Associations of dairy intake with incident prediabetes or diabetes in middle-aged adults vary by both dairy type and glycemic status

Authors: HRUBY, ADELA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; MA, JIANTAO - Framingham Heart Study; ROGERS, GAIL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; MEIGS, JAMES - Massachusetts General Hospital; JACQUES, PAUL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2017
Publication Date: 8/2/2017
Citation: Hruby, A., Ma, J., Rogers, G., Meigs, J.B., Jacques, P.F. 2017. Associations of dairy intake with incident prediabetes or diabetes in middle-aged adults vary by both dairy type and glycemic status. Journal of Nutrition. https://doi.org/10.3945/jn.117.253401.

Interpretive Summary: Dairy intake in relation to chronic diseases, such as type 2 diabetes, has been a topic of interest for nutrition researchers for many years. However, the evidence about dairy's relationship with health and disease is inconsistent. Some studies have shown that certain types of dairy products, such as yogurt, may be beneficial for health, whereas other studies have indicated that some dairy products are either not beneficial or possibly even harmful. With this mixed evidence in mind, we undertook a study to see whether dairy consumption was related to risk of developing type 2 diabetes, a chronic disease which affects an estimated 1 in 3 Americans, in a group of 2,800 middle-aged Americans who had been tracked by researchers since the early 1990s. These individuals reported their dietary intake, including dairy intake, using a questionnaire up to 4 times over the course of up to 17 years of follow-up. Dairy categories included all products made from cow's milk, including whole and skim/low-fat milks, yogurt, cheese, cream, and butter. At the start of the study, about 1/3 of the population had prediabetes, a condition of elevated blood sugar that may precede diabetes. Of these participants, 1 in 5 (21%) went on to develop diabetes. In these individuals, high-fat dairy and cheese appeared to be beneficial: those with the highest intake had the lowest risk of developing diabetes. In the approximately 2/3 of the study population who did not have prediabetes at the start of the study, nearly half (48%) of them developed prediabetes during follow-up. In this group, dairy (including total, low-fat, and high-fat dairy) was associated with lower risk of developing prediabetes. In addition, moderate intake of milk (including total, low-fat/skim, and whole milk) and yogurt was associated with lower risk of prediabetes than were either high or low intakes of these dairy products. Researchers concluded that the type of dairy that is most beneficial in lowering risk of prediabetes or diabetes may depend on an individual's health status.

Technical Abstract: Background: Evidence regarding associations between dairy intake and type 2 diabetes (T2D) is inconsistent, and there are limited long-term data on the relationship between dairy intake and stages of glucose impairment, such as prediabetes. Our objective was to assess associations between milk-based product consumption, incident prediabetes, and progression to T2D in the Framingham Offspring cohort. Methods: Total dairy and milk-based product consumption was assessed by up to four food frequency questionnaires across an average 12 years of follow-up. Prediabetes and T2D were defined as the first occurrence of fasting plasma glucose >/= 5.6 to <7.0 mmol/L (>/=100 to <126 mg/dL), and >/=7.0 mmol/L (>/=126 mg/dL) or diabetes treatment, respectively. Proportional hazards models were developed to estimate risk of incident outcomes relative to categories of dairy and specific products in subsets of the cohort at risk of developing the outcomes. Spline regressions were used to examine potential non-linear relationships. Results: In 1,867 participants free of prediabetes at baseline, 902 (48%) developed prediabetes. Total, low-fat, and high-fat dairy were associated with 39%, 32%, and 25% lower risk of incident prediabetes, respectively, in highest versus lowest intake categories. Total, low-fat/skim, and whole milk, and yogurt were associated non-linearly with incident prediabetes, with moderate intakes being associated with the greatest relative risk reduction. Neither cheese nor cream/butter was associated with prediabetes. In 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 highest and lowest intake categories. Conclusion: Associations of dairy intake with incident prediabetes or diabetes varied by both dairy product/type and baseline glycemic status. Baseline glycemic status may partially underlie prior equivocal evidence regarding dairy's role in disease progression to diabetes.