Nutritional Management of Acute Severe Ulcerative Colitis: Current Evidence, Clinical Practice, and Future Directions

Acute severe ulcerative colitis (ASUC) is a medical emergency in which inflammation, bloody diarrhea, anorexia, protein loss, dehydration, treatment toxicity, and the prospect of urgent surgery can rapidly turn a previously well-nourished person into a nutritionally fragile patient. Nutrition is therefore part of active supportive care, but it is not a stand-alone induction therapy, and it must never delay intravenous corticosteroids, rescue therapy, infection assessment, venous thromboembolism prophylaxis, or timely colectomy. Current guidance favors early nutritional screening, continued oral intake when safe, enteral nutrition when oral intake is inadequate and the gut is usable, and parenteral nutrition only when enteral feeding is impossible, contraindicated, or insufficient. The evidence base remains uneven: most studies pool inflammatory bowel disease phenotypes, include non-severe disease, or report nutritional endpoints rather than colectomy, steroid response, infection, or functional recovery. Older trials support enteral nutrition as the safer default compared with parenteral nutrition when the gut functions, and a small randomized trial suggests that seven days of exclusive enteral nutrition alongside standard therapy may improve early steroid response, though this signal has not yet become a universal standard. A 2025 meta-analysis of adults with ulcerative colitis found exclusive enteral nutrition well tolerated but found no statistically reliable reduction in steroid failure or colectomy in acute severe disease. Refeeding risk, electrolyte depletion, anemia, vitamin D deficiency, zinc deficiency, and steroid-related bone risk all require deliberate monitoring. Probiotics, prebiotics, synbiotics, fecal microbiota approaches, curcumin, and other microbiome-directed strategies remain adjunctive and should not be presented as substitutes for evidence-based medical or surgical treatment. Beyond the acute admission, this review also considers dietitian-led care, body composition, nutrition-related inequity, perioperative preparation, and the transition from hospital to home. Future research should prioritize ASUC-specific populations, phenotype-specific trial design, and patient-centered outcomes—including nutritional adequacy, muscle function, infection, rescue therapy, colectomy, functional recovery, affordability, and postdischarge sustainability.