Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND: Quercetin, the most abundant dietary flavonol, has antioxidant effects in cardiovascular disease, but the evidence regarding its effects on blood pressure (BP) has not been conclusive. We assessed the impact of quercetin on BP through a systematic review and meta-analysis of available randomized controlled trials. METHODS AND RESULTS: We searched PUBMED, Cochrane Library, Scopus, and EMBASE up to January 31, 2015 to identify placebo-controlled randomized controlled trials investigating the effect of quercetin on BP. Meta-analysis was performed using either a fixed-effects or random-effect model according to I(2) statistic. Effect size was expressed as weighted mean difference (WMD) and 95% CI. Overall, the impact of quercetin on BP was reported in 7 trials comprising 9 treatment arms (587 patients). The results of the meta-analysis showed significant reductions both in systolic BP (WMD: -3.04 mm Hg, 95% CI: -5.75, -0.33, P=0.028) and diastolic BP (WMD: -2.63 mm Hg, 95% CI: -3.26, -2.01, P CONCLUSIONS: The results of the meta-analysis showed a statistically significant effect of quercetin supplementation in the reduction of BP, possibly limited to, or greater with dosages of \u3e500 mg/day. Further studies are necessary to investigate the clinical relevance of these results and the possibility of quercetin application as an add-on to antihypertensive therapy