Effect of quercetin supplementation on serum CRP levels: a systematic review and meta-analysis of randomized controlled trials

Several studies have investigated the effect of quericitn supplementation on serum C - reactive protein (CRP). However, results were inconsistent. This systematic review and meta-analysis was designed to assess the effect of quercetin supplementation on CRP levels in randomize control trials (RCTs). We searched PubMed and Scopus up to July 2016 to identify RCTs investigating the effect of quercetin on serum CRP. Meta-analysis was performed using either a fixed-effects or random-effect model according to I² statistic. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated for net changes in CRP levels. Seven trials with eight data sets and 346 participants met the inclusion criteria. There was no significant differences for CRP reduction between subjects with quercetin supplementation and placebo control [WMD, 0.01 mg/L; 95% CI: -0.18 to 0.21, p =0.88] with significant heterogeneity (I²=48.9%; p=0.05). Subgroup analyses showed that dose, duration and country were not the potential sources of heterogeneity. Our results suggest that quercetin supplementation does not reduce serum CRP. Further large and well-designed studies are necessary to confirm this conclusion.