What is Licorice?

Licorice is the root of Glycyrrhiza glabra, a small legume shrub grown in southern Europe, the Middle East and western Asia. The root is very sweet. It has been used as a flavour, a sweet and a folk remedy for coughs and stomach upset.

Here is the honest verdict. Human evidence is thin for most of its uses, with a few small trials hinting at help for indigestion and sore throat. The harm side is far better documented than the benefit side.

Real licorice can raise blood pressure and drive potassium down when used daily for weeks. This is not rare or theoretical. It has put people in hospital, including people eating black licorice sweets.

Licorice has a long record in American folk and Eclectic practice and in much older systems. Long use is not proof that it works. It is also not proof that it is safe.

How does Licorice work?

The best-understood effect of licorice in people is on salt and water, and it is not a benefit. Glycyrrhizin, the sweet compound, blocks a kidney enzyme called 11-beta-HSD2. That lets cortisol, a stress hormone, act on salt-handling cells.

The body then holds sodium and water and loses potassium. Blood pressure can rise within a couple of weeks of heavy use. Doctors call this pseudoaldosteronism (the body acts as if it had too much aldosterone, the salt-holding hormone).

The stomach claims are much less clear. In lab and animal work, licorice compounds appear to raise protective mucus in the stomach lining. They also appear to slow Helicobacter pylori, a germ linked to ulcers.

Whether either of those things happens in a person who takes licorice is not established.

In cell studies, licorice flavonoids damp down inflammation signals. That has not been shown to produce results in people.

The cough and sore-throat use rests mostly on a coating effect. Sweet, sticky syrups and lozenges soothe irritated tissue for a short time. Tradition, not trial data, carries most of that claim.

What forms does Licorice come in?

Licorice is sold both as a food and as a supplement, and the two can carry similar risk.

Common forms include:

- dried cut root, simmered as a tea - root powder in capsules or tablets - liquid extracts, tinctures and fluid extracts - standardised extracts that state the glycyrrhizin percent - DGL chewable tablets, made for the stomach - lozenges, pastilles and cough syrups - gels and creams holding licorice extract, used on skin - black licorice sweets, herbal tea blends and some beers

One point confuses many buyers. Many sweets sold as "licorice" are flavoured with anise or fennel and hold no real licorice root at all.

The reverse is also true. Herbal tea blends, laxative teas and throat sweets often contain real licorice without saying much about it. If you are avoiding licorice for medical reasons, read the full ingredient list.

Where it comes from:

Licorice has been used as a medicine for thousands of years, from Egypt and Greece to China and India. American Eclectic doctors of the 1800s took it from that older record.

They listed it mainly for coughs, hoarse throats and irritated stomachs. Eclectic texts prized it as a demulcent (something that coats and soothes). It also hid the taste of bitter medicines.

It appeared in cough syrups, chest teas, lozenges and compound powders. Folk use across rural America followed the same lines.

Nineteenth-century writers did not know about its effect on potassium and blood pressure. That was worked out in the twentieth century, after patients became ill. Older sources therefore give amounts that no careful modern source would repeat.

What does Licorice help with?

• Indigestion and stomach discomfort: This is the use with the most human data, and the data are still modest. Small placebo-controlled trials of a standardised licorice extract reported less bloating, fullness and upper-belly pain over 2 to 4 weeks. The trials were small. Several were funded by the maker of the extract. Independent repeats are scarce.
• Stomach and duodenal ulcers (DGL form): DGL was studied for ulcers mainly in the 1970s and 1980s, with mixed results. Those trials were small and ran before modern acid-blocking drugs. They do not show licorice works as well as today's treatments. An untreated ulcer can bleed. See a doctor rather than self-treating.
• Sore throat and cough: Tradition treated licorice as a throat soother, and the coating effect is real but brief. Good trials in everyday coughs and colds are lacking. Any relief is comfort, not a treatment of the cause.
• Mouth ulcers (canker sores): Small studies of licorice patches and rinses reported less pain and faster healing of mouth ulcers. The studies were short and few. This is a promising but unproven use.
• Sore throat after surgery with a breathing tube: This is the best-supported use. A randomised trial found that gargling a licorice solution before surgery reduced throat pain and coughing afterwards. This was done in hospital, before anaesthesia. It is not something to copy at home.
• Eczema and skin irritation (applied to skin): A small trial of a gel containing licorice extract reported less redness, itching and swelling in eczema. One small trial is weak ground. Skin products avoid the blood pressure problem but can still irritate or cause a rash.
• Flavouring and taste-masking: This use is not in doubt. Licorice is strongly sweet and covers bitter tastes well. It is used in sweets, teas, tobacco and medicines for exactly that reason.

Which foods are rich in Licorice?

Licorice is a food as well as a herb. Black licorice sweets, some herbal tea blends, laxative teas, throat pastilles, chewing tobacco and a few beers and liqueurs can all contain real licorice root. Sweets flavoured with anise or fennel taste similar but hold none. If you must avoid licorice, read ingredient lists rather than trusting the flavour.

What are the side effects of Licorice?

• Rising blood pressure
• Low potassium (hypokalaemia)
• Fluid build-up and swelling in the face, hands or ankles
• Weight gain from held water
• Headache
• Muscle weakness, cramps or twitching
• Fast or irregular heartbeat
• Severe tiredness
• Muscle breakdown (rhabdomyolysis) in severe cases
• Lower testosterone in men, reported in small studies
• Changes to menstrual periods
• Upset stomach or loose stools
• Allergic rash, which is uncommon

Good to know:

Small, occasional amounts cause problems in few people. Heavy or long daily use is a different matter.

Most reported harm came from using licorice every day for weeks or months. Sweets counted just as much as supplements.

Sensitivity varies widely. Some people develop high blood pressure or low potassium at amounts others tolerate.

Effects usually settle after stopping. Potassium and blood pressure can take weeks or even months to return to normal.

How much Licorice should you take?

• Recommended daily: The amounts below are the kind of thing labels and food safety bodies state. They are not advice for you. European food safety advice is to keep glycyrrhizin intake under about 100 mg a day. That is roughly 60 to 70 g of black licorice sweets. US regulators have warned that about 2 ounces of black licorice a day for two weeks can cause heart rhythm problems in people over 40. Whole-root supplement labels often list 1 to 5 g of dried root a day. DGL chewable labels often list 380 to 760 mg taken before meals. Some people react at much lower amounts than these figures suggest. If you have high blood pressure, or heart, kidney or liver problems, the safe amount of whole licorice is none.
• Best time of day: Timing makes little difference to safety or to effect. DGL labels usually suggest taking it before meals, since it is meant to coat the stomach. Throat lozenges are used when the throat hurts. Spreading doses through the day does not reduce the blood pressure risk. The total daily amount is what counts.
• With or without food: Either works, and neither makes licorice safer. DGL is usually taken before food. Whole-root tea is often taken after meals. A salty diet makes the fluid and blood pressure effects worse. So does losing potassium for other reasons, such as frequent vomiting or diarrhoea.
• Time to effect: Throat soothing is immediate and short-lived. It lasts minutes, not hours. For indigestion, the small trials that exist reported change over 2 to 4 weeks. It may do nothing at all for you. Harm can arrive before any benefit. Blood pressure and potassium changes have appeared within 1 to 2 weeks of heavy daily use.
• How long to take it: Short. European herbal monographs limit whole licorice to about 4 to 6 weeks without medical supervision. The risk of high blood pressure and low potassium grows with both dose and time. Most reported cases of harm involved daily use over weeks or months. DGL is often used for longer. Good long-term safety data for DGL are thin.