Peppermint oil for irritable bowel syndrome: a critical review and metaanalysis.

OBJECTIVE: Peppermint oil is the major constituent of several over-the-counter remedies for symptoms of irritable bowel syndrome (IBS). As the etiology of IBS is not known and treatment is symptomatic, there is a ready market for such products. However, evidence to support their use is sparse. The aim of this study was to review the clinical trials of extracts of peppermint (Mentha X piperita L.) as a symptomatic treatment for IBS. METHODS: Computerized literature searches were performed to identify all randomized controlled trials of peppermint oil for IBS. Databases included Medline, Embase, Biosis, CISCOM, and the Cochrane Library. There were no restrictions on the language of publication. Data were extracted in a standardized, predefined fashion, independently by both authors. Five double blind, randomized, controlled trials were entered into a metaanalysis. RESULTS: Eight randomized, controlled trials were located. Collectively they indicate that peppermint oil could be efficacious for symptom relief in IBS. A metaanalysis of five placebo-controlled, double blind trials seems to support this notion. In view of the methodological flaws associated with most studies, no definitive judgment about efficacy can be given. CONCLUSION: The role of peppermint oil in the symptomatic treatment of IBS has so far not been established beyond reasonable doubt. Well designed and carefully executed studies are needed to clarify the issue.