Fiber and peppermint oil are both effective therapies for irritable bowel syndrome (IBS) and should become first-line treatments, according to a new study. National guidelines on the management of IBS should be updated in light of this evidence, according to the study’s authors.

IBS causes abdominal pain and an irregular bowel habit, and could affects as much as a fifth of the population. The exact cause of IBS is unknown, so it is difficult to treat.

Researchers performed a systematic review and meta-analysis of randomized trials comparing fiber, peppermint oil, and antispasmodics with a placebo or no treatment in more than 2500 adult patients with IBS. All of them were found to be effective. Peppermint oil seemed to be the most effective treatment of the three.