Green tea and liver cancer risk: A meta-analysis of prospective cohort studies in Asian populations

Objectives The aim of this meta-analysis was to investigate whether an association existed between green tea consumption and the risk for liver cancer in prospective cohort studies in Asian populations. Methods Relevant studies were identified by searching PubMed, EMBASE, ISI Web of Science, and the Chinese Bio-medicine Database published before April 2015. Study-specific risk estimates for the highest versus non- or lowest and increment of daily cup of green tea consumption levels were combined based on fixed- or random-effects models. STATA 11.0 (Stata Corporation, College Station, TX, USA) software was used for statistical analysis. Results Nine prospective cohort articles involving 465,274 participants and 3694 cases of liver cancer from China, Japan, and Singapore were included. The summary relative risk (RR) indicated a significant association between the highest green tea consumption and reduced risk for liver cancer (summary RR, 0.88; 95% confidence interval [CI], 0.81-0.97). However, no statistically significant association was observed when analyzing daily consumption of one cup (summary RR, 0.97; 95% CI, 0.95-1.00). When stratified by sex, the protective effect of green tea consumption on risk for liver cancer was observed only in the group of women (summary RR, 0.78; 95% CI, 0.64-0.96), but not in men (summary RR, 0.89; 95% CI, 0.79-1.00). Conclusions The present analysis indicated the preventive effects of green tea intake on the risk for liver cancer in female Asian populations. However, additional studies are needed to make a convincing case for this association.