A massive longitudinal study conducted in Norway and England has found that mothers who adhere to a healthy dietary pattern during pregnancy have 22% lower odds of having children diagnosed with autism compared to mothers with less healthy diets. The study also revealed that children of these mothers are less likely to experience social communication difficulties at ages 3 and 8. These findings were recently published in JAMA Network Open.
Autism, or autism spectrum disorder, is a developmental condition that manifests in challenges related to social communication, behavior, and sensory processing. The term “spectrum” is used because the symptoms and their severity can vary widely from one individual to another. Some people with autism may experience significant difficulties in communication, while others may have symptoms that are barely noticeable. Common characteristics of autism include repetitive behaviors, a strong preference for routines, and difficulty adapting to changes in the environment. It is estimated that 1 to 2% of the global population is affected by some form of autism.
The causes of autism are not fully understood, but it is believed that both genetic and environmental factors play a role. While genetics are a significant contributor, research has also identified several environmental factors that may be associated with an increased risk of autism in children. Recently, there has been growing interest in the potential link between prenatal dietary patterns and the risk of autism. Previous studies have suggested that women who take multivitamins, folic acid supplements, and consume adequate amounts of vitamin D and fish during pregnancy may have a lower risk of having children with autism.
Catherine Friel and her colleagues conducted this study to explore whether a more comprehensive approach to dietary patterns during pregnancy could be linked to autism in children. To do this, they analyzed data from two large, well-known cohort studies: the Norwegian Mother, Father, and Child Cohort Study (MoBa) and the Avon Longitudinal Study of Parents and Children (ALSPAC).
“I was drawn to this topic because while some studies have explored the relationship between prenatal diet and the risk of autism in offspring, their findings have been inconsistent and often based on small sample sizes. Smaller studies can be less reliable and so there was a clear need to investigate this link within a larger, more robust cohort, such as MoBa,” explained Friel, a dietitian and researcher affiliated with the MRC/CSO Social and Public Health Sciences Unit
at the University of Glasgow.
The MoBa study, conducted by the Norwegian Institute of Public Health, involved 95,200 pregnant women between 1999 and 2008. The ALSPAC study included 14,541 pregnant women from southwest England who were recruited between April 1991 and December 1992. Both studies followed the health and development of the mothers and their children over several years.
The participating women, all of whom had singleton pregnancies, completed detailed food frequency questionnaires. These questionnaires asked them to report how often they consumed various types of foods. The researchers used the responses to classify the women into three groups based on their adherence to a healthy dietary pattern. This pattern was characterized by high consumption of fruits, vegetables, fish, nuts, and whole grains, and low consumption of red and processed meats, sugary drinks, and foods high in fats and refined carbohydrates. The groups were categorized as having high, medium, or low adherence to this healthy dietary pattern.
To assess the potential impact of these dietary patterns, the researchers linked the MoBa data with autism diagnoses recorded in the Norwegian Patient Registry. They also analyzed assessments of social communication difficulties in the children at ages 3 and 8, completed by the mothers in the MoBa study. Similarly, in the ALSPAC study, the mothers completed a 12-item Social and Communication Disorders Checklist when their children were around 8 years old.
The results showed a significant association between high adherence to a healthy dietary pattern during pregnancy and a lower likelihood of autism in children. Specifically, mothers in the highest adherence group had 22% lower odds of having a child diagnosed with autism compared to those in the lowest adherence group.
“Given the mixed results from previous studies, we didn’t have a clear expectation of what we might find,” Friel told PsyPost. “The most surprising aspect was simply that our research uncovered a notable link between a ‘healthy’ prenatal diet and a reduced likelihood of autism in children.”
Additionally, these mothers had a 24% lower chance of having a child with social communication difficulties at age 3, according to the MoBa data. In the ALSPAC cohort, mothers with high adherence to a healthy diet also had 24% lower odds that their children would exhibit social communication difficulties at age 8.
“Our study suggests a potential link between following a ‘healthy’ prenatal dietary pattern and a reduced likelihood of having a child with autism,” Friel explained. “However, it is crucial to understand that this does not establish a cause-and-effect relationship. More research is needed to determine whether maternal diet directly influences the development of autism or if other factors might explain our findings.”
While the findings suggest that a healthy diet during pregnancy may reduce the risk of autism, it is also possible that other factors—such as genetics, socioeconomic status, or overall maternal health—could influence both the likelihood of autism and dietary choices during pregnancy. Another limitation is that the study relied on self-reported dietary data, which can be subject to errors or biases. Participants might not accurately remember or report their food intake, and the food frequency questionnaires used might not capture all aspects of their diet.
Given these limitations, more research is needed to fully understand the relationship between prenatal diet and autism.
“My long-term goal is to determine whether the associations we observed can be replicated in other large cohorts,” Friel said. “If replicated, I aim to further investigate the underlying mechanisms, whether dietary or otherwise, that could explain these findings.”
“To better understand why we observed a link between a healthy prenatal diet and a reduced risk of autism, it will be important to explore alternative explanations. These could include genetic factors, the role of paternal diet, or the impact of diet during childhood, among others. Such exploration could provide a more comprehensive understanding of the factors contributing to autism risk.”
The paper, “Healthy Prenatal Dietary Pattern and Offspring Autism,” was authored by Catherine Friel, Alastair H. Leyland, Jana J. Anderson, Alexandra Havdahl, Anne Lise Brantsæter, and Ruth Dundas.
