Inulin exacerbates disease severity in a mouse model of ulcerative colitis by causing osmotic diarrhea

Inulin, a soluble dietary fiber, is widely recognized for its gut health benefits; however, its role in the progression of ulcerative colitis remains unclear. In this study, we investigated the effects of inulin supplementation on colitis induced by administering dextran sodium sulfate (DSS) to BALB/c mice. Mice were fed diets containing 10% inulin or cellulose, followed by administration of 2% DSS in drinking water. Inulin-supplemented mice exhibited a higher disease activity index and more severe epithelial damage compared to cellulose-fed controls. Similar pathological features were observed in mice administered polyethylene glycol to induce osmotic diarrhea, suggesting that increased luminal osmotic pressure may exacerbate colitis. Notably, co-administration of polycarbophil calcium with inulin ameliorated clinical symptoms and attenuated tissue damage. These findings suggest that inulin may aggravate colitis, potentially through increased luminal osmotic pressure. Therefore, managing osmotic diarrhea may represent a therapeutic strategy to mitigate colitis symptoms associated with certain dietary fibers.