Effects of different types of milk consumption on Crohn's disease and the mediating effects of amino acids: A Mendelian randomization study

Dietary therapy is a common adjunctive treatment for Crohn's disease (CD). However, previous studies have presented conflicting views on whether dairy products should be included in dietary therapy. This controversy may be due to confounding factors. Thus, this study employed Mendelian randomization to investigate the effects of consumption of 6 different dairy products on CD. In addition, the mediating effects of 8 amino acids were explored. Three sensitivity analysis methods were employed to exclude horizontal pleiotropy and heterogeneity, ensuring the robustness of the conclusions. Ultimately, the study found that whole milk consumption can reduce the risk of CD (odds ratio = 0.504, 95% CI: 0.324-0.784). Mediation analysis demonstrated that serum isoleucine (mediation effect: -0.265, 95%CI: -0.533 to -0.068) and valine (mediation effect: -0.083, 95%CI: -0.198 to -0.002) are influenced by full-cream milk and modulate the onset of CD, with mediation effects accounting for 38.685% and 12.083%, respectively.