Two ingredients in parsley — myristicin and apiol — help increase urine volume by promoting blood flow to the kidneys. This helps relieve urinary-tract inflammation caused by infections. Additional urine also helps you pass kidney stones.

Commission E, the German agency charged with regulating herbal medicines, has approved parsley for these uses. The approval was based on parsley's long history of use in traditional medicine, on studies of the active ingredients, and studies of effectiveness in animals.

Parsley also is used as a breath freshener. This may be because of its chlorophyll content. Chlorophyll is used in many breath-freshening products, but there is no evidence that it produces a long-lasting effect.

It is doubtful that parsley could get rid of strong odors caused by garlic or onions. This is because garlic and onion odors do not just stay in the mouth; they enter the bloodstream and the lungs. The odor then shows up in our breath and sweat.

If you would like to use parsley as either a digestive aid or breath freshener, I would recommend eating a sprig of fresh parsley after meals rather than taking supplements. Supplements vary in the amount of active ingredients they contain. They also cost a lot more than fresh parsley.

Parsley supplements should not be used by pregnant women or those with kidney disease. Parsley oil should never be taken as a supplement as it can be toxic. In fact, parsley oil can cause uterine contractions in pregnant women.

Parsley is a good source of nutrients, including vitamins C and A. However as a drug, it has only limited usefulness.

Although it has some stomach calming and urine-producing properties, the effects may be too mild to help most people.

Next time you are in a restaurant, eat the sprig of parsley. It may calm your stomach after a big meal, or at least make your mouth feel fresh.

Amy Tousman is a registered dietitian with the Health Education Center of Straub Clinic & Hospital.

Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column.