Dietary flavonoid intakes and risk of type 2 diabetes in US men and women

Background: Data from mechanistic studies support a beneficial effect of specific flavonoids on insulin sensitivity. However, few studies have evaluated the relation between intakes of different flavonoid subclasses and type 2 diabetes. Objective: The objective was to evaluate whether dietary intakes of major flavonoid subclasses (ie, flavonols, flavones, flavanones, flavan-3-ols, and anthocyanins) are associated with the risk of type 2 diabetes in US adults. Design: We followed up a total of 70,359 women in the Nurses' Health Study (NHS; 1984-2008), 89,201 women in the NHS II (1991-2007), and 41,334 men in the Health Professionals Follow-Up Study (1986-2006) who were free of diabetes, cardiovascular disease, and cancer at baseline. Results: During 3,645,585 person-years of follow-up, we documented 12,611 incident cases of type 2 diabetes. Higher intakes of anthocyanins were significantly associated with a lower risk of type 2 diabetes (pooled HR for the 3 cohorts from a comparison of extreme quintiles: 0.85; 95% CI: 0.80, 0.91; P-trend < 0.001) after multivariate adjustment for age, BMI, and lifestyle and dietary factors. Consumption of anthocyanin-rich foods, particularly blueberries (pooled HR: 0.77 from a comparison of >= 2 servings/wk with <1 serving/mo; 95% CI: 0.68, 0.87; P-trend < 0.001) and apples/pears (pooled HR: 0.77 from a comparison of >= 5 servings/wk with <1 serving/mo; 95% CI: 0.65, 0.83; P-trend < 0.001), was also associated with a lower risk of type 2 diabetes. No significant associations were found for total flavonoid intake or other flavonoid subclasses. Conclusion: A higher consumption of anthocyanins and anthocyanin-rich fruit was associated with a lower risk of type 2 diabetes. Am J Clin Nutr 2012;95:925-33.