The effect of vitamin–mineral supplementation on CRP and IL-6: A systemic review and meta-analysis of randomised controlled trials

Background and AimsInflammation is regarded as a risk predictor for metabolic syndrome and atherogenesis. The objective of this study was to conduct a systematic review and a meta-analysis to confirm the effect of vitamin–mineral supplementation on cytokine levels.Methods and ResultsWe searched the PubMed, EMBASE and Cochrane databases up to May 2009 for randomised controlled trials regarding the effect of vitamin–mineral supplementation on C-reactive protein (CRP) and interleukin-6 (IL-6). Eighteen trials with 1747 participants for CRP and nine trials with 1037 participants for IL-6 were included, respectively. Pooled estimates and 95% confidence intervals (CIs) were calculated by fixed- or random-effects model. No significant differences were observed for CRP and IL-6 reduction between the subjects with vitamin–mineral supplementation and placebo control. A dose-dependent manner for different body mass index (BMI) subgroups in CRP analysis was observed (weighted mean difference (WMD), −0.057; 95%CI: −0.753 to 0.639 for BMI < 25; WMD, −0.426; 95%CI: −0.930 to 0.079 for 25 ≤ BMI < 30; WMD, −0.491; 95%CI: −1.407 to 0.424 for BMI ≥ 30). However, no significance was detected in meta-regression (−0.046, 95%CI: −0.135 to 0.044). Moreover, the best effect for reduction in CRP levels in a supplementation duration of 4 weeks–6 months (WMD, −0.449; 95%CI: −1.004 to 0.106) was observed compared with supplementation duration less than 4 weeks (WMD, −0.137; 95%CI, −0.816 to 0.541) and more than 6 months (WMD, −0.389; 95%CI, −1.034 to 0.257) without statistical significance (P = 0.059).ConclusionNo statistically significant evidences for the potential dose-dependent manner of BMI and best supplement duration were detected in this study. Large and well-designed studies are recommended to confirm this conclusion.