For most people, peppermint conjures up holiday memories of red-and-white candy canes. Other familiar products that contain the herb include chewing gum, breath mints, toothpaste, and mouthwash. While these are its most recognized uses, peppermint has a much older medicinal tradition. It has long been known to help soothe stomach discomfort and other digestive upsets, and it is found in many if not most OTC formulations for treating GI problems.

Peppermint belongs to the family of herbs classed as “carminatives.” A carminative product is a medicinal drug with anti-spasmodic activity that is used to relieve cramps and gas buildup in the digestive tract.1

Background

Peppermint, or Mentha piperita, is sometimes referred to as brandy mint or lamb mint and grows naturally throughout much of Europe, Canada, and the United States.2 In this country, Washington ranks No. 1 among those states involved in the production of peppermint oil.3 Archeological evidence has been discovered placing peppermint’s therapeutic use at least as far back as 10,000 years, resulting in its sometimes being touted as “the world’s oldest medicine.”3

Mechanism of action

The precise reason that peppermint works to soothe gastric distress is unknown. However, as a class, carminative products are thought to function by reducing esophageal and gastric sphincter tone.2 This action is attributable to an antagonistic effect on calcium channel function.4


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The essential volatile oil of peppermint is composed mostly of menthol. Fresh peppermint leaves also contain as much vitamin C as an orange and more provitamin A than carrots.4

The portions of the plant from which the essential oil is extracted are the leaves and flowers.4 Peppermint and related spearmint plants grow quite prodigiously, with long, running roots that produce smooth branching stems from one to three feet in height. The leaves are one to two inches long, slender, and pointed, and they have slightly jagged edges.5 In favorable conditions, peppermint can take over a planting area, crowding out other small plants. The plant flowers from July to September with small purplish blossoms surrounding the ends of the stem in a blunt spike formation.5

In a 2007 study, Italian investigators reported that 75% of patients who took peppermint oil capsules for four weeks experienced a reduction in irritable bowel syndrome symptoms, compared with just 38% of those who took a placebo pill.3 In a meta-analysis including 175 patients in five trials, a statistically significant benefit of peppermint oil compared with placebo was noted in the symptoms of irritable bowel.6

In addition to GI indications, peppermint oil has also been used extensively in topical form (menthol) for muscle aches and pains, tension headaches, and pruritus. The mechanism of action largely involved counterirritation by producing a cooling, tingling effect, thus distracting the sensory processes from the feeling of pain.2

Both the parenteral and topical uses noted here are supported by evidence level “B,” indicating inconsistent or limited-quality patient-oriented evidence.6,7 Available scientific evidence does not support claims that peppermint oil is effective in treating side effects related to chemotherapy and radiation, according to the American Cancer Society. However, some data show that it may be effective in controlling nausea after surgery. Preliminary studies also suggest that direct contact with peppermint oil may be helpful in reducing spasms in the esophagus and intestines during endoscopies and other procedures. 7

Other health benefits are attributed to the peppermint plant’s high manganese content, as well as trace amounts of various other nutrients, such as fiber, iron, calcium, folate, potassium, magnesium, tryptophan, omega-3 fatty acids, riboflavin, and copper.

Safety, side effects

Side effects from full therapeutic dosing are common. Allergic reactions are often noted, as well as heartburn, perianal burning, blurred vision, nausea, and vomiting. Interstitial nephritis and acute renal failure have also been observed, though rarely. In addition, inhibition of the cytochrome P450 1A2 enzyme system is possible, which indicates the potential for some drug-herb interactions that could be clinically significant.6

Patients with hiatal hernia, severe gastroesophageal reflux, or gallbladder disorders and those who are pregnant or lactating should avoid full-dose peppermint oil.6

When peppermint is used topically, allergic dermatitis is the primary side effect, but this condition readily resolves with cessation of the product.

Dose, cost, and how supplied

The most common uses of peppermint are as a mild fresh or dried leaf for tea or as flavoring in other medications. These uses have very little potential for adverse reactions or outcomes since they equate to very low concentrations of actual peppermint oil.

The recommended dose for treatment of digestive disorders is 0.2-0.4 mL three times daily in enteric-coated capsules for adults and 0.1-0.2 mL three times daily for children.6 The enteric coating is very important as a protection against gastric irritation. The cost of most peppermint oil products averages $25-$30 per month.

Summary

Peppermint oil is a moderately effective and relatively safe alternative treatment for mild GI conditions. When used in small amounts, such as teas, it is temporarily soothing. The doses required for full therapeutic effect, however, can induce significant side effects. For topical conditions, the side-effect profile is significantly lower and the risk/benefit ratio is more positive.

Patients insisting on use of a natural remedy for gastric distress should be screened first to assure their condition is not something serious and then cautioned regarding the proper dosing, use, and potential for side effects of peppermint oil.

Ms. Sego is a staff clinician at the Veterans Administration Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.

References

1. Wikipedia. Carminative. Available at http://en.wikipedia.org /wiki/Carminative. Accessed May 6, 2008.

2. Skidmore RL. Mosby’s Handbook of Herbs & Natural Supplements. 3rd ed. St. Louis, Mo.: Elsevier Mosby; 2006:821.

3. Wikipedia. Peppermint. Available at http://en.wikipedia.org /wiki/Peppermint. Accessed May 6, 2008.

4. Fetrow CW, Avila JR. Professional’s Handbook of Complementary & Alternative Medicines. Springhouse, Pa.: Springhouse Corp; 1999:434.

5. Purdue University Center for New Crops & Plant Products. Available at www.hort.purdue.edu/newcrop/herbhunters/peppermint.html. Accessed May 6, 2008.

6. Kligler B, Chaudhary S. Peppermint oil. Am Fam Physician. 2007;75:1027-1030.

7. American Cancer Society. Available at www.cancer.org/docroot/ETO/content/ETO_5_. Accessed May 9, 2008.