim milk helps not only control blood pressure, but also prevents the increase in blood sugar.

7 Almonds lower cholesterol levels. Contains mono fat (good cholesterol), which is not harmful to health, has the property of lowering the level of “bad” cholesterol. These nuts are high in protein, fiber, potassium, magnesium and vitamin E. These nuts are also good for those looking to lose weight.

8 Green tea breaks cholesterol plugs.He, like no other, is useful for the body. In addition, it contains powerful doses of antioxidants that prevent the aging process.

9 Dark chocolate contains antioxidants that contribute to heart health. As it turned out in the course of the study, dark chocolate is able to lower the pressure by 5 mm.

10 Skim milk is rich in potassium, calcium and vitamins. Scientists recommend that everyone drink three glasses of skim milk a day.

Prevention of arterial hypertension – Prevention of diseases and healthy lifestyle – Budgetary institution of the Khanty-Mansiysk Autonomous Okrug – Ugra

Prevention of arterial hypertension

Arterial hypertension is understood as an increase in blood pressure above 140 and 90 mm Hg.Art. If untreated, hypertension leads to an increased risk of coronary heart disease, strokes, kidney damage, and an increase in overall mortality.

Hypertension, like any chronic progressive disease, is easier to prevent than to cure. Therefore, the prevention of hypertension, especially for people with a burdened heredity, is a first priority.

First of all, everyone with high blood pressure or borderline norms should think about the prevention of hypertension, especially young people and adolescents

Prevention of arterial hypertension is primary and secondary.

primary means prevention of disease. These prevention methods should be followed by healthy people who have a high risk of developing hypertension (heredity, work). But not only them, everyone should live in accordance with the principles of primary prevention of hypertension, because this disease often overtakes at the most unexpected moment even those who do not have unfavorable heredity and other risk factors.

Primary prevention of hypertension includes:

  • Normalization of the function of the central nervous system (prevention of stress).
  • A clear daily routine (constant time of getting up and going to bed).
  • Outdoor exercise and exercise therapy (long walks in the fresh air, cycling, moderate gardening).
  • Daily loads in the gym and at home.
  • Normalization of sleep (sleep up to 8 hours).
  • Rational nutrition. Carefully count the calories consumed with food, do not allow excessive consumption of fat.Fats can be consumed per day no more than 50-60 grams, and 2/3 of them should be vegetable fats: corn, sunflower oil. Limit foods containing a large amount of animal fats – whole milk, butter, sour cream. The diet should contain a sufficient amount of proteins: low-fat varieties of fish, poultry, skimmed milk, cottage cheese, kefir, etc. It is necessary to limit the intake of easily digestible carbohydrates: sugar, honey, pastry products, chocolate, semolina, rice cereals.
  • Weight loss (obesity). Without weight loss, there is no need to talk about the prevention of hypertension. You cannot try to lose weight dramatically, you can reduce body weight by 5-10% per month.
  • Smoking cessation !!!
  • Reducing the consumption of table salt (consume no more than 6 grams per day).
  • Consumption of food products with a high content of potassium, calcium and magnesium salts (low-fat cottage cheese, parsley, beans, prunes, beets, baked potatoes, dried apricots, seedless raisins.)
  • Restriction of consumption of alcoholic beverages.

Secondary prophylaxis is carried out in patients in whom arterial hypertension has been established as a diagnosis. Its purpose is to prevent complications from occurring. Moreover, this type of prevention includes two components: non-drug treatment of arterial hypertension and antihypertensive (drug) therapy. Non-drug treatment, in principle, corresponds to primary prevention, only with more stringent requirements.If every individual person is unable to change heredity and the environment, then the way of life and nutrition is completely. Drug therapy – drugs prescribed by a doctor that target high blood pressure levels, lowering them. Patients with arterial hypertension should strictly adhere to the doctor’s recommendations and take drugs as prescribed, thereby preventing the risk of complications.

To the prevention of arterial hypertension can be attributed to the systematic monitoring of the level of pressure in the morning and evening.Persevering adherence to the recommendations of the attending physician, timely referral to him in case of deterioration.

Remember! Disease is easier (and cheaper) to prevent than to cure.

Arterial hypertension

IMPORTANT!

The information in this section cannot be used for self-diagnosis and self-medication. In case of pain or other exacerbation of the disease, only the attending physician should prescribe diagnostic tests.For a diagnosis and correct prescription of treatment, you should contact your doctor.

Arterial hypertension – the causes of the appearance, in what diseases it occurs, the diagnosis and methods of treatment.

According to world statistics, diseases of the cardiovascular system are in first place among all causes of mortality in the population.

Arterial hypertension is one of the most common diseases of the circulatory system, which also acts as a factor in the development of other diseases of the heart and blood vessels, such as coronary heart disease, chronic heart failure, hemorrhagic and ischemic stroke.

Arterial hypertension is a persistent increase in systolic (upper) blood pressure above 140 mm Hg. Art. and / or diastolic (lower) above 90 mm Hg. Art. According to the recommendations of the European Society of Arterial Hypertension and the European Society of Cardiology, the criterion for arterial hypertension from 135/85 mm Hg was adopted for home blood pressure measurement. Art. and higher.

The main symptoms accompanying high blood pressure include headache, nausea, tinnitus, palpitations, decreased visual acuity, irritability, sweating.

