The effect of bitter melon (Mormordica charantia) in patients with diabetes mellitus: a systematic review and meta-analysis

BACKGROUND: Mormordica charantia (bitter melon) has been investigated for lowering plasma glucose in patients with diabetes mellitus (DM). Previous data has offered inconclusive and inconsistent results about the benefits of bitter melon in patients with DM. Our current project aims to determine whether bitter melon has a favorable effect in lowering plasma glucose in patients with DM. METHODS: We searched PubMed, EMBASE and the Cochrane Library from inception to July 2013 without any language restrictions for randomized controlled trials (RCTs) evaluating bitter melon to no treatment in patients with type 1 or type 2 diabetes. Study selection, data extraction and validity of each article were independently assessed by two investigators. Articles were appraised for proper random sequence generation, allocation concealment, blinding, selective reporting and completeness of outcomes reporting to assess the risk for biases. The glycemic results of each RCT were analyzed to yield weighted mean differences (WMDs) and 95% confidence intervals (CIs). RESULTS: A total of four RCTs, each with 40–66 participants, followed between 4 and 12 weeks were identified in this meta-analysis. Overall risk of bias for each article included was determined to be unclear. In total, 208 participants with type 2 DM (mean age of 56.5 years) were evaluated. Compared with no treatment, bitter melon did not significantly lower A1C (WMD −0.13%, 95% CI −0.41 to 0.16) nor fasting plasma glucose (FPG) 47 (WMD 2.23 mg dl(−1), 95% CI −14.91 to 19.37). CONCLUSIONS: Bitter melon supplementation compared with no treatment did not show significant glycemic improvements on either A1c or FPG.