Vitamin D may play an important role in the etiology of Autism Spectrum Disorders (ASD). Vitamin D is regarded as a neuroactive steroid affecting brain development and function. It plays an essential role in myelination, which is important for connectivity in the brain. Studies have shown that decreased vitamin D levels in patients, decreased maternal vitamin D levels during pregnancy, and decreased exposure to solar UVB might increase the risk for ASD. In addition, autism symptoms and global functioning may improve after vitamin D supplementation. Here, we sought to aggregate information from previous publications on vitamin D levels and ASD, in order to achieve a higher statistical power and thereby to determine the validity of vitamin D deficiency as a risk factor for ASD. For this meta-analysis, 11 studies met the inclusion and exclusion criteria, accounting for a total of 870 ASD patients and 782 healthy controls. Levels of serum 25(OH) D in participants with ASD were significantly lower than controls, suggesting that lower vitamin D level might be a risk factor for ASD.

Treatment with bumetanide combined with ABA training may result in a better outcome in children with autism than ABA training alone.

The trial 'Association of Polymorphisms of Vitamin D Metabolism-Related Genes With Autism and the Treatment of Autism with Vitamin D' has been registered at www.chictr.org/cn/proj/show.aspx? proj=6135 (identifier ChiCTR-CCC-13004498).

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 D 3 (cholecaliferol) seems to play a significant role in the etiology of ASD because this vitamin is important for brain development. Lower concentrations of vitamin D 3 may lead to increased brain size, altered brain shape, and enlarged ventricles, which have been observed in patients with ASD. Vitamin D 3 is converted into 25-hydroxyvitamin D 3 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 D 3 deficiency may cause ASD symptoms. Here, we report on a 32-month-old boy with ASD and vitamin D 3 deficiency. His core symptoms of autism improved significantly after vitamin D 3 supplementation. This case suggests that vitamin D 3 may play an important role in the etiology of ASD, stressing the importance of clinical assessment of vitamin D 3 deficiency and the need for vitamin D 3 supplementation in case of deficiency.

This study is the first double-blinded RCT proving the efficacy of vitamin D3 in ASD patients. Depending on the parameters measured in the study, oral vitamin D supplementation may safely improve signs and symptoms of ASD and could be recommended for children with ASD. At this stage, this study is a single RCT with a small number of patients, and a great deal of additional wide-scale studies are needed to critically validate the efficacy of vitamin D in ASD.