Peppermint is the leaf of a hybrid between spearmint (M. spicata) and watermint (M. aquatica). Native to Europe, it was first grown commercially in England about 1750. Today peppermint is produced commercially in Indiana, Wisconsin, Oregon, Washington, and Idaho.
Peppermint is first mentioned in the medical literature of the early 1700s. Samuel Stern described it in 1801 in The American Herbal: "It is a stimulant. It restores the functions of the stomach, promotes digestion, stops vomiting, cures the hiccups, flatulent colic, hysterical depressions, and other like complaints." Peppermint leaf tea has been traditionally used for indigestion, nausea, colds, headache, and cramps.
Recent research on peppermint has examined its essential oil rather than the leaf Peppermint oil, which comprises about 0.3 to 0.4 percent of the leaf's weight, has been shown to be antibacterial and antiviral, and it reduces muscle spasms. The primary component is menthol at 30-48 percent of the oil.
A 1979 clinical trial studied use of the oil (in coated capsules so that they dissolve in the intestinal tract rather than the stomach) in eighteen patients with irritable bowel syndrome (colicky abdominal pain and a feeling of distention). One to two capsules were given three times a day, depending upon severity of symptoms, for as long as three weeks. Patients who took the peppermint oil capsules experienced more relief than those who received the placebo. Other researchers confirmed that for peppermint oil to be effective in treating irritable bowel syndrome, the oil had to reach the colon without first being digested in the stomach.
Inhalation of the vigor of peppermint essential oil is thought to help ease congestion from colds and improve breathing by stimulating cold receptors in the respiratory tract. In its 1990 review of overthe-counter drugs, the U. S. Food and Drug Administration dropped the oil from its former status as a nonprescription drug in the United States, most likely because no data on its safety or effectiveness were submitted by the industry. It is still widely used and approved in Europe.
Dried cut-and-sifted leaf, capsules, and tinctures are available in the American market, along with coated capsules of peppermint oil.
Coated peppermint oil capsules may sometimes open in the stomach, causing heartburn and relaxation of throat muscles. They should not be used by anyone diagnosed with an absence of hydrochloric acid in gastric juices (achlorhydria). Peppermint oil should not be applied directly to mucous membranes, such as the nostrils, especially of infants and children. The leaf and oil should not be used by anyone with gallbladder or bile duct obstruction, inflammation, or related conditions.