There has long been speculation that a deficiency of vitamin D during pregnancy might be one of the causes of autism.

But a study from Australia and the Netherlands has now confirmed that women with low levels of the vitamin by 20 weeks into their pregnancy are more likely to have a child who goes on to develop autistic traits. 

The authors of the study, Professor John McGrath of the University of Queensland’s Brain Institute and Dr. Henning Tiemeier from the Erasmus Medical Centre in The Netherlands have called for doctors to recommend the supplement during pregnancy. They cite that doctors recommending a folate supplement has reduced the incidence of spina bifida and hope that a widespread use of vitamin D supplements will do the same for autism.

During the study, doctors examined the blood of pregnant 4,200 Dutch women and then monitored their child’s development over the next several years. The correlation to of deficiency of vitamin D and autistic traits was enough for researchers to conclude that the two are inevitably linked.

Low levels of vitamin D in pregnancy have also been found to contribute to childhood asthma and eczema, as while as other childhood allergies. It has also been linked to schizophrenia.

Vitamin D can come from the sun, in addition to cheese, eggs, beef and fatty fish. However, doctors recommend that mothers-to-be seek the vitamin in a supplement form. They do not necessarily recommend that pregnant women spend more time out in the sun to replenish the vitamin, particularly in places like Australia where too much exposure can be potentially damaging.

Professor Andrew Whitehouse of the Telethon Kids Institute says that he is not surprised by the results, but also thinks more studies need to be done:

“There are likely dozens, if not hundreds, of different mechanisms that can lead to autism. Now this study gives us an inkling of one possible mechanism but before we think about anything we need to see a replication of this finding.”

He concluded with:

“What we know is that vitamin D during pregnancy is very important for how the baby develops.”


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