Whole-grain intake and the risk of type 2 diabetes: a prospective study in men

Background: Certain dietary components may play a role in the prevention of type 2 diabetes. Objective: We examined prospectively the associations between whole- and refined-grain intake and the risk of type 2 diabetes in a large cohort of men. Design: Men from the Health Professionals Follow-up Study without a history of diabetes or cardiovascular disease in 1986 (n = 42 898) were followed for less than or equal to 12 y. Intakes of whole and refined grains, measured every 4 y by use of food-frequency questionnaires, were used to predict subsequent type 2 diabetes risk through multivariate analysis. Results: We ascertained 1197 cases of incident type 2 diabetes. After adjustment for age; physical activity; cigarette smoking; alcohol consumption; family history of diabetes; and fruit, vegetable, and energy intakes, the relative risk of type 2 diabetes was 0.58 (95% Cl: 0.47, 0.70; P for trend < 0.0001) comparing the highest with the lowest quintile of whole-grain intake. The association was moderately attenuated when additionally adjusted for body mass index (relative risk: 0.70; 95% Cl: 0.57, 0.85; P for trend = 0.0006). Intake of refined grains was not significantly associated with risk of type 2 diabetes. After further adjustment for magnesium intake, cereal fiber intake, and glycemic load, the association between whole grains and type 2 diabetes was attenuated and the trend no longer significant. Conclusions: In men, a diet high in whole grains is associated with a reduced risk of type 2 diabetes in men that may be mediated by cereal fiber. Efforts should be made to replace refined-grain with whole-grain foods.