Microbiome and nutrition in autism spectrum disorder: current knowledge and research needs.

Autism spectrum disorder (ASD) is the fastest growing neurodevelopmental disorder in the United States. Besides genetic risks, environmental factors have been suggested to contribute to the increase in ASD diagnosis over the past decade. Several studies have reported abnormalities in microbiota composition and differences in microbial metabolites in children with ASD. Gastrointestinal discomfort is commonly reported in children with ASD. Additionally, food selectivity and picky eating patterns are commonly reported. A number of mechanisms underlying the interaction between nutrition, the gut microbiota, and ASD symptoms via the microbiota-gut-brain axis have been proposed, including immune, hormonal, or neuronal pathways. Here, the current evidence base regarding the gut environment and nutritional status of children with ASD is reviewed. Potential underlying mechanisms of the microbiota-gut-brain axis in ASD and the interplay between nutrition, microbiota, and ASD symptoms are also reviewed. Future studies investigating the microbiota in the context of dietary intake are needed to increase understanding of the interplay between diet and the gut microbiota in ASD and to identify potential dietary, probiotic, or prebiotic intervention strategies.