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Researchers are continuing to piece together one of the most mysterious modern day epidemics, autism spectrum disorder, a syndrome affecting one in 110 children. A growing body of evidence suggests low vitamin D levels may play a role.

Scientists studying autism and vitamin D believe there may be an association between a woman’s vitamin D levels during pregnancy, her child’s subsequent vitamin D levels, and autism symptoms. Researchers aren’t however, suggesting a vitamin D deficiency causes autism, rather that a number of incidental studies suggest a link.

Autism Epidemic Presents Five Unexplained Features

The Autism Society of America (ASA) describes autism as “a complex developmental disability that typically appears during the first three years of life and is the result of a neurological disorder that affects the normal functioning of the brain, impacting development in the areas of social interaction and communication skills.” Autism is considered a spectrum disorder because it impacts individuals differently and to varying degrees.

ASA estimates 1 to 1.5 million Americans are impacted by autism, making it a national health crisis costing about $35 billion annually. Yet, despite numerous exhaustive metabolic and genetic evaluations conducted by scientists all over the world, researchers still aren’t able to pinpoint the exact causes.

Dr. John Cannell, Executive Director of the Vitamin D Council, writes that scientific groups have been trying to account for the 20-year increase in autism. Yet any valid theory says Cannell, must account for the following five unexplained features:

1. significantly higher concordance (if one has it, the other is likely to have it) rates in identical, but not fraternal, twins
2. widely-varying symptoms, even among identical twins
3. striking 4:1 male to female sex ratio
4. increased rates in blacks
5. rapid increase in occurrence rates over the last 20 years

A 2009 Scientific American article “What if Vitamin D Deficiency is a Cause of Autism?” reported that five researchers at Harvard endorsed the vitamin D theory of autism, and that Dr. Darryl Eyles with the University of Queensland joined the expanding list of scientists who support the theory.

Despite the name, “vitamin” D is a secosteroid hormone that directly regulates more than 1,000 human genes. Not readily available in foods, vitamin D is made in large quantities when sunlight strikes bare skin.

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Vitamin D Regulates Long List of Genes

Geneticists believe that genetic codes may not properly transfer in children with autism, and that multiple genes aren’t expressed, possibly the result of environmental injury. Vitamin D, it seems, may protect an individual’s genome (entire genetic material) from damage from environmental toxins.

Researchers with the Autism Genetic Resource Exchange (AGRE) identified mutations in four genes within the AGRE families. Two of the genes were shown to be associated with autism and often are involved in forming or maintaining neural synapses, the point of connection between individual neurons. One of the new genes identified was neural cell adhesion molecule 2 (NCAM2). NCAM2 is expressed in the hippocampus of the human brain, a region previously associated with autism.

Dr. Lei, lead researcher on the study, explains the implications, “Studies such as this provide evidence that autism is a genetically based disease that affects neural connectivity.”

Dr. Cannell emphasizes that the vitamin D theory of autism doesn’t downplay the genetic role. In fact, he writes, “Without the genetic tendency for autism, I suspect that severe maternal or early childhood vitamin D deficiency may cause bone abnormalities, as referenced above, [but] with no evidence autism.” A vitamin D deficiency during pregnancy and early childhood may, however, trigger symptoms in a child who is genetically pre-disposed to the disorder.

Autism and Vitamin D Deficiency Linked Through Incidental Findings

In the May 2010 issue of Acta Pædiatrica, Dr. Cannell submitted a paper stating his position regarding D’s role in autism, “I have suggested that the primary environmental trigger for autism is not vaccinations, toxins or infections, but gestational and early childhood vitamin D deficiency (1,2),” he writes.

In the report, Cannell cited several studies that offer incidental evidence (unexpected clinical findings) of a link between D deficiency and autism:

A few of the findings include:

• Boys with autism have unexplained metacarpal bone thickness. At some point these boys developed less cortical bone than normal children, a finding consistent with undetected and untreated childhood or even intrauterine vitamin D deficiency.
• Melanin in the skin is an effective sunblock. Melanin is higher in dark-skinned people. Three of four recent U.S. studies found a higher incidence of autism in black children.
• A Somali immigrant study in Sweden found a higher rate of autism in the Somalian population. These refugees traded family compounds and regular exposure to the equatorial sun for cloistered high-rise apartments, and many of them Muslim, cover their bodies from head to toe (thus received minimal sun exposure).
• Studies showed autism in three U.S. states was higher in areas with more precipitation and clouds (less exposure to sunlight).
• Lower seafood consumption during pregnancy was associated with low verbal intelligence quotient, suboptimum outcomes for prosocial behavior, fine motor, communication and social development scores. Fish is one of the few foods with significant amounts of vitamin D.
• Autism is more common in mothers who take antiepileptic drugs. Antiepileptic drugs are one of the few classes of drugs that interferes with vitamin D metabolism, lowering 25(OH)D levels.

While the government’s advice to the public over the past few decades to use sunblock and to avoid excessive sun exposure to reduce the incidence of skin cancer was well-intentioned, an unfortunate side effect has contributed to two modern day epidemics, vitamin D deficiency and autism spectrum disorder.

Additional Resources: Autism Overview and More 

Footnotes: 

“Study adds to evidence that autism has genetic basis,” ScienceDaily, May 3, 2010. Accessed July 23, 2010.

Cannell JJ. “On the Aetiology of Autism.” Acta Paediatrica. May 2010.

Cannell JJ.” Autism and Vitamin D,” Medical Hypotheses 2008, Accessed July 23,2010.

Lite, J., “Vitamin D deficiency soars in the U.S.,” Scientific American, March 23, 2009. Accessed July 23,2010.

Copyright Laura Owens. Contact the author to obtain permission for republication.