Researchers from Johns Hopkins Bloomberg School of Public Health reported that too much folate in a new mother’s body may increase a child’s risk of developing an autism spectrum disorder. Findings from the study will be presented at the 2016 International Meeting for Autism Research. 

M. Daniele Fallin, PhD, one of the study’s senior authors, 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.”

The study authors analyzed data from 1,391 mother-child pairs in the Boston Birth Cohort; the mothers were recruited at the time of their child’s birth between 1998–2013. Folate levels were assessed once within the first 1–3 days of delivery. Ten percent of the women were found to have excessive folate levels (>59nmol/L) and 6% were found to have excessive vitamin B12 levels (>600pmol/L). 

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The data indicated a new mother with >4 times the adequate levels of folate right after giving birth was found to have twice the risk of her child developing an autism spectrum disorder. In addition, very high levels of vitamin B12 in new mothers potentially tripled the risk of their child developing an autism spectrum disorder. This risk increased 17.6-fold if the mother had extremely high levels of both folate and vitamin B12. A majority of the mothers reported having taken multivitamins throughout their pregnancy that contained folic acid and vitamin B12. Possible reasons for excess folate levels may be due to the mother consuming too many folic acid-fortified foods or supplements, mothers who are genetically predisposed to absorbing higher amounts of folate or metabolizing it slower, or a mix of both. 

Folate, a type of vitamin B, is naturally present in fruits and vegetables. Folic acid, its synthetic version, is added to fortify cereals and breads and is found in vitamin supplements. According to the World Health Organization, the adequate amount of folate for a woman during her first trimester of pregnancy is between 13.5–45.3nmol/L; there are not well-established levels for vitamin B12 levels. 

Dr. Fallin added that further research is needed to see how much folic acid should be consumed during pregnancy to ensure that the woman will have optimal folate levels for a healthy baby. 

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