Calcium – Better Health Channel

What is calcium?

The average adult’s weight is made up of about 2% calcium. Most of this is found in the skeleton and teeth – the rest is stored in the tissues or blood. Calcium is vital for healthy teeth and bones. It also plays a crucial role in other systems of the body, such as the health and functioning of nerves and muscle tissue.

Good sources of calcium include dairy foods like milk, yoghurt and cheese, and calcium-fortified products, such as some plant-based milks (for example, soy milk and rice milk) and breakfast cereals.

People at different life stages need different amounts of calcium – young children, teenagers and older women all have greater than average requirements.

According to the most recent National Nutrition and Physical Activity Survey of 2011-12External Link:

• Over half of all Australians aged 2 years and over consume inadequate levels of calcium from food sources.
• Females are less likely to have adequate intakes of calcium than males.
• 73% of females consume less calcium than recommended.
• 51% of males consume less calcium than recommended.

It is much better to get calcium from foods than from calcium supplements. Be guided by your doctor about whether you need additional supplements. Too much calcium from supplements may cause other health problems.

Role of calcium in the body

Calcium plays a role in:

• strengthening bones and teeth
• regulating muscle functioning, such as contraction and relaxation
• regulating heart functioning
• blood clotting
• transmission of nervous system messages
• enzyme function.

Calcium and dairy food

Australians receive most of their calcium from dairy foods. If milk and milk-based foods are removed from the diet, this can lead to an inadequate intake of calcium. This is of particular concern for children and adolescents, who have high calcium needs.

Calcium deficiency may lead to disorders like osteoporosis, a disease in which bones become fragile and brittle later in life. Osteoporosis affects both men and women.

Too little calcium can weaken bones

If not enough calcium is circulating in your blood, your body will use hormones to reduce the amount of calcium your kidneys excrete in your urine. If not enough calcium is absorbed through the gastrointestinal tract, calcium will be taken from the bones.

If your dietary intake of calcium is constantly low, your body will eventually remove so much calcium from the skeleton that your bones will become weak and brittle.

Calcium needs vary throughout life

The recommended dietary intake of calcium is different for people of different ages and life stages.

People with special calcium needs

It is particularly important that people from certain groups meet their calcium needs. These groups include:

• Babies – formula-fed babies are estimated to need more calcium than babies that are breastfed, because the calcium in infant formula may not be absorbed as efficiently as that found in breastmilk.
• Young children – skeletal tissue is constantly growing, so young children have high calcium requirements.
• Pre-teens and teenagers – puberty prompts a growth spurt, which in turn increases calcium requirements. This group also needs more calcium to build peak bone mass. If the skeleton is strengthened with enough calcium during these years, diseases like osteoporosis in the later years are thought to be less likely.
• Elderly people – as we age, the skeleton loses calcium. Women lose more calcium from their bones in the 5 to 10 years around the age of menopause. However, both men and women lose bone mass as they grow older and need to make sure they get enough calcium in their diet to offset these losses. While a diet high in calcium cannot reverse age-related bone loss, it can slow down the process.

Caucasian (white) people have larger frame sizes and generally have higher intakes of animal foods, caffeine and salt than non-Caucasian people. It is thought they may need more calcium as a result.

Pregnant and breastfeeding women and calcium

A developing baby needs a lot of calcium. However, there is no need for women to take additional dietary calcium during pregnancy because pregnant women absorb calcium from food more efficiently.

Breastfeeding women do not need to increase their calcium intake, unless they are adolescents.

Good sources of calcium

Good dietary sources of calcium include:

Calcium supplements

It is much better to get calcium from foods (which also provide other nutrients) than from calcium supplements. But if you have difficulty eating enough foods rich in calcium, you might need to consider a calcium supplement, especially if you are at risk of developing osteoporosis. Before taking supplements, it’s best to discuss this with your doctor or other registered healthcare professional.

If you do take calcium supplements, make sure you don’t take more than the amount recommended on the bottle. Too much calcium may cause gastrointestinal upsets such as bloating and constipation and, rarely, other complications such as kidney stones.

Calcium supplements – complications

A report published in 2010, and widely reported in the media, found a possible link between calcium supplements and an increased risk of heart disease – particularly in older women. The levels of calcium intake of participants in the trials reviewed were up to 2,400 mg/day, achieved by taking supplements. This is above the Recommended Dietary Intake (RDI), which is between 1,000 and 1,300 mg/day for adults, depending on age.

