Black licorice is a confectionery made using the root extract of the Glycyrrhiza glabra plant, which gives it a distinct flavor and color. This natural extract contains many compounds, the most significant being glycyrrhizin, which is intensely sweet and biologically active. While many people believe consuming black licorice causes constipation, its effect on the digestive system is often the opposite. This article clarifies the action of licorice root extract, the specific compound responsible, and the broader health implications of consuming too much.
The Reality of Black Licorice and Digestion
Contrary to common belief, black licorice containing real licorice root extract is more likely to have a mild laxative effect than to cause constipation. Traditionally, licorice root has been used to relieve occasional constipation by promoting bowel movements. This digestive effect is dose-dependent, occurring when a sufficient amount of the active compound is consumed.
The laxative result stems from how the active compounds interact with the body’s water balance. These compounds affect the balance of water and electrolytes, increasing fluid within the digestive tract. When the colon retains more water, the stool softens, making it easier to pass. Excessive consumption can easily lead to loose stools or diarrhea.
Glycyrrhizin The Active Compound
The substance responsible for the digestive effects of true black licorice is glycyrrhizin, a triterpenoid compound. When consumed, intestinal bacteria hydrolyze glycyrrhizin into its active metabolite, glycyrrhetic acid. This metabolite is absorbed into the bloodstream, where it exerts its biological effects.
Glycyrrhetic acid acts by inhibiting the enzyme 11-beta-hydroxysteroid dehydrogenase type 2 (11-ß-HSD2). This enzyme normally breaks down the stress hormone cortisol in the kidneys and other tissues. When 11-ß-HSD2 is inhibited, cortisol levels rise locally. The elevated cortisol then interacts with mineralocorticoid receptors, which are typically reserved for the hormone aldosterone.
This interaction mimics the action of aldosterone, resulting in pseudoaldosteronism. The body responds by retaining sodium and water while simultaneously excreting potassium. The retained water contributes to the laxative effect in the digestive tract. Note that licorice-flavored candies made with anise oil instead of true licorice root extract do not contain glycyrrhizin and will not produce these effects.
Dosage and Other Systemic Health Effects
The digestive and systemic effects of black licorice depend highly on the quantity of glycyrrhizin consumed over time. The European Union’s Scientific Committee on Food suggests 100 milligrams of glycyrrhizin per day as a provisional upper limit for most healthy adults. This amount roughly equates to consuming 60 to 70 grams of standard licorice confectionery daily.
Consuming quantities significantly above this level for several weeks can trigger serious systemic health consequences. The most recognized side effects of chronic, high-dose glycyrrhizin intake are a rise in blood pressure and hypokalemia, an abnormally low level of potassium in the blood. The same mechanism of sodium and water retention that causes the laxative effect also causes fluid buildup and hypertension.
The loss of potassium can cause muscle weakness, fatigue, and dangerous heart rhythm abnormalities in severe cases. Individuals over 40 or those with pre-existing heart disease, kidney issues, or high blood pressure should carefully monitor consumption of licorice containing glycyrrhizin. These potentially dangerous cardiovascular and electrolyte effects often manifest before or alongside severe digestive distress.