Ultra-Processed Foods in Inflammatory Bowel Disease and Irritable Bowel Syndrome: Epidemiology, the Intestinal Microenvironment and Implications for Dietary Management

Ultra-processed foods (UPFs) provide more than half of daily energy intake in several high-income countries, and their consumption is increasing worldwide. Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are chronic gastrointestinal conditions whose burden has grown alongside industrialized dietary patterns. Here, we summarize the epidemiological, mechanistic and clinical evidence linking UPF consumption to both conditions. Most prospective cohorts and meta-analyses associate higher UPF intake with incident Crohn’s disease, whereas associations with ulcerative colitis are weaker and inconsistent. In IBS, observational studies, including a large prospective cohort, suggest a modest, dose-dependent association with risk, although data are limited and the diagnostic criteria have recently changed with Rome V. Mechanistically, both disorders may converge on the intestinal microenvironment: in experimental models, emulsifiers alter microbial composition and metabolism, the mucus layer, epithelial barrier integrity and mucosal immune activation, and non-nutritive sweeteners alter microbial composition and epithelial barrier function, although human data are limited and causality has not been established. We also discuss IBS-like symptoms in quiescent IBD, dietary management in both conditions, and the main knowledge gaps, including exposure assessment, residual confounding and the need for adequately powered intervention trials.