A possible link between vitamin D and autism

Low levels of vitamin D during pregnancy and breastfeeding may be related to an unusual pattern of brain development that can lead to differences in offspring social behaviour later in life, according to a study published in the Journal of Endocrinology by Caitlin Wyrwoll and her colleagues at the University of Western Australia.

Differences in social behaviours such as communication and peer interaction are a hallmark of numerous human conditions, including autism spectrum disorder (ASD), a lifelong condition that ranges in severity.

Previous human studies in Scotland and the Netherlands have found that lower levels of maternal Vitamin D during the first trimester of pregnancy are associated with an increased risk of ASD in children.

Importantly, not all children with autism were born to mothers with low vitamin D, so there are certainly other environmental and genetic influences at play, with the biological mechanisms underpinning this relationship remaining unclear.

To examine how maternal vitamin D levels may influence brain development, Wyrwoll looked at changes in markers of brain function and social behaviours of adult rats born and suckled to mothers lacking it. Rats with deficient mothers displayed abnormal social behaviours, altered brain chemistry and impaired learning and memory, consistent with ASD-like behaviours in humans.

“Our work reinforces that vitamin D levels in early life influence brain development and can impact on how the brain functions in later life,” says Wyrwoll.

“We know that early life environment can be a powerful determinant of health outcomes in offspring and, although this is a rat study, these data indicate that vitamin D levels during pregnancy are important for brain development, and may point to a contributing factor in the development of neurodevelopmental conditions, such as ASD.

“However, further work is needed to establish whether these associations also apply to humans.”

Other researchers in the field have generally welcomed the study, although some urge caution in the interpretation of the results.

“This is a well-designed study which is comprehensively demonstrating the neural effects of perinatal maternal vitamin D deficiency in rats. It is well known that vitamin D plays an important role in brain development,” says Ulrich Schall, director of the School of Medicine and Public Health at The University of Newcastle in New South Wales.

“Any deficiency is therefore likely to increase the risk for so called ‘pervasive’ or ‘neurodevelopmental’ disorders, such as autism or schizophrenia.

“However, ‘risk’ means that the developing brain is more susceptible for these conditions, rather than that the vitamin D deficiency is ‘causing’ it.”

Robyn Young, from the College of Education, Psychology and Social Work at Flinders University in South Australia, notes that 2016 Swedish study identified a correlation between lifetime maternal vitamin D deficiency and autism in offspring. However, the type of deficiency implicated is uncommon.

“Given that this is so rare it cannot account for the majority of people with ASD,” she says.