Introduction and objective:
Both autism and vitamin D deficiency are increasingly prevalent among children. Vitamin D is believed to play a key role in many developmental pathways. The aim of this study is to review current knowledge of the relationship between autism spectrum disease and vitamin D deficiency among the paediatric population.

Review methods:
The review was performed using the PubMed and Cochrane database from the last 10 years. The terms ‘autism’ and ‘vitamin D deficiency’ were searched for. There were 15 articles in English on the PubMed database, 14 were included in the review. In the Cochrane database they were 16 position, 9 of which were included in the final analysis.

Brief description of the state of knowledge:
Autism spectrum disorder (ASD) is a neurodevelopmental disorder. Typical signs are limited social relations, communication disorder and stereotyped and repetitive behaviours of varying severity. The etiology is still unknown, but nowadays the role of vitamin D deficiency isbeing investigated as a possible risk factor for ASD. There are many scientific reports of the mechanisms of action of vitamin D on the nervous system, as well as on the immune system and all cellular processes, which focus mainly on the regulation of calcium-depending systems, and antioxidant pathways. Vitamin D deficiency during pregnancy and early childhood can significantly affect the developing brain, predisposing to diseases such as autism and schizophrenia.

Summary:
Further research is still needed to determine the real impact of vitamin D deficiency on the risk of neurodevelopmental disorders, as well as the possibility of using supplementation as a form of treatment.