Like cilantro and blue cheese, black licorice is a polarizing food. The people who love it are completely devoted to it, and the people who hate it wouldn't touch it with a 10-foot pole. As an adult, you might find that some tastes are acquired — you've probably grown to like many foods you couldn't stand as a kid. But if you develop a distaste for licorice in childhood, chances are it'll stick with you.
As it turns out, the licorice haters might be on to something. The U.S. Food and Drug Administration, on the heels of numerous studies, has issued a consumer advisory about the dangers of consuming licorice on a daily basis. One study went so far as to call such overconsumption "licorice abuse." It's a real phenomenon that could put some licorice lovers at risk — especially those who are over 40 and have a history of heart disease or hypertension.
Licorice is made from the root of the Glycyrrhiza glabra plant, which is native to subtropical areas of Asia and southern Europe. Its distinctive taste comes from the compound glycyrrhizin, which is 50 times sweeter than sugar and helps the kidneys release potassium. Your kidneys are responsible for keeping a good balance of potassium in your system, which helps your heart function properly. If you eat a decent amount of licorice every day (about 2 ounces, or 40 to 50 grams), all that glycyrrhizin will flush out too much potassium and could throw off that delicate balance [source: FDA]. People who are already susceptible to heart problems could experience arrhythmia, lethargy, muscle weakness and even congestive heart failure. (Note that red licorice is fine as it does not contain the real licorice root.)
Licorice has fans who love it solely for its taste, but it's also been valued for centuries for its healing properties. In various traditions it's been used to treat Addison's disease, hypotension, gastric ulcers and chronic hepatitis B. It's known as a thirst quencher in the Middle East, where licorice drinks are popular. But experts now say that the dangers of this potential side effect far outweigh its benefits. The good news is that the damage is usually temporary — if you lay off the licorice, your symptoms will disappear fairly quickly.