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Other common name(s): sweet root, licorice root

Scientific/medical name(s): gan cao, Glycyrrhiza glabra, Glycyrrhiza uralensis


Licorice is a perennial plant that grows in southern Europe, Asia, and the Mediterranean. The dried roots and underground stems of the plant are used in herbal remedies.


Licorice root is an ingredient in many traditional Chinese herbal remedies. It also has been used in other countries to treat a wide variety of health problems. However, it is linked to some fairly serious side effects. Whole-herb licorice can cause an imbalance of fluid and the mineral potassium in the body, which can lead to heart rhythm problems, high blood pressure, muscle weakness, and even paralysis. Although recent laboratory research has identified some components that might be useful in cancer prevention or treatment, there is almost no information available about their effectiveness in humans. More research is needed to find out whether licorice extract has any role in cancer prevention or treatment.

How is it promoted for use?

Licorice is promoted to treat peptic ulcers, eczema, skin infections, cold sores, menopausal symptoms, liver disease, respiratory ailments, inflammatory problems, chronic fatigue syndrome, AIDS, and even cancer. It has also been promoted to relieve symptoms of Addison’s disease, lower cholesterol and triglyceride levels, strengthen the immune system, and treat hepatitis.

Many food products are widely available that contain traces of licorice. Some licorice candy sold in the United States is actually flavored with anise and does not contain licorice. Glycyrrhizin (an active ingredient from the plant) is used as a flavoring in candy, gum, cookies, beverages, and cough syrup. Licorice is also used as a flavoring for tobacco products.

What does it involve?

Licorice is packaged as capsules, tablets, and as a liquid extract. It can be purchased at grocery stores, health food stores, or pharmacies. According to Commission E (Germany's regulatory agency for herbs), the recommended dosage ranges from 200 to 600 milligrams for no more than 4 weeks for peptic ulcers. Licorice is also an ingredient in many traditional Chinese herbal formulations. The best known of these are herbal products for prostate cancer treatment such as PC-HOPE and PC-CARE. Because of its side effects, glycyrrhizin is removed from many licorice formulas. This is called deglycyrrhizinated licorice (DGL).

What is the history behind it?

Licorice extract has been used in traditional Chinese medicine for centuries. The Chinese used it as a mild laxative and to help regulate the heartbeat in those with heart problems. Traditional Chinese herbalists often prescribe licorice with the intent of helping other herbs to work better together and promoting absorption of herbs. It was also used for medicinal purposes in ancient Egypt, Greece, and Rome.

What is the evidence?

Some research suggests that licorice can promote healing of peptic ulcers. However, most of the evidence is from older studies, smaller case series, and laboratory studies. Licorice is less effective than conventional prescriptions and over-the-counter medications for ulcers.

Laboratory studies have identified several substances in licorice that may help prevent DNA mutations, inhibit tumor formation, or even kill cancer cells. For example, Licochalcone-A, glabridin, and licocoumarone have been tested using cancer cells growing in laboratory dishes, and preliminary studies indicate that these chemicals can stop the growth of or even kill breast cancer, prostate cancer, and leukemia cells. In studies with mice, glycyrrhizin and glycyrrhizic acid reduced formation of skin, colon, liver, uterine, and breast cancers.

Although results of animal studies suggest some chemicals from licorice might be useful in preventing or treating some forms of cancer, no human clinical trials of licorice supplements or substances from licorice have been reported. Licorice is an ingredient in PC-SPES, an herbal product for prostate cancer treatment, and although there have been several clinical trials of PC-SPES (see our document PC-SPES), they do not address whether licorice contributed to its benefits.

Glycyrrhizin may be useful as a treatment for chronic hepatitis, and a Japanese study found that patients with chronic hepatitis C who took this supplement had lower risk of liver cancer. However, this study asked patients to remember and report whether they had used the supplement in the past. This kind of study is considered less reliable than a clinical trial that randomly assigns patients to various treatments and follows the patients over time.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must provide the FDA with results of detailed testing showing their product is safe and effective before the drug is approved for sale), the companies that make supplements do not have to show evidence of safety or health benefits to the FDA before selling their products. Supplement products without any reliable scientific evidence of health benefits may still be sold as long as the companies selling them do not claim the supplements can prevent, treat, or cure any specific disease. Some such products may not contain the amount of the herb or substance that is written on the label, and some may include other substances (contaminants). Though the FDA has written new rules to improve the quality of manufacturing processes for dietary supplements and the accurate listing of supplement ingredients, these rules do not take full effect until 2010. And, the new rules do not address the safety of supplement ingredients or their effects on health when proper manufacturing techniques are used.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Regular consumption of licorice has been shown to cause headaches, lethargy, water retention, high blood pressure, and muscle weakness. In extremely large amounts, it can cause paralysis and heart failure. People with high blood pressure, irregular heart beat, or cardiovascular, kidney, or liver diseases should avoid licorice unless given under a doctor’s supervision. Use of DGL, or deglycyrrhizinated licorice, helps to avoid the risk of more serious side effects.

Studies in laboratory animals have suggested that licorice may cause birth defects. Women who are pregnant should not use licorice. Most herbalists also recommend that women who are breast-feeding avoid this supplement.

In addition, the potential interactions between licorice and other drugs and herbs should be considered. For example, licorice can cause problems for patients taking heart medicines, steroids, diuretics, or insulin. Blood-thinning medications, and hormone therapy can interact with licorice and even DGL. Some of these combinations may be dangerous. Always tell your doctor and pharmacist about any herbs you are taking. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Additional resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 11/28/2008
Last Revised: 11/28/2008