Plain language summary
Animal studies have highlighted the importance of vitamin D in heart functioning and human studies have indicated that deficiencies in vitamin D are associated with disorders of the heart. This has led to the belief that vitamin D may have a role in protection against heart disease, however studies on this have failed to show a relationship. This review paper aimed to highlight the role of vitamin D in heart disease and to understand why associations have not been shown in trials. The paper highlighted how vitamin D derives from cholesterol and is regulated by a number of things including calcium. Vitamin D receptors are evident in heart tissues, however the reason for vitamin D in these tissues is unclear. The role of vitamin D in high blood pressure, the build-up of fat in heart arteries and heart failure were all reviewed, and it appears that data is conflicting in all conditions. It was concluded that there is strong evidence for a protective role of vitamin D in heart disease, but only from animal studies and randomised control trials with vitamin D supplements in humans, do not show any benefit. Issues with ethics and biological processes may be the reason that human studies have failed to show any associations. This study could be used by healthcare professionals to better understand the possible role of vitamin D in heart disease.
Vitamin D deficiency is the most common nutritional deficiency, affecting almost one billion people worldwide. Vitamin D is mostly known for its role in intestinal calcium absorption and bone mineralization. However, the observation of seasonal changes in blood pressure and the subsequent identification of vitamin D receptor (VDR) and 1α-hydroxylase in cardiomyocytes, as well as endothelial and vascular smooth muscle cells, implicated a role of vitamin D in the cardiovascular system. Animal studies provided compelling evidence that vitamin D signaling is essential for cardiovascular integrity, especially for the regulation of vascular tone and as an antifibrotic and antihypertrophic signaling pathway in the heart. In addition, observational studies reported an association between vitamin D deficiency and risk of hypertension, atherosclerosis, and heart failure. However, recent clinical intervention studies failed to prove the causal relationship between vitamin D supplementation and beneficial effects on cardiovascular health. In this review, we aim to highlight our current understanding of the role of vitamin D in the cardiovascular system and to find potential explanations for the large discrepancies between the outcome of experimental studies and clinical intervention trials.