A new retrospective study has found that women who consumed lower amounts of folic acid during the early stages of pregnancy were more likely to have a child who developed autism.
Consuming the recommended minimum of 600 milligrams per day of the B vitamin folate - found naturally in foods and in the form of folic acid in prenatal supplements and fortified foods - during the first month of pregnancy was associated with a 38 percent lower chance of having a child on the autism spectrum, researchers reported last week in the American Journal of Clinical Nutrition.
Folic acid supplementation has been recommended to pregnant women and those expecting to become pregnant since the link was made between deficiency and neural tube defects such as spina bifida. Fortification of processed foods in which natural folate is removed such as white bread, other white grains, and breakfast cereals has also been implemented in many countries.
Whether a lack of this important vitamin or difficulties metabolizing it efficienctly may also increase the risk for developmental disorders such as autism has remained an unanswered question. Folate is vital for the development of the brain and central nervous system which has led some scientists to conclude an insufficient supply to the foetus during pregnancy may contribute to autism; meanwhile other researchers hypothesize that the adoption of a high folate intake by pregnant women could equally have had negative consequences for brain development and function and linked it to the recent upward trend in the incidence of the disorder.
With these polar viewpoints on the role folate may play in the development or prevention of autism, researchers on the current study were understandably retiscent to predict the results they might get.
Rebecca Schmidt of the University of California, Davis, lead author of the study said: "When we starting looking at this, I thought it could go either way."
The study involved families in California enrolled in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study between 2003 and 2009.
Schmidt and her colleagues surveyed the mothers of 429 preschoolers with an autism spectrum disorder and 278 with normal development about their diet and supplement use before and during pregnancy. Using that information, they calculated how much daily folic acid women were getting each month.
Throughout their pregnancies, mothers of kids without autism got more folic acid through fortified foods and nutritional supplements than those who ended up having an autistic child.
That difference was greatest in the first month of pregnancy, when mothers of normally-developing babies remembered getting an average 779 micrograms of folic acid daily and 69 percent of them at least met the daily guidelines.
That compared to an average 655 micrograms in mothers of autistic kids, 54 percent of whom got the recommended 600 micrograms or more per day.
The link between folate and autism remained when the researchers accounted for other variables including mothers' age and race as well as whether they smoked or drank alcohol during their pregnancy.
While the results are compelling and come from an institution at the forefront of autism research, they must be looked upon cautiously and in the context of other studies. A drawback of this study is its retrospective design. Mother's had to remember their month-to-month diets and supplement use from a few years ago by the time they were surveyed; this introduces an element of unreliability to the data and thus the results and conclusions.
To say conclusively that a lower folate intake during pregnancy raises the risk for developmental disorders such as autism, scientists in future studies will have to show the biological mechanisms linking the two, assuming they are there to be found.
Source: Schmidt RJ, Tancredi DJ, Ozonoff S, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tassone F, Hertz-Picciotto I (2012) Maternal periconceptional folic acid intake and risk of autism spectrum disorders and developmental delay in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study American Journal of Clinical Nutrition doi: 10.3945/ajcn.110.004416