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Licorice (gan cao)

What is licorice? What is it used for?

Licorice is a plant originally grown in central Europe, but now found all across Europe and Asia. Aside from its medicinal properties, it has been used to flavor foods for centuries. Licorice root is used medicinally.

The two most important components of licorice are glychrrhizin and flavonoids. Glycyrrhizin works as an anti-inflammatory and antiviral and inhibits the breakdown of cortisol. Licorice flavonoids are powerful antioxidants; they work to protect liver cells and help digestive tract cells heal. Test tube studies have found that licorice flavonoids kill heliobacter pylori, the bacteria responsible for most ulcers and stomach inflammation.

Today, licorice remains one of the most important herbs in traditional Chinese medicine. It addition to its use as a flavoring, licorice has traditionally been employed to sooth coughs and sore throats; coat the digestive and urinary tracts; and treat various conditions ranging from diabetes to tuberculosis.

Several studies have been conducted on deglycyrrhizinated licorice, or DGL. Studies have found that DGL tablets are effective in treating ulcers of the stomach and small intestine; one preliminary study found DGL can inhibit the growth and spread of canker sores. Other clinical studies have used licorice extracts to treat eczema and herpes.

How much licorice should I take?

For respiratory conditions, chronic fatigue syndrome and herpes, many herbalists recommend using "standard," or glycyrrhizinated, licorice. Licorice root capsules (5-6 grams per day) can be used, as can concentrated licorice extracts (250-500mg three times per day).

DGL is used for ulcers of the mouth, stomach and digestive tract. Most practitioners recommend one 200-300mg tablet three times per day before meals and before going to bed.

What forms of licorice are available?

Licorice root can be found at some health food stores and most Asian markets. Many health stores also sell standard and DGL licorice tablets, capsules and extracts.

What can happen if I take too much licorice? Are there any interactions I should be aware of? What precautions should I take?

Licorice products that contain glycyrrhizin may increase a person's blood pressure and cause water retention. Consumption of more than seven grams of licorice per day for more than seven days consecutively could increase blood testosterone levels. According to the German Commission E monographs, licorice should not be used by pregnant women or people with liver and/or kidney disorders.


  • Abe Y, et al. Effectiveness of interferon, glycyrrhizin combination therapy in patients with chronic hepatitis C [in Japanese]. Nippon Rinsho 1994;52:1817-22.
  • Blumenthal M, Busse WR, Goldberg A, et al. (eds.) The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, pp. 161-2.
  • Das SK, Das V, Gulati AD, Singh VP. Deglycyrrhizinated licorice in aphthous ulcers. J Assoc Physicians India 1989;37:647.
  • Murray MT. The Healing Power of Herbs. Rocklin, CA: Prima Publishing, 1995, pp. 228-39.
  • Soma R, Ikeda M, Morise T, et al. Effect of glychrrhizin on cortisol metabolism in humans. Endocrin Regulations 1994;28:31-4.
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