title: 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.
authors.affiliation: Department of Science and Education, First People's Hospital of Changde City, No. 818, Renming road, Changde, 415003, Hunan, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Department of Oncology, First People's Hospital of Changde City, No. 818, Renming road, Changde, 415003, Hunan, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Oncology, Affiliated Hospital of Zunyi Medical University, Zunyi Medical University, No. 149, Dalian road, Zunyi, 563000, Guizhou, China.
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Zhou
authors.affiliation: Department of Acupuncture and Moxibustion, Liaoning University of Traditional Chinese Medicine, No. 79, Chongshan road, Shenyang, 110032, Liaoning, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Oncology, First People's Hospital of Changde City, No. 818, Renming road, Changde, 415003, Hunan, China. cdyymike@163.com.
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.affiliation: Department of Oncology, Affiliated Hospital of Zunyi Medical University, Zunyi Medical University, No. 149, Dalian road, Zunyi, 563000, Guizhou, China. mahuab@163.com.
authors.forename: Hu
authors.initials: H
authors.lastname: Ma
mesh_terms: D016889:Endometrial Neoplasms / Q000517:prevention & control*; D005260:Female; D006801:Humans; D010936:Plant Extracts / Q000008:administration & dosage*; D011446:Prospective Studies; D012306:Risk; D013662:Tea
chemical_list: D010936:Plant Extracts; D013662:Tea
keywords: Black tea; Dose–response relationship; Endometrial cancer; Green tea; Meta-analysis; Systematic review