title: Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trial.
abstract: BACKGROUND
  Coffee consumption has been associated with a lower risk of type 2 diabetes in prospective cohort studies, but the underlying mechanisms remain unclear. The aim of this study was to evaluate the effects of regular and decaffeinated coffee on biological risk factors for type 2 diabetes.
  
  
  METHODS
  Randomized parallel-arm intervention conducted in 45 healthy overweight volunteers who were nonsmokers and regular coffee consumers. Participants were assigned to consumption of 5 cups (177 mL each) per day of instant caffeinated coffee, decaffeinated coffee, or no coffee (i.e., water) for 8 weeks.
  
  
  RESULTS
  Average age was 40 years and body mass index was 29.5 kg/m2. Compared with consuming no coffee, consumption of caffeinated coffee increased adiponectin (difference in change from baseline 1.4 μg/mL; 95% CI: 0.2, 2.7) and interleukin-6 (difference: 60%; 95% CI: 8, 138) concentrations and consumption of decaffeinated coffee decreased fetuin-A concentrations (difference: -20%; 95% CI: -35, -1). For measures of glucose tolerance, insulin sensitivity, and insulin secretion, no significant differences were found between treatment groups.
  
  
  CONCLUSIONS
  Although no changes in glycemia and/or insulin sensitivity were observed after 8 weeks of coffee consumption, improvements in adipocyte and liver function as indicated by changes in adiponectin and fetuin-A concentrations may contribute to beneficial metabolic effects of long-term coffee consumption.
  
  
  BACKGROUND
  clinicaltrials.gov NCT00305097.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, MA, USA. nwedick@hsph.harvard.edu
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Wedick
authors.forename: Aoife M
authors.initials: AM
authors.lastname: Brennan
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.forename: Frank B
authors.initials: FB
authors.lastname: Hu
authors.forename: Christos S
authors.initials: CS
authors.lastname: Mantzoros
authors.forename: Rob M
authors.initials: RM
authors.lastname: van Dam
mesh_terms: D052242:Adiponectin; D000328:Adult; D001628:Beverages; D001786:Blood Glucose; D002110:Caffeine / Q000009:adverse effects*; D003069:Coffee / Q000009:adverse effects*; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology*; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000503:physiopathology; D012307:Risk Factors; D060749:alpha-2-HS-Glycoprotein / Q000378:metabolism
chemical_list: D052242:Adiponectin; D001786:Blood Glucose; D003069:Coffee; D015850:Interleukin-6; D060749:alpha-2-HS-Glycoprotein; D002110:Caffeine