Effect of Epigallocatechin Gallate on Glycemic Index: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Epigallocatechin gallate (EGCG), a major catechin found in green tea, has been suggested to influence glycemic control. This systematic review and meta-analysis aim to evaluate the effects of EGCG on the glycemic index (GI) and related glycemic parameters.

Using predefined keywords, online databases (PubMed, Scopus, Web of Science Core Collection, and Google Scholar) were searched for relevant studies, published from inception up to May 2024. Initially 1994 studies were obtained out of which 41 RCTs were decided to be included for further analyses.

The meta-analysis demonstrated that EGCG supplementation led to statistically significant, but modest, reductions in fasting blood glucose (FBG), HbA1c, and HOMA-IR. Notably, the reduction in HbA1c (WMD: -0.18%, 95% CI: -0.35, -0.02; P = 0.029) was small and may not equate to clinically meaningful benefits for all populations. Furthermore, the effect on fasting insulin was not statistically significant (WMD: -0.50; 95% CI: -1.46, 0.47; P = 0.313), indicating a lack of robust or consistent impact on this parameter across studies.

Although EGCG supplementation is associated with improvements in some glycemic parameters, these effects especially for HbA1c and fasting insulin are modest and may not be clinically meaningful for most population. Therefore, current evidence does not strongly support the use of EGCG as a stand-alone intervention for glycemic control.