(See also Overview of Medicinal Herbs and Nutraceuticals.)
Natural licorice, which has a very sweet taste, is extracted from the root of a shrub and used medicinally as a capsule, tablet, or liquid extract. Most licorice candy made in the United States is artificially flavored and does not contain natural licorice. Glycyrrhizin is the active ingredient in natural licorice. For people who are particularly sensitive to the effects of glycyrrhizin, licorice products that are specially treated to contain a much lower amount of glycyrrhizin (about one tenth of the usual amount) are available. These products are called deglycyrrhizinated licorice.
People most often take licorice to suppress coughs, to soothe a sore throat, and to relieve stomach upset. Applied externally, it is thought to soothe skin irritation (for example, eczema).
When licorice is consumed normally or at lower doses, there are few side effects. However, at high doses, glycyrrhizin causes the kidneys to retain salt and water, possibly leading to high blood pressure. It also causes the kidneys to excrete potassium, possibly causing low potassium levels in the blood. Increased potassium excretion can be a particular problem for people who have heart disease and for those who take digoxin or diuretics that increase potassium excretion in urine. Such people and those who have high blood pressure should avoid taking licorice.
Licorice may increase the risk of premature delivery. Thus, pregnant women should avoid licorice.