Should pregnant women avoid licorice?

Licorice is from the root of Glycyrrhiza glabra, prized for centuries because it is sweet and because of purported medical properties. Believers in traditional Chinese medicine consider it vital for the 12 regular meridians while Ayurveda claims it rejuvenates the body. Given that it is natural, and has been in use for hundreds of years across the world, it is odd that believers in organic food and other ancient practices are now being told this natural product will harm pregnant women. 

In animal models, glycyrrhizin intensifies the effects of the stress hormone cortisol by inhibiting the enzyme that inactivates cortisol. Cortisol is essential to the development of a fetus, but like lots of things it is detrimental in large amounts. Mice are not little people and no one has shown harm in humans yet.

Yet the new paper uses epidemiology to claim what toxicology cannot, and leaves the notion of a biological mechanism out. A new paper finds that the natural sweetener in licorice, glycyrrhizin, can have long-term harmful effects on the development of babies. In the epidemiology analysis, the authors compared 378 Finnish youths of about 13 years whose mothers had consumed "large amounts" or "little/no" licorice during pregnancy and determined that those 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 approximately seven IQ points.

A large amount was defined as over 500 mg and little/no as less than 249 mg glycyrrhizin per week. 500 mg glycyrrhizin corresponds on average to about a half pound of licorice. The authors are recommending that pregnant women and women planning pregnancy should be informed of the harmful effects of products containing glycyrrhizin. In Finland, that is already the case. In January 2016, their National Institute for Health and Welfare published food recommendations for families with children, in which licorice was placed in the ‘not recommended’ category for pregnant women.

What about the large number of Finns that were exposed to glycyrrhizin in the womb for centuries? It's still an epidemiology study with a weak association, but it may be one more thing young people can blame their mothers for.

Citation: Katri Räikkönen et al., Maternal licorice consumption during pregnancy and pubertal, cognitive and psychiatric outcomes in children. American Journal of Epidemiology. DOI:10.1093/aje/kww172.