This meta-analysis was done to assess the association between tea consumption and endometrial cancer. A total of 7 studies with 2 cohort studies and 5 case-control studies met the criteria for inclusion in this meta-analysis. Green teas and black teas were included in the search. A total of 3487 cases and of endometrial cancer and 104,643 non cases appeared in the pooled analysis. The results suggested that tea consumption was statistically significantly associated with reduced risk of endometrial cancer. The combine relative risk for ever drinkers vs. non/lowest drinkers was 0.85. Compared with non/lowest drinkers, the relative risk was 0.88 for low to moderate drinkers and 0.75 for high drinkers. An increase in tea intake of 2 cups per day was associated with a 25% decreased risk of endometrial cancer. In analysis by subgroup, green tea consumption was significantly associated with decreased risk whereas an association with black tea was not observed.
Commentary: The mechanisms whereby tea reduces the risk of endometrial cancer are multifactorial. Tea, even green tea, contains caffeine, which lowers free estrogen levels. A number of antioxidants are in green tea, and these “catechins” affect carcinogenesis in numerous ways including inducing apoptosis (cell death), inhibiting estrogen-induced activation of endometrial cells and scavenging free radicals. Tea also contains phytoestrogens and can have an estrogen antagonist effect on endometrial cells. Tea consumption also modifies genetic polymorphisms relevant in the development of endometrial cancer.
Tang N, Hua L, Qiu Y, Zhou G, Ma J. Tea consumption and risk of endometrial cancer : a metaanalysis. Am J Obstet Gynecol 2009;201:605.e1-8