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Lack of vitamin D during pregnancy increases the risk of autism

- especially among boys

Lack of vitamin D during pregnancy increases the risk of autismVitamin D controls a variety of processes in the brain and that is important for the child in a number of different ways. According to a new study from University of Queensland, Australia, there is an increased risk of autism – especially among boys – if the mother lacks vitamin D during her pregnancy. The explanation lies in the fact that the vitamin deficiency can affect levels of sex hormones in the brain. Several studies link vitamin D deficiency to autism and show that vitamin D supplements can improve hyperactivity and other signs of impaired functioning in children with autism.

There are different degrees of autism and the condition is characterized by a somewhat different and often delayed development in areas such as speech, communication, and social behavior. People with autism may also be sensitive to sensory input, have phobias, throw tantrums, and display self-harming behavior. The number of autism diagnoses has increased steadily over the past decades. There are many different risk factors and vitamin D seems to be a common thread that can be determining for the possible impact of genetic and environmental variables.

Vitamin D is involved in regulating the sex hormone balance

In the most recent study, one that was carried out on rats, Professor Darryl Eyles and Dr. Asad Ali from the University of Queensland’s Brain Institute demonstrated that lack of vitamin D during pregnancy caused levels of testosterone to increase in the developing brains of male rat fetuses.
The scientists also found that lack of vitamin D during rat pregnancy resulted in a deficiency of an enzyme that breaks down testosterone.
According to the scientists, excessive influence of testosterone levels in the brain may be an underlying cause of autism but the exact mechanisms remain unknown.
Professor Eyles’ earlier research shows that vitamin D plays a significant role in brain development and supplements given to pregnant rats effectively prevented signs of autism in their offspring.
Vitamin D regulates around 10 percent of our genes by affecting different on-off switches. According to Dr. Ali, vitamin D is also involved in regulating levels of sex hormones. When pregnant rats were fed a diet that lacked vitamin D, the male fetuses had increased levels of testosterone in the brain, and this may me one of the reasons why autism is more common among baby boys.
The study is published in Molecular Autism and is the first study to show a link between vitamin D, autism, and testosterone levels. The next step for the scientists is to study other risk factors that are linked to autism – including stress during pregnancy and lack of oxygen – to see if it has any effect.

  • As a result of sun awareness campaigns and spending far too much time indoors, people are not getting enough sunshine. Therefore, vitamin D deficiency is so widespread.
  • This may contribute to the increased rate of autism.

Vitamin D also regulates serotonin levels in the brain and gut

In earlier research, the two scientists Rhonda Patrick and Bruce Ames at Children’s Hospital Oakland Research Institute (CHORI) found the mechanisms that involve vitamin D, autism, and serotonin. They observed that vitamin D regulates a gene that is responsible for converting the amino acid tryptophane into serotonin. Serotonin is primarily known for its role as a neurotransmitter that affects our mood, but it has many other functions in the brain and the rest of the body.
People with autism often have low serotonin levels in their brain and high serotonin levels in their gut. The studies showed that vitamin D can increase serotonin levels in the brain and lower the serotonin synthesis in the intestinal system by activating certain genes.

Serotonin’s role in brain development

During pregnancy, serotonin plays an important role in the development of the baby’s brain. If there is too little serotonin, it may affect the structure and function of the brain.
According to Rhonda Patrick, mouse studies reveal that lack of serotonin causes signs of autism. She has also observed that the fetuses are totally dependent on the mother’s vitamin D status
During the pregnancy, vitamin D is transferred from the mother via the placenta. Vitamin D then crosses the fetuses’ blood-brain-barrier in order to allow for vitamin D-dependent enzyme processes to convert tryptophane into serotonin. If the mother lacks vitamin D, it may therefore affect the development of the fetal brain.

Other studies of vitamin D and children with autism

In a book from 2015, Dr. John Cannell describes two studies where supplements of vitamin D have been given to children with autism. In one study, 83 autistic children received high daily doses of vitamin D for three months. Sixty-seven children (80 percent) showed significant improvement in such areas as stereotypic behavior, eye contact, and attention.

Make sure to get plenty of vitamin D during pregnancy

Women who are planning to become pregnant or are pregnant, already, should have their vitamin D status measured. They must also take vitamin D supplements all year round as advised by the health authorities. Vitamin D is lipid-soluble. Therefore, oil-filled capsules with vitamin D give better bioavailability.


Ali, A. A. et al. Developmental vitamin D deficiency increases foetal exposure to testosterone. Molecular Autism. 2020

Emily Henderson. Vitamin D deficiency could explain why autism spectrum disorder is more common in boys. Dec 11, 2020

Khaled Sall et al. Randomized controlled trial of vitamin D supplementation in children with autism spectrum disorder. Journal of Child Psychology and Psychiatry. 2016

John J Cannell. Autism Causes, Prevention and Treatment: Vitamin D Deficiency and the Explosive Rise in Autism Spectrum Disorder. Sunrise River Press. 2015

R.P. Patrick, B.N. Ames. Vitamin D hormones regulates serotonin synthesis. The FASEB Journal 2014

Science News. Causal link found between vitamin D, serotonin synthesis and autism in new study. Science Daily. 2014

Rhonda P. Patrick and Bruce Ames. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar schizophrenia, and impulsive behavior. The FASEB Journal 2015.

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