Are all dietary fibers equal for patients with inflammatory bowel disease? A systematic review of randomized controlled trials

CONTEXT: Conflicting practice-based dietary recommendations are sometimes given to patients with inflammatory bowel disease (IBD); whereas intake of fiber should increase during remission, it should be avoided during relapse. Moreover, European countries set daily requirements of total fiber and do not specify any types. OBJECTIVE: This systematic review appraised data from randomized clinical trials (RCTs) of the types of fibers beneficial for patients in the treatment of IBD to guide dietary fiber advice. DATA SOURCES: The PubMED database was searched following PRISMA guidelines. DATA EXTRACTION: RCTs evaluating the effects of any type of fiber on clinical and physiological outcomes in patients with IBD were assessed. Quality assessment of the selected full-text articles was conducted using the Cochrane Risk of Bias Tool. DATA ANALYSIS: Eight studies were included reporting on 5 types of fibers. In 2 RCTs, germinated barley foodstuff (GBF) was shown to lower pro-inflammatory cytokines and clinical disease activity scores. Fructo-oligosaccharides (FOS) were demonstrated to lower IBD Questionnaire scores (lower well-being), in contrast to inulin, which decreased disease activity scores. An RCT could not find lower remission rates in the psyllium treatment group, while another RCT reported that administration led to less symptoms in patients. In RCTs, no concrete evidence was found that wheat bran improves disease course. CONCLUSIONS: Although the evidence is sparse, GBF and inulin seem propitious and merit further exploration. Evidence on wheat bran and psyllium is still too limited. Adequately powered long-term human RCTs with objective outcomes are needed to improve dietary advice on types of fiber in IBD.