Recent research links gut microbiota alterations to Autism Spectrum Disorders (ASD), a neurobiological condition with multifactorial bases. In some ASD patients, altered gut flora and increased intestinal permeability are observed, influencing the central nervous system's development and function. Chronic gastrointestinal (GI) symptoms are commonly associated with ASD and correlate with its severity. This non-pharmacological interventional clinical study aims to investigate the role of gut microbiota on ASD and the effectiveness of postbiotic-based dietary supplements in children aged 3-8 years old. Gastrointestinal symptoms, behavioral profile and analysis of intestinal metagenomic and metabolomic profiles will be assessed before and after one-month treatment. The results of the study could enhance understanding of non-pharmacological therapeutic approaches in ASD and improve clinical management strategies and the behavioural functioning for children with ASD.