Hamed Khalili1, Punyanganie S de Silva, Ashwin N Ananthakrishnan, Paul Lochhead, Amit Joshi, John J Garber, James R Richter, Jenny Sauk, Andrew T Chan. 1. *Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts; †Clinical and Translation Epidemiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts; ‡Division of Gastroenterology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; §Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and ‖The Broad Institute, Cambridge, Massachusetts.
Abstract
BACKGROUND: Dietary iron and heme, likely through their effect on gut commensal bacteria and colonic barrier function, have been shown to modulate colonic inflammation in animal models of colitis. Nonetheless, the link between dietary total and heme iron and risk of Crohn's disease (CD) and ulcerative colitis (UC) has not been previously explored. METHODS: We conducted a prospective cohort study of 165,331 U.S. women enrolled in the Nurses' Health Study and Nurses' Health Study II. Dietary information was collected using a validated food frequency questionnaire at baseline (1984) and updated every 2 to 4 years. Self-reported CD and UC diagnoses were confirmed through medical records review. We used Cox proportional hazard models to calculate hazard ratios and 95% confidence intervals while adjusting for potential confounders. In a case-control study nested within these cohorts, we evaluated the interaction between single-nucleotide polymorphisms associated with genome-wide susceptibility to CD and UC and dietary total and heme iron intake on risk of CD and UC using logistic regression modeling. RESULTS: Through 2011, over 3,038,049 person-years of follow-up, we documented 261 incident cases of CD and 321 incident cases of UC. Dietary heme iron was nonsignificantly associated with increased risk of UC (Ptrend = 0.12). This association seemed to be modified by the UC susceptibility locus, rs1801274, a coding variant in the FcγRIIA gene (Pinteraction = 7.00E-05). In contrast, there was no association between dietary heme iron and risk of CD (Ptrend = 0.67). We also did not observe an association between total dietary intake of iron and risk of CD or UC (All Ptrend > 0.35). CONCLUSION: In 2 large prospective cohort studies, dietary total and heme iron were not associated with risk of CD or UC. Our suggestive finding that the association between dietary heme iron intake and risk of UC may be modified by a coding variant in FcγRIIA gene warrants additional investigation.
BACKGROUND: Dietary iron and heme, likely through their effect on gut commensal bacteria and colonic barrier function, have been shown to modulate colonic inflammation in animal models of colitis. Nonetheless, the link between dietary total and hemeiron and risk of Crohn's disease (CD) and ulcerative colitis (UC) has not been previously explored. METHODS: We conducted a prospective cohort study of 165,331 U.S. women enrolled in the Nurses' Health Study and Nurses' Health Study II. Dietary information was collected using a validated food frequency questionnaire at baseline (1984) and updated every 2 to 4 years. Self-reported CD and UC diagnoses were confirmed through medical records review. We used Cox proportional hazard models to calculate hazard ratios and 95% confidence intervals while adjusting for potential confounders. In a case-control study nested within these cohorts, we evaluated the interaction between single-nucleotide polymorphisms associated with genome-wide susceptibility to CD and UC and dietary total and hemeiron intake on risk of CD and UC using logistic regression modeling. RESULTS: Through 2011, over 3,038,049 person-years of follow-up, we documented 261 incident cases of CD and 321 incident cases of UC. Dietary hemeiron was nonsignificantly associated with increased risk of UC (Ptrend = 0.12). This association seemed to be modified by the UC susceptibility locus, rs1801274, a coding variant in the FcγRIIA gene (Pinteraction = 7.00E-05). In contrast, there was no association between dietary hemeiron and risk of CD (Ptrend = 0.67). We also did not observe an association between total dietary intake of iron and risk of CD or UC (All Ptrend > 0.35). CONCLUSION: In 2 large prospective cohort studies, dietary total and hemeiron were not associated with risk of CD or UC. Our suggestive finding that the association between dietary hemeiron intake and risk of UC may be modified by a coding variant in FcγRIIA gene warrants additional investigation.
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