In a new study, children whose mothers consumed large amounts of licorice root while pregnant were more likely to have behavioral and cognitive problems.
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Pregnant women should avoid eating large amounts of licorice root or black licorice candy, say Finnish scientists, after a study found that prenatal exposure to the sweet-tasting herb may be linked to earlier puberty, lower IQ, and behavioral problems in children.

The study compared the results of cognitive and memory tests for 378 children (with an average age of 13) whose mothers had either consumed little to no licorice during pregnancy or had consumed large amounts—defined as more than 500 milligrams of glycyrrhizin, the compound that gives licorice its signature taste, per week. (That’s about equal to 8 ounces of pure licorice root.)

The researchers found that kids who’d been exposed to large amounts of glycyrrhizin in the womb had poorer cognitive reasoning skills, and scored about 7 points lower on IQ tests, than those who’d been exposed to little or none. They also performed worse on memory tests and, according to reports from their parents, were more than three times likely to have symptoms of attention deficit hyperactivity disorder (ADHD).

For the girls in the study, higher glycyrrhizin exposure was also associated with earlier and more advanced puberty. Girls in the high-licorice group were more than an inch taller, on average, and weighed about 18 pounds more than those in the low-licorice group. The results were published last week in the American Journal of Epidemiology.

Does that mean licorice should be entirely off limits for expectant mothers? Not exactly, say the study authors from the University of Helsinki, but they do say that women should be informed of its potentially harmful effects.

In Finland, where black licorice and “salty licorice” candies (also known as salmiakki) are popular treats, the government already warns against consuming glycyrrhizin during pregnancy. While occasional consumption of licorice-flavored sweets or ice cream is not dangerous, the national guidelines state, licorice is generally “not recommended” for pregnant women.

In the United States, the National Institutes of Health also recommends that pregnant women avoid consuming large amounts of licorice root in food, or using licorice root as a supplement. In dried or capsule form, licorice root is sometimes used to treat ulcers and stomach ailments, sore throats, and viral infections.

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Research in animals has shown that glycyrrhizin can intensity the effects of cortisol, a stress hormone that’s essential to developing fetuses but can be harmful in large amounts. In humans, glycyrrhizin is also known to cause high blood pressure, low sodium levels, and premature births.

The researchers adjusted their results to account for factors such as the mother’s age, smoking status, alcohol and caffeine consumption, and stress during pregnancy—as well as the children’s own licorice consumption. But the study still couldn’t determine a cause-and-effect relationship between licorice exposure and the children’s various outcomes, and they say that other factors could have played a role, as well.

While the study only asked women about the quantities and brands of “licorice-containing confectionaries” they ate, glycyrrhizin can also be found in chewing gum, cookies, ice creams, herbal teas, and beverages.

In their paper, the authors write that their findings are comparable to the effects of binge drinking during pregnancy on children’s cognitive and behavioral problems. Just as women are warned against drinking while pregnant, they say, they should also be informed of the potential risks of too much licorice.

The authors also wrote that they “cannot determine the extent to which our findings generalize to countries where licorice is not as commonly consumed.” But they point out that even in the U.S. the average daily consumption of glycyrrhizin can be up to 215 mg—suggesting that some women might be wise to cut back while they’re expecting.