Q. Is it safe to take peppermint oil for stomachaches?

A. Peppermint oil can be a safe and effective treatment for digestive disorders as well as tension headaches. This is the conclusion of a review reported in the April 1 issue of American Family Physician.

Medicinal use of peppermint dates back to ancient Greece, where peppermint was used internally as a digestive aid. Most modern preparations of peppermint use its oil, which is extracted from the stem, leaves, and flowers of the plant. It can be taken as a capsule or in liquid form. Some folks make a tea from the leaves to soothe an upset stomach.

Several studies show peppermint oil to be mildly effective for the gas, bloating, and stomach pain caused by irritable bowel syndrome. Some evidence suggests peppermint oil combined with caraway oil may help relieve indigestion. Research has also shown that peppermint applied to the forehead and temples compares favorably with acetaminophen (the active ingredient in Tylenol) in reducing tension headache symptoms.

Menthol is the main active ingredient in peppermint oil. It is believed to relax the smooth muscles in the walls of the intestine.

It also relaxes the muscle that controls the opening between the stomach and the esophagus. This allows trapped air to be released. This muscle also helps keep the contents of the stomach from backing up into your esophagus.

If peppermint backed up into your esophagus, it would cause heartburn. This is why peppermint oil is often sold as enteric-coated capsules designed to dissolve in the intestine instead of the stomach.

Although peppermint oil is safe at the commonly recommended dosage, it may cause side effects at higher dosages. These effects include allergic reaction, heartburn, and nausea.

The recommended dosage for adults is 0.2 to 0.4 milliliters of peppermint oil three times daily in enteric-coated capsules. For children older than 8, 0.1 to 0.2 milliliters three times daily is recommended. For tea, use 1 tablespoon of leaves with 1 cup of hot water. Peppermint oil should not be given to infants or young children.

Peppermint oil can raise the blood levels of some blood pressure and cholesterol medications. It can also interfere with the action of antacids. Check with your pharmacist about possible interactions.

Folks with severe gastric reflux disease, hiatal hernia, or gallbladder disorders should not use peppermint oil.

Amy Tousman is a registered dietitian and certified diabetes educator with Nutrition Unlimited in Kailua. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.