Dietary inflammatory and insulinemic potential and risk of type 2 diabetes: Results from three prospective U.S. cohort studies

OBJECTIVE To examine whether proinflammatory and hyperinsulinemic diets are associated with increased risk of type 2 diabetes. RESEARCH DESIGN AND METHODS We prospectively followed 74,767 women from the Nurses’ Health Study (1984– 2016), 90,786 women from the Nurses’ Health Study II (1989–2017), and 39,442 men from the Health Professionals Follow-up Study (1986–2016). Using repeated measures of food-frequency questionnaires, we calculated empirical dietary inflammatory pattern (EDIP) and empirical dietary index for hyperinsulinemia (EDIH) scores, which are food-based indices that characterize dietary inflammatory or insulinemic potential based on circulating biomarkers of inflammation or C-peptide. Diagnoses of type 2 diabetes were confirmed by validated supplementary questionnaires. RESULTS We documented 19,666 incident type 2 diabetes cases over 4.9 million person-years of follow-up. In the pooled multivariable-adjusted analyses, individuals in the highest EDIP or EDIH quintile had 3.11 times (95% CI 2.96–3.27) and 3.40 times (95% CI 3.23–3.58) higher type 2 diabetes risk, respectively, compared with those in the lowest quintile. Additional adjustment for BMI attenuated the associations (hazard ratio 1.95 [95% CI 1.85–2.05] for EDIP and hazard ratio 1.87 [95% CI 1.78–1.98] for EDIH), suggesting adiposity partly mediates the observed associations. Moreover, individuals in both highest EDIP and EDIH quintiles had 2.34 times higher type 2 diabetes risk (95% CI 2.17–2.52), compared with those in both lowest quintiles, after adjustment for BMI. CONCLUSIONS Higher dietary inflammatory and insulinemic potential were associated with increased type 2 diabetes incidence. Findings suggest that inflammation and hyperinsulinemia are potential mechanisms linking dietary patterns and type 2 diabetes development.