Green tea supplementation significantly lowers fasting glucose levels but does not significantly affect fasting insulin and haemoglobin A1c values.
The researchers performed a systematic review and meta-analysis of randomized control trials which examined the effect of green tea on glycemic control. Using online databases like PubMed, Embase, and Cochrane Library, they identified relevant trials up until February 2020. They then employed a random-effects model in order to estimate the weighted mean difference.
In the discussion of the results, it was found that twenty-seven trials, including 2194 subjects, were part of the meta-analysis. The collected data indicated that green tea lowered fasting blood glucose levels significantly. However, the same was not observed for fasting insulin and HbA1c values, which remained relatively unchanged despite green tea consumption. Moreover, substantial differences were noted in the range of responses, indicating significant heterogeneity, especially for fasting insulin levels. Despite these discrepancies, the short-term trials collectively demonstrated the beneficial effect of green tea supplementation in reducing fasting glucose levels.
