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May 2007 - The Vitamin D Council - Autism and Vitamin D

John Cannell MD


This thought-provoking article appeared in the May 2007 newsletter of the Vitamin D Council, and was then further developed into a research review article, which was the first publication to suggest Vitamin D deficiency as a factor in autism. See

Since then, more evidence supporting a role for Vitamin D in the development of autism (and related developmental disorders, including ADHD and schizophrenia) has continued to emerge, and the Vitamin D Council has continued to provide regular updates on this subject.

The original article below has therefore been superceded on the Vitamin D Council website, but the first few sections and the outline structure of the original article are provided here.


We already know that 'autism' is not a single disorder, and that the risk factors for autistic spectrum disorders (ASD) and related neurodevelopmental conditions are both genetic and environmental, with strong interactions between these. 

In this article, John Cannell presents a very strong case that deficiencies of Vitamin D - the 'sunshine vitamin' - in early life may be one of the key environmental factors involved.

Vitamin D deficiency has become widespread in developed countries, and increasing evidence shows that it can affect mental as well as physical health. Although the formal studies needed to test this theory will take years, it deserves to be taken seriously.

As Dr Cannell points out, there are no risks - and many potential benefits - from ensuring that everyone has adequate Vitamin D levels in any case.

What's more, the best form of 'treatment' for Vitamin D deficiency - i.e. exposure to adequate sunlight on the skin - is free. (But could that be why funding for research in this area is not very forthcoming?)

Vitamin D Theory of Autism

In addition to the current epidemic of vitamin D deficiency, say another epidemic-an epidemic of autism-was upon our children? What if the autism epidemic began at the same time the epidemic of vitamin D deficiency began? What if both epidemics had worsened in unison? What if one theory explained all the unexplained facts about autism? What if both epidemics had the same root cause: sun avoidance? What if both were iatrogenic, that is, medical advice to avoid the sun had caused both epidemics? Be warned, what follows is not light reading-autism is not a light disease.

Does The Vitamin D Theory Best Explain Autism?

The theory that vitamin D deficiency, during pregnancy or childhood, causes autism is just a theory. However, the theory has a plausible mechanism of action, explains all the unexplained facts about autism, subsumes several other theories, implies simple prevention, and is easily disprovable-all components of a useful theory. A genetic lesion (abnormality) in some component of the vitamin D system-a lesion vitamin D's unique pharmacology could overcome-would explain why monozygotic (identical) twins are highly affected while fraternal twins are not. Varying brain levels of activated vitamin D during later life would explain why some identical twins get severe disease while others are barely affected. Falling vitamin D levels over the last 20 years due to sun-avoidance explain autism's rapid increase in incidence during that same time. The very different effects estrogen and testosterone have on vitamin D metabolism may explain why boys are much more likely to get it than girls are. Lower vitamin D levels in blacks may explain their higher rates of autism. The vitamin D theory has tenable explanations for all the epidemiological features of autism.

What is the risk of going in the sun?

The window of opportunity to affect brain development is limited. Time is of the essence if the vitamin D theory of autism is correct. Ask yourself, what is the risk of taking your autistic child outside to play in the sun? What's the risk of pregnant women sunbathing for a few minutes every day? Children always played in the sun before the epidemic of autism; your pregnant grandmother spent time in the sun as well. Physicians considered that sunshine was healthy before the sun scare, that is, before autism became an epidemic.

What Is Autism?

  • What are the five unexplained features of autism?
  • Are autism rates increasing?
  • The Vitamin D Connection

Predisposition-what gene should we be looking for?

  • Two clues: rare genetic malformations of the vitamin D system
  • What is the role of the vitamin D receptor in autism?

The Role of Sunlight

  • Vitamin D intake-are children and pregnant women getting as much as they used to?
  • When did health authorities recommend sun-avoidance?
  • Did authorities recommend compensatory vitamin D intakes?
  • Have vitamin D levels fallen as autism has increased?

About Vitamin D

  • How is vitamin D unique?
  • Does human behavior determine vitamin D levels?

Vitamin D and the Brain

  • Is vitamin D required for normal brain development?
  • Does maternal vitamin D deficiency injure the developing brain?
  • Is autism an ongoing destructive inflammatory disease process?
  • Do brains function better with higher vitamin D?
  • Does vitamin D explain the role of vaccines, mercury, and heavy metals?

Vitamin D Deficiency's Role In Autism

  • Do children with common rickets show signs of autism?
  • Does vitamin D explain autism's frequent infections?
  • Drugs that interfere with vitamin D metabolism-do they cause autism?
  • Does vitamin D explain seizures, which are common in autism?

Vitamin D Explains Autism

  • Why are boys at higher risk?
  • Does vitamin D-rich fish prevent autism?
  • Is autism less common at the equator?
  • Sunscreen-does it increase risk?
  • Why do children first develop signs around the age of weaning?

Evidence Autism Responds To Sunlight and Vitamin D

  • Do vitamin D-containing multivitamins help children's brains?
  • Does autism improve in the summer?
  • Can autistic children ever get better?

The Black Community: A Tragic Injustice

  • Is autism more common in dark-skinned people?
  • Do blacks have a higher risk of pregnancy problems?
  • Are black, pregnant women more likely to be vitamin D deficient?
  • Are black children at a disadvantage, right from conception?

What Should We Do Right Now?

  • I prefer to avoid sunlight, what should I do?
  • How much vitamin D should I take?
  • Is Autism Iatrogenic?