Vitamin D status is linked to vascular health

It's become well known that an optimal level of vitamin D is important for systems throughout the body. A study just published in the Journal of the American College of Cardiology illuminates in greater detail how vitamin D is necessary for blood vessels to relax and expand properly. The authors state:

"The primary objective of this study was to elucidate mechanisms underlying the link between vitamin D status and cardiovascular disease by exploring the relationship between 25-hydroxyvitamin D (25-OH D), an established marker of vitamin D status, and vascular function in healthy adults."

Moreover...

"Vitamin D influences endothelial and smooth muscle cell function, mediates inflammation, and modulates the renin-angiotensin-aldosterone axis. We investigated the relationship between vitamin D status and vascular function in humans, with the hypothesis that vitamin D insufficiency will be associated with increased arterial stiffness and abnormal vascular function."

They measured serum 25-OH D in 554 subjects and assessed endothelial (blood vessel lining) function by the ability to dilate the flow of blood in the brachial artery. Microvascular function was determined by the digital reactive hyperemia index (how readily blood flows into small surface capillaries). Carotid-femoral pulse wave velocity, the radial tonometry-derived central augmentation index and the subendocardial viability ratio were used to assess arterial stiffness. Vitamin D showed effects throughout these parameters:

"...25-OH D remained independently associated with flow-mediated vasodilation, reactive hyperemia index, pulse wave velocity, augmentation index, and subendocardial viability ratio. In 42 subjects with vitamin D insufficiency, normalization of 25-OH D at 6 months was associated with increases in reactive hyperemia index and subendocardial viability ratio, and a decrease in mean arterial pressure."

I think it is fair to assert that no cardiovascular workup is complete without measuring 25-OH vitamin D. For optimal function in most cases my preference is at least 50 ng/ml (with the usual care for rare signs of intolerance—hypercalcemia, etc.). The authors conclude:

"Vitamin D insufficiency is associated with increased arterial stiffness and endothelial dysfunction in the conductance and resistance blood vessels in humans, irrespective of traditional risk burden."