Re Post by - Ray Williamson Posted on: 2014-04-28 12:00 AM 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.
High coffee consumption has been associated with better glucose tolerance and a substantially lower risk of type 2 diabetes in diverse populations in Europe, the U.S., and Japan (1–3). However, it remains unclear what coffee components may be responsible for the apparent beneficial effect of coffee on glucose metabolism. In rats, intakes of the coffee components chlorogenic acid (4, 5), quinic acid (6), trigonelline (7), and the lignan secoisolariciresinol (8) improved glucose metabolism. Short-term metabolic studies in humans have shown that caffeine can acutely lower insulin sensitivity (9–11). However, the long-term effects of caffeine intake on glucose metabolism are unknown, and beneficial effects on insulin sensitivity through increased expression of uncoupling proteins have also been suggested (12).
In most of the populations in which the relation between coffee consumption and type 2 diabetes has been studied, drip-filtered caffeinated coffee was the predominant type of coffee consumed (1). Data on decaffeinated coffee and various methods of coffee preparation in relation to risk of type 2 diabetes are sparse (3, 13, 14). In addition, in previous studies consumption of five or more cups of coffee per day was consistently associated with a lower risk of type 2 diabetes, but results for lower levels of consumption have been mixed (1). We therefore examined the consumption of different types of coffee and the intake of caffeine in relation to risk of type 2 diabetes in a large cohort of younger and middle-aged U.S. women.
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