Older treatments for irritable bowel syndrome like peppermint oil safely help ease symptoms and should be used, a review suggests.

IBS is characterized by abdominal pain and discomfort accompanied by changes in bowel function, diarrhea, constipation or a combination of both, typically over months or years.

It is estimated to affect 13 to 20 per cent of Canadians, according to the Canadian Society of Intestinal Research.

In Canada and most western nations, IBS occurs more often in women. It can occur at any age, but often begins in adolescence or early adulthood.

The cause is unknown. According to the U.S. National Institutes of Health's website, risk factors may include:

• A low-fibre diet.
• Emotional stress.
• Use of laxatives.
• Having infectious diarrhea or other temporary bowel inflammation.

Some newer and more expensive drugs have been pulled from the market over safety concerns or fallen out of favour over lack of efficacy, the researchers said.

In Friday's issue of the British Medical Journal, Dr. Alexander Ford of the gastroenterology division at McMaster University in Hamilton and his colleagues concluded fibre, antispasmodics and peppermint oil were all effective therapies for IBS, based on their review of studies comparing the therapies with placebo or no treatment in more than 2, 500 adult patients with the disorder.

"This systematic review and meta-analysis has shown that fibre, antispasmodics and peppermint oil are all more effective than placebo in the treatment of irritable bowel syndrome. The number needed to treat to prevent one patient having persistent symptoms was 11 for fibre, five for antispasmodics and 2.5 for peppermint oil," the study's authors wrote.

None of the treatments had serious adverse effects.

Preferred form of fibre

National guidelines on the management of the condition should be updated to include the latest findings, the team said.

The beneficial effect of fibre seemed to be limited to ispaghula husk, a soluble form of fibre, rather than insoluble forms such as wheat bran, the researchers said.

When fibre supplements are required, British guidelines recommend soluble fibres such as ispaghula, the study's authors noted.

Hyoscine, which is extracted from the corkwood tree, was the most successful antispasmodic drug looked at and should be the first choice for doctors to prescribe, the team suggested.

Peppermint oil seemed to be the most promising based on the number needed to treat, but the figure was based on four trials involving fewer than 400 patients in total, Roger Jones, a professor in the department of general practice and primary care at King's College London, said in a journal commentary.

"It may be a little premature to follow the authors' recommendation that national guidelines should be updated to include therapeutic guidance on these agents, but the results should reawaken an interest in the pharmacotherapy of irritable bowel syndrome and stimulate further research."

The study did not identify which types of patients would benefit from each treatment. Since the treatments are safe and cheap, patients could test what works best for them, Jones said.