Mothers' diets during pregnancy may affect their child's likelihood of developing autism, new research suggests.
Autism spectrum disorders are a diverse group of conditions characterized by some degree of difficulty with social interaction and communication, affecting roughly one in 36 children in the U.S., according to the U.S. Centers for Disease Control and Prevention.
There are many potential causes of autism spectrum disorders, which include both environmental and genetic factors. Previous research has also suggested a link between prenatal dietary patterns and autism development.
Studies have shown that prenatal multivitamins and folic acid supplement use, as well as adequate vitamin D and high fish intakes, are all associated with a reduced likelihood of childhood autism diagnoses. However, considering these factors in isolation neglects the synergistic and antagonistic effects that nutrients can have when consumed as part of a realistic prenatal diet.
To date, studies into these holistic associations have been based on small sample sizes with inconsistent results. Now, for the first time, researchers from the University of Glasgow in the U.K. have conducted a large study of over 95,000 mothers and their children to determine whether there is a statistically significant association between maternal diet quality and their baby's likelihood of developing autism.
Data was gathered from two large prospective cohort studies: the Norwegian Mother, Father, and Child Cohort Study and the Avon Longitudinal Study of Parents and Children. Data was collected from 2002 to 2008 and 1990 to 1992, respectively, and children were followed up until the age of 8, or older.
Diet quality was assessed based on global dietary guidelines, including a high intake of fruits, vegetables, fish, nuts, and whole grains, and a low intake of red and processed meats, soft drinks, and foods high in saturated fats and refined carbohydrates. Participants were then categorized as having high adherence to healthy dietary patterns, medium adherence, and low adherence.
After adjusting for potentially confounding factors, such as maternal BMI, education levels and supplement use, a high adherence to healthy dietary patterns during pregnancy was associated with a 22 percent reduction in likelihood of the child being diagnosed with autism. High adherence was also associated with a 24 percent lower likelihood that the child would go on to develop social communication difficulties.
The associations held particularly strong among mothers with baby girls.
Exactly why we see these associations is not completely clear, although the researchers have suggested that prenatal diets may affect DNA expression and regulate immune processes. Autism has also been linked to disruptions of the microbiome, which may be affected by dietary patterns.
However, the researchers stressed that these results a purely observational. "At present, we remain uncertain as to whether the associations observed are causal," they write.
There may also still be confounding factors that were not accounted for in the analysis, such as genetics, parental caregiving and childhood diets.
Even if a causal relationship is found, maternal diets are not the only factor influencing a child's likelihood of developing autism, and it is estimated that around 80 percent of autism cases can be linked to inherited genetic mutations.
In other words, a mother could follow a perfectly balanced, healthy diet and still see their child receiving an autism diagnosis.
"Further research should substantiate our findings, especially given the inconsistency in the previous literature," the researchers write.
The full study can be read in the journal Jama Network Open.
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