Could the answer to reducing the incidence of autism be as simple as pregnant women popping a vitamin D supplement?

That is the suggestion from a large study led by researchers at the Queensland Brain Institute.

An analysis of more than 4,000 blood samples from pregnant women and their children found those who were deficient in vitamin D had "significantly higher" scores on autism scales than those who had adequate vitamin D levels.

Lead author Professor John McGrath said the study found pregnant women with low vitamin D were more likely to have children with autistic traits by the age of six.

"Just as taking folate in pregnancy has reduced the incidence of spina bifida, the results of this study suggest that prenatal vitamin D supplements may reduce the incidence of autism," he said.

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Professor McGrath said his research suggested that low vitamin D disrupts brain development.

"Vitamin D is a very safe, cheap, publicly acceptable supplement to take and reducing vitamin D deficiencies is so easy to do," he said.

"Maybe we could prevent serious mental disorders like autism by making sure women have optimal vitamin D during pregnancy."

What is Vitamin D? Vitamin D is a hormone that controls calcium levels in the blood.

Vitamin D is a hormone that controls calcium levels in the blood. It is crucial for bone and muscle development and for preventing osteoporosis.

It is crucial for bone and muscle development and for preventing osteoporosis. Vitamin D deficiency can have significant health effects

Vitamin D deficiency can have significant health effects It can increase a person's risk of conditions including bone and muscle pain

It can increase a person's risk of conditions including bone and muscle pain Low vitamin D has linked to an increased risk of multiple sclerosis, diabetes, cancers, heart disease and mental health conditions Source: Better Health Australia

He said the finding had important implications from a public health perspective.

The study examined 4,200 blood samples from pregnant women and their children, who were being monitored as part of the "Generation R" study in Rotterdam, the Netherlands.

Scientists found the link between low vitamin D and autism was strongest at mid-gestation and at the time of birth.

Vitamin D can be absorbed through the skin with sun exposure and is found in some fruits and vegetables.

Autism is a lifelong developmental condition that affects, among other things, the way an individual relates to his or her environment and their interaction with other people.

The main areas of difficulty are in social communication, social interaction and restricted or repetitive behaviours and interests.

Previous research by Professor McGrath has found a link between low vitamin D in babies' blood and an increased risk of schizophrenia.

Professor Andrew Whitehouse from the Telethon Kids Institute said the study offers interesting possibilities, but needs to be put into perspective.

"Autism is linked to dozens if not hundreds of different mechanisms which lead to this condition," he said.

"This study gives us an inkling of one of these possible mechanisms but I think before we think about anything else, and that includes treatment studies, we need to see this finding replicated.

"We know that genetic factors play a major role in the developmental pathways that may lead to autism."