Blacks have significantly higher rates of hypertension than whites, and lower circulating levels of 25-hydroxyvitamin D. There are few data about the effect of vitamin D3 (cholecalciferol) supplementation on blood pressure in blacks. During 2 winters from 2008 to 2010, 283 blacks (median age, 51 years) were randomized into a 4-arm, double-blind trial for 3 months of placebo, 1000, 2000, or 4000 international units of cholecalciferol per day. At baseline, 3 months, and 6 months, systolic and diastolic pressure and 25-hydroxyvitamin D were measured. The 3-month follow-up was completed in 250 (88%) participants. The difference in systolic pressure between baseline and 3 months was +1.7 mm Hg for those receiving placebo, -0.66 mm Hg for 1000 U/d, -3.4 mm Hg for 2000 U/d, and -4.0 mm Hg for 4000 U/d of cholecalciferol (-1.4 mm Hg for each additional 1000 U/d of cholecalciferol; P=0.04). For each 1-ng/mL increase in plasma 25-hydroxyvitamin D, there was a significant 0.2-mm Hg reduction in systolic pressure (P=0.02). There was no effect of cholecalciferol supplementation on diastolic pressure (P=0.37). Within an unselected population of blacks, 3 months of oral vitamin D3 supplementation significantly, yet modestly, lowered systolic pressure. Future trials of vitamin D supplementation on blood pressure are needed to confirm these promising results, particularly among blacks, a population for whom vitamin D deficiency may play a more specific mechanistic role in the pathogenesis of hypertension.
Trial registration: ClinicalTrials.gov NCT00585637.