Women who consume liquorice during pregnancy might be more likely to have children with cognitive or behavioural problems than mothers who don't eat a lot of this candy while they're pregnant, a small Finnish study suggests.
Some previous lab experiments have linked glycyrrhizin, a natural sweetener in liquorice root, to changes in the placenta that may make it easier for the stress hormone cortisol to travel from mothers to their developing babies, said lead study author Katri Raikkonen of the University of Helsinki.
Some cortisol aids fetal development, but too much may alter neurodevelopmental processes and contribute to cognitive or behaviour issues later in life, Raikkonen said by email.
For the current study, researchers examined data on 378 children born in Helsinki in 1998 and their mothers, quizzing the women on liquorice consumption after they gave birth and then assessing children for developmental issues when they were about 13 years old.
Girls and boys born to mothers who ate a lot of liquorice during pregnancy - which researchers defined as an amount containing at least 500 milligrams (0.02 ounces) of glycyrrhizin a week - scored lower on intelligence tests, had poorer memory and higher odds of attention deficit hyperactivity disorder than children whose mothers consumed little or no liquorice during pregnancy, the study found.
Girls also appeared to start puberty sooner when mothers ate a lot of liquorice during pregnancy.
"Our findings therefore suggest that it would be sensible to avoid liquorice and other food products that contain glycyrrhizin during the 40 weeks of pregnancy," Raikkonen said.
Because liquorice extracts are used extensively as sweeteners in food, drinks and some herbal products, one 2006 study estimated average glycyrrhizin consumption in the US at anywhere from 1.85 mg to 205 mg per day for a 150-pound person.
In the current study, 327 of the children were exposed to no liquorice at all in utero or no more than 249 milligrams of glycyrrhizin a week, researchers report in the American Journal of Epidemiology. Mothers of these kids consumed 47 mg of glycyrrhizin a week on average while they were pregnant.
Another 51 kids had mothers who consumed at least 500 mg of glycyrrhizin a week during pregnancy, or about 845 mg a week on average.
When compared to the children exposed to little or no liquorice in utero, kids exposed to a lot of liquorice scored more than 7 age-standardized points lower for estimated general, verbal and performance IQ and also did worse on tests measuring verbal productivity and memory.
Kids with high glycyrrhizin exposure also had more than three-fold higher odds of attention deficit hyperactivity disorder, the study found.
Girls with higher glycyrrhizin exposure in the womb appeared to weigh more and start breast development sooner than girls whose mothers consumed little or no liquorice.
Beyond its small size, another limitation of the study is that it's not a controlled experiment designed to prove that liquorice consumption during pregnancy directly causes developmental problems in children, researchers note.
They also lacked data on the amount of glycyrrhizin in any liquorice women ate during pregnancy or other food or drink they might have consumed with glycyrrhizin in it.
Not all liquorice contains a lot of glycyrrhizin, Katherine Keyes, a public health researcher at Columbia University Medical Center in New York said in a phone interview.
"If you are going to avoid something in pregnancy, there is much more evidence for avoiding alcohol or smoking," said Keyes, who wasn't involved in the study. "With liquorice consumption, the science is still not clear."
"Women are bombarded during pregnancy with so many things they can't do and not listen because it's too much," Keyes added. "Focusing on alcohol and tobacco is the most important, and focusing on other things like liquorice is less important."