Circulating Biomarkers of Dairy Fat and Risk of Incident Diabetes Mellitus Among US Men and Women in Two Large Prospective Cohorts
Background—In prospective studies, relationship of self-reported consumption of dairy foods with risk of diabetes mellitus is inconsistent. Few studies have assessed dairy fat, using circulating biomarkers, and incident diabetes. We tested hypothesis that circulating fatty acid biomarkers of dairy fat, 15:0, 17:0, and t-16:1n-7, are associated with lower incident diabetes.
Methods and Results—Among 3,333 adults aged 30-75 years and free of prevalent diabetes at baseline, total plasma and erythrocyte fatty acids were measured in blood collected in 1989-90 (Nurses' Health Study) and 1993-94 (Health Professionals Follow-Up Study). Incident diabetes through 2010 was confirmed by validated supplementary questionnaire based on symptoms, diagnostic tests, and medications. Risk was assessed using Cox proportional hazards, with cohort findings combined by meta-analysis. During mean±SD follow-up of 15.2±5.6 years, 277 new cases of diabetes were diagnosed. In pooled multivariate analyses adjusting for demographics, metabolic risk-factors, lifestyle, diet, and other circulating fatty acids, individuals with higher plasma 15:0 had 44% lower risk of diabetes (quartiles 4 vs. 1, HR=0.56, 95%CI=0.37-0.86; P-trend=0.01); higher plasma 17:0, 43% lower risk (HR=0.57, 95%CI=0.39-0.83, P-trend=0.01); and higher t-16:1n-7, 52% lower risk (HR=0.48, 95%CI=0.33-0.70, P-trend <0.001). Findings were similar for erythrocyte 15:0, 17:0, and t-16:1n-7, although with broader CIs that only achieved statistical significance for 17:0.
Conclusions—In two prospective cohorts, higher plasma dairy fatty acid concentrations were associated with lower incident diabetes. Results were similar for erythrocyte 17:0. Our findings highlight need to better understand potential health effects of dairy fat; and dietary and metabolic determinants of these fatty acids.
- Received July 31, 2015.
- Revision received December 19, 2015.
- Accepted March 9, 2016.