Mothers-to-be, take note! Eating large amounts of liquorice, commonly known as mulethi in India, during pregnancy may adversely affect the development of your child's brain, a new study has warned.

In the study, youths that were exposed to large amounts of liquorice in the womb performed less well than others in cognitive reasoning tests carried out by a psychologist. The difference was equivalent to about seven IQ points.

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Those exposed to liquorice also performed less well in tasks measuring memory capacity and according to parental estimates, they had more ADHD-type problems than others. With girls, puberty had started earlier and advanced further.

Researchers, including those from the University of Helsinki in Finland, compared 378 youths of about 13 years whose mothers had consumed "large amounts" or "little/no" liquorice during pregnancy.

In the study a large amount was defined as over 500 milligrammes (mg) and little/no as less than 249 mg glycyrrhizin per week.

These cutoffs are not based on health effects. 500 mg glycyrrhizin corresponds on average to 250 grammes liquorice.

Researchers suggest that pregnant women and women planning pregnancy should be informed of the harmful effects that products containing glycyrrhizin – such as liquorice and salty liquorice – may have on the foetus.

Glycyrrhizin is one of many factors that affect the development of a foetus but it is impossible to say whether it was glycyrrhizin expressly that affected the development of a certain individual.

As a result of animal experiments, the biological mechanism of the effects of liquorice is well known.

Glycyrrhizin intensifies the effects of stress hormone cortisol by inhibiting the enzyme that inactivates cortisol.

While cortisol is essential to the development of a foetus, it is detrimental in large amounts.

It has long been known that glycyrrhizin causes higher blood pressure and shorter pregnancies in humans, but such long-lasting effects on the foetus have not been proven before.

The study was published in the American Journal of Epidemiology.