The efficacy of Phaseolus vulgaris as a weight-loss supplement: a systematic review and meta-analysis of randomised clinical trials

A variety of dietary supplements are presently available as slimming aids, but their efficacy has not been proven. One such slimming aid is the bean extract, Phaseolus vulgaris. The aim of the present systematic review is to evaluate the evidence for or against the efficacy of P. vulgaris. Electronic and non-electronic searches were conducted to identify relevant human randomised clinical trials (RCT). Hand searches of bibliographies were also conducted. No age, time or language restrictions were imposed. The eligibility of studies was determined by two reviewers independently, and the methodological quality of the included studies was assessed. We identified eleven eligible trials, and six were included. All the included RCT had serious methodological flaws. A meta-analysis revealed a statistically non-significant difference in weight loss between P. vulgaris and placebo groups (mean difference (MD) -1.77 kg, 95% CI -3.33, 0.33). A further meta-analysis revealed a statistically significant reduction in body fat favouring P. vulgaris over placebo (MD -1.86 kg, 95% CI -3.39, -0.32). Heterogeneity was evident in both analyses. The poor quality of the included RCT prevents us from drawing any firm conclusions about the effects of P. vulgaris supplementation on body weight. Larger and more rigorous trials are needed to objectively assess the effects of this herbal supplement.