Associations of Dairy Intake with Incident Prediabetes or Diabetes in Middle-Aged Adults Vary by Both Dairy Type and Glycemic Status

Background: Inconsistent evidence describes the association between dietary intake of dairy and milk-based products and type 2 diabetes (T2D) risk. Objective: Our objective was to assess associations between consumption of milk-based products, incident prediabetes, and progression to T2D in the Framingham Heart Study Offspring Cohort. Methods: Total dairy and milk-based product consumption was assessed by <= 4 food-frequency questionnaires across a mean of 12 y of follow-up in 2809 participants [mean +/- SD age: 54.0 +/- 9.7 y; body mass index (in kg/m(2)): 27.1 +/- 4.7; 54% female]. Prediabetes was defined as the first occurrence of fasting plasma glucose >= 5.6 to <7.0 mmol/L (>= 100 to <126 mg/dL), and T2D was defined as the first occurrence of fasting plasma glucose >= 7.0 mmol/L (>= 126 mg/dL) or diabetes treatment. Proportional hazards models were used to estimate the risk of incident outcomes relative to dairy product intake in subsets of the cohort who were at risk of developing the outcomes. Spline regressions were used to examine potential nonlinear relations. Results: Of 1867 participants free of prediabetes at baseline, 902 (48%) developed prediabetes. Total, low-fat, and high-fat dairy consumptions were associated with a 39%, 32%, and 25% lower risk of incident prediabetes, respectively, in the highest compared with the lowest intakes (>= 14 compared with <4 servings/wk). Total, low-fat and skimmilk, whole-milk, and yogurt intakes were associated nonlinearly with incident prediabetes; moderate intake was associated with the greatest relative risk reduction. Neither cheese nor cream and butter was associated with prediabetes. Of 925 participants with prediabetes at baseline, 196 (21%) developed T2D. Only high-fat dairy and cheese showed evidence of dose-response, inverse associations with incident T2D, with 70% and 63% lower risk, respectively, of incident T2D between the highest and lowest intake categories (> 14 compared with <1 serving/wk for high-fat dairy, >= 4 compared with <1 serving/wk for cheese). Conclusion: Associations of dairy with incident prediabetes or diabetes varied both by dairy product and type and by baseline glycemic status in this middle-aged US population. Baseline glycemic status may partially underlie prior equivocal evidence regarding the role of dairy intake in diabetes.