Dose responses of vitamin D3 supplementation on arterial stiffness in overweight African Americans with vitamin D deficiency: A placebo controlled randomized trial

Placebo-controlled randomized trial in overweight African American adolescents and young adults with vitamin D deficiency/suboptimal status (25[OH]D <20 ng/mL), aged 13 to 45 years, conducted in Augusta, Georgia. The active intervention arms included 17 participants at ~600 IU/day, 18 at ~2,000 IU/day, and 18 at ~4,000 IU/day.

Oral vitamin D3 capsules were given under supervised monthly dosing for 16 weeks at 18,000 IU/month (~600 IU/day), 60,000 IU/month (~2,000 IU/day), or 120,000 IU/month (~4,000 IU/day), with placebo as the comparator. The active regimen was dose-ranging and designed to test a dose-response effect on arterial stiffness.

Vitamin D3 improved arterial stiffness in a dose-dependent manner, with the largest benefit seen at 4,000 IU/day. Carotid-femoral PWV changed from 6.71 to 6.01 m/s in the 4,000 IU/day group (change -0.70, 95% CI -1.07 to -0.32), compared with 0.02 (-0.34 to 0.38) in the 600 IU/day group and -0.11 (-0.50 to 0.27) in the 2,000 IU/day group; the group-by-time interaction was P<0.01. Carotid-radial PWV also favored the higher dose, with a group-by-time interaction of P=0.03. Serum 25(OH)D increased with dose, and no significant blood pressure changes or adverse events were reported.

The trial was small, with only 17 to 18 participants per active dose arm, and lasted only 16 weeks. The sample was limited to overweight African Americans with vitamin D deficiency from one geographic region, which reduces generalizability. Cardiovascular clinical events were not measured, and the placebo arm sample size was not provided in the extracted data.