nutrients Review Vitamin D and Autism Spectrum Disorder: A Literature Review Hajar Mazahery 1, Carlos A. Camargo Jr. 2, Cathryn Conlon 1, Kathryn L. Beck 1, Marlena C. Kruger 1 and Pamela R. von Hurst 1,* 1 Institute of Food Science and Technology—School of Food and Nutrition, Massey University, Palmerston North 4474, New Zealand;
[email protected] (H.M.);
[email protected] (C.C.);
[email protected] (K.L.B.);
[email protected] (M.C.K.) 2 Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA;
[email protected] * Correspondence:
[email protected]; Tel.: +64-9-213-6657 Received: 14 March 2016; Accepted: 14 April 2016; Published: 21 April 2016 Abstract: Low vitamin D status in early development has been hypothesised as an environmental risk factor for Autism Spectrum Disorder (ASD), given the concurrent increase in the prevalence of these two conditions, and the association of vitamin D with many ASD-associated medical conditions. Identification of vitamin D-ASD factors may provide indications for primary and secondary prevention interventions. We systematically reviewed the literature for studies on vitamin D-ASD relationship, including potential mechanistic pathways. We identified seven specific areas, including: latitude, season of conception/birth, maternal migration/ethnicity, vitamin D status of mothers and ASD patients, and vitamin D intervention to prevent and treat ASD. Due to differences in the methodological procedures and inconsistent results, drawing conclusions from the first three areas is difficult. Using a more direct measure of vitamin D status—that is, serum 25(OH)D level during pregnancy or childhood—we found growing evidence for a relationship between vitamin D and ASD.