Autism and Vitamin D Deficiency: How they are related.
Autism is a neurodevelopmental disorder characterized by impaired social interaction, verbal and non-verbal communication, and restricted and repetitive behavior. Parents usually notice signs in the first two years of their child's life. These signs often develop gradually, though some children with autism reach their developmental milestones at a normal pace and then regress. The diagnostic criteria require that symptoms become apparent in early childhood, typically before age three.
Globally, autism affects an estimated 21.7 million people as of 2013, and it is estimated that there is a prevalence of 1-2 people affected per 1000. The main question to ask, however, is why are so many people being affected by autism?
There is a belief is today’s society that autism is caused due to a vaccination. Although children are being vaccinated more now than ever before, there was only found to be a correlation between the first MMR (Measles-Mumps-Rubella) vaccine and African American boys which could indicated a role of the vaccine in the etiology of autism within this population group. There was a statistically significant increase in autism causes of African American males who received the first MMR prior to 36 months of age. The present study provides new epidemiologic evidence showing that African American males receiving the MMR vaccine prior to 24 months of age are more likely to receive an autism diagnosis.
The primary environmental trigger for autism is not vaccinations, toxins or infections, but gestational and early childhood vitamin D deficiency.  Vitamin D has a multitude of physiological functions. Vitamin D receptors have been found in many different tissues including the small intestine, colon, osteoblasts, activated T and B lymphocytes, islet cells and most organs in the body. It is also implicated in many important physiological processes including modulation of activated T and B lymphocyte function. Vitamin D prevents inflammatory bowel disease and African American women who have lower vitamin D status are more susceptible to Lupus. 
In an article in Scientific American from 2009 and two articles in Acta Paediatrica in 2010 support the evidence that “vitamin D deficiency, either during pregnancy or early childhood, may be an environmental trigger for the genetic disease of autism”. The current recommendation for amount of vitamin D per day is 5000 iu. Vitamin D does a lot more than build healthy bones. It is critical for immune system function and for brain physiology. Most Americans are significantly low in vitamin D levels, and supplementation is necessary for almost everyone.
Studies have also shown that there is an increased incidence of autism in the children of richer college-educated, wealthy parents. This may be explained by noting that such parents are more likely to practice sun avoidance and the use of sun block. Also noteworthy is that the melanin found in darker skin an effective sun block. Consequently, it has been found that people with darker skin have a higher incidence of autism 
Another association to autism and vitamin D deficiency is seen in the winter months. Autism rates are higher in children born in the winter, when vitamin D sun exposure is low. This can also be correlated to more people born with autism in cities when compared to a rural setting. City life affords less Vitamin D because of tall buildings, indoor occupations and increased air pollution, all of which blow ultraviolet B light from penetrating the atmosphere.
To some real but unknown extent, autism is an iatrogenic disease, caused by governments, organizations, committees, newspapers and physicians who promulgated the current warnings about sun exposure for pregnant women and young children without any understanding of the tragedy they engendered. Theoretically, prevention and perhaps treatment of autism with physiological doses of vitamin D3 “is so simple, so safe, so inexpensive, so readily available and so easy, that it defies imagination.” 
-Cory T. O’Lear-Zebroski, DC
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- Hooker, B. “Measles-mumps-rubella vaccination timing and autism among young African American boys: a reanalysis of CDC data. Translational Neurodegeneration. Vol. 3 (16). 2014