Although high levels of calcium intake through supplementation may be of concern, calcium supplementation at levels of 500 to 600 mg/day is both safe and effective for reducing the risk fractures in people who don’t get enough calcium from their diet. If you have any concerns about calcium supplements, talk to your doctor or other registered healthcare professional.

Lifestyle can affect bone strength

Some of the factors that can reduce calcium in your bones and lower your bone density (weaken your bones) include:

• high-salt diet
• more than 6 drinks per day of caffeine-containing drinks – for example, coffee, cola and energy drinks (and, to a lesser extent, tea)
• excessive alcohol intake
• very low body weight
• very high intakes of fibre (more than 50 g per day, from wheat bran)
• low levels of physical activity
• low levels of vitamin D – people who are housebound or cover their bodies completely when they are outside are at increased risk
• smoking.

Where to get help

• Your GP (doctor)
• Dietitians AustraliaExternal Link Tel. 1800 812 942
• Nutrition Australia (Victoria)External Link Tel. (03) 8341 5800

How to Increase the Absorption of Iron from Foods

Eating iron along with foods containing certain vitamins and minerals, such as vitamin C, vitamin A, and beta carotene, may help you absorb more iron. Other foods may hinder your iron absorption.

Iron is an essential mineral your body needs to function properly.

Thus, it’s vitally important to consume adequate amounts of it through your daily diet.

Interestingly, the foods you eat influence not only how much iron you consume but also how well it’s absorbed into your body (1).

Once your body absorbs iron, it’s used as a building block for hemoglobin, a protein found in red blood cells that helps shuttle oxygen around your body.

Iron is also a component of myoglobin, an oxygen storage protein found in your muscles. This oxygen is used when you use your muscles.

The recommended iron intake range is 7–18 milligrams (mg) per day for the general population and up to 27 (mg) for pregnant women (2).

You may have heard that you can get iron from red meat, but there are many other foods that naturally contain iron.

In foods, iron is present in two forms: heme and non-heme.

Sources of heme iron

Heme iron is found in animal foods that contain hemoglobin, such as meat, fish, and poultry.

Heme iron is the best form of iron, as your body readily absorbs up to 40% of it (3).

Good food sources of heme iron include:

• beef
• pork
• chicken
• veal
• fish such as halibut, haddock, perch, salmon, or tuna
• shellfish such as clams, oysters, and mussels

Red meat and organ meat like liver are particularly good sources of iron.

Sources of non-heme iron

Non-heme iron primarily comes from plant sources and is present in grains, vegetables, and fortified foods.

This is the form added to iron-enriched or iron-fortified foods, as well as many supplements.

It’s estimated that 85–90% of total dietary iron intake in Western populations comes from the non-heme form, while 10–15% comes from the heme form (3). Up to 40% of iron that the body absorbs comes from the heme form. (3)

In terms of its bioavailability, non-heme iron is absorbed much less efficiently than heme iron.

Good sources of non-heme iron include:

• fortified cereals, rice, wheat, and oats
• dark green leafy vegetables like spinach and kale
• dried fruits like raisins and apricots
• beans like lentils and soybeans

Summary

Heme iron is found in animal foods, while non-heme iron comes from plant sources. Your body can better absorb heme iron than the non-heme form.

Iron deficiency is the most common cause of anemia, which affects about 25% of the world’s population (4, 5).

A person who is iron deficient may have various symptoms, including fatigue, dizziness, headaches, sensitivity to cold, and shortness of breath when doing simple tasks. (6)

Moreover, iron deficiency can result in poorer attention span and mental function. In fact, iron deficiency in early childhood has been linked to learning challenges (2).

Children, adolescents, and women of reproductive age, particularly during pregnancy, are most at risk of iron deficiency. This is because their iron intake typically does not meet their body’s high demand for it (2).

Additionally, it’s commonly thought that vegetarians and vegans are more prone to iron deficiency. But there are conflicting studies on this point.

A 2018 research review found that vegetarians are more likely to have low iron stores than non-vegetarians. The authors of the analysis nonetheless recommended that people eat more plants and less meat given that high iron stores are a risk factor for some noncommunicable diseases (7).

Meanwhile, a 2021 study found that after inflammation was eliminated as a factor, vegetarians had the same prevalence of iron deficiency as those following an omnivore (meat-and-plant) diet. (8)

It’s generally recommended that vegetarians multiply their recommended iron intake by 1.8 to compensate for the reduced absorption of non-heme iron (2).

Summary

Iron deficiency is very common. Those who are most at risk include children, adolescents, women of reproductive age, pregnant women, vegetarians, and vegans.

