Autism spectrum disorder: a systematic review about nutritional aspects and gut-brain axis

Abstract

The number of individuals diagnosed with autism spectrum disorder (ASD) had an evident increase in the last decade. The primary symptoms exhibited amongst these patients were mostly digestive and neurological disorders; with nutritional interventions being one of the most promising therapies to assuage this clinical symptomology. As such, following the PRISMA guidelines, we systematically reviewed the research studies apropos of the ASD patients manifesting said digestive disorders, to comprehend how dietary behavior can influence the etiopathogenesis and clinical manifestations of the disease, with primary focus on the gut-brain axis. From a comprehensive and structured search through electronic databases, 23 studies were retrieved and admitted in this review. The inclusion criteria defined that there be original articles consociating ASD with nutritional disorders and/or with the gut-brain axis. These studies analyzed the composition of the intestinal flora of diagnosed patients, subsequently discerning cases of varying imbalances. Alterations in the gene expression of the proteins involved in the digestion and absorption of food, the mucous barrier and the intestinal permeability were described. Accordingly, restrictive diets and the modulation of the microbiota by administering specific anti- & probiotics were initially identified as promissory therapies. In conclusion, the gut-brain axis was observed to be a determinant factor in both the etiology and clinical symptomology of ASD - though it is still debatable the correlation of intestinal alterations with neurological changes. At present, there is no concrete scientific proof accrediting to restrictive diets and the use of specific anti- & probiotics, as successful treatments for ASD.