Licorice roots have a diverse history, having been used throughout history as a flavoring agent and as an ingredient in some licorice candies, while in ancient Egyptian times it was a tea and the Chinese used it for medicinal purposes.
One trend in the alternative medicine movement, which seeks to replace approved pharmacology with essentially untested natural products (as long as they carry a disclaimer FDA has not verified their efficacy or safety), is for women to take licorice extracts as supplements to treat hot flashes and other menopausal symptoms.
That local supplement store won't know any better, but it is a health risk if women take real medications.
At the American Chemical Society meeting, the presenters note that just because a substance is sold as a supplement in a self-proclaimed "health food" store, that doesn't mean it is safe for all people to take. The U.S. Food and Drug Administration recommends that licorice not be eaten in large amounts during one sitting, and warns that excessive consumption can lead to irregular heart rhythm and muscle fatigue.
"Concerns about the risk of stroke and breast cancer associated with conventional hormone therapy are prompting women to seek alternatives," says Richard B. van Breemen, Ph.D., of the University of Illinois at Chicago. "Some take botanical dietary supplements, such as licorice, to treat menopausal symptoms like hot flashes."
Breemen and colleagues wondered if the small amounts in dietary supplements might also cause problems by interfering with drug metabolism or transportation.
"The liver has enzymes that process medications, and if these enzymes are induced or inhibited, the drugs will either be processed too quickly or too slowly, respectively."
These changes could pose a significant safety risk to those who take a daily licorice dietary supplement along with other medication.
Van Breemen's team analyzed how three types of licorice -- two North American species, Glycyrrhiza uralensis and G. inflata, and a European species called G. glabra -- affected liver enzymes involved in drug metabolism. They found that all three species inhibit several of these enzymes. Only G. uralensis and G. inflata extracts were found to induce some of these enzymes. Therefore, the researchers say that G. uralensis and G. inflata are more likely to interfere with drug metabolism when compared to G. glabra.
Consumers would have a difficult time using this information, however, because most supplements don't list the species on their labels. But the researchers are using this knowledge to develop their own licorice therapy that would be safe and effective for women experiencing menopausal symptoms, such as hot flashes. They plan to start clinical trials on their G. glabra-based supplements next year.