Bitter gourd (Momordica charantia L.) supplementation for twelve weeks improves biomarkers of glucose homeostasis in a prediabetic population

Ethnopharmacological relevance: Bitter gourd (Momordica charantia L.) is known for its ability to reduce parameters of diabetes, but its effects on prediabetic subjects have been scarcely studied. Aim of the study: To assess the efficacy of Momordica charantia supplementation in a prediabetic population on markers of glucose homeostasis. Methods: Two randomized controlled studies were conducted to assess the effect of bitter gourd supplementation in a prediabetic population. Study 1 was a 4-week cross-over intervention trial (n = 30), with freeze-dried bitter gourd (BG) fruit juice (2.4 g/day) or a cucumber-based control product (CC). Study 2 was a parallel trial (n = 38) lasting 12 weeks, with freeze-dried whole fruits (3.6 g/day) or a cucumber-based matched control supplement. Effects on fasting plasma glucose (FPG), insulin, HbA1c, fructosamine, postprandial glucose after an oral glucose tolerance test, and several safety biomarkers were also analyzed in both trials before and after the interventions. Results: In Study 1, no significant differences were found between the bitter gourd and placebo interventions. However, a reduction in FPG in subjects with higher baseline values were found following bitter gourd supplementation, which was not observed in the control group. However, in Study 2, we observed significant reductions of FPG (p = 0.014), fasting insulin (p = 0.007), and HOMA-IR (p = 0.003) after a 12-week intervention with the bitter gourd supplement. In addition, between treatment analysis resulted in significant effects on FPG levels (p = 0.026) and HOMA-IR (p = 0.045) with no significant effects on other biomarkers related to glucose metabolism. On average, bitter gourd intervention reduced FPG by ∼0.05 mmol/L per week, whereas FPG remained unchanged following placebo. In both studies, there were no indications of health risks or side effects from consumption of the supplements. Conclusion: Results suggest that supplementation with bitter gourd fruit can have positive effects on fasting plasma glucose and insulin among prediabetic subjects when provided over an extended period of at least 12 weeks.