Vitamin D and the cardiovascular system

Vitamin D is important in the homeostasis of critical tissues involved in vascular disease. The vitamin D receptor (VDR) and the 1α-hydroxylase enzyme are present in cells implicated in vascular disease development. Vitamin D influences multiple mechanisms to decrease vascular inflammation: it suppresses the renin-angiotensin system, promotes endothelial nitric oxide release, decreases vascular inflammatory markers and cholesterol deposition, and imbues immune cells with anti-inflammatory properties. Studies in mouse models of diet-induced insulin resistance show that vitamin D deficiency or VDR deletion promotes renin-dependent hypertension and accelerates atherosclerosis. However, the effects of vitamin D supplementation on blood pressure and atherosclerosis have been mixed and depend on baseline vitamin D status, dose and compound administered, and animal model. Human observational studies demonstrate associations between low 25(OH)D levels and increased cardiovascular disease, but the effects of vitamin D supplementation for prevention are conflicting, and study design limitations preclude adequate conclusions.