The Role of Gut Microbiota in Autism

Some studies point to the influence of the microbiota in autism. In fact, there's a relationship between the brain and the gut that could help explain certain symptoms of autism spectrum disorder.
The Role of Gut Microbiota in Autism

Last update: 12 June, 2021

Although autism is a disease associated with neurological disorders, the gut microbiota of a person with this disease is also altered. In fact, most autistic people suffer from gastrointestinal problems and alterations in the immune system. With this in mind, in the following article, we’ll take a look at how the intestinal flora is related to this disorder.

The intestinal microbiota

Individuals with autism have a different gut microbial composition than other people. The composition of the intestinal microbiota is different in the stomach, small intestine, and colon. Therefore, the thousands of microbial species – bacteria, viruses, and some fungi – that inhabit it comprise the main protective system of the gastrointestinal tract.

The microbiota participates in the correct functioning of the organism in different ways:

  • Establishing an intestinal barrier that selects the passage of different substances, preventing pathogenic species from crossing it
  • Maturing the immune system, stimulating innate and acquired immunity
  • And finally, managing the synthesis and metabolism of nutrients, hormones, and vitamins, as well as the elimination of toxic substances

Modifications in the bacterial composition of this microbiota are influenced by diet, antibiotic use, lifestyle, and genetics. What’s more, recent studies suggest that there could be a relationship between flora alterations and some psychiatric disorders – autism, schizophrenia, Parkinson’s disease.

The brain-gut connection

Dysbiosis is the alteration in intestinal bacterial composition that leads to the production and spread of lipopolysaccharide (LSP) into the blood, a pro-inflammatory endotoxin. This molecule influences the modulation of the central nervous system, controlling emotions.

There’s a bidirectional connection between the central nervous system and the gut. Neurons can change the microbial composition of the intestinal flora and alter intestinal permeability. In this way, the brain directly influences the intestinal microbiota.

At the same time, publications are showing that this microbiota controls the activities of the central nervous system. A study in the journal Brain, Behavior and Immunity investigated how Campylobacter jejuni bacteria elevated anxiety levels in mice.

A drawing illustrating the relationship between the gut microbiota and the brain.
The brain-gut connection explains the influence of gut microbiota in autism.

Continue reading: Children with Autism: 4 Important Exercises

Autism Spectrum Disorder (ASD)

This condition encompasses a set of neurological alternations that are characterized by restricted and repetitive behavior, as well as deficits in social interaction and communication.

People with autism are often treated with antibiotics to medicate other underlying diseases, such as chronic otitis media. Consequently, this affects the protective gut microbiota and facilitates the colonization of neurotoxin-producing bacteria.

In addition, many children with autism suffer from gastrointestinal problems, such as inflammatory bowel disease (IBD), which presents the following symptoms:

  • Diarrhea
  • Constipation
  • Abdominal pain
  • Vomiting
  • Sleep disturbances
  • Irritability

Microorganisms of the gut microbiota in autism

Clostridium

Clostridia are present at a higher concentration in patients with ASD. Although many of these bacteria are beneficial and are part of healthy gut microbiota, there are pathogenic species, such as C. tetani and C. perfrigens, which produce toxins and cause serious diseases in humans.

In a study that appeared in the Journal of Child Neurology, most children with regressive autism who underwent treatment with vancomycin displayed improvements in gastrointestinal and neurobehavioral symptoms. This points to the influence of the microbiota in autism and its possible modification.

Sutterella

Also, researchers have found this bacterium in biopsies taken from the mucosa of the gastrointestinal tract and stool of children with ASD. Since it’s hardly present in non-autistic individuals, experts consider Sutterella to be the main component of the microbiota in people with autism.

Desulfovibrio, Lactobacillus, and Bifidobacterium

Finally, experts link species of Desulfovibrio with the most severe symptomatologies of autism. These bacteria species produce propionic acid. This seems to have to do with the pathogenesis of ASD.

Also, lactobacilli are also present at a higher concentration in patients with ASD. Plus, bifidobacteria are present in lower quantities than normal.

A child pointing to his shadow on a wall.
Recent studies link changes in gut microbiota to certain central nervous system disorders

Find out more: The 5 Most Common Signs of Autism

Treatments for alterations in gut microbiota in autism

Given that the microbiota seems to play an important role in the pathophysiology of ASD, treatments are based on modifications of the bacterial composition. The aim is to restore balance so as not to alter the nervous system.

In this regard, some of the options that have been tested are:

  • Probiotics: Probiotics have the ability to normalize the microbiota and intestinal problems. It’s useful as an alternative to treat gastrointestinal symptoms and autism.
  • Fecal microbiota transplantation: This procedure transfers the fecal microbiota of a healthy person to a patient suffering from dysbiosis. It has been useful in the treatment of cases of inflammatory bowel disease. In addition, it’s helped improve symptoms of constipation.
  • Diet: Individuals with autism often have issues when it comes to eating. These individuals may eat fewer fruits, vegetables, and proteins. Therefore, an improvement in their diets could help the health of their intestinal microbiota.
  • Antibiotics: These compounds produce alterations in the microbiota. However, specific drugs such as vancomycin or minocycline have been tested.

Microbiota in autism: A field of research

Overall, there seems to be substantial scientific evidence of the influence of the intestinal microbiota in people with autism.

In any case, it’s essential to continue with research to be more certain. For the time being, if you have a family member with autism, you should consult specialists in the field to choose the best treatment approach.

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