What is the relationship between calcium and vitamin D? How do they impact skeletal and extraskeletal health. Let’s explore the research.

The Importance of Vitamin D Deficiency

Vitamin D deficiency is a widespread problem, with a comprehensive review by Holick MF highlighting the significant health implications.1 Vitamin D plays a crucial role in maintaining calcium homeostasis and bone health, and its deficiency can lead to serious consequences, including increased risk of fractures, reduced muscle function, and a higher susceptibility to various chronic diseases.

Vitamin D and Cancer Growth

Emerging research suggests that vitamin D deficiency may also influence the growth of certain types of cancer. A study by Tangpricha et al. found that vitamin D deficiency enhanced the growth of MC-26 colon cancer xenografts in Balb/c mice, indicating a potential link between vitamin D status and cancer progression.2

Mechanisms of Drug-Induced Osteomalacia

The mechanism behind drug-induced osteomalacia, a condition characterized by impaired bone mineralization, has been elucidated in a study by Zhou et al. They demonstrated that the steroid and xenobiotic receptor (SXR) and vitamin D receptor (VDR) interact to mediate the expression of CYP24, an enzyme involved in the degradation of active vitamin D metabolites, leading to the development of osteomalacia in patients taking certain medications.3

Age-Related Changes in Intestinal Calcium Absorption

Researchers have investigated the relationship between age, vitamin D metabolism, and intestinal calcium absorption. Walters et al. found that the expression of the calcium channel TRPV6 in the human duodenum varies between men and women and is influenced by the vitamin D system and aging.4 Additionally, Pattanaungkul et al. demonstrated that elderly women exhibit age-related intestinal resistance to the actions of 1,25-dihydroxyvitamin D, leading to decreased calcium absorption.5

Regulation of Calcium Transporter Genes by Vitamin D Metabolites

The effects of vitamin D metabolites on the expression of genes involved in calcium transport in the human duodenum have been examined by Walters et al.6 Their findings shed light on the molecular mechanisms underlying the regulation of intestinal calcium absorption by vitamin D.

Skeletal Phenotype Rescue in Vitamin D Receptor-Ablated Mice

Amling et al. conducted a study to investigate the skeletal phenotype of vitamin D receptor-ablated mice in the setting of normal mineral ion homeostasis. They were able to rescue the skeletal phenotype, highlighting the complex interplay between vitamin D, mineral homeostasis, and bone health.7

Defining Normal Serum Vitamin D Levels

Establishing the appropriate range for normal serum vitamin D levels is essential for clinical practice. Hollis and Wagner addressed this issue, emphasizing the need for a clear definition of vitamin D sufficiency.8 Additionally, Chapuy et al. reported on the prevalence of vitamin D insufficiency in an adult normal population, underscoring the widespread nature of this problem.9

The relationship between serum 25-hydroxyvitamin D levels and calcium absorption has also been explored. Heaney et al. found that calcium absorption varies within the reference range for serum 25-hydroxyvitamin D, highlighting the complex interplay between these two factors.10

Vitamin D and Calcium Supplementation for Fracture Prevention

Several studies have investigated the efficacy of vitamin D and calcium supplementation in reducing the risk of fractures, particularly in elderly populations. Chapuy et al. demonstrated that the combination of vitamin D3 and calcium supplementation can effectively prevent hip fractures in elderly women.11,12 Trivedi et al. and Dawson-Hughes et al. also reported positive effects of vitamin D and calcium supplementation on fracture risk and bone density in older adults.13,14 Larsen et al. further confirmed the benefits of this intervention in a pragmatic population-based study.15

The prevalence of vitamin D deficiency in medical inpatients has been highlighted by Thomas et al., emphasizing the importance of addressing this issue in clinical settings.16 Moreover, van der Wielen et al. reported on the geographical variations in serum vitamin D concentrations among elderly people across Europe, underscoring the need for targeted interventions.17

Holick et al. examined the prevalence of vitamin D inadequacy among postmenopausal North American women receiving osteoporosis treatment, finding that a significant proportion of these individuals had suboptimal vitamin D levels.18