Human milk oligosaccharides and the GI microbiota: is there a rationale for the use of HMOs in autism?

Abstract

The gastrointestinal (GI) microbiota plays a key role in health and disease. It also has a longdistance effect influencing the brain through the gut–brain axis. The establishment of an effective GI microbiota is associated with human milk oligosaccharides (HMOs). In animal studies there is evidence that HMOs can influence brain activity and cognitive development. This further suggests that management of the GI microbiota by dietary means could impact upon a wide range of diseases. Autism, which is the familiar name for autism spectrum disorder (ASD), comprises a group of heterogeneous neurodevelopmental disorders characterized by social deficits, repetitive and stereotypical behaviours, insistence on routines and communication impairments. GI abnormalities are a characteristic of a substantial number of children with ASD. These children possess a lower overall abundance of beneficial taxa, such as Bifidobacteria and Akkermansia, in the GI microbiota. Many children with ASD have higher counts of potentially pathogenic Clostridia than normally developing children. The underlying pathophysiology of ASD remains unknown although sub-optimal breast-feeding practices are associated with ASD. HMOs selectively promote the growth of Bifidobacteria in the GI tract, which is associated with numerous beneficial health outcomes. There are two potential benefits of HMOs in alleviating autism. Firstly, supplying HMOs to infants though breast-feeding can help establish a functional GI microbiota and thus avoid GI dysbiosis which is commonly related to the onset of autism. Secondly, administration of HMOs may alleviate the symptoms of autism through an effect on the gut–brain axis.