Coffee, caffeine, and risk of type 2 diabetes: a prospective cohort study in younger and middle-aged U.S. women

Diabetes Care. 2006 Feb;29(2):398-403. doi: 10.2337/diacare.29.02.06.dc05-1512.


Objective: High habitual coffee consumption has been associated with a lower risk of type 2 diabetes, but data on lower levels of consumption and on different types of coffee are sparse.

Research design and methods: This is a prospective cohort study including 88,259 U.S. women of the Nurses' Health Study II aged 26-46 years without history of diabetes at baseline. Consumption of coffee and other caffeine-containing foods and drinks was assessed in 1991, 1995, and 1999. We documented 1,263 incident cases of confirmed type 2 diabetes between 1991 and 2001.

Results: After adjustment for potential confounders, the relative risk of type 2 diabetes was 0.87 (95% CI 0.73-1.03) for one cup per day, 0.58 (0.49-0.68) for two to three cups per day, and 0.53 (0.41-0.68) for four or more cups per day compared with nondrinkers (P for trend <0.0001). Associations were similar for caffeinated (0.87 [0.83-0.91] for a one-cup increment per day) and decaffeinated (0.81 [0.73-0.90]) coffee and for filtered (0.86 [0.82-0.90]) and instant (0.83 [0.74-0.93]) coffee. Tea consumption was not substantially associated with risk of type 2 diabetes (0.88 [0.64-1.23] for four or more versus no cups per day; P for trend = 0.81).

Conclusions: These results suggest that moderate consumption of both caffeinated and decaffeinated coffee may lower risk of type 2 diabetes in younger and middle-aged women. Coffee constituents other than caffeine may affect the development of type 2 diabetes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Body Mass Index
  • Caffeine / administration & dosage*
  • Coffee*
  • Cohort Studies
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / prevention & control*
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Middle Aged
  • Multivariate Analysis
  • Proportional Hazards Models
  • Prospective Studies
  • Risk
  • Risk Factors
  • Smoking
  • Tea


  • Coffee
  • Tea
  • Caffeine