Dietary inflammatory index and type 2 diabetes risk in a prospective cohort of 70,991 women followed for 20 years: the mediating role of BMI.

Aims/hypothesis: Diet is one of the main lifestyle-related factors that can modulate the inflammatory process. Surprisingly the dietary inflammatory index (DII) has been little investigated in relation to type 2 diabetes, and the role of BMI in this relationship is not well established. We studied this association and the role of BMI in the inflammatory process in a large population-based observational study.

Methods: A total of 70,991 women from the E3N (Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale) cohort study were followed for 20 years. Incident type 2 diabetes cases were identified using diabetes-specific questionnaires and drug reimbursement insurance databases, and 3292 incident cases were validated. The DII was derived from a validated food frequency questionnaire. Multivariable Cox regression models estimated HRs and 95% CIs between DII and incident type 2 diabetes. Interactions were tested between DII and BMI on incident type 2 diabetes and a mediation analysis of BMI was performed.

Results: Higher DII scores, corresponding to a higher anti-inflammatory potential of the diet, were associated with a lower risk of type 2 diabetes. Compared with the 1st quintile group, women from the 2nd quintile group (HR 0.85 [95% CI 0.77, 0.94]) up to the 5th quintile group (HR 0.77 [95% CI 0.69, 0.85]) had a lower risk of type 2 diabetes before adjustment for BMI. There was an interaction between DII and BMI on type 2 diabetes risk (p < 0.0001). The overall association was partly mediated by BMI (58%).

Conclusions/interpretation: Our findings suggest that a higher anti-inflammatory potential of the diet is associated with a lower risk of type 2 diabetes, and the association may be mediated by BMI. These results may improve our understanding of the mechanisms underlying the role of diet-related anti-inflammation in the pathogenesis of type 2 diabetes in women. Further studies are warranted to validate our results and evaluate whether the results are similar in men.