Effect of vitamin D supplementation on serum C-reactive protein level: a meta-analysis of randomized controlled trials

Vitamin D may have anti-inflammatory actions however; there is no consensus on the effects of vitamin D supplementation on C-reactive protein (CRP) level in randomized clinical trials. In a systematic review and meta-analysis, we hypothesized that vitamin D supplementation would reduce serum CRP levels.
A systematic research of randomized controlled trials has been conducted on MEDLINE and EMBASE through PubMed, Scopus, and completed by a manual review of the literature up from January 2000 to May 2015. Pooled effect estimated by using random-effect model and heterogeneity was assessed by Cochran’s Q and I2 tests.
Of 157 potentially relevant studies we found in a systematic search, 20 clinical trials met the inclusion criteria. Mean baseline CRP levels in the intervention group and in the control group were 3.5±2.6 and 3.3±2.3 mg/L, respectively. Mean duration of the studies were 29.0±30.2.0 (SD) weeks (8 to 144 weeks). Doses of vitamin D3 supplementation varied between 200 to 57142 IU/day. Pooled analysis showed a non-significant increase of 0.04 mg/L (95% CI, −0.12 to 0.21; p The results of this meta-analysis showed that vitamin D supplementation may not be effective for the reduction of CRP. However, a more accurate estimate of the effect requires further large and well-designed clinical trials.