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Vitamin D has significant roles in cell proliferation, the immune system and the nervous system as well as in bone development. Adult studies indicate that vitamin D deficiency may be related to some neurological and psychiatric disorders like Parkinson's disease, Alzheimer's disease and depression (1). Childhood studies on this subject are mainly related to the impact of vitamin D deficiency on the development of autism. Because vitamin D has an essential role in the development of the nervous system, some investigators suggest that vitamin D deficiency during pregnancy may contribute to the development of autism. Autism is stated to be more frequent in people with dark skin and people who live in countries at higher latitudes. Additionally, children of mothers who consume more vitamin D in pregnancy have better mental development and present with fewer autistic signs. This knowledge indicates that vitamin D may be a mediator in the emergence of autism for genetically vulnerable people (2). Autism frequency has increased in recent years and this increase has occurred at the same time as the suggestions on the avoidance of sunlight have arisen. This coincidence is claimed to be supportive of the autism-vitamin D hypothesis (2,3). This hypothesis suggests two possible mechanisms: 1) vitamin D deficiency during pregnancy may cause inappropriate development of the fetal brain and then autistic signs may emerge, 2) in light of the hypotheses that autism is an autoimmune disorder and vitamin D is important for immune system functions, it may be assumed that vitamin D deficiency may cause autistic signs in vulnerable individuals (4). Some studies have stated that autism is more frequent in children of winter pregnancies and people of higher latitude countries (4). Additionally, it is stated that autistic patients have the lowest vitamin D levels among all kinds of psychiatric disorders in a psychiatry inpatient clinic (5). In another recent study, autistic children have lower 25-hydroxy vitamin D, 1,25-hydroxy vitamin D and calcium levels in comparison with healthy children (6). These findings are supportive of this hypothesis.
According to this hypothesis, it can be estimated that children with rickets would have more autistic symptoms. There is no recent study on this assumption. However, in past studies it has been stated that these children had more mental disorders, which disappeared after treatment (7).
On the other hand, because children with autism may have food selectivity, vitamin D and calcium deficiency may occur in these children more frequently. Some investigations were made on this subject and many of them found supportive findings (8,9).
We may conclude that autism-vitamin D relationship needs to be investigated more with larger sample studies.
References:
1. Kesby JP, Eyles DW, Burne TH, McGrath JJ. The effects of vitamin D on brain development and adult brain function. Mol Cell Endocrinol 2011; Article in press.
2. Cannell JJ. Autism and Vitamin D. Med Hypotheses 2008; 70: 750-759
3. Cannell JJ, Hollis BW. Use of Vitamin D in Clinical Practice. Altern Med Rev 2008; 13:6-20.
4. Grant WB, Connie MS. Epidemiologic evidence supporting the role of maternal vitamin D deficiency as a risk factor for the development of infantile autism.Dermatoendocrinol 2009; 1:223-228.
5. Humble MB, Gustafsson S, Bejerot S. Low serum levels of 25-hydroxyvitamin D (25-OHD) among psychiatric out-patients in Sweden: relations with season, age, ethnic origin and psychiatric diagnosis. J Steroid Biochem Mol Biol 2010;121:467-470.
6. Meguid NA, Hashish AF, Anwar M, Sidhom G. Reduced Serum Levels of 25-Hydroxy and 1,25-Dihydroxy Vitamin D in Egyptian Children with Autis J Altern Complement Med 2010; 16:641-645.
7. Cannell JJ. On the aetiology of autism. Acta Paediatr 2010; 99:1128–1130.
8. Zimmer MH, Hart LC, Manning-Courtney P, Murray DS, Bing NM, Summer S. Food Variety as a Predictor of Nutritional Status Among Children with Autism. J Autism Dev Disord. 2011 Article in press.
9. Emond A, Emmett P, Steer C, Golding J. Feeding Symptoms, Dietary Patterns, and Growth in Young Children With Autism Spectrum Disorders Pediatrics 2010; 126:337-342.