In the study by Dr Pål Surén, a researcher at the Norwegian Institute of Public Health, expectant mothers' dietary habits were recorded and the families were regularly surveyed for three to ten years to measure the development of autism spectrum disorders. The study population was 85,176 babies born between 2002/2008 derived from the prospective Norwegian Mother and Child Cohort Study (MoBa).
Dr Surén said, ‘It appears that the reduced risk of childhood autism only reflects folic acid supplements, not food or other supplements, and that the crucial time interval is from four weeks before conception to eight weeks into pregnancy.’
He added, ‘The study does not prove that folic acid supplements can prevent childhood autism. However, the findings are so apparent that they constitute a good argument to further examine possible causal mechanisms. It should also be ascertained whether folic acid is associated with a reduced risk of other brain disorders in children.’
A total of 270 cases of autism spectrum disorders were indentified within the population of the study – 114 autistic disorders; 56 with Aspergers syndrome and 100 cases of atypical or unspecified autism.
Mothers who took folic acid supplements in early pregnancy had a 40 per cent reduced risk of having children with an autistic disorder compared with mothers who did not take the supplement.
Researchers also analysed whether the risk of autistic disorder was influenced by the use of other dietary supplements, such as cod liver oil and omega-3 fatty acids or vitamins and minerals but they could not find a link.
Folic acid is required for DNA synthesis and repairs. Its naturally occurring form, folate, is found in leafy vegetables, peas, lentils, beans, eggs, yeast and liver. It is known to protect against spina bifida and other neural tube defects.
The study is published in the Journal of the American Medical Association (JAMA).