Neuronutrition in ASD: Involvement of gut microbiota, oxidative stress and inflammatory markers

Autism spectrum disorder (ASD) is a neurodevelopmental disorder displaying altered human behaviors, such as social interaction impairments, stereotypical/repetitive activities and emotional dysregulation. Children with ASD are often affected by gastrointestinal problems and gut microbiota dysbiosis. Inflammation and immune dysfunction are key contributors to ASD, as shown by high proinflammatory cytokines and oxidative stress. Indeed, notable implication of the nuclear factor kappa B in the severity of ASD derives from its ability to amplify neuroinflammation. This narrative review focused attention on neuronutrition and gut microbiota manipulation for mitigation of ASD symptoms, including neuroinflammation and oxidative stress. Studies in both rodents and humans with ASD have revealed that both pure and mixed Lactobacillus and Bifidobacterium were effective in ameliorating behavioral symptoms and GABA/glutamate imbalance. Often, the combined use of probiotics and prebiotics can have greater health benefits in ASD. Additionally, dietary interventions and microbiota transfer therapies along with low-to-moderate-intensity exercise have been proposed to improve gastrointestinal and behavioral symptoms. However, despite some encouraging results, biases in the neuronutrition/microbiota literature still exist. Indeed, many studies rely on small sample sizes, cross-sectional designs, and heterogeneous populations that differ in diet, medications, and comorbidities. In this context, the development of a precision diet tailored to individual gut microbiome profiles will allow for a broader understanding of the microbial ecosystem and relative therapeutical applications. Hence, by integrating metagenomics, metabolomics, epigenomics, with evaluation of environmental and nutritional factors, it will be possible to significantly improve the quality of life for people with ASD and their families.