Gut Microbiota, Nutrition and Adverse Reactions to Food in Children With Autism Spectrum Disorders

To date, it is well documented that the gut microbiota (GM) influences numerous physiological processes in the healthy "host". The alteration of the composition and function of the intestinal microbiota, commonly referred to as "dysbiosis", is associated with many pathological conditions. The high co-morbidity between inflammatory bowel diseases and psychiatric symptoms such as anxiety and stress and the frequent presence of gastrointestinal dysfunctions in autistic patients have highlighted a possible implication of GM in psychiatric disorders. The ability of GM to communicate with the central nervous system and the possible influence on behavior led to the discovery of the existence of a microbiota-gut-brain axis. Clinical and experimental data suggest a possible role of modifications in the composition and function of the intestinal microbiota (impaired production of short-chain fatty acids, SCFAs) in major psychiatric disorders such as autism spectrum disorders (ASD). ASD is a severe neurological condition characterized by severe stereotypical behaviors and deficits in linguistic and social interaction. The prevalence of ASD in children is continuously increasing in Western countries. The pathogenesis of ASD is still poorly defined. The clinical manifestations of ASD are the result of complex interactions between genetic, epigenetic, environmental and microbiological factors. The improvement in gastrointestinal symptoms of autistic patients after short-term oral treatment with antibiotics and probiotics clearly indicated a role of the metabolites of MI in ASD. In particular, an alteration in the phyla of Bacteroidetes and Firmicutes in fecal samples from autistic children has been described with conflicting results. Williams and colleagues (2011) evaluated a significant increase in the Firmicutes / Bacteroidetes ratio in intestinal biopsies of autistic children with gastrointestinal disorders. It has also been shown in animal models of ASD that dysbiosis is positively associated with an increase in butyrate levels and inversely associated with the "score" of the severity of ASD symptoms. Alterations in nutritional status, eating habits and adverse reactions to food appear to be more frequent in children with ASD. Several studies support the hypothesis that children with ASD have a greater refusal of food, requiring specific food presentations or eating a reduced variety of foods compared to children without ASD. These conditions are associated with dysbiosis. Preliminary data suggest that particular elimination diets and / or modifications of the intestinal microbiota can determine a positive effect on the symptoms of ASD. A better knowledge of the composition and functions of the intestinal microbiota also in relation to eating habits and the presence of adverse reactions to food in the child with ASD could facilitate new effective strategies for the prevention and treatment of these conditions.