On The Shelf
Mickie Cathers
Licorice is more than your granddad’s favorite candy. Licorice root is also available as an herbal supplement advertised as promoting digestive function, benefiting respiratory health, and supporting immunity. But licorice root may also adversely raise BP.
Background
Licorice is derived from the roots of the Glycyrrhiza glabra plant species and has been used as a flavoring in food, candy, and tobacco. The herbal extract also has a long history as a remedy for many conditions including GI disorders, upper respiratory infections, and symptoms of menopause. Licorice may aid acne and eczema, acid reflux and indigestion, peptic ulcers, asthma, and strep throat, and possibly provide anticancer properties.
Is there a benefit?
Research has shown that licorice root has anti-inflammatory, antioxidant, and antineoplastic benefits due to its primary active compound, glycyrrhizic acid (glycyrrhizin). Glycyrrhizin is what makes licorice taste sweet, and it has been linked to many pharmacological and biological benefits. Glycyrrhizic acid inhibits elevated cortisol levels, the production of proinflammatory cytokines such as tumor necrosis factor-a, interleukin-1a, -1b, and -6, and prostaglandin E2. Glycyrrhizic acid has been shown to inhibit the replication of SARS-CoV-2, as well as hepatic apoptosis and necrosis. It has also been reported to have antiphotoaging properties preventing ultraviolet-b–induced DNA damage. However, glycyrrhizin is also responsible for some adverse effects associated with high doses.
Several studies suggest chronic use and large doses of licorice root products may lead to glycyrrhizin accumulation that can raise BP, lower potassium levels, and cause arrhythmia, kidney failure, congestive heart failure, and pulmonary edema. High doses of licorice have not been reported as causing serum aminotransferase elevations or clinically apparent liver injury.
A safe level of glycyrrhizic acid per day for most individuals is no more than 100 mg, as recommended by WHO and the European Scientific Committee of Food.
Authors from Linköping University in Sweden wanted to test that safety limit. Geijerstam and colleagues published a study in the March 2024 issue of The American Journal of Clinical Nutrition The American Journal of Clinical Nutrition analyzing the effects of daily licorice intake on BP. The nonblinded crossover study included 28 participants aged 18 years to 30 years randomly assigned to eat either 3 g of licorice containing 100 mg of glycyrrhizic acid or a placebo control product. The participants ate either the licorice or the control for 2 weeks, took a 2-week break, and then switched groups for the following 2 weeks. Study participants measured their BP at home daily, and researchers measured hormone and salt levels as well as heart workload at the end of each intake period.
Results indicated that daily intake of licorice containing 100 mg glycyrrhizic acid significantly raised BP in the study participants. BP was found to increase by an average of 3.1 mm Hg in participants when they ate the licorice. Hormone levels of renin and aldosterone measured by researchers decreased after ingestion of licorice. A quarter of the participants who experienced higher reduction of hormone levels after eating licorice also experienced elevated levels of N-terminal pro-brain natriuretic peptide, a protein the heart secretes when it works harder to pump blood throughout the body. The authors concluded that the safe limit of intake needs to be reconsidered.
Dosage and availability
Licorice herbal supplements are available as liquid extracts, capsules, tablets, powder, lozenges, in tea bags, and raw (cut and sifted). Some are sold as deglycyrrhizinated to avoid the adverse effects associated with chronic use of licorice. However, it’s unclear if the deglycyrrhizinated products lead to the same health benefits. Dosages range from 150 mg/day to 1,200 mg/day. Licorice root is also sold as a cosmetic, advertised as a skin brightening serum.
What to tell your patients
Alert patients to check labels as many “licorice” products are not actually made of licorice but instead contain anise oil, which smells and tastes like licorice. Caution patients that while licorice root is generally considered safe, even small doses of 100 mg may adversely impact BP, and repeated use or large doses may pose a risk for patients with heart disease, hypertension, kidney disease, and those who are pregnant or nursing. ■