Vitamin D and Atherosclerotic Cardiovascular Disease

Abstract

Context: A large body of experimental and observational data has implicated vitamin D deficiency in the development of cardiovascular disease. However, evidence to support routine vitamin D supplementation to prevent or treat cardiovascular disease is lacking.

Design and results: A comprehensive literature review was performed using PubMed and other literature search engines. Mounting epidemiological evidence and data from Mendelian randomization studies support a link between vitamin D deficiency and adverse cardiovascular health outcomes, but randomized trial evidence to support vitamin D supplementation is sparse. Current public health guidelines restrict vitamin D intake recommendations to the maintenance of bone health and prevention of fractures. Two recently published large trials (VITAL and ViDA) that assessed the role of moderate- to high-dose vitamin D supplementation as primary prevention for cardiovascular outcomes in the general population had null results, and previous randomized trials have also been generally negative. These findings from general population cohorts that are largely replete in vitamin D may not be applicable to chronic kidney disease (CKD) populations, in which the use of active (1α-hydroxylated) vitamin D compounds is prevalent, or to other high-risk populations. Additionally, recent trials in the CKD population, as well as trials using vitamin D analogs, have been limited.

Conclusions: Current randomized trials of vitamin D supplementation do not support benefits for cardiovascular health, but the evidence remains inconclusive. Additional randomized trials assessing larger numbers of participants with low baseline vitamin D levels, having longer follow-up periods, and testing higher vitamin D dosages are needed to guide clinical practice.

Figure 1:. Vitamin D compounds and synthesis:

Choleclaciferol is formed through dermal photoconversion of 7-dehydrocholesterol (7DHC). Cholecalciferol is biologically inert, but is converted by various enzymes to compounds that bind the nuclear vitamin D receptor (VDR). 1,25-dihydroxyvitamin D (1,25(OH)₂D, calcitriol) is the active form of vitamin D that is synthesized from 25(OH) ₂D by 1α-hydroxylase (CYP27B1), now known to be expressed in almost all human tissues. 1,25(OH) ₂D has a high affinity for the VDR.

Figure 2:. Vitamin D receptor (VDR) activation and the atherogenic process:

VDR activation can exert pleiotropic cardiovasculo-protective effects through multiple mechanisms. VSMCs (Vascular smooth muscle cells); VEGF (vascular endothelial growth factor).