The effects of grape seed extract on glycemic control, serum lipoproteins, inflammation, and body weight: A systematic review and meta-analysis of randomized controlled trials

The aim of this systematic review and meta-analysis was to analyze the effects of grape seed extract (GSE) on glycemic control and serum lipoproteins, inflammation and body weight. Two independent authors systematically searched online databases including EMBASE, Scopus, PubMed, Cochrane Library, and Web of Science from inception until May 30, 2019. Cochrane Collaboration risk of bias tool was applied to assess the methodological quality of included trials. The heterogeneity among the included studies was assessed using Cochrane's Q test and I-square (I-2) statistic. Data were pooled using a random-effects model and weighted mean difference (WMD) was considered as the overall effect size. Fifty trials were included in this meta-analysis. Pooling effect sizes from studies demonstrated a significant decrease in fasting plasma glucose (FPG) (WMD): -2.01; 95% confidence interval (CI): -3.14, -0.86), total cholesterol (TC; WMD: -6.03; 95% CI: -9.71, -2.35), low-density lipoprotein (LDL) cholesterol (WMD: -4.97; 95% CI: -8.37, -1.57), triglycerides (WMD: -6.55; 95% CI: -9.28, -3.83), and C-reactive protein (CRP) concentrations (WMD: -0.81; 95% CI: -1.25, -0.38) following GSE therapy. Grape seed did not influence HbA1c, HDL cholesterol levels, and anthropometric measurements. This meta-analysis demonstrated that GSE intake significantly reduced FPG, TC, LDL cholesterol, triglycerides, and CRP levels.