Green tea, black tea consumption and risk of endometrial cancer: a systematic review and meta-analysis

Abstract

Background: Several studies have assessed the association between green and black tea consumption and the risk of endometrial cancer (EC) and have yielded inconsistent results.

Objective: The purpose of this meta-analysis is to systematically analyze the effect of green tea and black tea on EC risk.

Methods: PubMed, Embase, Cochrane Library and China Biological Medicine Database were searched through February 2, 2015 to identify studies that met pre-stated inclusion criteria. Overall relative risk (RR) was estimated based on the highest and lowest levels of green/black tea consumption. Dose-response relationships were evaluated with the data from categories of green/black tea intake in each study.

Results: For green tea, the summary RR indicated that the highest green tea consumption was associated with a reduced risk of EC (RR 0.78, 95 % CI 0.66-0.92). Furthermore, an increase in green tea consumption of one cup per day was associated with an 11 % decreased risk of developing EC. (RR 0.89, 95 % CI 0.84-0.94). For black tea, no statistically significant association was observed in the meta-analysis (highest versus non/lowest, RR 0.99, 95 % CI 0.79-1.23; increment of one cup/day, RR 0.99, 95 % CI 0.94-1.03). The power of the estimate of green tea and black tea with risk of EC was 84.33 and 5.07 %, respectively. The quality of evidence for the association between green and black tea with EC risk was moderate and very low, respectively.

Conclusions: The results from this meta-analysis indicate that green tea, but not black tea, may be related to a reduction of EC risk. Large population-based randomized controlled trials and large prospective cohort studies are required to obtain a definitive conclusion and determine the mechanisms underlying this association.

Keywords: Black tea; Dose–response relationship; Endometrial cancer; Green tea; Meta-analysis; Systematic review.