With autism now affecting one in 88 children in the U.S., many parents are searching for any step they can take to help lower their child's risk of developing the disorder. A new Norwegian study joins a small but growing body of research that suggests a simple, low-cost option already exists: Taking folic acid during the earliest stages of pregnancy could lower a child's odds of developing autism by nearly 40 percent.
"This is a relatively inexpensive way that parents can take action to possibly prevent risk of tube birth defects and autism," Alycia Halladay, senior director for environmental and clinical Sciences for the advocacy group Autism Speaks, told The Huffington Post. Halladay did not work on the new study, which was published online in the Journal of the American Medical Association on Tuesday.
Researchers analyzed a sample of more than 85,000 children born in Norway between 2002 and 2008 to study the effect of taking a folic acid supplement -- typically between 200 and 400 micrograms per day -- from one month before a woman got pregnant to two months after. Some .10 percent of children whose moms took folic acid supplements were diagnosed with autism, compared to .21 percent of those whose moms did not -- which is equal to 39 percent lower odds.
The study does not establish a cause and effect relationship between the vitamin and subsequent autism, and its authors do not know why folic acid may have a protective effect. Study researcher Pal Suren of the Norwegian Institute of Public Health told HuffPost that folic acid is critical to the synthesis of DNA, which could play some role in the connection. Folic acid may also affect how certain genes are turned on and off in the body, he hypothesized, saying it was "not biologically implausible" that folic acid supplementation has certain epigenetic effects.
The new study also raises questions about how much folic acid may be needed to lower autism risk, as well as what form it must come in.
"We do not know how other dosages would have affected the risk of autism, or whether it matters if folic acid is taken as single tablets or as part of a prenatal multivitamin supplement," Suren said.
The researchers took steps to ensure that the decreased risk was not just because women who took folic acid were also engaged in other healthy behaviors. To control for that, they looked at fish oil use (assuming women who took fish oil were also likely to be healthy in other ways) and found no link between lower autism risk.
Since the early 1990s, groups like the Centers for Disease Control and Prevention and the U.S. Public Health Service have recommended that all women of childbearing age take 400 micrograms of folic acid daily to help prevent neural tube defects -- birth defects of the brain and spinal cord including spina bifida and anencephaly. Since folic acid was added to the grain supply in 1998, the U.S. has seen a 26 percent decrease in those neural tube disorders, according to figures compiled by the March of Dimes.
The possibility of a link between folic acid consumption and lower autism risk is far more preliminary. A 2011, California-based study in the journal Epidemiology found that mothers of children with autism were less likely to have taken a prenatal vitamin in the three months before pregnancy or in the first month after getting pregnant, suggesting that so-called "periconceptional" use of prenatal vitamins may reduce autism risk. In the U.S., prenatal vitamins typically include between 400 and 800 micrograms of folic acid.
But folic acid is by no means a magic pill, experts caution. The fact that rates of autism diagnosis have skyrocketed in the past several decades despite more and more women taking folic acid shows how complex the origins of autism are. The exact causes of the disorder, which is characterized by social and communication difficulties and repetitive behaviors, are still unknown.
"This is one way that risk may be reduced, but this isn't the only way," said Halladay. "It's an inexpensive way to potentially reduce the risk of autism, but there are a number of risk factors -- genetics and other environmental factors -- that solidly contribute to risk."