Overview
Peppermint is a relative of numerous wild mint plants, deliberately bred in the late seventeenth century in England to become the delightful-tasting plant so well known today. It is widely used as a beverage tea and as a flavoring or scent in a wide variety of products.
Peppermint tea also has a long history of medicinal use, primarily as a digestive aid and for the symptomatic treatment of cough, colds, and fever. Peppermint oil is used for chest congestion (Vicks VapoRub), as a local anesthetic (Solarcaine, Ben-Gay), and most recently in the treatment of irritable bowel disease, also known as spastic colon.
Therapeutic Dosages
The proper dosage of peppermint oil when treating irritable bowel
syndrome is 0.2 to 0.4 milliliter (ml) three times a day of
an enteric-coated capsule. The capsule has to be enteric-coated to prevent stomach
distress. When used in herbal combinations to treat stomach problems, peppermint
oil is taken at lower doses, and it is not enteric-coated.
Therapeutic Uses
Peppermint oil has shown promise for a variety of conditions that involve spasm of the intestinal tract. Most studies have involved irritable bowel syndrome (IBS), for which peppermint oil has shown considerable promise. Peppermint oil may also be helpful for reducing the pain caused by medical examinations of the colon and stomach, as well for decreasing the intestinal gas pain that frequently follows surgery. Peppermint oil may also be helpful for dyspepsia (a condition that is similar to IBS but involves the stomach instead of the intestines). Weak evidence, far too preliminary to rely upon, hints that peppermint oil might help dissolve gallstones.
Peppermint oil is also used in another way: as aromatherapy.
This means that it is inhaled, often by adding it to a humidifier. Weak evidence
hints that inhaled peppermint oil might be helpful for relief of mucus congestion
of the lungs and sinuses. Even weaker evidence hints that inhaled peppermint oil
might relieve postsurgical nausea. Similarly weak evidence hints that peppermint
oil, applied to the forehead, might relieve tension headaches. Finally, a study
performed in Iran reported that applying peppermint water (essentially, lukewarm
peppermint tea) directly to the nipples helped prevent dryness and cracking caused
by breast-feeding.
Scientific Evidence
Irritable bowel syndrome (IBS). There have been numerous studies of peppermint oil for IBS. In one of the larger studies, 110 people with IBS were given either enteric-coated peppermint oil (187 milligrams, or mg) or a placebo three to four times daily, fifteen to thirty minutes before meals, for four weeks. The results showed significant improvements in abdominal pain, bloating, stool frequency, and flatulence. In a similar study, people who took peppermint oil capsules for eight weeks also had less abdominal pain and discomfort compared with the placebo group.
Not all of these studies have shown that peppermint oil is beneficial, though. It has been suggested that these inconsistencies were caused by the accidental inclusion of people who had conditions unrelated to IBS that cause similar symptoms. Presumably, peppermint oil may be less effective for these problems. A study published in 2007 pretested participants for lactose intolerance and celiac disease, the two conditions most easily mistaken for IBS. A total of fifty-seven people with IBS symptoms and no evidence of the other two problems were enrolled in the study. Over a period of four weeks, participants were given either a placebo or peppermint oil. At the end of the study period, 75 percent of the patients in the peppermint oil group showed a marked reduction of IBS symptoms (defined, for this purpose, as a reduction of IBS symptom scores by more than 50 percent). In comparison, only 38 percent of the participants given a placebo showed an improvement of this magnitude, and this difference was statistically significant.
Other forms of spasm in the digestive tract. A barium enema
involves introducing a solution containing the metal barium into the lower
intestines. It commonly causes intestinal pain and spasm. A double-blind study of
141 individuals found that adding peppermint oil to the barium reduced the
severity of intestinal spasm that occurred. Benefits were also seen in a large
study conducted by different researchers. Another study found that peppermint oil
reduced spasm in the stomach during a procedure called upper endoscopy. One study
found that use of peppermint oil after C-section surgery reduced discomfort caused
by intestinal gas.
Dyspepsia (minor indigestion). Peppermint oil is often used in
combination with other essential oils to treat minor
indigestion. For example, a double-blind, placebo-controlled study including
thirty-nine individuals found that an enteric-coated peppermint-caraway oil
combination taken three times daily for four weeks significantly reduced dyspepsia
pain compared with placebo. Of the treatment group, 63.2 percent was free of pain
after four weeks, compared with 25 percent of the placebo group.
Results from a double-blind, comparative study including 118 individuals suggest that the combination of peppermint and caraway oil is comparably effective to the no-longer-available drug cisapride. After four weeks, the herbal combination reduced dyspepsia pain by 69.7 percent, whereas the conventional treatment reduced pain by 70.2 percent.
A preparation of peppermint, caraway, fennel, and wormwood oils was compared with the drug metoclopramide in another double-blind study enrolling sixty individuals. After seven days, 43.3 percent of the treatment group was pain free compared with 13.3 percent of the metoclopramide group. Metoclopramide works by reducing gastric emptying time (in other words, speeding the passage of food from the stomach into the intestines). Interestingly, some evidence suggests that peppermint oil may have the same effect.
Safety Issues
At the normal dosage, enteric-coated peppermint oil is believed to be reasonably safe in healthy adults. However, case reports and one study in rats hint that peppermint might reduce male fertility. The species Mentha spicata may be more problematic in this regard than the more common M. piperita. Excessive doses of peppermint oil can be toxic, causing kidney failure and even death. Very high intake of peppermint oil can also cause nausea, loss of appetite, heart problems, loss of balance, and other nervous system problems. Safety in young children, pregnant or nursing women, and those with severe liver or kidney disease has not been established. In particular, peppermint can cause jaundice in newborn babies, so it should not be used for colic.
Use of peppermint oil may increase levels of the drug cyclosporine
in the body. Persons taking cyclosporine who wish to take peppermint oil should
notify their physician in advance, so that their blood levels of cyclosporine can
be monitored and their dose adjusted if necessary. Conversely, those persons
already taking both peppermint oil and cyclosporine should not stop taking the
peppermint without informing their physicians. Ceasing to take peppermint may
cause cyclosporine levels to fall.
Important Interactions
Those taking cyclosporine should not use peppermint oil (or stop using it) except in consultation with a physician.
Bibliography
Cappello, G., et al. “Peppermint Oil (Mintoil) in the Treatment of Irritable Bowel Syndrome.” Digestive Liver Disease 39, no. 6 (2007): 530-536.
Ford, A. C., et al. “Effect of Fibre, Antispasmodics, and Peppermint Oil in the Treatment of Irritable Bowel Syndrome.” British Medical Journal 337 (2008) a2313.
Inamori, M., et al. “Early Effects of Peppermint Oil on Gastric Emptying: A Crossover Study Using a Continuous Real-Time (13)c Breath Test (BreathID System).” Journal of Gastroenterology 42 (2007): 539-542.
Merat, S., et al. “The Effect of Enteric-Coated, Delayed-Release Peppermint Oil on Irritable Bowel Syndrome.” Digestive Diseases and Sciences 55, no. 5 (2010): 1385-1390.
Sayyah, Melli M., et al. “Effect of Peppermint Water on Prevention of Nipple Cracks in Lactating Primiparous Women.” International Breastfeeding Journal 2 (2007): 7.
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