Plasma 25(OH)D concentration in children with autism spectrum disorder

Autism spectrum disorders (ASD) are a class of neurodevelopmental disorders characterized by impairments in communication and social reciprocity, and by the presence of restricted and repetitive interests and behaviors.1 The prevalence of ASD is currently estimated to be 6.7 per 1000 school-age children in the United States,2 making ASD and co-occurring conditions an important public health issue. One condition that may occur more often in children with ASD than in children with typical development is vitamin D deficiency. Vitamin D is a fat-soluble vitamin, long known to be important in calcium homeostasis and bone health. As evidence has accumulated that vitamin D receptors are present in a wide variety of tissues, vitamin D deficiency has been implicated in numerous disease states.3 Having ASD could potentially put a child at greater risk of vitamin D deficiency secondary to dietary restrictions or decreased exposure to sunlight. Children with ASD may limit their own diet because of sensory aversions or restricted interests. The diet may also be restricted by parents to eliminate exposure to certain dietary proteins, such as the milk protein casein, in an attempt to treat the ASD symptoms.4 Children with ASD may have decreased exposure to sunlight because their after-school hours are often devoted to table-based therapies, they do not commonly participate in organized outdoor sports, and their preferred leisure activities often involve video game, computer, or TV screens in an indoor setting. We previously reported that children with ASD have decreased mean metacarpal bone cortical thickness (BCT) compared with a reference population.5 Based on this, our overarching hypothesis is that children with ASD are at risk of decreased bone mineral density compared with typically developing children. For this study our focus was limited to one component contributing to bone mineral density, vitamin D. The aim was to test the hypothesis that children with ASD have a lower concentration of circulating vitamin D – plasma 25(OH)D. We compared plasma concentration of 25(OH)D in Caucasian males with and without ASD and 25(OH)D concentration in males with ASD with and without a casein-free diet.