New Research on the Link Between Vitamin D and Autism
Recent reports have speculated on the role of Vitamin D in autism spectrum disorders (ASD). While no direct link to autism has been established, Vitamin D is an important dietary component and there is widespread concern about the increase in Vitamin D insufficiency and deficiency across the world. The term “insufficiency” is used when there is biological evidence of a deficiency of Vitamin D in the absence of any clinical signs.
Autism Speaks is currently supporting research to better identify and characterize the role of Vitamin D, the genes which are activated by Vitamin D, and how environmental factors may mediate autism symptoms. Last year, the National Health and Nutrition Examination Survey released data collected from 2001 to 2004 showing that the prevalence of Vitamin D insufficiency is on the rise from previous years. Coincidentally, the Vitamin D council issued a report which hypothesized that these lower levels of Vitamin D may be associated with the increase in autism seen in the last decade.
In order to study this further, in 2010, two separate research groups in Sweden have studied the relationship between maternal and child Vitamin D levels in families affected with autism. Results showed that children with autism and their mothers both showed the lower Vitamin D levels compared to families with children with other conditions, such as depression. The group differences in Vitamin D levels was not statistically significant, however. The authors suggest that lower Vitamin D levels may be a predisposing factor in autism, not a specific cause.
These studies did not attempt to examine genetic variants associated with the Vitamin D hormone receptor (VDR). This receptor is activated by the active forms of Vitamin D, and signals target genes to turn on or off. Through its Environmental Factors Initiative, Autism Speaks is currently supporting a project at the University of California at Davis, led by Bruce Hammock, Ph.D. to investigate variants in the VDR and their relationship to immune problems in children enrolled in the on-going Childhood Autism Risks from Genetics and the Environment (CHARGE) study. This study will provide a more complete picture of the source of Vitamin D insufficiency, the biological consequences, and the contributions to autism and co-morbid symptoms. The goal is to possibly identify a group of children who would benefit from additional Vitamin D supplement therapy.
What does this mean for autism?
Studies examining the diet of children with autism suggest that some children on the spectrum may not be receiving proper nutritional values of foods rich in Vitamin E and D, as well as fiber and iron. The American Academy of Pediatrics released new guidelines in 2008 to prevent Vitamin D deficiency symptoms in all children, including use of at least 400 IU Vitamin D supplements to ensure serum levels of 25-hydroxyvitamin D (the form detected in blood) are at least 50 nmol/L. Because previous studies have not demonstrated a direct link between low Vitamin D and autism, families should talk to their doctors before beginning a therapy regimen that differs from current guidelines on dietary and sun exposure. Additional research in this area examining Vitamin D, as well as sources of Vitamin D, will identify possible gene x environment interactions in the role of this prohormone in ASD.
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