In a recent report, researchers examined the association between use of prenatal folic acid supplements and subsequent risk of autism spectrum disorders, including Asperger’s syndrome, autistic disorder, and pervasive developmental disorder in children.

The study, which was published in JAMA, followed 85,176 children. At the end of the follow-up, the children’s ages ranged from 3.3 to 10.2 years. The authors were interested in the use of folic acid from 4 weeks before to 8 weeks after the start of pregnancy.

At the end of the study, 270 children were diagnosed with autism. There was a 2.1 times higher risk of autism in children whose mothers did not take folic acid. Supplementing with folic acid meant a 39 percent decrease in the chance of developing autism.

Folic acid is a B vitamin that is water soluble, inexpensive, and has few side effects. In previous studies, it was shown to lower the risk of neural tube defects in children.

The U.S. government has recognized the benefits of folic acid supplementation by mandating that flour be fortified with folic acid.

When taking folic acid, it is important to supplement vitamin B12 with it.

How much folic acid should you take? I suggest 1 mg a day before becoming pregnant, along with 1 mg of natural vitamin B12 in the form of hydroxy- or methyl-cobalamin.