Licorice Side Effects: Dangers and Contraindications
Licorice was thought dangerous only at a high, prolonged dose. A recent clinical trial shows that a small daily amount is enough to measure a real effect on blood pressure.
Does licorice (Glycyrrhiza glabra) cause side effects? In small, occasional amounts (a candy, a tea now and then), generally not. But a recent clinical trial measured something important: even a modest dose of glycyrrhizin — fennel/">licorice's active compound — taken daily for just two weeks is enough to raise blood pressure and disrupt two key hormones that regulate it.
This article details what this study shows and what it changes in practice. For turmeric/">licorice's traditional uses, see our page licorice; precautions already covered appear in licorice dangers.
What the most recent clinical trial shows
The reference study is the one by af Geijerstam, Joelsson, Radholm and Nystrom, published in 2024 in the American Journal of Clinical Nutrition. It is a randomized crossover trial in 28 healthy volunteers, comparing a daily intake of just 100 mg of glycyrrhizic acid for two weeks against a control product. Result: home-measured systolic blood pressure rose on average by 3.1 mmHg, while two key hormones regulating blood pressure collapsed — renin dropped by 30% and aldosterone by more than 45% (see the study on Google Scholar).
This hormonal signature — both renin and aldosterone low despite rising blood pressure — matches exactly licorice's known mechanism: pseudohyperaldosteronism. Glycyrrhizin blocks an enzyme that normally protects mineralocorticoid receptors; the body then behaves as if it were producing too much aldosterone, without actually doing so. The authors themselves conclude that licorice is more active than previously thought, even at a low dose, and suggest revising "safe" thresholds downward.
Potassium, the second point of caution
| Measured effect | Mechanism | Practical consequence |
|---|---|---|
| Rise in blood pressure | Pseudohyperaldosteronism | Caution with hypertension or antihypertensive treatment |
| Drop in blood potassium (hypokalemia) | Same mechanism, mineralocorticoid effect | Risk of cramps, muscle weakness, heart-rhythm disturbances at a high dose |
| Water and sodium retention | Mineralocorticoid effect | Caution with heart or kidney failure |
Hypokalemia is the most documented and most serious effect of prolonged licorice use at a significant dose: it can cause cramps, muscle weakness, and in the most pronounced cases, heart-rhythm disturbances. This is why European health authorities recommend not exceeding a modest daily glycyrrhizin intake over time.
Who should avoid licorice or be especially cautious?
- Hypertension or antihypertensive treatment: licorice can worsen blood pressure or reduce the treatment's effectiveness.
- Pregnancy: observational studies associate high licorice consumption during pregnancy with effects on child development; best avoided as a precaution.
- Heart or kidney disease: water and sodium retention can worsen these conditions.
- Diuretic or digitalis treatment: the potassium drop caused by licorice can worsen their side effects, particularly cardiac ones.
- Prolonged use without a break: even at a modest dose, the 2024 study calls for limiting the length of continuous cures.
How to limit the risk day to day
Pure licorice (candy, tea, supplements) is different from artificially "licorice-flavored" candy, which generally contains none — only real licorice carries this risk. For occasional digestive use, see our article bloating and difficult digestion or acid reflux and heartburn. If in doubt about a product, check its glycyrrhizin content on the label and limit continuous consumption.
Licorice never replaces a prescribed treatment for blood pressure or the heart. General safety guidelines for Ayurvedic herbs are detailed in our safety and precautions guide.
Your questions about licorice side effects
Can a small amount of licorice really raise blood pressure?
Yes, a 2024 clinical trial measured a rise in blood pressure with just 100 mg per day of glycyrrhizic acid over two weeks, a much lower dose than previously thought.
Why does licorice lower potassium?
Through the same mechanism as its effect on blood pressure: glycyrrhizin blocks an enzyme that normally protects the body from an excess aldosterone effect. The body retains water and sodium and eliminates more potassium, hence the hypokalemia risk with prolonged dosing.
Is licorice dangerous during pregnancy?
Best avoided as a precaution: observational studies associate high licorice consumption during pregnancy with effects on child development. It is better to abstain or seek medical advice.
How long can you consume licorice continuously?
No universal "safe" duration is established, but the 2024 study shows a measurable effect appears within two weeks at a modest dose. It is better to limit cures and take breaks rather than continuous daily consumption.
Do licorice-flavored candies carry the same risk?
Generally not: most commercial "licorice-flavored" candies are artificially flavored and contain no real glycyrrhizin. The risk concerns pure licorice — tea, chewing sticks, supplements, or confections made with real licorice extract.
Who should avoid licorice entirely?
People with hypertension or on antihypertensive treatment, people with heart or kidney disease, pregnant women, and anyone on diuretics or digitalis, due to the risk of a potassium drop.
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