Dear Doctor: My wife wants me to quit eating black licorice because she heard it’s bad for you. I think it’s just that she can’t stand the taste of it herself. I told her I was writing this email, and she said I have to include that I’m 42 and on blood pressure meds.
Dear Reader: Your wife is remembering a warning about black licorice issued by the Food and Drug Administration in 2017, just a few weeks before Halloween. Considering that Americans now spend upward of $2.7 billion (yes, with a B; and yes, we’re kind of shocked) per year on Halloween candy, the FDA’s timing seems spot on. According to the warning, “If you’re 40 or older, eating 2 ounces of black licorice a day for at least two weeks could land you in the hospital with an irregular heart rhythm or arrhythmia.”
To understand why, we need to talk about Glycyrrhiza glabra, the plant used to give licorice candy its distinctive flavor. Commonly referred to as licorice root, Glycyrrhiza glabra is a member of the pea and bean family, and is native to certain areas of Europe, the Middle East and western Asia. Its fleshy roots contain a compound called glycyrrhizin, which is 50 times sweeter than sugar.
Licorice root has medicinal properties, and it is a centuries-old treatment for a variety of ailments, including heartburn, stomach upset, ulcers, sore throat and bronchitis. However, one of the side effects of consuming glycyrrhizin is a potentially dangerous drop in the levels of potassium in the body. This means eating too much licorice can lead to a range of symptoms including high blood pressure, leg swelling, exhaustion, lethargy, cramping, abnormal heart rhythms and even congestive heart failure. Research shows that when you stop eating black licorice, potassium levels will usually return to normal on their own.
If you’re wondering why your wife wanted you to share your age and health status in your email, it’s because according to the FDA, people over the age of 40 who also have a history of hypertension or heart disease should be particularly careful not to eat too much licorice. Eating as little as 2 ounces — that’s four small pieces — of licorice every day for two weeks is enough to land someone in the hospital. Scientists at the National Institutes of Health, who take an even dimmer view of the candy, state that even 1 ounce of licorice per day consumed over the course of several weeks may be “potentially unsafe.” To avoid problems, black licorice lovers of any age should never eat large amounts of the candy at one time.
It’s also important to note that glycyrrhizin, the flavoring compound in licorice root, has the potential to interact with some medications, herbs and dietary supplements. For instance, the NIH warns that black licorice blunts the effects of the blood thinner warfarin, and it interferes with certain blood pressure drugs, steroid drugs and diuretics. If black licorice is a constant in your diet and you regularly take any medications or supplements, it would be wise to check with your doctor or pharmacist for any potentially adverse interactions.
Dr. Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health.