A study from the United States has found that the brain development of mice embryos is harmed if their mothers take high amounts of folic acid during pregnancy.

The researchers liken this to a ‘Goldilocks effect’ where too much folic acid may be as detrimental as too little. The study involved pregnant mice who were given either a normal amount of folic acid, 10 times the recommended amount, or none. The offspring of the mice that received the largest amount showed significant brain changes which mimicked those associated with a deficiency of folic acid.

Folic acid supplementation is widely recommended for women of child-bearing age as it has been shown to reduce the risk of neural tube defects, such as spina bifida. However, the findings of this study suggest that while addition of folic acid to the diet is a good thing, there is a ‘best amount’ and some women may be getting too much.

This study is highly problematic for women who have given birth to a child with neural tube defects or who have certain conditions like epilepsy and have therefore been advised to take much higher doses of folic acid in pregnancy. There is now an urgent need for research to re-evaluate the amount of folic acid that is optimal for pregnant women.

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Read more: De Crescenzo, A. et al. (2020) Deficient or excess folic acid supply during pregnancy alter cortical neurodevelopment in mouse offspring. Cerebral Cortex (September) doi.org/10.1093/cercor/bhaa248