Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. 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.12 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 (To view, roll mouse over the "References" heading; to hide, click on the heading)
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.
The information presented in Aisle7 is for informational purposes only.
It is based on scientific studies (human, animal, or in vitro), clinical experience,
or traditional usage as cited in each article. The results reported may not necessarily occur
in all individuals. For many of the conditions discussed, treatment with prescription or over
the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist
for any health problem and before using any supplements or before making any changes in
prescribed medications.
