I was hesitant to blog about this case report in the journal Pediatrics. I decided that it was better for me to write about it and emphasize the limitations, since it seems likely that supplement manufactures and some media will make exaggerated claims. The report:
“Autism spectrum disorder (ASD) is a common neurodevelopmental disorder caused by a complex interaction between genetic and environmental risk factors. Among the environmental factors, vitamin D3 (cholecaliferol) seems to play a significant role in the etiology of ASD because this vitamin is important for brain development. Lower concentrations of vitamin D3 may lead to increased brain size, altered brain shape, and enlarged ventricles, which have been observed in patients with ASD. Vitamin D3 is converted into 25-hydroxyvitamin D3 in the liver. Higher serum concentrations of this steroid may reduce the risk of autism. Importantly, children with ASD are at an increased risk of vitamin D deficiency, possibly due to environmental factors. It has also been suggested that vitamin D3 deficiency may cause ASD symptoms. Here, we report on a 32-month-old boy with ASD and vitamin D3 deficiency. His core symptoms of autism improved significantly after vitamin D3 supplementation. This case suggests that vitamin D3 may play an important role in the etiology of ASD, stressing the importance of clinical assessment of vitamin D3 deficiency and the need for vitamin D3 supplementation in case of deficiency.”
The most important thing to note is that this is a case study, an observation of a single individual. We cannot know if the ASD symptoms would have lessened without vitamin D supplementation. Also, there is certain amount of subjectivity in evaluating ASD symptoms. At best this study is suggestive of an important avenue of research. The claim that vitamin D deficiency is a cause of autism is plausible, but we need randomized double blind research to have confidence in this claim.