title: Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  The effect of green tea catechins (GTCs) with or without caffeine on glycemic control is controversial.
  
  
  OBJECTIVE
  We aimed to identify and quantify the effects of GTCs or GTC-caffeine mixtures on glucose metabolism in adults.
  
  
  METHODS
  A comprehensive literature search was conducted to identify relevant trials of GTCs with or without caffeine on markers of glycemic control [fasting blood glucose (FBG), fasting blood insulin (FBI), glycated hemoglobin (Hb A1c), and homeostatic model assessment of insulin resistance (HOMA-IR)]. Weighted mean differences were calculated for net changes by using fixed-effects models. Prespecified subgroup analyses were performed to explore the influence of covariates on net changes in FBG and FBI concentrations.
  
  
  RESULTS
  Twenty-two eligible randomized controlled trials with 1584 subjects were identified. Pooled analyses showed that FBG (-1.48 mg/dL; 95% CI: -2.57, -0.40 mg/dL) decreased significantly with GTCs with or without caffeine, whereas FBI (0.04 μU/mL; 95% CI: -0.36, 0.45 μU/mL), Hb A1c (-0.04%; 95% CI: -0.15, 0.08%), and HOMA-IR (-0.05; 95% CI: -0.37, 0.26) did not. Subgroup analyses indicated that the glucose-lowering effect was apparent when the duration of follow-up was over a median of 12 wk. Overall, no significant heterogeneity was detected for FBG, FBI, Hb A1c, or HOMA-IR.
  
  
  CONCLUSIONS
  The meta-analysis showed that the administration of GTCs with or without caffeine resulted in a significant reduction in FBG. The limited data available on GTCs did not support a positive effect on FBI, Hb A1c, or HOMA-IR. Thus, more large and well-designed trials are needed in the future. This trial was registered at http://www.crd.york.ac.uk/prospero as CRD42012002139.
authors: Department of Cardiology and Key Laboratory for Clinical Cardiovascular Genetics & Sino-German Laboratory for Molecular Medicine, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
authors: Xin-Xin
authors: XX
authors: Zheng
authors: Yan-Lu
authors: YL
authors: Xu
authors: Shao-Hua
authors: SH
authors: Li
authors: Rutai
authors: R
authors: Hui
authors: Yong-Jian
authors: YJ
authors: Wu
authors: Xiao-Hong
authors: XH
authors: Huang
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology* / Q000627:therapeutic use; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000494:pharmacology* / Q000627:therapeutic use; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000188:drug therapy; D007004:Hypoglycemic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D008659:Metabolic Diseases / Q000097:blood*; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D001786:Blood Glucose; D002110:Caffeine; D002392:Catechin; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D007328:Insulin; D010936:Plant Extracts