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Introduction

A member of the pea family, licorice root has been used since ancient times both as food and as medicine. In Chinese herbology, licorice is an ingredient in nearly all herbal formulas for the traditional purpose of "harmonizing" the separate herbs involved.

Licorice possesses a variety of active ingredients. The most analyzed is glycyrrhizin, which has been found to possess anti-inflammatory, cough-suppressant, antiviral, estrogen-like, corticosteroid-enhancing, and aldosterone-like activities. The natural hormone aldosterone can cause fluid retention, increased blood pressure, and potassium loss. Glycyrrhizin can produce similar effects, which may cause a problem (see the discussion under Safety Issues). To avoid the aldosterone-like effects, manufacturers have found a way to remove glycyrrhizin from licorice, producing the much safer product deglycyrrhizinated licorice, or DGL. However, it is not clear that DGL provides all the same benefits as whole licorice.

What Is Licorice Used for Today?

Licorice appears to have a positive effect on the cells of the stomach, including increasing blood flow. Licorice or DGL was once a standard European treatment for ulcers. Although it has been replaced by synthetic medications, there is a significant amount of evidence that DGL can be helpful. In particular, preliminary evidence suggests that DGL might help prevent ulcers caused by aspirin. Licorice (primarily DGL) is also used to relieve the discomfort of canker sores and other mouth sores. Creams containing whole licorice (often combined with chamomile extract) are often used for eczema, psoriasis, and herpes.

Whole licorice, not DGL, is used as an expectorant for respiratory problems such as coughs and asthma.

Recently, licorice has been suggested as a treatment for chronic fatigue syndrome (CFS), based on the observation that people with CFS appear to suffer from low levels of certain adrenal hormones. The glycyrrhizin portion of licorice may relieve symptoms by mimicking the effects of these hormones. However, this is a fairly dangerous approach to treatment that should be tried only under medical supervision. In addition, studies of drugs that even more closely imitate adrenal hormones have not found benefit.

Licorice has also been suggested as a treatment for numerous other conditions, including hepatitis and menopausal symptoms, and for the prevention of cancer, but there is as yet little evidence that it really works.

What Is the Scientific Evidence for Licorice?

Two controlled, but not double-blind, studies suggest that regular use of DGL in a combination product also containing antacids can heal ulcers as effectively as drugs in the Zantac family. However, DGL must be taken continuously or the ulcer can be expected to return. Modern medical treatment tries to prevent the recurrence of ulcers permanently by eradicating the bacteria Helicobacter pylori. There is no evidence that DGL can do the same.

There is no solid evidence for the other proposed uses of licorice.

Dosage

For supportive treatment of ulcer pain along with conventional medical care, chew two to four 380-mg tablets of DGL before meals and at bedtime.

Sucking on these tablets may symptomatically relieve mouth sores, although some people find the taste unpleasant.

For the treatment of eczema, psoriasis, or herpes, licorice cream is applied twice daily to the affected area.

Safety Issues

Due to its aldosterone-like effects, whole licorice can cause fluid retention, high blood pressure, and potassium loss when taken at dosages exceeding 3 g daily for more than 6 weeks. These effects can be especially dangerous if you take digitalis, or if you have high blood pressure, heart disease, diabetes, or kidney disease.

Licorice may reduce testosterone levels in men. For this reason, men with impotence, infertility, or decreased libido may wish to avoid this herb. Licorice may also increase both the positive and negative effects of corticosteroids such as prednisone and hydrocortisone cream. Some evidence suggests that licorice might interact with other medications as well, but the extent of this effect has not been fully determined.

DGL is believed to be safe, although extensive safety studies have not been performed. Side effects are rare.

Safety for either form of licorice in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established. According to one report, licorice possesses significant estrogenic activity and, as such, shouldn't be taken by pregnant women or women who have had breast cancer. In addition, an observational study found evidence that heavy licorice use might lead to risk of premature birth.24

Interactions You Should Know About

If you are taking
Digitalis drugs: Long-term use of licorice can be dangerous.
Thiazide or loop diuretics: Use of licorice might lead to excessive potassium loss.
Corticosteroid treatment: Licorice could increase both its negative and positive effects. Do not take licorice internally if using corticosteroids.
Aspirin or other anti-inflammatory drugs: Regular use of DGL might help lower the risk of ulcers.