Bitter gourd reduces elevated fasting plasma glucose levels in an intervention study among prediabetics in Tanzania

Ethnopharmacological relevance: Impaired glucose tolerance and diabetes mellitus have become major health issues even in non-industrialized countries. As access to clinical management is often poor, dietary interventions and alternative medicines are required. For bitter gourd, Momordica charantia L., antidiabetic properties have been claimed. Aim of the study: The main objective of the intervention study was to assess antidiabetic effects of daily bitter gourd consumption of 2.5 g powder over the course of eight weeks among prediabetic individuals. Materials and methods: In a randomized placebo-controlled single blinded clinical trial, 52 individuals with prediabetes were studied after consuming a bitter gourd or a cucumber juice. For reducing the impact of between subject differences in the study population, a crossover design was chosen with eight weeks for each study period and four weeks washout in between. Fasting plasma glucose was chosen as the primary outcome variable. Results: Comparing the different exposures, the CROS analysis (t=−2.23, p=0.031, r=0.326) revealed a significant difference in the change of FPG of 0.31 mmol/L (5.6 mg/dL) with a trend (R²=0,42387). The number of 44 finally complete data sets achieved a power of 0.82, with a medium-to-large effect size (Cohen's d 0.62). The effect was also proven by a general linear mixed model (estimate 0.31; SE: 0.12; p: 0.01; 95%CI: 0.08; 0.54). Not all participants responded, but the higher the initial blood glucose levels were, the more pronounced the effect was. No serious adverse effects were observed. Conclusions: Bitter gourd supplementation appeared to have benefits in lowering elevated fasting plasma glucose in prediabetes. The findings should be replicated in other intervention studies to further investigate glucose lowering effects and the opportunity to use bitter gourd for dietary self-management, especially in places where access to professional medical care is not easily assured.