The genus Mentha consists of many plants: peppermint, spearmint, watermint, Corsican field mint, and Japanese field mint, to name a few. Some other familiar herbs, such as marjoram, oregano, and lavender, are also in the mint family. Mint has been prized for as long as plants have been cultivated. It’s used in tea and in cooking worldwide, and to flavor chewing gums, candies, beverages, toothpastes, and other products.
Mint has a long history of being used medicinally, particularly for indigestion, and various mints are found in many dietary supplements marketed for digestive ailments. Mint oils are used in soothing baths, in essential oils used for aromatherapy, and in a variety of topical preparations promoted for a host of conditions, from headaches to joint pain. Is all this wishful thinking, or is science catching up to tradition?
Like other plants, various kinds of mint contain a wide array of bioactive compounds, including polyphenols, along with menthol, a powerful volatile oil that gives the leaves their distinctive scent and flavor. Peppermint (Mentha piperita), a hybrid of spearmint and watermint, has been most widely used medicinally and most often studied. Lab and animal studies indicate that some compounds in peppermint may have digestive benefits, as well as anti-cancer, antibacterial, antioxidant, and anti-inflammatory effects.
Mint research in humans
Some human studies of peppermint in enteric-coated capsule form suggest it can lessen the abdominal pain and other symptoms of irritable bowel syndrome (IBS). The Natural Medicines database (which evaluates research on alternative remedies) concluded that peppermint is “likely effective” for IBS. Among several mechanisms, it may activate a specific anti-pain process in the gut, thus countering pain-sensing nerve fibers. For instance, a study in Digestive Diseases and Sciences in 2016 compared an enteric-coated sustained-release peppermint oil supplement marketed specifically for IBS (IBgard) to a placebo in 72 people with the condition. Taken before all meals for four weeks, the supplement produced a significant reduction in IBS symptoms compared with the placebo. Some of the researchers were affiliated with the manufacturer of the supplement.
As for topical peppermint, an Egyptian study in Clinical, Cosmetic, and Investigational Dermatology in 2016 tested it in 50 people who had chronic itchy skin (pruritus) because of diabetes, kidney, or liver disease. Half applied peppermint oil blended in petroleum jelly, half plain petroleum jelly to their skin twice a day for two weeks. The peppermint group had significant improvements in symptoms. It’s thought that peppermint helps alleviate itching by affecting specific types of nerve receptors and fibers that may help reduce related pain sensation.
As for peppermint aromatherapy, a small study in the Journal of Holistic Nursing in 2012 tested it in women who had nausea after giving birth via a scheduled C-section. One group inhaled peppermint spirits (containing alcohol, which may also help counter nausea), one group inhaled a placebo (green-colored water, no scent), and one group took a standard anti-nausea medication. When nausea was evaluated two and five minutes after the interventions, those in the peppermint spirits group rated their nausea as significantly lower than the other two groups.
Potential mint detriments
Peppermint oil, consumed orally, can actually cause some of the digestive symptoms it’s supposed to help treat—notably nausea, belching, and heartburn—and worsen conditions such as reflux disease. Enteric-coated capsules reduce the likelihood of such symptoms by preventing the oil’s release in the stomach.
In addition, high doses of peppermint oil may interact with certain drugs, including some statins, itraconazole (Sporanox), triazolam (Halcion), and fexofenadine (Allegra). Mint teas and candies are unlikely to have side effects since they usually contain very little, if any, mint oil.
When studying peppermint and other mints, it’s often hard to separate possible biochemical actions from the psychologically soothing effects of their flavors and scents. Drinking a cup of mint tea or sucking on peppermint candy when your stomach is queasy may make you feel better, even if they contain little or no mint oil. If you have IBS that hasn’t responded to dietary or other lifestyle changes, you might want to try a supplement such as IBgard.
This article first appeared in the UC Berkeley Wellness Letter.
Also see Green Herbs for Fresh Flavor.