Effect of Isoflavones and Genistein on Glucose Metabolism in Peri- and Post-Menopausal Women: An Overview of Meta-Analysis

The purpose of the present overview of meta-analysis is to summarize and critically assess the effect of isoflavones and genistein on glucose metabolism among the peri- and post-menopausal women. Two independent authors searched the databases of MEDLINE, Scopus and Cochrane Library for meta-analysis. Three databases were searched from inception to January 2018. Methodological quality of each meta-analysis of randomized controlled trials was evaluated using the AMSTAR (a measurement tool used to assess systematic reviews). Four meta-analyses were included to the current overview. Fasting insulin levels and homeostatic model assessment of insulin resistance (HOMA-IR) values were significantly lower in peri-menopausal and postmenopausal. Two meta-analyses showed that treatment with isoflavones could not alter fasting blood glucose. However, one meta-analysis depicted that isoflavones significantly improved blood glucose levels in non-Asian postmenopausal women. Treatment with genistein could have significant beneficial effects on fasting insulin, blood glucose and HOMA-IR in comparison to the control group. Regardless of the population, the treatment with genistein is effective in improving fasting insulin, HOMA-IR and glucose levels. Nevertheless, the high heterogeneity among studies and poor methodology of reviews made it difficult to draw a definite conclusion on the positive impacts of soy on glucose metabolism.