Could Too Much Folate During Pregnancy Cause Autism?

According to recent research, this important pregnancy nutrient might be linked to autism in children—but only if you have too much.

Pregnant Taking Prenatal Vitamins DONOT6_STUDIO/Shutterstock
Folic acid is a really important nutrient for pregnant women—it's necessary for women to consume enough of it to help ensure their babies develop properly—but according to new research, too much of this good thing might be a problem.

Researchers from Johns Hopkins University found that serious risks come with consuming too much folate, the naturally-occuring version of the nutrient. They discovered that if a mother's folate level is very high after giving birth, the risk of her child developing autism doubles. Folate isn't the only nutrient that could cause problems when consumed in excess: High vitamin B12 levels in new moms can triple the risk of autism. (Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, and dairy.) If both folate and B12 levels are very high, the risk autism is 17.6 times more likely.

Related: Preventing Autism in Pregnancy: Is It Possible?

Don't fear the folate

It's important to note that this research does not mean you should stop taking folic acid. What it does mean, however, is that moderation is key. The findings presented are associated with women whose folate levels were four times the adequate amount—so taking a supplement as recommended by your doctor is just fine. Folate naturally occurs in fruits and vegetables as well (particularly in oranges, grapefruit, grapes, bananas, asparagus, broccoli and spinach)—just be conscious of the amount your taking in via those sources and have a conversation with your OBGYN about how much you should be incorporating in total. According to the World Health Organization, between 13.5 and 45.3 nanomoles per liter is an adequate amount of folate for first trimester women to consume.

"Adequate supplementation is protective: That's still the story with folic acid," one of the study's senior authors, M. Daniele Fallin, Ph.D., said. "We have long known that a folate deficiency in pregnant mothers is detrimental to her child's development. But what this tells us is that excessive amounts may also cause harm. We must aim for optimal levels of this important nutrient."

How much is too much?

Researchers looked at data from 1,391 mother-child pairs for their research. Many of the women observed took multivitamins (which include folic acid and B12) during pregnancy, but researchers are still unsure why some of them had such high levels of the nutrients in their blood—it could have something to do with their consumption of folate-rich foods or excessive supplement consumption. It could also be genetic: some women may just be predisposed to absorbing more folate and metabolizing it slowly. It could also be a combination of factors.

More research is needed to fully understand this link—and to determine how much folic acid pregnant women should really be eating.

"This research suggests that this could be the case of too much of a good thing," study lead author Ramkripa Raghavan, M.P.H., M.Sc., a Dr.P.H. candidate in the Department of Population, Family and Reproductive Health at the Bloomberg School, said. "We tell women to be sure to get folate early in pregnancy. What we need to figure out now is whether there should be additional recommendations about just what an optimal dose is throughout pregnancy."