Quercetin Actions on Lipid Profiles in Overweight and Obese Individuals: A Systematic Review and Meta-analysis.

BACKGROUND The lipid distribution in people who are overweight and obese is directly related to metabolic diseases. Quercetin supplementation may be an appropriate approach for reducing the risk factors of metabolic diseases in people who are obese. METHOD Two independent authors systematically searched online databases including EMBASE, PubMed, Cochrane Library, and Web of Science through March 20, 2019. The Cochrane Collaboration risk of bias tool was applied to assess the methodological quality of the included trials. Heterogeneity was measured using a Cochran's Q test and I-square (I2) statistic. Data were pooled using a random-effects-model and Std mean difference (SMD) was considered as the overall effect size. RESULTS Out of 170 potential papers, 5 RCTs were appropriate to be included in our meta-analysis. Combined estimate of effect size for the impact of quercetin on LDL-cholesterol (SMD: 0.09; 95% CI: -0.21-0.40), HDL-cholesterol (SMD: -0.07; 95% CI: -0.22-0.08) , triglycerides (SMD: 0.14; 95% CI: -0.01-0.29) and total-cholesterol (SMD: 0.03; 95% CI: -0.12-0.18) were not statistically significant. When the analysis was confined to the subgroups of studies follow-up of >6 weeks, a significant reduction in LDL-cholesterol (SMD: -0.8 ; 95% CI: -1.21--0.39, p < 0.00001), but HDL-cholesterol, triglycerides and total-cholesterol remained unchanged (p > 0.05). CONCLUSION Available evidence from RCTs does not suggest any clinically relevant effect of quercetin supplementation on plasma lipids of patients who are overweight and obese, apart from a significant reduction of LDL-cholesterol in >6 weeks, at doses ≥150 mg/day.