Excess folic acid during pregnancy may raise child’s risk of autism spectrum disorder, diabetes, and obesity

Excess folic acid during pregnancy may raise child’s risk of autismExcess folic acid during pregnancy may raise child’s risk of autism spectrum disorder, diabetes, and obesity. Pregnant women are generally advised to boost their folic acid intake as it contributes to healthy brain development and protects the baby against birth defects. The new study observed that excessive intake of folate and vitamin B12 may increase the risk of the baby developing autism spectrum disorder.

Co-researcher Daniele Fallin said, “The new research question before us is to understand the optimal dose. Some [folate] is a good thing. It does appear the levels in the body could get too high, and that would be a bad thing. Supplementation is indeed an important thing. We would not want anyone to interpret from this that they should stop taking vitamin supplements if they are intending to get pregnant or if they are pregnant.”


The study showed that mothers with high levels of folate at the time of delivery had double the risk of autistic child, compared to mothers with normal levels. Furthermore, mothers with excessive B12 were also three times more likely to have a child with autism. The risk was highest in mothers with excess folate and vitamin B12 – 17 times greater, compared to mothers with normal levels of both nutrients.

Folate is found naturally in fruits and vegetables, and the synthetic version – folic acid – is commonly found in fortified cereals.

Although the researchers found an association, they did not establish a cause-and-effect relationship. They do not recommend that pregnant women lay off the supplements altogether, as other studies have shown that pregnant women who take folate and vitamin B12 up to five times a week have lower risks of having an autistic child, especially when taken during the first and second trimester.

Fallin explain, “We saw those women who had extremely high, much higher than the recommended amount, of folate or vitamin B12 were more likely to have children who later had a diagnosis of autism.”

The researchers can’t explain why these women had higher levels of folate and vitamin B12, whether it had to do with a genetic predisposition to higher levels or excess supplements or food containing such nutrients. Fallin does suggest that pregnant women should speak to their doctors about their nutrition to see where they need to increase or maybe even lower their intake.

It is still too early in the studies to start advising women on the risks of folate and vitamin B12, so additional research is required to further understand the mechanisms at work.

Excessive folic acid during pregnancy may put daughters at risk of diabetes and obesity

An alternative study found that too much folic acid while pregnant may put daughters at risk of diabetes and obesity. The findings suggest there is a need for revisions for safer upper limit recommended intake of folic acid in pregnant women.

Portuguese researchers gave excessive amounts of folic acid – 20 times greater than the recommended dose – to 20 rats throughout their mating, pregnancy period, and lactation.

The offspring were overweight and insulin resistant in adulthood. They grew up to be deficient in adiponectin, which is a hormone that protects against diabetes. These traits were seen in female offspring only.

Proper intake of folic acid can protect babies against neural tube defects, and the World Health Organization recommends 0.4 mg of folic acid daily unless a woman has a family history of neural tube syndrome – then she should increase her intake tenfold.

Lead author Professor Elisa Keating said, “While taking a minimum of 0.4 mg of folic acid per day is essential when pregnant, our study shows that it is possible to have too much of a good thing. Considering the increasing amount of folic acid consumed during pregnancy through fortified foods, multivitamin pills, and supplements, the search for a safe upper dose of folic acid is urgently needed. Our study clarifies the potential effects of excess folic acid exposure and may play an important role on rethinking current public health policies surrounding folic acid supplementation.”

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