Dietary fat intake and risk of type 2 diabetes in women

Background: The long-term relations between specific types of dietary fat a nd risk of type 2 diabetes remain unclear. Objective: Our objective was to examine the relations between dietary fat i ntakes and the risk of type 2 diabetes. Design: We prospectively followed 84204 women aged 34-59 y with no diabetes , cardiovascular disease, or cancer in 1980. Detailed dietary information w as assessed at baseline and updated in 1984, 1986, and 1990 by using valida ted questionnaires. Relative risks of type 2 diabetes were obtained from po oled logistic models adjusted for nondietary and dietary covariates. Results: During 14 y of follow-up, 2507 incident cases of type 2 diabetes w ere documented. Total fat intake, compared with equivalent energy intake fr om carbohydrates, was not associated with risk of type 2 diabetes; for a 5% increase in total energy from fat, the relative risk (RR) was 0.98 (95% CI : 0.94, 1.02). Intakes of saturated or monounsaturated fatty acids were als o not significantly associated with the risk of diabetes. However, for a 5% increase in energy from polyunsaturated fat, the RR was 0.63 (0.53, 0.76; P < 0.0001) and for a 2% increase in energy from trans fatty acids the RR w as 1.39 (1.15, 1.67; P = 0.0006). We estimated that replacing 2% of energy from trans fatty acids isoenergetically with polyunsaturated fat would lead to a 40% lower risk (RR: 0.60; 95% CI: 0.48, 0.75). Conclusions: These data suggest that total fat and saturated and monounsatu rated fatty acid intakes are not associated with risk of type 2 diabetes in women, but that trans fatty acids increase and polyunsaturated fatty acids reduce risk, Substituting nonhydrogenated polyunsaturated fatty acids for trans fatty acids would likely reduce the risk of type 2 diabetes substanti ally.