A new study supports growing evidence that prenatal folic acid (vitamin B-9) significantly reduces the risk of autism. The findings support previous research showing lower risk of autism in children of mothers who take folic acid in the weeks before and after conception. The report appears today in the Journal of the American Medical Association.
The Autism Birth Cohort study is funded by the U.S. National Institute of Neurological Disorders and Stroke. It uses information on more than 85,000 children from the Norwegian Mother and Child Cohort. Norway does not fortify food with folic acid. So supplements represented the women’s only source of vitamin B-9 beyond diet. Researchers noted the use of folic acid supplements from four weeks before the start of pregnancy to eight weeks after.
The study found that children whose mothers took folic acid had a 39 percent reduced risk of developing autistic disorder. Due to smaller numbers, the findings were not clear for higher-functioning forms of autism such as Asperger syndrome and pervasive developmental disorder-not otherwise specified (PDD-NOS). [Note: The American Psychiatric Association is combining these autism subtypes into a common diagnosis of autism spectrum disorder (ASD) in the forthcoming DSM-5 diagnostic manual. More on the DSM-5 here.]
Past research with American families found a similar association. It suggested that prenatal folic acid’s association with reduced autism risk is particularly dramatic among women with gene changes that impair the body’s regulation of folate. Folate is the form of vitamin B-9 found in food. Other research, from the Norwegian cohort, suggested that folic acid supplements around conception substantially reduce the risk of severe language delay. Taking folic acid supplements during early pregnancy is also known to protect against spina bifida and other neural tube defects in children.
Folate is found in leafy vegetables, peas, lentils, beans, eggs and liver. In addition, folic acid is added to flour in the U.S. and Canada.
"Our findings extend earlier work on the significance of folate in brain development,” says joint senior author Ezra Susser, M.D., Dr.P.H. “They also raise the possibility of an important and inexpensive public health intervention for reducing autism spectrum disorders." Dr. Susser is a professor of epidemiology at Columbia University's Mailman School of Public Health and professor of psychiatry at the College of Physicians and Surgeons. He is also a member of Autism Speaks scientific advisory committee.
“These important findings provide further support for the beneficial role of folic acid intake during pregnancy,” concurs Alycia Halladay, Ph.D., Autism Speaks senior director of environmental and clinical sciences. “It’s among the first to show that very early folic acid intake may reduce the risk of autism.” Such insights should inform public health strategies for all women, she adds. Dr. Halladay also urges further research into the ways that many types of “environmental exposures” during pregnancy – including maternal nutrition – can increase or decrease autism risk.
[From the Editors: Please note, these research findings should not be interpreted as assigning blame for autism to whether or not a woman was taking folic acid supplements when she became pregnant. Nor do they indicate that prenatal folic acid can ensure that a child will not develop autism. Rather they show an overall reduction in autism risk across a large group of women who took such supplements. For more perspective, please see “Risk vs Cause” and “Communicating Autism Risk,” on the Autism Speaks Science Blog.]