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Licorice

Also indexed as: DGL (Licorice)

Botanical names: Glycyrrhiza glabra, Glycyrrhiza uralensis

Photo

© Steven Foster

Parts used and where grown

Originally from central Europe, licorice now grows all across Europe and Asia. The root is used medicinally.

Licorice has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns
3Stars

Infection

Peptic ulcer (chewable DGL)

2Stars

Canker sores (DGL)

Colic (in combination with vervain, fennel and lemon balm)

Epilepsy (in combination with bupleurum, peony root, pinellia root, cassia bark, ginger root, jujube fruit, Asian ginseng root, and Asian scullcap root)

Gastroesophageal reflux disease (GERD) (DGL)

Hepatitis (intravenous glycyrrhizin)

HIV support

Infections (viral)

1Star

Asthma

Chronic fatigue syndrome

Cold sores (topical)

Cough

Crohn’s disease

Eczema

Gastritis

Genital herpes (topical)

Hay fever (Sho-seiryu-to: contains licorice, cassia bark, schisandra, ma huang [ephedra], ginger, peony root, pinellia, and asiasarum root)

Hepatitis (oral glycyrrhizin)

Indigestion and heartburn (DGL)

Melasma (topical liquirtin)

Menopause

Shingles (herpes zoster)/postherpetic neuralgia (topical gel)

Ulcerative colitis

3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies)

Licorice has a long and highly varied record of uses. It was and remains one of the most important herbs in Traditional Chinese Medicine. Among its most consistent and important uses are as a demulcent (soothing, coating agent) in the digestive and urinary tracts, to help with coughs, to soothe sore throats, and as a flavoring. It has also been used in Traditional Chinese Medicine to treat conditions ranging from diabetes to tuberculosis.

Active constituents

The two major constituents of licorice are glycyrrhizin and flavonoids. According to test tube studies, glycyrrhizin has anti-inflammatory actions and may inhibit the breakdown of the cortisol produced by the body.1 2 Licorice may also have antiviral properties, although this has not been proven in human pharmacological studies. Licorice flavonoids, as well as the closely related chalcones, help heal digestive tract cells. They are also potent antioxidants and work to protect liver cells. In test tubes, the flavonoids have been shown to kill Helicobacter pylori, the bacteria that causes most ulcers and stomach inflammation.3 However, it is unclear whether this action applies to the use of oral licorice for the treatment of ulcers in humans.

An extract of licorice, called liquiritin, has been used as a treatment for melasma, a pigmentation disorder of the skin. In a preliminary trial,4 topical application of liquiritin cream twice daily for four weeks led to a 70% improvement, compared to only 20% improvement in the placebo group.

A preliminary trial found that while the acid-blocking drug cimetidine (Tagamet®) led to quicker symptom relief, chewable deglycyrrhizinated licorice (DGL) tablets were just as effective at healing and maintaining the healing of stomach ulcers.5 Chewable DGL may also be helpful in treating ulcers of the duodenum, the first part of the small intestine.6 Capsules of DGL may not work for ulcers, however, as DGL must mix with saliva to be activated.7 One preliminary human trial has found DGL used as a mouthwash was effective in quickening the healing of canker sores.8

How much is usually taken?

There are two types of licorice, “standard” licorice and “de-glycyrrhizinated” licorice (DGL). Each type is suitable for different conditions. The standard licorice containing glycyrrhizin should be used for respiratory infections, chronic fatigue syndrome or herpes (topical). Licorice root in capsules, 5–6 grams per day, can be used. Concentrated extracts, 250–500 mg three times per day, are another option. Alternatively, a tea can be made by boiling 1/2 ounce (14 grams) of root in 1 pint (500 ml) of water for fifteen minutes, then drinking two to three cups (500–750 ml) per day. Long-term internal use (more than two to three weeks) of high amounts (over 10 grams per day) of glycyrrhizin-containing products should be attempted only under the supervision of a doctor. Licorice creams or gels can be applied directly to herpes sores three to four times per day.

DGL is prepared without the glycyrrhizin in order to circumvent potential safety problems (see below), and is used for conditions of the digestive tract, such as ulcers. For best results, one 200–300 mg tablet is chewed three times per day before meals and before bed.9 For canker sores, 200 mg of DGL powder can be mixed with 200 ml warm water, swished in the mouth for three minutes, and then expelled. This may be repeated three or four times per day.

Are there any side effects or interactions?

Licorice products that include glycyrrhizin may increase blood pressure and cause water retention.10 Some people are more sensitive to this effect than others. Long-term intake (more than two to three weeks) of products containing more than 1 gram of glycyrrhizin (the amount in approximately 10 grams of root) daily is the usual amount required to cause these effects. Consumption of 7 grams licorice (containing 500 mg glycyrrhizin) per day for seven days has been shown to decrease serum testosterone levels in healthy men by blocking the enzymes needed to synthesize testosterone.11 However, in another study, a similar amount of licorice had only a small and statistically insignificant effect on testosterone levels.12 As a result of these possible side effects, long-term intake of high levels of glycyrrhizin is discouraged and should only be undertaken if prescribed by a qualified healthcare professional. Consumption of plenty of fresh fruits and vegetables to increase potassium intake is recommended to help decrease the chance of side effects. According to the German Commission E monograph, licorice is inadvisable for pregnant women as well as for people with liver and kidney disorders.13

De-glycyrrhizinated licorice extracts do not cause these side effects since they contain no glycyrrhizin.

Are there any drug interactions?
Certain medicines may interact with licorice. Refer to drug interactions for a list of those medicines.

References:

1. Whorwood CB, Shepard MC, Stewart PM. Licorice inhibits 11ß-hydroxysteroid dehydrogenase messenger ribonucleic acid levels and potentiates glucocorticoid hormone action. Endocrinology 1993;132:2287–92.

2. Soma R, Ikeda M, Morise T, et al. Effect of glycyrrhizin on cortisol metabolism in humans. Endocrin Regulations 1994;28:31–4.

3. Beil W, Birkholz C, Sewing KF. Effects of flavonoids on parietal cell acid secretion, gastric mucosal prostaglandin production and Helicobacter pylori growth. Arzneim Forsch 1995;45:697–700.

4. Amer M, Metwalli M. Topical liquiritin improves melasma. Int J Dermatol 2000;39:299–301.

5. Morgan AG, McAdam WAF, Pacsoo C, Darnborough A. Comparison between cimetidine and Caved-S in the treatment of gastric ulceration, and subsequent maintenance therapy. Gut 1982;23:545–51.

6. Kassir ZA. Endoscopic controlled trial of four drug regimens in the treatment of chronic duodenal ulceration. Irish Med J 1985;78:153–6.

7. Bardhan KD, Cumberland DC, Dixon RA, Holdsworth CD. Clinical trial of deglycyrrhizinised liquorice in gastric ulcer. Gut 1978;19:779–82.

8. Das SK, Das V, Gulati AD, Singh VP. Deglycyrrhizinated licorice in aphthous ulcers. J Assoc Physicians India 1989;37:647.

9. Murray MT. The Healing Power of Herbs. Rocklin, CA: Prima Publishing, 1995, 228–39.

10. 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, 161–2.

11. Armanini D, Bonanni G, Palermo M. Reduction of serum testosterone in men by licorice. New Engl J Med 1999;341:1158 [letter].

12. Josephs RA, Guinn JS, Harper ML, Askari F. Liquorice consumption and salivary testosterone concentrations. Lancet 2001;358:1613–4.

13. 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, 161–2.

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