Writing in the American Journal of Epidemiology, scientists at the University of Helsinki and the University of Edinburgh raised serious concerns about liquorice consumption among pregnant women.
Looking at a group of eight year olds born in Finland, the researchers found that those children whose mothers ate a lot of liquorice when pregnant performed worse than other youngsters in cognitive tests.
These children were also more likely to have poor attention spans and suffer from disruptive behaviour problems such as attention deficit hyperactivity disorder (ADHD).
Researchers said a component in liquorice called glycyrrhizin may be to blame. They said the chemical may impair the placenta, allowing stress hormones to cross from the mother to the baby.
High levels of such hormones, known as glucocorticoids, are thought to affect fetal brain development and have been linked to behavioural disorders in children, according to the scientists.
“Expectant mothers should avoid eating excessive amounts of liquorice,” said Professor Katri Räikkönen, from the University of Helsinki's Department of Psychology.
The threshold for excessive liquorice consumption was put at 100g a week, which works out at 500mg of glycyrrhizin. Women who ate more than this were found to be more likely to have children with lower intelligence levels and more behavioural problems.
Of the children who took part in the study, 64 were exposed to such high levels of glycyrrhizin in liquorice, 46 to moderate levels and 211 to low levels.
The study follows on from research published in the American Journal of Epidemiology back in 2001 that looked into the impact of liquorice eating on birth weight. The research team, which also included scientists from the University of Helsinki, found no link between eating large amounts of liquorice and low birth weight but did find a link with shorter pregnancies.
Source: American Journal of Epidemiology
October 4, 2009; (2009) kwp272v1
“Maternal Licorice Consumption and Detrimental Cognitive and Psychiatric Outcomes in Children”
Authors: K. Raikkonen, A.-K. Pesonen, K. Heinonen, J. Lahti, N. Komsi, J. G. Eriksson, J. R. Seckl, A.-L. Jarvenpaa, and T. E. Strandberg