Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by the presence of repetitive or restrictive behaviors and deficits in social and communication skills. There has been a pervasive increase over the last decade in the number of children being diagnosed with ASD. An interrelationship between dietary intake, neurodevelopment, and cognitive function has been observed in healthy children and ensuring adequate nutrition has been suggested as an important aspect in the treatment and etiology of some psychiatric disorders. Microbiome research in ASD has offered a particular focus on the class Clostridia and the genus Clostridium, due to the fact that Clostridium was one of the first and most consistent microbes shown to be elevated in children with ASD. In animal models, diet-induced changes in the microbiota composition led to behavioral changes, supporting the idea that diet could be used as a future therapeutic avenue for psychiatric disorders.