Changes in red meat consumption and subsequent risk of type 2 diabetes mellitus: three cohorts of US men and women.

IMPORTANCE: Red meat consumption has been consistently associated with an increased risk of type 2 diabetes mellitus (T2DM). However, whether changes in red meat intake are related to subsequent T2DM risk remains unknown.
OBJECTIVE: To evaluate the association between changes in red meat consumption during a 4-year period and subsequent 4-year risk of T2DM in US adults. DESIGN AND
SETTING: Three prospective cohort studies in US men and women. PARTICIPANTS: We followed up 26,357 men in the Health Professionals Follow-up Study (1986-2006), 48,709 women in the Nurses' Health Study (1986-2006), and 74,077 women in the Nurses' Health Study II (1991-2007). Diet was assessed by validated food frequency questionnaires and updated every 4 years. Time-dependent Cox proportional hazards regression models were used to calculate hazard ratios with adjustment for age, family history, race, marital status, initial red meat consumption, smoking status, and initial and changes in other lifestyle factors (physical activity, alcohol intake, total energy intake, and diet quality). Results across cohorts were pooled by an inverse variance-weighted, fixed-effect meta-analysis. MAIN OUTCOMES AND MEASURES: Incident T2DM cases validated by supplementary questionnaires.
RESULTS: During 1,965,824 person-years of follow-up, we documented 7540 incident T2DM cases. In the multivariate-adjusted models, increasing red meat intake during a 4-year interval was associated with an elevated risk of T2DM during the subsequent 4 years in each cohort (all P < .001 for trend). Compared with the reference group of no change in red meat intake, increasing red meat intake of more than 0.50 servings per day was associated with a 48% (pooled hazard ratio, 1.48; 95% CI, 1.37-1.59) elevated risk in the subsequent 4-year period, and the association was modestly attenuated after further adjustment for initial body mass index and concurrent weight gain (1.30; 95% CI, 1.21-1.41). Reducing red meat consumption by more than 0.50 servings per day from baseline to the first 4 years of follow-up was associated with a 14% (pooled hazard ratio, 0.86; 95% CI, 0.80-0.93) lower risk during the subsequent entire follow-up through 2006 or 2007. CONCLUSIONS AND RELEVANCE: Increasing red meat consumption over time is associated with an elevated subsequent risk of T2DM, and the association is partly mediated by body weight. Our results add further evidence that limiting red meat consumption over time confers benefits for T2DM prevention.