Effects of a high-fiber diet on symptoms of irritable bowel syndrome: a randomized clinical trial

OBJECTIVE: We investigated the effects of dietary fiber on symptoms of irritable bowel syndrome. METHODS: A single-blind randomized clinical trial was designed. Fifty-six subjects with irritable bowel syndrome were prospectively and randomly assigned to one of two groups: group 1 received a diet containing 10.4 g/d of fiber and group 2 received a diet containing 30.5 g/d of fiber. Patients' body weights, nutritional intakes as assessed with 3-d written food records, and symptom scores were assessed at baseline and at 3 mo. RESULTS: There were no dropouts during the study. Total energy intake and the distribution of macronutrients were not significantly different between groups. Total dietary fiber intake did not reach recommended levels in either group but was higher in group 2 than in group 1 (25.95 +/- 2.12 g/d versus 6.06 +/- 2.7 g/d, P < 0.05). Initial fiber intake did not differ significantly between groups. Pain scores, bowel scores, and general scores improved in both groups (from baseline to 3 mo), and no significant differences were detected between groups. CONCLUSIONS: A modest fiber intake in patients with irritable bowel syndrome relieved symptoms, but this therapeutic benefit of fiber may have been due to a placebo effect because the results were similar in the low-fiber group.