Increasing fiber intake (either through the consumption of fiber-rich foods or through the use of a bulk fiber agent) is a frequent recommendation given to patients suffering from irritable bowel syndrome (IBS) with constipation (IBS-C). The efficacy and the tolerability of fiber in this patient population, however, are controversial.
C. J. Bijkerk, MD, and colleagues recently conducted a systematic review of 17 studies published from 1966 to 2002 on the use of fiber in the treatment of patients with IBS, including patients with IBS-C. The results, which were published in the February 2004 issue of Alimentary Pharmacology and Therapeutics, showed that although patients with IBS-C may receive benefit from fiber therapy (relative risk, 1.56; 95% confidence interval [CI], 1.21?2.02), evidence that fiber is effective in relieving abdominal pain in these patients is not available. Also, soluble fiber and insoluble fiber were found to have different effects on IBS symptoms. Soluble fiber showed symptom improvement, whereas insoluble fiber showed no significant difference in symptoms compared with placebo (relative risk, 0.89; 95% CI, 0.72?1.11) and, in some cases, worsened the clinical outcome.
The authors concluded that the benefits of fiber in the treatment of patients with IBS and IBS-C are marginal.