Vitamin D improves blood flow, and low vitamin D levels create endothelial dysfunction. Large, randomized clinical trials on Vitamin D supplementation, UV rays, and vascular health are just beginning.
"It is worthy to note that both observational and interventional studies have established an association between vitamin D levels and endothelial dysfunction. In a small cohort of young asymptomatic patients, flow mediated dilatation (FMD) measurements were significantly lower in 25(OH)D-deficient subjects than controls, and improved after acute treatment with calcitriol."


Vitamin D: a novel player in endothelial function and dysfunction
www.ncbi.nlm.nih.gov
Vitamin D is produced endogenously in the skin after exposure to the ultraviolet B spectrum of sunlight. Importantly, only few foods are natural sources of a consistent amount of vitamin D. Consequently, vitamin D insufficiency and deficiency are widespread among humans due to limited sun exposure a...