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Q&A: Can Taking Vitamin D Help Prevent my Child from Developing Autism?

For the first time in 12 years, the American Academy of Pediatrics revised their guidelines on identifying, evaluating and managing children experiencing autism spectrum disorders (ASD). One out of every 59 children has been diagnosed with ASD.

To mark the occasion, the Drexel News Blog caught up with Brian K. Lee, PhD, an associate professor in Drexel University’s Dornsife School of Public Health to discuss his recently published research on the possible role of vitamin D in preventing ASD and what we know about how to minimize risk.

According to the findings published in Molecular Psychiatry, a vitamin D deficiency at birth may increase a child’s risk of developing autism by as much as 33 percent. In the largest study to date on a link between vitamin D deficiency and ASD, the team looked at vitamin D levels in blood samples of mothers and more than 3,000 newborns in Sweden – 1,399 of whom were diagnosed with ASD. The authors found that higher levels of vitamin D were associated with slightly reduced risk of developing the condition.

This is not the first paper Lee and colleagues have published on the topic. Lee is also senior author on a 2017 paper in the bmj showing that multivitamins during pregnancy may reduce autism risk.

There is no medical test for ASD, so clinicians review a patient’s behavior – such as poor communication or struggles with emotional and social skills — and development to determine whether it meets the criteria of ASD.

Lee discussed what researchers know about vitamin D and autism and what expectant mothers should do with these findings:

Can autism be prevented? Can a healthy lifestyle through exercise, good diet, etc. help prevent it?

Autism is a complex, multifactorial condition with both genetic and environmental determinants. My colleague Kristen Lyall, ScD, an assistant professor at the AJ Drexel Autism Institute, and I focus on identifying modifiable risk factors for autism, in the hopes that risk can be mitigated. Specifically, we target environmental factors like chemical or dietary exposures that perhaps can be modified to influence risk.

Our work has shown, for example, that exposures to some factors during pregnancy, such as obstetric complications, infection and certain medications such as antidepressants may increase risk, while dietary aspects such as multivitamins, anemia and fatty acids can also influence risk. Vitamin D is often referred to as the “sunshine vitamin,” as the sun serves as our main source of this important substance in the body – but people can also get vitamin D in much smaller doses through a healthy diet.


So, what’s the takeaway here? Should women who are pregnant or may soon become pregnant run out to get vitamin D supplements right away?

Nutrition during pregnancy and early life can alter development of children in different ways, and our research suggests that lower vitamin D levels may increase risk of autism. This is consistent with a larger body of evidence indicating that higher vitamin D levels correspond with optimal neurodevelopment. And this is also part of a larger story of high levels of vitamin D insufficiency among pregnant women in the U.S. – depending on how you define insufficiency, between 33 percent to 70 percent of pregnant women have insufficient vitamin D. But this doesn’t translate to actionable evidence at this point.

For one thing, this study is an observational study and not a randomized controlled trial: more studies are needed. We don’t know if other factors influenced the findings, such as the possibility that healthier mothers who were at lower risk for having a child with autism tended to have higher vitamin D levels (although we controlled for such confounding to the best of our ability). We don’t know if our findings are generalizable to different populations – Sweden is notably different in terms of sunlight exposure from much of the world. And perhaps most importantly, nutrition is not necessarily as simple as popping a pill. We don’t know enough about aspects of timing and dosage in relation to neurodevelopmental outcomes to even begin talking about supplements. Overnutrition is a potentially dangerous possibility. For example, high doses of vitamin A are known to cause congenital birth defects. Thus, more studies really are needed.

A JAMA Psychiatry study published in February of 241 children who have a sibling with ASD found that prenatal vitamins were associated with a reduced likelihood of ASD diagnosis. That study was also observational. How far is the field from a randomized controlled trial to find a causal link between vitamin D and ASD?

That study is consistent with our 2017 bmj study, and adds to an increasing body of evidence suggesting that such supplements might influence autism risk. I think that a randomized controlled trial is a high priority, but likely very difficult to conduct in an ethical fashion (i.e. the problem of randomizing pregnant women to specific diets) and in a way that produces clear results. This is something I am thinking quite a bit about.

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