Peppermint oil

Peppermint oil has antispasmodic properties, relaxing smooth muscle in the gut wall, which is why it is grouped with the antispasmodic drugs prescribed as first-line therapy PMID 35942669. Most products studied are enteric-coated or sustained-release capsules designed to pass through the stomach and open in the small intestine.

A 2022 meta-analysis of 10 randomised trials (1,030 patients) found peppermint oil more effective than placebo for global symptoms (number needed to treat 4) and for abdominal pain (number needed to treat 7), but adverse events were also more frequent and the authors rated the quality of evidence very low PMID 35942669. In a network meta-analysis of traditional first- and second-line IBS therapies, peppermint oil ranked first for global symptoms, with the caveat that only 13 of 51 included trials were at low risk of bias and that treatment duration in most trials was only 4 to 12 weeks PMID 31859183.

The mixed signal comes from the largest modern trial, the Dutch PERSUADE study (189 patients, 8 weeks): neither a small-intestinal-release nor an ileocolonic-release formulation met the FDA- or EMA-style primary endpoints for abdominal pain response or overall relief, although the small-intestinal-release product did improve secondary measures of pain, discomfort, and symptom severity, and mild adverse events were more common with both PMID 31470006. This is the study the later meta-analysis describes as casting doubt on peppermint oil’s role PMID 35942669.

Points clinicians commonly raise: heartburn and reflux are the usual complaints, which is one reason enteric coating matters PMID 33903147; the ACG lists it among options for global symptoms rather than for any single subtype PMID 33315591; and supplements are not standardised the way prescription drugs are, so products differ in dose and release.

Talk to a clinician before starting or stopping anything.