Fiber in the Treatment and Maintenance of Inflammatory Bowel Disease: A Systematic Review of Randomized Controlled Trials

Background: Dietary fiber may favorably influence fermentation, gastrointestinal inflammation, and disease progression in Crohn's disease, ulcerative colitis (UC), and pouchitis and offer an attractive therapeutic addition to pharmacological treatment. This systematic review appraised data from randomized controlled trials of fiber in the management of inflammatory bowel disease. Methods: The review followed Cochrane and PRISMA recommendations. Seven electronic databases were searched along with hand searching and contacting experts. Inclusion criteria were randomized controlled trials of the effects of fiber on clinical endpoints (primarily disease activity for treatment or maintenance) or physiological outcomes in patients with inflammatory bowel disease. Results: In total, 23 randomized controlled trials fulfilled the inclusion criteria (UC, 10; Crohn's disease, 12; and pouchitis, 1) recruiting 1296 patients. In UC, 3/10 studies reported fiber supplementation to benefit disease outcomes. In Crohn's disease, 0/12 studies and in pouchitis 1/1 study reported a benefit on disease activity. Despite this, a number of studies reported favorable intragroup effects on physiological outcomes including fecal butyrate, fecal calprotectin, inflammatory cytokines, microbiota, and gastrointestinal symptom indices. Meta-analysis was not possible. Conclusions: There is limited weak evidence for the efficacy of fiber in improving disease outcomes in UC and pouchitis. The potential antiinflammatory role of fiber is intriguing and merits further investigation in adequately powered clinical trials. Excluding overt gastrointestinal obstruction, there was no evidence that fiber intake should be restricted in patients with inflammatory bowel disease.