Does Eating Licorice During Pregnancy Raise ADHD Risk?

Eating licorice in pregnancy is linked to a range of developmental issues, according to a recent Finnish study on almost 400 young adolescents with an average age of 12.5. Licorice consumption is thought to be higher in Finland than in many other countries, thanks to the popularity of salmiakki, a popular salty licorice snack.

Researchers found girls whose mothers had consumed high amounts of licorice during pregnancy were more likely to go through puberty at a younger age.

And girls and boys whose mothers consumed high amounts scored seven points lower on intelligence tests, and higher for attention deficit hyperactivity disorder.

Glycyrrhizin

As with many other diet studies, however, the picture is too complex for us to assume a direct cause and effect relationship.

The component in licorice thought to cause damage is called glycyrrhizin. But it’s also found in a range of other foods, drinks and medicines.

Only licorice intake was measured in the study, so the actual level of glycyrrhizin the women ate is merely an estimate.

Many other factors influence cognitive development, and it’s not clear if the researchers fully adjusted for all possible factors. But, as a precaution, it’s advised pregnant women avoid the herbal remedy licorice root, as it has a particularly high concentration of glycyrrhizin.

The study was carried out by researchers from the University of Helsinki in Finland.

Longitudinal Cohort Study

This was a longitudinal cohort study of Finnish mothers and children.

The study previously looked at the children when they were eight years old and found those whose mothers reported high licorice consumption during pregnancy scored lower on tests of intelligence and memory, and had a higher risk of behavioral problems.

The researchers aimed to follow up on this cohort of children again, now with a mean age of 12.5 years, to explore associations with puberty maturation and cognitive and behavioral factors.

A cohort study can show links between factors – in this case, licorice consumption in pregnancy and later outcomes in childhood and adolescence – but cannot show that one factor causes another.

Methodology

The study looked at 378 children born in 1998, now with a mean age of 12.5 years, whose mothers had either consumed large amounts of glycyrrhizin, a natural constituent of licorice, of more than 500mg a week, or a low amount of less than 249mg a week.

While on the maternity ward, mothers reported the brand and how much licorice they ate on a weekly basis during pregnancy. The researchers used this amount to calculate the quantity of glycyrrhizin consumed a week in mg.

Of the 378 children, 327 children were exposed to low amounts of glycyrrhizin in the womb and 51 were exposed to high amounts.

At follow-up, children were assessed for:

  • stages and signs of puberty, based on three measures of growth and development – this included height, weight, body mass index (BMI) for age, and the difference between current and expected adult height; the researchers also looked at Tanner staging for pubertal stage and the Pubertal Development Scale, both well-validated ways of measuring pubertal development
  • cognition – based on tests of intelligence, memory and learning, social perception, attention and executive function
  • psychiatric problems – based on their mother’s completion of the Child Behaviour Checklist
  • neuroendocrine function – studying how hormones like cortisol could affect the function of the nervous system and, in turn, other functions, such as the metabolism

Confounding variables were adjusted for, including:

  • child’s age
  • educational level of either parent
  • maternal age and BMI
  • maternal smoking and alcohol intake
  • coffee, tea and chocolate consumption
  • stress during pregnancy

Results

Girls whose mothers consumed high amounts of licorice during pregnancy, compared with those whose mothers consumed low amounts:

  • were 3cm taller on average (mean difference [MD] 0.4 standard deviations [SD], 95% confidence interval [CI] 0.1 to 0.8)
  • were 8kg heavier on average (MD 0.6 SD, 95% CI 0.2 to 1.9)
  • had BMIs 2.2 higher (MD 0.6 SD, 95% CI 0.2 to 0.9)
  • 37.9% scored “development definitely under way” on the Pubertal Development Scale Score, compared with 10.4%

For boys, there were no consistent associations between maternal licorice consumption during pregnancy and pubertal maturation at this age.

Girls and boys whose mothers consumed high amounts of licorice during pregnancy, compared with those whose mothers consumed low amounts:

  • scored seven points lower on tests of intelligence quotient on a scale of 100 points (95% CI 3.1 to 11.2)
  • had threefold greater odds of attention deficit hyperactivity disorder (ADHD) problems (95% CI 1.4 to 7.7)

No difference was found in cortisol levels.

Conclusions

The authors concluded that,

“Nutritional recommendations of various expert organisations do not mention glycyrrhizin use during pregnancy.

The present findings suggest that pregnant women should be informed that consumption of licorice and other food products containing glycyrrhizin may be associated with harm for their developing offspring.”

This study provides evidence of some link between how much licorice a pregnant woman eats and earlier puberty in girls, but not boys.

It also shows some association between pregnant women eating licorice and their children scoring lower for intelligence and being more likely to have ADHD.

However, this study has some limitations to consider:

  • Glycyrrhizin is found in other food products, such as chewing gum, sweets, cookies, ice creams, herbal teas, and herbal and traditional medicines, as well as alcoholic and non-alcoholic drinks.
  • The amount of these products the women ate was not reported, which means their intake of glycyrrhizin may not have been measured accurately.
  • Although the study accounted for some confounding variables, there are other factors that might have affected the results that were not reported – for example, income or social class.
  • The study was carried out on healthy babies all born in Helsinki, Finland. People in this region may consume larger amounts of licorice than people in other countries, especially a salty licorice called salmiakki, so the results may not be generalisable to women in the UK or elsewhere.
  • There were only 51 children in the group who had mothers who consumed large amounts of licorice. This is a fairly low number, and a bigger study may have shown less difference between the groups.

As a precaution, it’s advised pregnant women avoid the herbal remedy licorice root, as it contains high levels of the active ingredient glycyrrhizin.

There’s also evidence that all people – not just pregnant women – should avoid regularly eating very high levels of licorice of more than 57g (two ounces) a day for more than two weeks as this could lead to potentially serious health problems, such as increased blood pressure and an irregular heart rhythm (arrhythmia).

Räikkönen K, Martikainen S, Pesonen A, et al.
Maternal Licorice Consumption During Pregnancy and Pubertal, Cognitive, and Psychiatric Outcomes in Children
Am J Epidemiol (2017) 1-12. DOI: https://doi.org/10.1093/aje/kww172

Image: Marcin Floryan CC BY-SA 2.5

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