• ‘Fix your gut, fix your brain’ used to be an underrated idea, but it is gaining in relevance today as more and more research throws light on the role of the community of bacteria living in your gut, that is, the gut microbiome.
  • A healthy gut microbiome is not a panacea but it may be able to help improve the quality of life of individuals with various diseases that lack other proven interventions.
  • Differences in gut microbiome composition have been implicated in several diseases, including Crohn’s disease, celiac disease and particularly, autism.

Autism spectrum disorder

  • Autism spectrum disorder (ASD) is the term for a group of neurodevelopmental disorders. Researchers are yet to fully understand the aetiology of ASD. (Aetiology is the study of factors that cause a condition or disease.)
  • However, they are beginning to find that a disorder in the gut-brain axis could have a prominent role.
  • According to the WHO, ASD affects one in 100 children. Children with ASD have impaired social interactions, lack verbal and nonverbal communication skills, and display restricted and repetitive behaviours.
  • These characteristics can adversely affect one’s cognitive abilities and, over time, diminish one’s quality of life.
  • A relatively under-researched aspect of ASD is the gastrointestinal problems associated with a subset of children with ASD. Limited research findings as well as anecdotal evidence indicate the presence of various gastrointestinal problems, like constipation, diarrhoea, flatulence, and bloating, among others, in children with ASD.
  • But even as researchers have proposed several theories to explain the aetiology of ASD, the pathophysiology of the disorder remains largely unknown. (Pathophysiology is the study of a condition’s impact on biological processes.)
  • At present, there are no known cures and therapeutic interventions available to treat or reverse ASD.

Studying the link

  • Increasingly profound exploration of the human microbiome by researchers, aided by advances in gene-sequencing technologies and high-end bioinformatic analysis, is dramatically reshaping our understanding of the connections between human health, diseases, and microbiomes.
  • The gut microbiome is believed to have a big impact on immune modulation and metabolic activities in the human body.
  • Immune modulation refers, among other things, to the efforts of the immune system to ensure its response is proportionate to a threat. Investigations of the dynamic cross-talk between the gut microbiome and the host environment have revealed potential connections to ASD symptoms.
  • For example, aberrant antigen trafficking through an impaired intestinal barrier could allow these antigens to eventually pass through the barrier surrounding the brain, triggering a chain of events that worsen ASD symptoms.
  • Some scientists have disputed the significance of the gut microbiome by contending that the microbiome can’t cause ASD and therefore its role in the pathophysiology of ASD is limited.
  • But research has shown that even if the gut microbiome doesn’t play a causative role, abnormalities in it can challenge a person with toxic metabolites and keep the person from synthesising the metabolites required to produce neurotransmitters involved in cognition, behaviour, mood, and sleep.
  • As a result, ‘fixing’ the gut in ASD can reduce the toxic burden — including that which moves through the blood-brain barrier — and/or help complete the necessary neurotransmitter synthesis pathways.

Ongoing research

  • In our own research, we have explored the gut microbiome in children with and without ASD, and have reported several interesting microbial biomarkers in children with ASD.
  • We observed dysbiosis — an imbalance — in the gut microbiome of children with ASD. They had a higher abundance of lactobacillaceae, bifidobacteriaceae, and veillonellaceae bacteria.
  • The fraction of bacteria of the phylum firmicutes was found to be significantly higher in the guts of children with ASD.
  • We also found an underrepresentation of certain microbes that produce short-chain fatty acids (SCFA), such as faecalibacterium and roseburia, in children with ASD.
  • This supports the hypothesis that a lower level of SCFAs in ASD could lead to an imbalance in brain function and behaviour.
  • This is the source of proposals to introduce these strains of bacteria as a probiotic for children with ASD, to help alleviate common gastrointestinal problems and in turn positively influence cognitive and behavioural functions.
  • However, since these are emerging areas of study, there are pockets of agreement as well as disagreement in the community; consensus lies in the future.

What can you do?

  • Reinstating a balance in the gut microbiome and reversing gut dysbiosis among children with ASD could alleviate many problems they face and improve their quality of life. One promising approach to reverse gut dysbiosis is faecal microbial transplantation (FMT), where stool samples from healthy individuals are transplanted into the large intestines of affected children.
  • A small study conducted by Ohio State University in 2017 reported that FMT improved both gastrointestinal and ASD-related symptoms. Since FMT is a cost-effective strategy with low risk, we need to build consensus among all stakeholders — including parents, clinicians, and educators — and create incentives to adopt it. There is also some evidence that gluten-free and casein-free diets can help children with ASD.
  • This could be because some of these children have been found to lack the bacteria that helps break down casein and gluten into metabolites.
  • In all, the role of diet, prebiotics, probiotics, synbiotics (which combine the benefits of probiotics and prebiotics), and FMT for the efficient management of ASD can be said to be encouraging.


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