Peppermint essential oil – a natural remedy for irritable bowel syndrome

by Alix Williams

In a recent review, Shen & Nahas^[1] recommended the use of peppermint essential oil as part of an evidence-based approach to the treatment of patients with irritable bowel syndrome (IBS).

IBS is a common gastrointestinal disorder characterized by chronic abdominal pain or discomfort and altered bowel habits. The drugs currently available for the treatment of this condition are of limited benefit, however, and management tends to focus on diet and stress management, education and reassurance. As a result, many patients turn to complementary and alternative medicine therapies for the alleviation of their symptoms, but the efficacy of many of these therapies remains to be determined.

Peppermint essential oil (Mentha piperita Linnaeus) has traditionally been used to alleviate stomach problems, such as dyspepsia, heartburn, abdominal pain and nausea. However, the oil is an irritant to the stomach. To allow the oil to be taken internally, enteric-coated formulations have been developed, which delay release of the oil until it reaches the intestine. In the past few years, the results of a number of small studies have suggested that peppermint oil, administered as enteric-coated capsules, could be useful in the treatment of IBS.^[2–5] The aim of the review by Shen & Nahas was to investigate complementary and/or alternative therapies for IBS, for which safety and efficacy are supported by clinical evidence.

In this review, the authors obtained details of published clinical trials, systematic reviews and meta-analyses of a range of complementary and/or alternative therapies (including acupuncture, fibre, peppermint oil, herbal, traditional, yoga, massage, meditation, mind, relaxation, probiotics, hypnotherapy, psychotherapy, cognitive therapy or behavioural therapy) in patients with IBS from widely recognized clinical publication databases. I discuss here only the findings for peppermint oil.

The body of evidence for the efficacy of peppermint essential oil in the management of IBS symptoms reviewed by Shen & Nahas consisted of two meta-analyses,^[6,7] involving five and four randomized controlled trials of 2–4 weeks’ duration, respectively, and one, more recently published, randomized controlled trial of 4 weeks’ duration.^[8] Both meta-analyses favoured peppermint oil over placebo in the improvement of overall symptoms, with one meta-analysis reporting an odds ratio of 2.70 (95% confidence interval 1.56–4.76).^[6] Data from the other meta-analysis indicated that only three patients needed to be treated with 0.2–0.4 mL peppermint oil three times daily in order to show an improvement in symptoms.^[9] However, both meta-analyses included trials with a large degree of heterogeneity, which, the authors of this review recognized, limits the interpretability of these results.

In the more recent double-blind, placebo-controlled trial,^[8] 57 patients with IBS received peppermint oil in enteric-coated capsules or placebo for 4 weeks. After 4 weeks of therapy, significantly more patients receiving peppermint oil experienced a more than 50% reduction in their IBS symptoms (compared with baseline levels) than those taking placebo (75% versus 38%, P<0.01). Four weeks after stopping treatment, this reduction in symptoms still differed significantly from baseline in the patients who had received peppermint essential oil (P<0.01) (there was no difference in those who had received placebo).

Overall, Shen & Nahas concluded that the use of peppermint essential oil is supported by sufficient evidence to recommend its use in all patients with symptoms of IBS.^[1]

Shen & Nahas also noted that the administration of peppermint oil has been associated with the occasional report of perianal burning and nausea, and that the safety of the oil during pregnancy has not been demonstrated. Reports that peppermint tea may also be effective in the alleviation of symptoms of IBS are not currently supported by clinical trials.^[10]

One the basis of currently available evidence, the authors of this review concluded that the use of peppermint essential oil could be recommended as part of an evidence-based approach to the treatment of patients with IBS.

Sources

1. Shen YH, Nahas R. Complementary and alternative medicine for treatment of irritable bowel syndrome. Can Fam Physician 2009;55:143–8. Free copy available at: http://www.cfp.ca/cgi/content/full/55/2/143
2. Kline RM, Kline JJ, Di Palma J et al. Enteric-coated, pH-dependent peppermint oil capsules for the treatment of irritable bowel syndrome in children. J Pediatr 2001;138:125-8.
3. Liu JH, Chen GH, Yeh HZ et al. Enteric-coated peppermint oil capsules in the treatment of irritable bowel syndrome: a prospective, randomized trial. J Gastroenterol 1997;32:765-8.
4. Rees WD, Evans BK, Rhodes J. Treating irritable bowel syndrome with peppermint oil. Br Med J 1979;2(6194):835-6.
5. Dew MJ, Evans BK, Rhodes J. Peppermint oil for the irritable bowel syndrome: a multicentre trial. Br J Clin Pract 1984;38:394-8.
6. Spanier JA, Howden CW, Jones MP. A systematic review of alternative therapies in the irritable bowel syndrome. Arch Intern Med 2003;163:265-74.
7. Pittler MH, Ernst E. Peppermint oil for irritable bowel syndrome: a critical review and metaanalysis. Am J Gastroenterol 1998;93:1131-5.
8. Cappello G, Spezzaferro M, Grossi L et al. Peppermint oil (mintoil) in the treatment of irritable bowel syndrome: a prospective double blind placebo-controlled randomized trial. Dig Liver Dis 2007;39:530-6.
9. Birtwhistle RV. Irritable bowel syndrome: are complementary and alternative medicine treatments useful? Can Fam Physician 2009;55:126-7, 128-9.
10. McKay DL, Blumberg JB. A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.). Phytother Res 2006;20:619-33.