Mendelian randomization studies reveal the risk of inflammatory bowel disease onset associated with certain dietary factors

Abstract Aims: Dietary factors have been extensively explored as an environmental factor that can affect the onset of inflammatory bowel disease (IBD) in observational studies. However, the pres-ence of multiple unavoidable confounding factors has made direct and accurate elucidation of the conclusions difficult. We used Mendelian randomization (MR) analysis to explore the causal effect of dietary factors on the onset of IBD. Methods: We conducted MR analysis of the impact of diet on IBD by using inverse-variance–weighted, weighted median, weighted mode, MR-Egger, and MR-Robust Adjusted Profile Score methods with genome-wide association study data from the UK Biobank and the International IBD Genetics Consortium (IIBDGC). Results: MR studies showed that consuming mashed potatoes, sweet corn, baked beans, broad beans, whole-wheat pasta, cheese spreads, ham, and tinned tuna increased the risk of IBD. Consumption of plums, grapes, watercress, ham, sausages, fruit compotes, and artificially sweetened coffee increased the risk of Crohn’s disease. Additionally, consuming blue cheese, instant coffee, and chocolate cookies increased the risk of ulcerative colitis. Conclusion: Different fruits and vegetables showed variable effects on the onset of IBD and its subtypes. Baked goods, dairy products, processed foods, and instant coffee had path-ogenic effects on IBD, while meat consumption did not show a direct association with IBD onset. The findings imply that changes in dietary patterns, rather than simply eliminating specific foods, are required to prevent the occurrence of IBD.