Effect of Probiotic Supplementation on Autism Spectrum Disorder: A Review of Randomized Controlled Trials

Abstract

Introduction: Autism spectrum disorder (ASD) is frequently associated with gut dysbiosis and gastrointestinal symptoms, prompting interest in therapeutic strategies targeting the microbiota, such as probiotic supplementation. This structured narrative review evaluates the effectiveness of probiotics in modulating core symptoms of ASD.

Methods: A structured narrative review was conducted following SANRA guidelines. Randomized controlled trials (RCTs) published between March 2015 and March 2025 were retrieved from the Epistemonikos Database of Trials. Study selection was performed independently by two reviewers, with discrepancies resolved by a third. Key data from eight selected RCTs were extracted and synthesized.

Results: Most included studies reported positive outcomes in domains such as gastrointestinal symptom improvement, reduction in repetitive behaviors, increased social interest, and gut microbiota modulation. Specific strains like Lactobacillus plantarum PS128 showed beneficial effects on neurobehavioral parameters. However, substantial heterogeneity was observed in strain types, doses, duration, and assessment tools.

Conclusions: Probiotic supplementation appears to be a promising dietary approach for managing ASD, especially in alleviating behavioral, social, and gastrointestinal symptoms. Nevertheless, effects are not universal, and further standardized RCTs are necessary to support robust clinical recommendations.