Background: Previous studies have examined the association between dairy fat intake and incident Type 2 Diabetes (T2D) by conducting analyses of dairy products stratified by fat content, although data linking dairy fat intake and incident T2D and their substitution for other nutrients are sparse.
Objective: The aim of this study is to evaluate the association between dairy fat intake and risk of T2D. We assessed the hypothesis that replacing calories from dairy fat for other animal fat or refined carbohydrates will result in modest increases in T2D risk.
Methods: We followed up 41,670 men in the Health Professionals Follow-Up Study (1986-2010), 84, 685 women in the Nurses’ Health Study (NHS; 1980-2012), and 90,325 women in the NHSII (1991-2011). Diet was assessed every 4 years with the use of validated food-frequency questionnaires, and other health and lifestyle covariates were collected biennially. Dairy fat contents were determined for dairy products and food items that contain dairy. Dairy fat intake from all relevant food items was summed to calculate total intake, which was expressed as percent of total energy. Incident T2D cases were identified by self-reports during follow-up and confirmed by a validated supplementary questionnaire. A time-dependent Cox proportional hazards regression was used to estimate the hazard ratio for dairy fat intake and T2D risk.
Results: During 4,661,518 years of follow-up, we documented 18,298 incident T2D cases. In multivariate models, a 5% increase in energy dairy fat was associated with a 2% risk increase in T2D (RR: 1.02; 95% CI: 1.00, 1.05). In isocaloric substitution models, the replacement of 5% of calories from dairy fat with the equivalent energy from other sources of animal fat or carbohydrate from refined grains was associated with an 7% [RR: 1.07; 95% CI: 1.04, 1.09], and a 7% [RR: 1.07; 95% CI: 1.04, 1.11] increased risk of T2D, respectively. Conversely, a 5% calorie substitution of carbohydrate from whole grains was associated with 7% lower risk of T2D [RR: 0.93; 95% CI: 0.89, 0.97].
Conclusions: In conclusion, dairy fat intake was modestly associated with a higher T2D risk. The replacement of dairy fat with carbohydrates from whole grains may decrease incident T2D risk. Further research is warranted to elucidate the role of other components in dairy products that may contribute to previously reported null associations with T2D.