What is the role of probiotics in IBS?
Probiotics are live organisms (bacteria) that are thought to exert a health benefit on the host. Probiotics exert their beneficial effects via several proposed mechanisms including modulation of bacterial flora, improvement of the barrier function of the epithelium, and alteration of the immune activity of the host. The mechanistic evidence for these hypotheses in IBS is still very limited.
Well-conducted large multicenter dose ranging studies are generally lacking. One of the few exceptions was performed in a primary care setting. Three hundred sixty-two women with IBS were randomized to three different doses of Bifidobacterium infantis 35624 or placebo. After 4 weeks of treatment, patients receiving B. infantis at a dose of 1 × 10 8 colony-forming units were significantly superior to placebo and the other bifidobacterium doses. There was also significant decrease in abdominal pain and discomfort, bloating, and distention, as well as bowel function.
In another study, 274 IBS-C patients were randomized to placebo or fermented milk yogurt (Activia, Dannon), which contains Bifidobacterium animalis (regularis) DN-173 010 for 6 weeks. In the treatment group, the HR-QOL discomfort score improved, as did bloating symptoms. There was an increase in stool frequency only in patients with fewer than three stools per week.
A metaanalysis published in 2010 included 16 randomized, controlled trials evaluating the efficacy, safety, and tolerability of probiotics in IBS patients and found that only B. infantis 35624 showed any significant benefit in the composite symptom score of IBS patients.