Probiotic products, which contain living microbes that aid digestion, may help relieve the symptoms of irritable bowel syndrome, according to Dr. Nourieh Hoveyda and colleagues from University of Oxford, UK.

Irritable bowel syndrome, or IBS, is a common disorder affecting up to 30 percent of the population by some estimates. Symptoms may include chronic abdominal pain, bloating, diarrhea, and constipation.

The causes of IBS are unclear and there has been debate whether it is mostly due to psychological factors or biological triggers, or perhaps a combination.

The evidence supporting the effectiveness of most treatments for IBS is weak, the authors of the current study explain in the journal BMC Gastroenterology. Hoveyda’s team conducted an analysis of published studies to assess whether probiotics alleviate symptoms in patients with IBS.

Treatment duration ranged from 4 weeks in six studies to 6 weeks in two studies, 8 weeks in three studies, and 6 months in two studies, plus one study of 20 weeks.

Combined data from the studies suggested a modest improvement in overall symptoms after a few weeks of treatment, the authors report.

As many as half of the trials reported significant improvements in abdominal pain, flatulence, bloating, and quality of life.

Only a few trials reported side effects connected to treatment, but there were few differences between probiotics and placebo groups in this area.

“In patients with IBS, probiotics showed a modest improvement in overall symptoms,” the researchers conclude. Interestingly, however, the two studies that contributed the most data to the analysis failed to show a beneficial effect with probiotics, they point out. This may relate to the type of microorganisms found in the probiotic products.

“Longer term trials are recommended as IBS is a condition that is chronic and usually intermittent,” the investigators add. “However, further research should focus on the type, optimal dose of probiotics, and the subgroups of patients who are likely to benefit the most.”

SOURCE: BMC Gastroenterology, February 16, 2009.