Impact of vitamin D supplementation on inflammatory markers in African Americans: results of a four-arm, randomized, placebo-controlled trial.

African Americans have a disproportionate burden of inflammation-associated chronic diseases such as cancer and lower circulating levels of 25-hydroxyvitamin D [25(OH)D]. The effect of vitamin D3 (cholecalciferol) supplementation on inflammatory markers is uncertain. We conducted a randomized, double-blind, placebo-controlled trial of supplemental oral vitamin D (placebo, 1,000, 2,000, or 4,000 IU/day of vitamin D3 orally for 3 months) in 328 African Americans (median age, 51 years) of public housing communities in Boston, MA, who were enrolled over three consecutive winter periods (2007-2010). Change from 0 to 3 months of plasma levels of 25(OH)D, high-sensitivity C-reactive protein (CRP), interleukin (IL)-6, IL-10, and soluble TNF-α receptor type 2 (sTNF-R2) in 292 (89%) participants were measured. Overall, no statistically significant changes in CRP, IL-6, IL-10, and sTNF-R2 were observed after the vitamin D supplementation period. Baseline CRP was significantly inversely associated with the baseline 25(OH)D level (P < 0.001) in unadjusted and adjusted models. An interaction between baseline 25(OH)D and vitamin D supplementation was observed for outcome change in log CRP (month 3-month 0; P for interaction = 0.04). Within an unselected population of African Americans, short-term exposure to vitamin D supplementation produced no change in circulating inflammatory markers. This study confirms the strong independent association of CRP with 25(OH)D status even after adjusting for body mass index. Future studies of longer supplemental vitamin D3 duration are necessary to examine the complex influence of vitamin D3 on CRP and other chronic inflammatory cytokines for possible reduction of cancer health disparities in African Americans.