Effect of Vitamin D Supplementation on Blood Pressure in African-Americans

African-Americans 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 African-Americans. During two winter periods from 2008–2010, 283 African-Americans (median age, 51 years) were randomized into a four-arm, double-blind trial for three months of placebo, 1,000, 2,000, or 4,000 international units of cholecalciferol per day. At baseline, three months, and six 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 mmHg for those receiving placebo, −0.66 mmHg for 1,000 units/day, −3.4 mmHg for 2,000 units/day, and −4.0 mmHg for 4,000 units/day of cholecalciferol (−1.4 mmHg for each additional 1000 units/day of cholecalciferol; p=0.04). For each 1 ng/mL increase in plasma 25-hydroxyvitamin D, there was a significant 0.2 mmHg 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 African-Americans, three 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 African-Americans, a population for whom vitamin D deficiency may play a more specific mechanistic role in the pathogenesis of hypertension.