While not all dietary iron is absorbed equally, some foods can enhance your body’s ability to absorb it.

Foods rich in vitamin C

Vitamin C has been shown to enhance iron absorption. It captures non-heme iron and stores it in a form that your body can absorb more easily (1).

Foods high in vitamin C include citrus fruits, dark green leafy vegetables, bell peppers, melons, and strawberries.

Hence, drinking citrus juice or eating other foods rich in vitamin C while you’re eating high-iron foods can increase your body’s absorption.

In vegetarian and vegan diets, iron absorption may be optimized by including vitamin C–containing vegetables during meals (1).

Foods with vitamin A and beta-carotene

Vitamin A plays a critical role in maintaining healthy vision, bone growth, and your immune system.

Beta-carotene is a red-orange pigment found in plants and fruits. It can be turned into vitamin A in your body.

Good food sources of beta-carotene and vitamin A include carrots, sweet potatoes, spinach, kale, squash, red peppers, cantaloupe, apricots, oranges, and peaches.

Vitamin A helps to release iron that the body stores. Therefore, adequate vitamin A plays an important role in preventing iron deficiency anemia (9).

Meat, fish, and poultry

Meat, fish, and poultry not only provide well-absorbed heme iron, but they can also stimulate the absorption of the non-heme form. Eating a meal that combines heme iron with non-heme iron can help increase the amount of non-heme iron the body absorbs (10).

Summary

Eating foods high in vitamin C, vitamin A, or beta-carotene can enhance your body’s absorption of iron from meals. Eating meat, fish, or poultry with other foods can also help.

Just as some foods can improve iron absorption, others can hinder it.

Foods containing phytate

Phytate, or phytic acid, is found in foods like whole grains, cereals, soy, nuts, and legumes (3). It’s important to note that proper soaking can remove phytic acid from beans and lentils.

Even a small amount of phytate can significantly decrease iron absorption (1).

Nonetheless, the negative effect of phytate can be counteracted by consuming foods that enhance non-heme iron absorption, such as vitamin C or meat.

Calcium-rich foods

Calcium is an essential mineral for bone health.

But some evidence shows that it hinders the absorption of heme and non-heme iron (1).

A 2021 research review found that calcium had a negative effect on the short-term absorption of iron, but the effect was low. (11)

To maximize absorption, calcium-rich foods should not be eaten with meals that provide most of your dietary iron.

Regarding supplements, calcium and iron supplements should be taken at different times of the day if possible.

Foods containing polyphenols

Polyphenols are found in various amounts in plant foods and beverages, including vegetables, fruits, some cereals and legumes, tea, coffee, and wine.

Coffee and tea, both of which are widely consumed around meals, have a high content of polyphenols, and they have been shown to inhibit the absorption of non-heme iron (3).

A 2019 review of studies found that polyphenols did not interfere with iron bioavailability. But the review’s authors noted the limitations of the research and recommended further study (12).

To counteract the negative effect of polyphenols, be sure to leave a couple of hours between your iron-rich meal and your afternoon tea or coffee.

Summary

Foods containing phytates, calcium, and polyphenols can significantly reduce iron absorption.

Iron toxicity from food sources is rare. Once it’s consumed, your body has its own balancing system to make certain that it gets just enough.

But fatal overdoses and adverse health effects are possible with excessive intake of iron supplements (2).

Excessive iron levels can also occur in some people with a condition called hemochromatosis. This is usually caused by a gene that enhances absorption (13).

Other causes of iron overload include repeated blood transfusions, massive doses from the diet, and rare metabolic disorders.

Additionally, consuming too much iron over time may cause large deposits of the mineral to form in the liver and other tissues.

It can be helpful to talk with a healthcare professional if you’re considering taking an iron supplement.

Summary

Consuming too much iron can have health risks. Because of this risk, supplements are not recommended for most people.

The tips below can help you maximize your dietary iron intake:

• Eat lean red meat: This is the best source of easily absorbed heme iron. Eating it several times per week can help if you’re deficient.
• Eat chicken and fish: These are also good sources of heme iron. Eat a variety of them.
• Consume vitamin C-rich foods: Eat vitamin C-rich foods during meals to help increase the absorption of non-heme iron. For example, drizzling lemon juice over leafy greens increases the amount of iron you absorb.
• Avoid coffee, tea, or milk near meals that contain iron-rich foods: Have your coffee or tea between meals instead.
• Choose foods rich in non-heme iron: If you don’t eat meat and fish, include plenty of iron-rich plant foods in your diet.

