title: Tea consumption and risk of type 2 diabetes: a meta-analysis of cohort studies.
abstract: BACKGROUND
  Tea consumption has been extensively studied in relation to various diseases, several epidemiologic studies have been performed to investigate the association of tea consumption with type 2 diabetes; however, the results of these studies were not entirely consistent.
  
  
  OBJECTIVE
  To conduct a meta-analysis of studies that assessed the association of tea consumption and the risk of type 2 diabetes.
  
  
  METHODS
  We performed a systematic literature search through November 2008 in PUBMED, MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews. The search was limited to English-language studies. Studies were excluded if they were type 1 diabetes, animal studies. Nine cohort studies were identified by two authors, and summary relative risks (RRs) were calculated using a random-effects model.
  
  
  RESULTS
  We identified nine cohort studies, including 324,141 participants and 11,400 incident cases of type 2 diabetes with follow-up ranging from 5 to 18 years. The summary adjusted RR did not show that tea consumption was associated with a reduced type 2 diabetes risk (RR, 0.96; 95% confidence interval (CI), 0.92-1.01). Evidence from the results of our stratified analyses revealed that tea consumption > or =4 cups per day (RR, 0.8; 95% CI, 0.7-0.93) might play a role in the prevention of type 2 diabetes. However, no statistically significant association was observed for sex and the follow-up durations stratified between tea consumption and type 2 diabetes.
  
  
  CONCLUSIONS
  This meta-analysis indicates that tea consumption > or =4 cups per day may lower the risk of type 2 diabetes.
authors.affiliation: Department of Endocrinology, Drum Tower Clinical Medical College of Nanjing Medical University, Nanjing, Jiangsu Province, China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Jing
authors.forename: Guanjun
authors.initials: G
authors.lastname: Han
authors.forename: Yun
authors.initials: Y
authors.lastname: Hu
authors.forename: Yan
authors.initials: Y
authors.lastname: Bi
authors.forename: Lirong
authors.initials: L
authors.lastname: Li
authors.forename: Dalong
authors.initials: D
authors.lastname: Zhu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013662:Tea
chemical_list: D013662:Tea