Peppermint
Mentha × piperita
Evidence: Moderate
Peppermint's primary active component, L-menthol, acts as a calcium channel blocker on intestinal smooth muscle. This leads to relaxation of gut muscles, effectively reducing spasms, bloating, and gas. It is well-documented for its effectiveness in alleviating symptoms of functional bowel disorders.
There are 2457 peer-reviewed scientific studies on this ingredient.
Selected Study:
Scarpellini E, Broeders B, Schol J, Santori P, Addarii M, Boccuto L, Carbone F, Abenavoli L, Tack J. The Use of Peppermint Oil in Gastroenterology. Curr Pharm Des. 2023;29(8):576-583. doi: 10.2174/1381612829666230328163449. PMID: 36994979.
Study summary:
Study type: This paper is a narrative review, not a new clinical trial. The authors searched major medical databases for original studies, meta-analyses, randomized controlled trials and case series on peppermint oil and selected functional gastrointestinal endpoints; therefore no participants were enrolled directly in this article, but the review draws on data from multiple human and pre-clinical studies.
Observed benefits: Across the literature surveyed, peppermint oil (and its chief constituent menthol) consistently shows smooth-muscle–relaxant and antispasmodic effects in the oesophagus, stomach, duodenum and colon. Clinically, these actions translate into symptomatic relief in functional dyspepsia and irritable-bowel syndrome, where several trials report reduced abdominal pain, bloating and post-prandial discomfort.
Mechanisms of action: Menthol appears to block calcium channels and activate the cold-sensing TRPM8 receptor on enteric smooth muscle, leading to transient relaxation; it may also modulate transient lower-esophageal-sphincter relaxations and dampen visceral afferent signaling to the central nervous system, thereby reducing hypersensitivity. Together these effects improve motility patterns and lower pain perception in functional gastrointestinal disorders.
Side effects: The review emphasises an “attractive safety profile” compared with conventional drugs for FGIDs. Reported adverse events are generally mild—transient heartburn or anal/perioral burning when non-enteric capsules are used—and serious events are rare.
Strength of evidence: Because this is a narrative (not systematic) review and many underlying trials are small or heterogeneous in dose and formulation, the overall evidence is moderate. Nevertheless, the convergence of pharmacological data, several placebo-controlled RCTs and long clinical experience lends reasonably strong support for peppermint oil as an adjunct or alternative therapy for functional dyspepsia, IBS and endoscopic spasm control, while larger standardized trials would help refine optimal dosing and confirm long-term safety.