Probiotics Appear to Help Alleviate the Symptoms of Irritable Bowel Syndrome

Clinical trials have shown that probiotics are somewhat effective as therapy for irritable bowel syndrome, but many of the studies have been short-term and of poor quality.

The authors of “Probiotics in the Management of Irritable Bowel Syndrome and Inflammatory Bowel Disease,” published in Current Opinion in Gastroenterology, assert that “there is direct evidence that the pathogenesis of inflammatory bowel disease (IBD) involves the gastrointestinal microbiota and some evidence that the microbiota might also play a similar role in irritable bowel syndrome (IBS).” To investigate this connection, they reviewed the emerging evidence for the mechanisms and effectiveness of probiotics in the management of these disorders.

They report that the literature shows “Probiotics may be effective through their impact on the host gastrointestinal microbiota and promotion of mucosal immunoregulation.” Studies and clinical experience show that probiotics are considered to be well tolerated, although the authors note that “the quality of studies and health claims has been variable.”

Several short-term studies have demonstrated the effectiveness of probiotics in IBS, although the authors of this article believe that “recommendations should be made for specific strains and for specific symptoms.” Other clinical trials “have shown the benefits of a range of probiotics in pouchitis and in ulcerative colitis, although current evidence in Crohn's disease is less promising.”

Other recent studies that have found the use of probiotics as therapy for IBS to be beneficial include “Probiotics Use to Treat Irritable Bowel Syndrome,” published in Expert Opinion on Biological Therapy, which noted that “recent major meta-analyses” have revealed several benefits of probiotics in patients with IBS. The authors wrote that “inhibition of binding of pathogenic bacteria to intestinal epithelial cells, enhancing barrier function of intestinal epithelial, acidification of the colon, suppression of the growth of pathogens, modulation of immunity, inhibition of visceral hypersensitivity, alteration in mucosal response to stress, and improvement of bowel dysmotility” are possible mechanisms by which probiotics may act.

The authors of “Probiotics for the Treatment of Irritable Bowel Syndrome — Focus on Lactic Acid Bacteria,” published in Alimentary Pharmacology & Therapeutics, reviewed 42 clinical trials that studied the use of lactic acid bacteria (LAB) to treat IBS. They reported that 34 trials “found beneficial effects in at least one of the endpoints or symptoms examined.” However, they also reported that there was “tremendous variation in both the magnitude of effect and the choice of outcome under consideration” and that “numerous concerns have been expressed over deficits of trial design and execution relating to strain selection, optimum dosage, mode of action, safety and long-term tolerability.” Nonetheless, they concluded that there is “a strong rationale behind their use, solid evidence for strain specific efficacy and emerging data identifying potential mechanism of action for agents that have an enviable safety profile compared with pharmacological agents.”