Effect of Vitamin D on Endothelial Function: A Randomized, Double-Blind, Placebo-Controlled Trial.

BACKGROUND

In nonhypertensive individuals, lower levels of 25-hydroxyvitamin D (25[OH]D) have been associated with an increased risk of hypertension, and vitamin D deficiency has been associated with endothelial dysfunction in such individuals. However, the effect of vitamin D supplementation on endothelial dysfunction in nonhypertensive individuals has not been examined in a rigorous fashion.

METHODS

In this randomized, double-blind, placebo-controlled trial of nonhypertensive, nondiabetic overweight, or obese individuals with vitamin D deficiency (body mass index ≥25 and 25[OH]D ≤ 20 ng/ml), we assigned subjects to receive either ergocalciferol (50,000 units) or matching placebo, once a week for 8 weeks. Our primary outcome was endothelial-dependent vasodilation (EDV) measured by brachial artery ultrasound at baseline and 8 weeks postrandomization.

RESULTS

By the end of the trial, 46 and 47 participants were allocated to receive ergocalciferol and placebo, respectively. Mean 25(OH)D levels increased from 14.9 to 30.3 in the vitamin D group and 14.4 to 17.4 in the placebo. EDV did not change significantly with either vitamin D repletion (from 6.3 ± 3.6% at baseline to 6.1 ± 4.6% at 8 weeks; P value = 0.78) or placebo (7.9 ± 4.7% to 6.8 ± 4.7%; P = 0.17). The treatment effect P value (comparing the 8-week change with ergocalciferol to the change with placebo) was 0.35.

CONCLUSIONS

In this randomized, double-blind, placebo-controlled trial, there was no improvement in endothelial function (measured as EDV) after repletion of vitamin D in overweight/obese nonhypertensive individuals.