Peppermint cures what ails you -- or does it

Candy and ice cream come to mind. Some of us, dating ourselves, may start singing a little bit of "Peppermint Twist," the 1962 hit song by Joey Dee and the Starliters: "Well, they've got a new dance and it goes like this..."

But peppermint is also an age-old herbal medicine that has been used to treat a wide range of abdominal woes, from flatulence to stomach cancer to gallbladder disease.

Traditional medicine doesn't necessarily mean effective medicine, and doctors now have far better answers to many of the problems that peppermint supposedly treated or cured. But peppermint has fared a bit better than many herbal medicines in clinical trials.

Several studies have shown that peppermint oil seems to be fairly effective at relieving irritable bowel syndrome (IBS), a collection of symptoms that includes abdominal cramping and pain, bloating, constipation and diarrhea. In 2007, Italian investigators reported that 75 percent of the patients in their study who took peppermint oil capsules for four weeks had a major reduction in their IBS symptoms, compared with just 38 percent of those who took a placebo pill.

There are also findings -- admittedly from studies of iffy quality -- that topical application of peppermint oil helps relieve tension headaches and that a combination of peppermint and caraway oils can help with recurrent indigestion.

The oil that's extracted from the peppermint plant contains lots of compounds. Menthol is the most abundant and pharmacologically important.

Menthol is an ingredient in many conventional over-the-counter products, including cough lozenges and muscle pain ointments like Bengay. Menthol creates that familiar cooling sensation by stimulating nerves that sense cold (your mouth has some of these nerves, which is the reason products containing menthol "taste" cool); it also inhibits those that react to painful stimuli. The effect doesn't last long, but sometimes a brief reprieve or distraction from a cough or a muscle ache does wonders.

One explanation for how peppermint oil might help IBS sufferers is that the oil -- and perhaps especially the menthol -- blocks calcium channels, which has the effect of relaxing the "smooth'' muscles in the walls of the intestine.

Peppermint oil also relaxes the sphincter that keeps the contents of the stomach from backing up into your esophagus. That's why people troubled by heartburn (gastroesophageal reflux) are advised to avoid peppermint. It's also the reason peppermint oil is often sold these days in enteric-coated capsules designed to bypass the stomach and dissolve in the small intestine.

People do occasionally have bad reactions to menthol and peppermint. In 2007, Swedish doctors reported the case of a 44-year-old man who got a runny nose every time he brushed his teeth. Allergy tests showed he was allergic to the menthol in his toothpaste. Several years ago, Israeli doctors reported the case of a woman whose mouth and throat were chemically burned by the large amount of peppermint oil she took to treat a cold.