Controversial Study Investigates Association Between High Folate Intake and Autism

It’s at the top of the healthy pregnancy checklist: Take those prenatal vitamins! Prenatal multivitamins contain nutrients that are vital to your baby’s growth and development. Folic acid (the form of folate used in supplements), for instance, is known to reduce the risk of spinal birth defects. This proven health benefit is the reason that findings from a new study are so controversial: Mothers with very high levels of folate and vitamin B12 at the time of delivery were found to have an increased risk of having a child with an autism spectrum disorder. The study was reported in a press release from Johns Hopkins University Bloomberg School of Public Health. According to the press release, the study looked at data from 1,391 mother-child pairs participating in the Boston Birth Cohort study. The mothers signed up for the study at the time of their child's birth, between 1998 and 2013. Researchers measured the mother’s blood folate and B12 levels within one to three days after delivery, and then followed the mother-child pairs for several years. The researchers found:

  • One in ten of the women had excess folate (more than 59 nanomoles per liter, 30% higher than what is deemed adequate) and 6% percent had excess B12 (more than 600 picomoles per liter) at the time of their child’s birth.
  • Mothers with very high levels of folate—more than four times the adequate levels— were twice as likely to have a child who developed autism, and mothers with very high levels of B12 were three times as likely to have a child who developed autism.
  • Mothers with extremely high levels of both folate and B12 were 17.6 times as likely to have a child who developed autism.

This study does not establish a cause and effect relationship between high intakes of folic acid and B12 and autism, but it does raise new questions about whether unusually high intakes or differences in absorption or metabolism among mothers might contribute to their children’s autism risk. Nevertheless, it is important to bear in mind that folate and B12 are critical for babies’ healthy growth and development, and deficiencies during pregnancy can be harmful to the growing fetus. And there is also conflicting research suggesting that high levels of folate may reduce the risk for autism. Food sources for folate include leafy green vegetables, beans, citrus fruits, and beets; B12 is found in dairy, eggs, and meat; and both of these nutrients are commonly found in regular and prenatal multivitamins, as well as B-complex supplements. If you have concerns about your vitamin intake while pregnant or if you are considering pregnancy, talk with your healthcare practitioner to ensure you are getting the nutrients you need.

Source: Johns Hopkins University Bloomberg School of Public Health

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