Background & Aims: Inflammation is a potential mechanism through which diet modulates the onset of inflammatory bowel disease. We analyzed data from 3 large prospective cohorts to determine the effects of dietary inflammatory potential on the risk of developing Crohn's disease (CD) and ulcerative colitis (UC).

Methods: We collected data from 166,903 women and 41,931 men in the Nurses' Health Study (1984-2014), Nurses' Health Study II (1991-2015), and Health Professionals Follow-up Study (1986-2012). Empirical dietary inflammatory pattern (EDIP) scores were calculated based on the weighted sums of 18 food groups obtained via food frequency questionnaires. Self-reported CD and UC were confirmed by medical record review. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).

Results: We documented 328 cases of CD and 428 cases of UC over 4,949,938 person-years of follow-up. The median age at IBD diagnosis was 55 years (range 29-85 years). Compared with participants in the lowest quartile of cumulative average EDIP score, those in the highest quartile (highest dietary inflammatory potential) had a 51% higher risk of CD (HR 1.51; 95% CI 1.10-2.07; Ptrend = .01). Compared with participants with persistently low EDIP scores (at 2 time points, separated by 8 years), those with a shift from a low to high inflammatory potential of diet or persistently consumed a proinflammatory diet had greater risk of CD (HR 2.05; 95% CI 1.10-3.79 and HR 1.77; 95% CI 1.10-2.84). In contrast, dietary inflammatory potential was not associated with the risk of developing UC (Ptrend = .62).

Conclusions: In an analysis of 3 large prospective cohorts, we found dietary patterns with high inflammatory potential to be associated with increased risk of CD but not UC.