Licorice root tea, derived from the Glycyrrhiza glabra plant, is an herbal beverage prized for its sweet flavor and soothing properties, particularly for digestive and respiratory discomfort. However, the plant contains a potent compound that can lead to serious health complications if consumed in excess or over a prolonged period. Understanding the mechanism of its potential toxicity and defining safe consumption limits is necessary.
The Compound Requiring Caution: Glycyrrhizin
The need for strict dosage control stems from the compound glycyrrhizin (glycyrrhizic acid). Once ingested, gut microbiota converts glycyrrhizin into its active metabolite, glycyrrhetinic acid, which interferes with hormone regulation.
Glycyrrhetinic acid inhibits the enzyme 11-beta-hydroxysteroid dehydrogenase type 2 (11\(\beta\)-HSD2) in the kidneys. This enzyme normally inactivates cortisol. Inhibition allows active cortisol to rise and bind to mineralocorticoid receptors.
This binding mimics aldosterone, causing pseudoaldosteronism. Excessive activation of these receptors causes the kidneys to retain sodium and water while increasing potassium excretion, leading to adverse health effects.
Determining Safe Daily Consumption Limits
The safe intake of licorice tea depends on the concentration of glycyrrhizin. Health organizations, including the World Health Organization, advise that a safe daily limit for glycyrrhizin intake is no more than 100 milligrams (mg) per day for a healthy adult. This threshold prevents the development of pseudoaldosteronism.
Translating this chemical limit into cups is challenging due to significant variability in tea products. Glycyrrhizin content ranges widely depending on the Glycyrrhiza glabra species used, the amount of root, and the brewing time. Surveys show glycyrrhizin levels from 2 mg per liter up to 450 mg per liter.
A typical cup of licorice tea, based on average content, may contain around 30 mg of the compound. Consuming more than three cups daily could easily exceed the 100 mg limit, especially if the tea is strongly brewed. The risk increases with sustained daily consumption, as glycyrrhizin and its metabolite can accumulate in the body over several weeks.
Recognizing Symptoms of Overconsumption
When the safe daily limit of glycyrrhizin is exceeded, pseudoaldosteronism manifests through specific symptoms. The most common outcome is hypertension (high blood pressure) due to the retention of sodium and water. This fluid retention can also lead to noticeable edema, particularly swelling in the ankles and legs.
Another symptom is hypokalemia (low potassium), caused by excessive renal excretion of potassium. Hypokalemia presents as generalized muscle weakness, fatigue, and muscle pain. Severe cases can disrupt the heart’s electrical activity, leading to cardiac arrhythmias and palpitations.
The combination of high blood pressure and low potassium can lead to severe complications, including hypertensive emergencies or rhabdomyolysis. These symptoms indicate the mineralocorticoid system is overloaded, requiring immediate medical attention to correct the electrolyte imbalance and manage blood pressure.
Specific Health Conditions Requiring Strict Avoidance
Certain individuals should avoid licorice tea entirely due to sensitivity to glycyrrhizin. People with pre-existing hypertension are at heightened risk, as licorice can exacerbate their condition and lead to a hypertensive crisis. Those with heart disease, including congestive heart failure, should also abstain, as increased sodium and water retention strains the heart muscle.
Individuals with existing kidney disease or low potassium levels (hypokalemia) should avoid the tea, as its mechanism directly impacts the kidneys’ ability to manage electrolytes. Licorice tea can also interact negatively with several medications, including diuretics, blood pressure medications, and certain blood thinners. Pregnant women are advised to avoid licorice root products due to potential adverse effects on pregnancy outcomes.