WebMD Newsroom

by Daniel J. DeNoon

Eat too much candy and you’ll be sorry. Eat too much black licorice, and you could be dead.

This creepy Halloween warning comes from the FDA. Too much black licorice, the federal agency says, can lead to “abnormal heart rhythms, as well as high blood pressure, edema (swelling), lethargy, and congestive heart failure.”

How much is too much? The FDA warns people age 40 and older not to eat 2 ounces of black licorice a day for two weeks or more.

And that’s a conservative warning. The NIH has warned that it’s “possibly unsafe” to eat just 1 ounce of black licorice a day for several weeks. In addition to the FDA’s list of drastic possible too-much-licorice results, the NIH adds paralysis, brain damage, and erectile dysfunction.

And if you eat a lot of salt, if you have high blood pressure, or if you have heart or kidney disease, the NIH says as little as a sixth of an ounce of licorice a day could cause these problems.

The issue, well known to many forms of traditional medicine, is that licorice root contains a drug: glycyrrhizin.

Many of those who use licorice as an herbal remedy seek relief of sore throat, cough, infections, arthritis, lupus, or chronic fatigue syndrome. It’s been used to treat all kinds of ailments ranging from muscle cramps to prostate cancer, although there’s no solid scientific evidence that it actually works.

But the potential side effects are real enough. That’s because licorice — real black licorice, not the phony licorice-flavored stuff flavored with anise oil — causes a drop in potassium levels. It may also mimic the activity of the female sex hormone estrogen.

The NIH advises women NOT to eat black licorice while they are pregnant or breast feeding. People with hormone sensitive conditions, such as breast cancer or endometriosis, should avoid licorice.

And don’t eat licorice for at least two weeks before planned surgery. It can interfere with blood pressure during and after your procedure.

The NIH warns people taking Coumadin (warfarin) never to eat black licorice, as licorice makes the drug less effective. And the NIH says licorice also may interfere with digoxin, estrogens, furosemide, blood pressure drugs, steroid drugs, and diuretics (water pills). Also, licorice may alter the activity of drugs processed by the liver.

Interest declared: I love black licorice. But this Halloween, I’m cutting back.