Vitamin D Could Explain Why Autism Is Three Times More Common in Boys

A deficiency in vitamin D on the mother’s side could explain why autism spectrum disorder is three times more common in boys, say Queensland Brain Institute researchers.

In their latest study, Professor Darryl Eyles and Dr. Asad Ali found vitamin D deficiency during pregnancy caused an increase in testosterone in the developing brain of male rats.

Increase in testosterone in the brain

“The biological cause of autism spectrum disorder (ASD) is unknown but we have shown that one of the many risk factors—low vitamin D in mothers—causes an increase in testosterone in the brain of the male fetuses, as well as the maternal blood and amniotic fluid,” Professor Eyles said.

“In addition to its role in calcium absorption, vitamin D is crucial to many developmental processes.

“Our research also showed that in vitamin D-deficient male fetuses, an enzyme which breaks down testosterone was silenced and could be contributing to the presence of high testosterone levels.”

Vitamin D is critical in brain development

Professor Eyles’ previous research has shown that vitamin D plays a critical role in brain development and that giving vitamin D supplements to mice during pregnancy completely prevented autism-like traits in their offspring.

Co-author Dr. Ali said that excessive exposure of the developing brain to sex hormones like testosterone was thought to be an underlying cause of ASD, but the reasons remained unclear.

“Vitamin D is involved in pathways controlling many sex hormones,” Dr. Ali said.

“When the rat mothers were fed a low vitamin D diet, it caused male fetal brains to have high levels of exposure to testosterone.”

Time to study more risk factors for ASD

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