Summary

To maximize your iron intake, try to include meat, fish, poultry, and iron-rich plant foods in your diet, as well as vitamin C-rich foods during your meals. Also, spread out your tea, coffee, and dairy intake between meals.

Iron is a vital mineral that’s essential for your body to function well. Two types of it are found in food — heme and non-heme.

Meat, fish, and poultry contain the heme form, which your body easily absorbs.

Non-heme iron is mainly found in plant foods, but your body has a harder time absorbing it. You can improve your body’s absorption by eating foods containing vitamin C, vitamin A, along with meat, fish, and poultry during your meals.

On the other hand, foods containing phytates (cereals and grains), calcium (milk and dairy), and polyphenols (tea and coffee) can hinder iron absorption.

By carefully selecting the foods you eat and knowing how certain foods can enhance or inhibit absorption, you can make sure you’re getting the iron you need.

Calcium. General information

In the human body, more than 98% of Ca is fixed in bone tissue, and only 1–2% is in soft tissues and extracellular fluid, incl. in blood. In the blood serum, 40% Ca circulates in complex with proteins, 9% in the form of salts (phosphates, citrate), the remaining 50% are present in the ionized (free) form (Ca2+) and therefore are able to diffuse into the intercellular fluid. It is free calcium that is the regulator of intracellular processes.

Physiologically, the action of Ca is associated with the regulation of the permeability of cell membranes. In the cell, its concentration is very low; on the outer side of the plasma membrane, the Ca2+ content is many times higher. The establishment of such a balance of concentrations is ensured by the energy-dependent operation of membrane channels and pumps. Due to the low content of Ca2+ in the cytoplasm and the high concentration gradient on both sides of the plasma membrane, this ion is important in the regulation of cell activity. The plasma membrane of cells has a low permeability to calcium; the removal of the ion from the cell is energy dependent. Changes in the conductivity of the calcium channels of the membrane and the intracellular content of Ca2+ change the functioning of many systems, including the processes of cell division. Calcium ions play an important role in the transmission of nerve impulses, muscle contractility, in the process of blood coagulation, and are cofactors in a number of enzymatic reactions. Determining the level of calcium is a diagnostically and prognostically significant test for a number of pathological conditions.

To maintain a normal level of calcium in the blood serum, it is necessary to adequately supply it with food. The intake of calcium in the body is affected by its content in food and their composition. The presence in the diet of substances that bind calcium, primarily phosphates and fatty acids, significantly reduces its absorption. Calcium absorption occurs predominantly in the proximal small intestine and in the jejunum. The intestines absorb from 30 to 70% of the calcium supplied with food.

Clinically, hypercalcemia manifests itself as a violation of the kidneys (polyuria, urolithiasis), gastrointestinal tract (nausea, vomiting, constipation), heart (shortening of the QT interval on the ECG), neurological symptoms (weakness, fatigue, confusion, stupor and coma). Clinical manifestations of hypercalcemia are more pronounced with its rapid development.

Clinical manifestations of hypocalcemia vary depending on the degree of calcium reduction. Muscle fatigue, weakness, twitching of individual muscle groups, positive symptoms of Khvostek, Trousseau, Lust are noted with a mild degree of hypocalcemia. Alkalosis increases the albumin-bound calcium fraction, exacerbating symptoms. Severe hypocalcemia causes drowsiness, confusion, spasms of smooth muscles, hypertonicity and convulsions, prolongation of the QT interval on the ECG. Chronic hypocalcemia can cause cataracts and calcification of the basal ganglia.

The exchange of calcium in the body is closely related to the exchange of phosphorus. The main factors regulating the metabolism of phosphates and calcium include PTH, calcitonin and vitamin D. When hypocalcemia occurs, an increase in PTH synthesis occurs, which provides increased tubular reabsorption and a decrease in calcium excretion in the urine. At the same time, under the influence of PTH, the excretion of phosphorus by the kidneys increases, which leads to a decrease in the concentration of phosphorus in the blood serum and extracellular fluid and a subsequent increase in the level of calcium in the blood. Hyperphosphatemia is accompanied by a decrease in calcium concentration, which leads to stimulation of the release of PTH, a decrease in tubular reabsorption of phosphate and an increase in its excretion by the kidneys.

The content of Ca in blood serum and urine changes with dysfunction of the parathyroid and thyroid glands, neoplasms of different localization, especially with bone metastasis, and renal failure. Prolonged hypercalcemia in combination with both hyper- and normophosphatemia can cause calcium phosphate deposition in the wall of blood vessels, connective tissue, gastric mucosa, and other organs and tissues.

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