By taking folic-acid supplements in early pregnancy, women may be able to significantly reduce the chances of their children developing autism, new research suggests.
The findings are based on an assessment of more than 85,000 babies born between 2002 and 2008 in Norway. Of those children, 270 were diagnosed with Autism Spectrum Disorders. At the beginning of the study the mothers completed detailed questionnaires, and the researchers did frequent follow-ups with the families.
The analysis, published Tuesday in the Journal of the American Medical Association, indicates that folic-acid supplements may reduce a child's chances of autism by 40 per cent. But timing is critical. The risk was lessened only when the 400-microgram (mcg) tablets were taken at least four weeks before and eight weeks after the start of pregnancy.
That means mothers-to-be should be popping the supplements even before they are certain they are pregnant.
"You never know when you are going to be in that particularly vulnerable period during the development of a fetus," said Columbia University professor Dr. Ian Lipkin who was part of the joint American-Norwegian research team that conducted the study.
Folic acid is the synthetic form of folate, a B vitamin found in green leafy vegetables such as spinach, and in legumes like lentils and kidney beans. Folate is a building block of DNA and is needed for normal cell division. Previous research has already shown that folate helps prevent certain birth defects such as spina bifida.
Since 1998, food manufacturers in Canada and the United States have been required by law to add folic acid to bread, pasta, flour and other grain products.
Norway does not have mandatory folic-acid food fortification rules, but Norwegians generally consume higher levels of naturally folate-rich foods than their North American counterparts, said Lipkin.
"The conclusion we have come to is that diet is not sufficient. You have to take the vitamins," he added. "So we strongly encourage supplemental folate for women of child-bearing age."
Some scientists believe autism likely results from a combination of genetic factors and environmental triggers – which might occur both before birth and in early childhood.
Lipkin noted that previous studies have hinted that folate levels might play a role in some cases of autism. "There was some earlier work that suggested language disorders were less likely in children of mothers who had taken folic acid during pregnancy. And autism, in a sense, can be thought of as a language disorder – it is a social disorder, it is a problem with communication."
Still, folic-acid supplementation is not without controversy. In recent years, some animal studies have hinted that high levels of folate may fuel the growth of pre-existing tumours. Other studies, however, found no such links.
"I have not been persuaded by the evidence" of a cancer connection, said Lipkin. He noted 400 mcg a day is a relatively small amount of the B vitamin, and by no means a big dose. What's more, all B vitamins are water-soluble which means they are not stored up in the body.
"This is a wise course. It is a prudent way to go," he said. Indeed, many health organizations already recommend this amount of folic acid for potential mothers as a safeguard against neural-tube birth defects including spina bifida in which the spine can be severely deformed.