The effect of barberry (Berberis vulgaris L.) on glycemic indices: A systematic review and meta-analysis of randomized controlled trials

Objective: We performed a meta-analysis to evaluate the efficacy of barberry (Berberis vulgaris L.) supplementation on glycemic indices in adults. Methods: A comprehensive search was conducted in PubMed, Scopus, Cochrane Library, and ISI Web of Science from inception up to January 2020, to identify randomized controlled trials (RCTs) investigating the effect of barberry supplementation on glycemic markers including fasting blood sugar (FBS) concentrations, insulin levels, homeostatic model assessment for insulin resistance (HOMA-IR), and glycosylated hemoglobin (HbA1c) percentage. The results of this meta-analysis were reported, based on the random effects model. Results: In total, 7 studies, comprising 452 participants, were included in the systematic review. The meta-analysis revealed that barberry significantly reduces insulin levels (Hedges's: -0.67; 95% CI: -1.31 to -0.03, P = 0.04, I² = 73.3%). However, no considerable changes was observed for FBS levels (WMD: -8.06 mg/dL; 95% CI: -20.46 to 4.33, P = 0.23, I² = 96.1%), HbA1c percentage (WMD: -0.83 %; 95% CI: -2.33 to 0.67, P = 0.27, I² = 88.3%), and HOMA-IR index (WMD: -0.55; 95% CI: -1.60 to 0.50, P = 0.30, I² = 99.4%). Conclusion: The present study suggests that although barberry supplementation significantly improves insulin levels; however, other glycemic indices might not be affected. However, more high-quality RCTs with longer duration are needed to further clarify the effects of barberry on blood glucose control, especially among patients with diabetes.