The offspring of mice given vitamin D supplements early in pregnancy have reduced autism-like symptoms. The discovery adds to evidence that vitamin D deficiency during pregnancy, and possibly early in life, is a contributing factor to autism spectrum disorder.
Professor Darryl Eyles of the University of Queensland has spent years studying the effect of vitamin D, and its absence, on the development of the brain. He's been part of work showing that deficiency of the vitamin during fetal development is a major risk factor for schizophrenia, and is now examining evidence for a link to autism.
The possibility of such a link has been suggested based on observations that autism probability varies with birth month. Although alternative explanations exist, for example the timing of the annual cold and flu season, Eyles told IFLScience: “Vitamin D is the most seasonally regulated factor known.”
Eyles turned to a breed of mice known as C57BL6/N, which are prone to behaviors considered analogous to autism in humans, including greater anxiety, reduced social interaction, and obsessive burying of marbles. “We found pregnant females treated with active vitamin D in the equivalent of the first trimester of pregnancy produced offspring that did not develop these deficits,” Eyles said in a statement.
In Molecular Autism, however, Eyles reports something unexpected. Eyles anticipated that autism could be the result of an inflammatory reaction in the brain suppressed by vitamin D's anti-inflammatory effects. Yet supplements made no difference to inflammation for either mother or child.
Eyles admitted that the mechanism remains unclear. “We didn't look at every inflammatory agent,” he said. It's possible that inflammation differences occurred in ways the team's tests missed or that something else is occuring entirely.
Establishing that vitamin D deficiency contributes to autism in humans is challenging because randomized testing would struggle to get ethics approval. However, Eyles told IFLScience that large-scale studies have been done in the United States comparing rates of complications during pregnancy for women given vitamin D supplements and placebos.
By following up on the children born in these trials, Eyles hopes to “hitch a ride” on the research of others and see if autism diagnosis rates differ. He pointed out that such studies are far more practical than equivalent trials of schizophrenia, as those individuals are usually not diagnosed until their 20s.
Many people with autism argue that the condition should be treated as a form of diversity to be celebrated, but even pregnant women hoping for neurotypical children should be aware that although vitamin D helps maintain healthy bones, the active hormonal form can strip calcium from forming bones. Eyles' lab are investigating the dosage of the safe form of vitamin D supplements that might change brain formation.