Zinc intake and risk of Crohn's disease and ulcerative colitis: a prospective cohort study

Background: Diet plays a role in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). Dietary zinc may influence risk of disease through effects on autophagy, innate and adaptive immune response and maintenance of the intestinal barrier. Methods: We analysed data from 170 776 women from the Nurses Health Study I and Nurses Health Study II, who were followed for 26 years. Zinc intake was assessed using semi-quantitative food frequency questionnaires administered every 4 years. Incident CD and UC were ascertained by medical record review. Cox proportional hazards models adjusting for potential confounders determined the independent association between zinc intake and incident disease. Results: Over 3 317 550 person-years (p-y) of follow-up, we identified 269 incident cases of CD and 338 incident cases of UC. Zinc intake ranged from 9 mg/day in the lowest quintile to 27 mg/day in the highest quintile. Compared with women with the lowest quintile of intake, the multivariate hazard ratios (HR) for CD were 0.92 [95% confidence interval (CI), 0.65 - 1.29) for women in the second quintile of intake, 0.60 (95% CI, 0.40 - 0.89) for the third quintile, 0.57 (95% CI, 0.38 - 0.86) for fourth quintile and 0.74 (95% CI, 0.50 - 1.10) for the highest quintile (P-trend = 0.003). The association was stronger for dietary zinc (HR 0.63, 95% CI, 0.43 - 0.93, comparing extreme quintiles) than for zinc intake from supplements. Neither dietary nor supplemental zinc modified risk of UC. Conclusions: In two large prospective cohorts of women, intake of zinc was inversely associated with risk of CD but not UC.