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Probiotics and Irritable Bowel Syndrome: Rationale, Putative Mechanisms, and Evidence of Clinical Efficacy

Camilleri, Michael MD

Journal of Clinical Gastroenterology: March 2006 - Volume 40 - Issue 3 - p 264-269

The irritable bowel syndrome (IBS) follows an acute, presumably infectious diarrheal illness in ∼15% of patients. There may be a persistent, mild inflammatory state with changes in mucosal function or structure. Changes in the colonic bacterial flora reported in IBS seem related to predominant bowel. Colonic bacteria normally metabolize nutrients with the formation of gas and short chain fatty acids. The latter may induce propulsive contractions and accelerate colonic transit or they may enhance fluid and sodium absorption in the colon. This review addresses the mechanisms, rationale and current evidence for the efficacy of probiotics, including Lactobacilli, Bifidobacteria, and VSL♯3, in the treatment of IBS. The mechanisms influenced by probiotics include immune function, motility, and the intraluminal milieu. Probiotics may suppress the low-grade inflammation associated with IBS or restore normal local immune function. Lactobacilli and Bifidobacteria subspecies are able to deconjugate and absorb bile acids, potentially reducing the colonic mucosal secretion of mucin and fluids that may contribute to functional diarrhea or IBS with diarrhea. Therapeutic trials show the potential benefit of Bifidobacteria or Lactobacilli species alone or in the specific probiotic combination, VSL♯3, on symptoms in IBS. Colonic transit was retarded in IBS patients treated with VSL♯3 without induction of significant changes in bowel function. In summary, probiotics are promising therapies in IBS.

Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN

Reprints: Michael Camilleri, MD, Mayo Clinic, Charlton 8-110, 200 First Street, S.W., Rochester, MN 55905 (e-mail:

Received for publication August 25, 2005; accepted November 16, 2005

Copyright © 2006 Wolters Kluwer Health, Inc. All rights reserved.