Effects of green tea or green tea catechin on liver enzymes in healthy individuals and people with nonalcoholic fatty liver disease: A systematic review and meta-analysis of randomized clinical trials

The therapeutic potential of green tea as a rich source of antioxidants and anti-inflammatory compounds has been investigated by several studies. The present study aimed to systematically review and analyze randomized clinical trials (RCTs) assessing the effects of green tea, catechin, and other forms of green tea supplementation on levels of liver enzymes. PubMed, SCOPUS, EMBASE, and Cochrane databases were searched until February 2019. All RCTs investigating the effect of green tea or its catechin on liver enzymes including alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bilirubin were included. A total of 15 RCTs were included. The overall effect of green tea on liver enzymes was nonsignificant (ALT [Standardized mean difference (SMD)= -0.17, CI -0.42 to 0.08, p = .19], AST [SMD = -0.07, CI -0.43 to 0.29, p = .69], and ALP [SMD = -0.17, CI -0.45 to 0.1, p = .22]). However, subgroup analyses showed that green tea reduced the levels of liver enzymes in participants with nonalcoholic fatty liver disease (NAFLD) but in healthy subjects, a small significant increase in liver enzymes was observed. In conclusion, the results of this study suggest that the effect of green tea on liver enzymes is dependent on the health status of individuals. While a moderate reducing effect was observed in patients with NAFLD, in healthy subjects, a small increasing effect was found.