Occasionally, an increase in blood pressure may be asymptomatic. In this case, blood pressure monitoring is required.

Varieties of arterial hypertension

Before talking about high blood pressure (BP), you need to understand what the normal pressure should be. For each person, blood pressure values ​​are individual. However, there is a generally accepted classification of blood pressure.

  • Optimal, where systolic blood pressure is less than 120 mm Hg. Art., and diastolic blood pressure less than 80 mm Hg. Art.
  • Normal, where the upper BP values ​​are in the range from 120 to 129 and the lower values ​​are from 80 to 84 mm Hg. Art.
  • High normal, where the upper BP values ​​are in the range from 130 to 139 mm Hg. Art. and lower in the range from 85 to 89 mm Hg. Art.

Arterial hypertension is divided into degrees depending on the maximum values ​​obtained by measuring pressure.

1st degree – systolic blood pressure 140-159 mm Hg. Art. and / or diastolic blood pressure 90-99 mm Hg. Art.

2nd degree – systolic blood pressure 160-179 mm Hg. Art. and / or diastolic blood pressure 100-109 mm Hg. Art.

3rd degree – systolic blood pressure 180 and more mm Hg. Art. and / or diastolic blood pressure of 110 or more mm Hg. Art.

Isolated arterial hypertension is isolated separately, when only systolic blood pressure rises above 140 mm Hg.Art, and the diastolic remains within the normal range.

Causes of high blood pressure

It is believed that the majority of patients with high blood pressure suffer from primary arterial hypertension , the development of which cannot be attributed to specific causes. This is the so-called essential arterial hypertension, which often occurs in older patients.

In other cases, when a specific cause of an increase in pressure is identified, they mean secondary arterial hypertension.

Among the main reasons leading to the occurrence of secondary arterial hypertension are:

  1. Diseases of the kidneys and renal vessels . These pathologies lead to a decrease in the intensity of blood flow in the kidneys and, as a consequence, to the excretion of substances by the kidneys that contribute to an increase in blood pressure and compensation for impaired renal blood flow. Chronic kidney disease, chronic glomerulonephritis, urolithiasis – these diseases can lead to the development of arterial hypertension.Among renal vascular diseases, narrowing (stenosis) of the renal arteries is most often noted, which can be a congenital pathology or occur with atherosclerosis in adulthood.
  2. Various endocrine diseases lead to the development of arterial hypertension and other associated symptoms. For example, with thyrotoxicosis, the production of thyroid hormones increases, which is accompanied by the appearance of a goiter (an increase in the gland itself), an increase in systolic blood pressure, palpitations, increased excitability and a decrease in body weight.

    In hypothyroidism, the production of thyroid hormones decreases. Pathology is accompanied by endothelial dysfunction and impaired relaxation of vascular smooth muscle cells, which leads to an increase in peripheral vascular resistance. This increases blood pressure. These patients are characterized by an increase in diastolic blood pressure, slow heart rate, weakness and fatigue.

    With pheochromocytoma (adrenal gland tumor), the release of catecholamines (adrenaline, norepinephrine) into the blood increases, which leads to sharp jumps in blood pressure to very high values.

    Arterial hypertension is a frequent companion of obesity. The cells of adipose tissue (adipocytes) produce biologically active substances that affect the entire body as a whole and, in particular, the vessels. Also, do not forget that “excess” tissue also needs to be supplied with blood, and this leads to additional stress on the cardiovascular system.

  3. Various diseases of the heart and blood vessels can lead to high blood pressure. For example, coarctation of the aorta – local narrowing of the lumen of the aorta, often congenital pathology; atherosclerotic vasoconstriction.
  4. Pregnancy (preeclampsia) .
  5. Arterial hypertension while taking certain drugs : oral contraceptives, anabolic steroids, glucocorticosteroids, antidepressants.

It should be remembered about the factors contributing to the development of arterial hypertension: hereditary predisposition, prolonged nervous overstrain, frequent stressful situations, excessive physical activity, smoking, alcohol and coffee abuse, consumption of large amounts of salt and fatty foods.

In what diseases does arterial hypertension occur?

Arterial hypertension is divided into degrees depending on the maximum values ​​obtained by measuring pressure.

Here are some of them.

  • Atherosclerosis, including renal arteries.
  • Damage to the renal vessels (thrombosis, embolism, stenosis, compression of the renal vessels by a tumor or organ).
  • Chronic pyelonephritis.
  • Chronic glomerulonephritis.
  • Chronic kidney disease.
  • Diseases of the thyroid gland (hypo- and hyperthyroidism).
  • Itsenko-Cushing’s disease and syndrome.
  • Pheochromocytoma.
  • Primary hyperaldosteronism.
  • Metabolic syndrome.
  • Coarctation of the aorta.
  • Preeclampsia.

Which doctor should i contact if i have high blood pressure?

To identify the reasons for the increase in pressure, you should first contact
therapist.The doctor will conduct an examination and prescribe the required amount of examinations and specialist consultations. Among them may be:

Diagnostics and examinations with increased blood pressure

First of all, self-monitoring of blood pressure at home is necessary with a diary, where all blood pressure measurements should be recorded over time, medications and episodes of stress that could provoke an increase in blood pressure.