Leveraging the Impact of Gluten-free, Casein-free, Ketogenic, Probiotics, Essential Fatty Acids, and Other Nutritional Interventions in Autism Spectrum Disorder: A Narrative Review

Autism spectrum disorder (ASD), a complex neurological condition, is characterized by challenges in communication, behavior, and social interaction. ASD is often accompanied by food selectivity, gastrointestinal problems, and micronutrient imbalances, which have led to growing interest in dietary interventions as adjuncts to management. However, the available approaches remain conceptually fragmented and understudied. This narrative review synthesizes evidence on 21 dietary interventions, organizing them within a reduction-addition-substitution-elimination (RASE) framework together with an evidence-maturity and clinical impact map. Overall, ketogenic diet, balanced essential fatty acids, probiotics/prebiotics, and gluten-free/gluten-free casein-free approaches have accumulated comparatively more studies than other diets, whereas several others remain supported mainly by theoretical or limited evidence. Across interventions, small samples, heterogeneous study designs, limited controlled trials, and practical barriers, such as dietary complexity and caregiver burden, constrain firm conclusions. This Review provides an integrated reference for clinicians, researchers, and caregivers and identifies priorities for future research.