Remedy · root & spice
Licorice root: limited benefits and real risks to blood pressure and potassium
A traditional throat and stomach remedy with thin evidence and a well-documented downside: regular licorice can raise blood pressure and drop potassium.
By the editors of Alimentotherapy Last reviewed 3 min read Not medical advice
Licorice root
Glycyrrhiza glabra
Best-supported use: Sore throat after a breathing tube (gargle)
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The short answer
A licorice gargle before surgery roughly halved post-operative sore throat in one large trial, and licorice rinses may help canker sores, but evidence for digestive use is unclear Ruetzler 2013; NCCIH. The bigger story is safety: regular intake of glycyrrhizin, licorice's sweet compound, raised blood pressure and lowered blood potassium in a meta-analysis of 18 studies Penninkilampi 2017.
The evidence, use by use
Each claim graded on human studies only. How we grade
| Use | Grade | What the research found |
|---|---|---|
| Sore throat after intubation (gargle before surgery) | Limited | In a trial of 236 patients, a 0.5 g licorice gargle before anesthesia cut post-operative sore throat at 4 hours from 45% to 21% compared with sugar water. It was given by the surgical team, not as home care. Ruetzler 2013; NCCIH |
| Recurrent canker sores (mouth rinse or topical) | Limited | NCCIH reports that licorice rinses might reduce ulcer size and pain in people with recurrent canker sores, from small studies. NCCIH |
| Indigestion, heartburn and other digestive symptoms | Not supported | NCCIH says it is unclear whether licorice alone, outside herbal blends, has any effect on digestive symptoms. NCCIH |
Glycyrrhizin: why licorice is not harmless
Licorice root contains glycyrrhizin (glycyrrhizic acid), which is many times sweeter than sugar. Taken regularly, it makes the body hold on to salt and lose potassium. A meta-analysis of 18 studies (337 people) in which participants took at least 100 mg of glycyrrhizic acid a day found systolic blood pressure rose by about 5.5 mm Hg and blood potassium fell, with higher doses linked to bigger rises in blood pressurePenninkilampi 2017.
NCCIH warns that glycyrrhizin can cause irregular heartbeat and cardiac arrest, especially with large amounts or long use, and that even small amounts have been linked to severe problems in people who eat a lot of salt, have high blood pressure, or have heart or kidney conditions NCCIH.
Safety
Not every licorice-flavored sweet contains licorice root, but real licorice sweets, licorice root tea and some herbal blends do contain glycyrrhizin. Check the ingredient list for licorice root or extract.
Deglycyrrhizinated licorice (DGL)
DGL is licorice with the glycyrrhizin removed, sold as chewable tablets for the stomach. NCCIH says oral products without glycyrrhizin might be safe for up to 4 months, but that does not mean they work; evidence for licorice alone on digestive symptoms is unclear NCCIH. For the foods with better evidence, see digestion.
If you drink licorice root tea
An occasional cup is unlikely to matter for a healthy adult, but daily cups add up, and herbal teas rarely state how much glycyrrhizin they contain. Skip it entirely if you have high blood pressure, heart or kidney disease, or take the medicines listed below. Loose licorice root and single-ingredient teas are sold by iHerb and many grocers; treat them as an occasional drink, not a daily habit.
Before you try it: safety and interactions
Who should avoid it or ask first
- You have high blood pressure, heart disease or kidney disease.
- You take diuretics, other blood pressure medicines, digoxin or corticosteroids: ask your prescriber.
- You eat a high-salt diet or are 40 or older and eat black licorice regularly.
Possible side effects
- Raised blood pressure, low potassium, fluid retention and swelling with regular use.
- Irregular heart rhythm, muscle weakness and, rarely, cardiac arrest with large or long-term intake.
- Skin irritation from topical products.
Pregnancy and breastfeeding
Avoid it. NCCIH says large amounts of licorice in pregnancy (about 250 grams a week) are unsafe and can increase the risk of delivery before 38 weeks; little is known about breastfeeding. NCCIH; Penninkilampi 2017
Medicine interactions
- Black licorice and licorice root (glycyrrhizin) and blood pressure medicines and diuretics (water pills)Regular licorice raises blood pressure and lowers potassium, working against blood pressure treatment. Reviews of interaction reports include low potassium after licorice combined with antihypertensives.Established
- Black licorice and licorice root (glycyrrhizin) and digoxin (Lanoxin)Licorice can lower blood potassium, and low potassium makes digoxin toxicity more likely. The combination could raise the risk of dangerous heart rhythm problems.Theoretical
Check another food or medicine in the interactions list.
Common questions
Is licorice bad for blood pressure?
Yes, real licorice can raise it. In a meta-analysis of 18 studies, regular intake of at least 100 mg of glycyrrhizic acid a day raised systolic blood pressure by about 5.5 mm Hg and lowered blood potassium. People with hypertension, heart or kidney disease should avoid it.
How much black licorice is too much?
There is no single safe amount for everyone. In the studies pooled in a 2017 meta-analysis, at least 100 mg of glycyrrhizic acid a day raised blood pressure and lowered potassium, and NCCIH notes that even small amounts have caused serious problems in people with high blood pressure or heart or kidney conditions. Candy labels rarely state glycyrrhizin content, so treat real licorice as an occasional food.
Is DGL licorice safe?
Deglycyrrhizinated licorice has the glycyrrhizin removed, and NCCIH says such products might be safe for up to 4 months. Whether licorice alone helps digestive symptoms is unclear.
Sources
Primary research and government sources, each checked on the date this page was reviewed.
- PubMedPenninkilampi R, Eslick EM, Eslick GD. The association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysis. J Hum Hypertens. 2017. PMID 28660884.
- PubMedRuetzler K, et al. A randomized, double-blind comparison of licorice versus sugar-water gargle for prevention of postoperative sore throat and postextubation coughing. Anesth Analg. 2013. PMID 23921656.
- NCCIHNational Center for Complementary and Integrative Health. Licorice Root: Usefulness and Safety.
Keep reading
- GoalFood for a healthy heart: blood pressure and cholesterolEating patterns have the strongest heart evidence: DASH for blood pressure, Mediterranean for heart events, and soluble fiber from oats, barley or psyllium for cholesterol.
- GoalFood and digestive comfort: bloating, gas and sensitive gutsFor a sensitive gut, enteric-coated peppermint oil and a short, dietitian-guided low FODMAP trial have the strongest evidence. Most bloating comes from what and how fast we eat.
- RemedyFennelA traditional after-dinner seed for wind and bloating, recognized by European regulators on the strength of long use rather than trials. Colic studies in babies are small.
- ToolFood and drug interactionsCheck a remedy or food against common medicines.