Diet may contribute to inflammatory bowel disease (IBD) pathogenesis. In a previous French cohort, we found an association between high protein intake and increased risk of IBD. We aimed to investigate this relationship in the EPIC-IBD (European Prospective Investigation into Cancer and Nutrition – Inflammatory Bowel Diseases) cohort.
413 593 participants from 8 European countries were included. Dietary data were collected at baseline from validated food frequency questionnaires. Mean daily intake of nutrients was assessed using the EPIC nutrient database. To reduce bias in the estimation of relative risks, calibrated dietary data were obtained from the country and sex-specific calibration models for all participants. Associations between proteins (total, animal, and vegetable) or food sources of animal proteins, and IBD risk were estimated by Cox proportional hazard models.
After a mean follow-up of 16 years, 595 incident cases of IBD were identified, including 177 Crohn’s disease (CD) and 418 ulcerative colitis (UC) cases. No association was observed between total protein intake and IBD risk (adjusted HR for the fourth vs. the first quartile = 1.25; CI 95% = 0.89–1.77, P-trend = 0.33). There was a significant association between the calibrated continuous variable of animal protein intake and IBD risk (adjusted HR per 10 g/day: 1.10; 95% CI = 1.004–1.21) although no association was found for extreme quartiles (HR: 0.99; 95% CI = 0.73–1.34; P-trend = 0.91). There was no association between vegetable protein intake and IBD risk. There was an association between meat consumption and IBD risk (adjusted HR for the fourth vs.. the first quartile = 1.37; CI95% = 1.02–1.82, P-trend = 0.003) and between red meat consumption and IBD risk (adjusted HR for the fourth vs. the first quartile = 1.41; CI95% = 1.03–1.92, P-trend = 0.006). In separate analyses for CD and UC, there was an association between total meat and UC risk, and between red meat and UC risk. No association was found between food sources of animal proteins and CD risk.
Animal protein intake is associated with IBD risk in the EPIC-IBD cohort. Observed associations between meat consumption and IBD or UC risk, and between red meat consumption and IBD or UC risk deserve further investigation.