What’s the deal about autism and the microbiome? The following studies suggest a close link between the developmental condition and gut health, so keep reading to find out more.
In this article:
- What is Autism?
- What is the Gut Microbiome?
- Studies that Connect Autism and Gut Health
- Autism Microbiome Link
- Can Treatment for Gastrointestinal Problems Work for Autism?
Autism and the Microbiome: The Ties That Bind Gut Bacteria and Autism
In 2019, The Economist published an article about autism and the microbiome. It revealed two things:
- There’s a closer association between autism spectrum disorders (ASD) and gut microbes than most people think.
- A process called fecal microbiota transplantation showed promise in alleviating autism symptoms.
These are salient points that may be harder to understand unless we break down the two important factors in the story. These are gut bacteria and autism.
Let’s begin with the latter.
What is Autism?
According to Autism Speaks, this is a behavioral disorder and a spectrum disorder. As a behavioral issue, people with autism struggle with social behaviors, such as:
- They may not be able to look a person in the eyes.
- They may also not speak or interact.
- Some are prone to outbursts or tantrums.
- They find communicating their thoughts and feelings difficult.
As a spectrum disorder, the symptoms can vary. Many therapists or clinicians describe autistic children and adults in the following terms:
- High-functioning autism (which is sometimes used to describe those with Asperger’s syndrome)
- Mild autism
- Severe autism
What is Asperger’s syndrome? It is a developmental disorder characterized by the ability to function while struggling with social interaction. People with this condition tend to be intellectual.
Some of the most common behavioral symptoms associated with the disorder are:
- Unusual patterns in eating or sleeping
- Difficulty in communicating and socializing
- Short attention span
- Repetitive and restricted behaviors
- Lack of facial expression
- Inability to express proper emotions
So far, there’s no test to confirm autism in both an unborn child and an infant. These symptoms of ASD usually appear once the child reaches two years old.
The prevalence of autism is high. The data from Autism Speaks suggests that the number of children with ASD increased to 1 in every 59 kids.
In only 20 years, the reported number of cases rose by 600%! More comprehensive screening or awareness could have contributed to a significant increase.
Either way, it only highlights the importance of learning the actual cause of autism. Until now, scientists don’t have a definite answer.
What is the Gut Microbiome?
One of the possible explanations for autism is the microbiome. Some studies suggest that a link between the gut microbiome and autism does exist.
What is the gut microbiome, by the way? It refers to a community of bacteria and fungi living in the body.
This flora of microorganisms is abundant in the skin and mouth. They are also in the gastrointestinal tract (GI), where they can number in the billions.
As living organisms, they interact with one another and produce substances such as short-chain fatty acids (SCFAs). They also create metabolites, which are the by-products of metabolism.
About 70% of the immune system is also close to the GI tract. These gut microbes may have a direct impact on the immune response, said a 2018 Immunity study.
The gut also affects the way the brain functions because of the gut-brain axis. This “highway” connects the organs physically and biochemically.
For example, both of these organs produce neurons. These are cells that serve as the building blocks for the nervous system, including the brain.
A 2017 research cites how these microbes can lead to the development of Alzheimer’s disease. An example of these changes is gut dysbiosis or imbalance.
Studies that Connect Autism and Gut Health
If microbes in the gut can affect the brain, does it have something to do with the behavioral disorder as well? The answer is yes based on the different types of research.
In a 2019 study, 90% of children with ASD were shown to also suffer from gastrointestinal problems. According to this research, they were also prone to irritable bowel syndrome and gastrointestinal symptoms like:
- Abdominal pain
Meanwhile, a 2018 research tied autism microbiome and inflammation. People with autism may also be at risk of inflammatory bowel diseases such as:
- Crohn’s disease, which is inflammation of the digestive tract
- Ulcerative colitis, which forms sores or ulcers in the intestinal lining
A cohort study in PLoS One revealed that prenatal antibiotics may lead to a small, increased risk of autism symptoms in children. The scientists want to emphasize that these odds are not significant.
The connection may lie on the fact that antibiotics can alter the gut microbiome. For example, certain antibiotics can cause or worsen Clostridium difficile infection (C. diff).
This infection can be life-threatening since it leads to inflammation of the colon.
Autism Microbiome Link
Then there’s the 2019 study by RMIT University. It focused on a mutated gene that may be a potential cause for autism by changing the way the neurons work.
This gene could impact the “Velcro” that keeps the neurons close and prevent cells from communicating well, leading to symptoms of autism.
The same gene, though, could disrupt the functions of the gastrointestinal tract, including creating gut contractions and maintaining the number of neurons in the tract.
Food that lingers longer in the large intestine can increase bacterial fermentation. In the long term, it may lead to gut microbiome imbalance.
In the same year, some researchers conducted an experiment using germ-free mice. The goal was to test the effects of gut bacteria on behavior.
In the animal model, the team transplanted fecal microbiota samples. These came from children with ASD.
They placed it on mice with no microbiome, who then mated. They then performed behavioral tests on their offspring.
Based on their analysis, they learned that:
- Baby mice with the autism microbiome showed symptoms of the disorder. They were less social and repeated some of their behaviors.
- Their gut also had fewer species of bacteria. Diversity is essential for a healthy microbiome.
- The mice with the autism microbiome also showed marked differences in splicing (the ability of the DNA to convert proteins, which is vital in many cellular processes).
- The splicing affected many genes, including 52 associated with the development of autism.
- They also produced lower levels of certain metabolites. One of these is taurine, which attaches itself to neurons, controlling their hyperactivity.
Can Treatment for Gastrointestinal Problems Work for Autism?
Another question: if the link between the disorder and gut health is strong, does it mean the treatment for gastrointestinal symptoms can also work for people with autism?
The 2019 study in Scientific Reports suggests that it could. One of these is the fecal microbiota transplant.
What is this clinical procedure? Doctors transplant poop from people with a healthy gut to patients.
The process may involve injecting the sample to the rectum or taking a poop pill.
It may be gross, but it’s not as novel a procedure as before. It’s becoming a go-to treatment for people with Clostridium difficile infection.
After the children went through the procedure, the researchers noted the following:
- The patients experienced a reduction of the intestinal symptoms by 58%. These improvements remained the same even after two years of the fecal transplant.
- The evaluators reported a 45% decrease in the core symptoms of ASD. These include repetitive behaviors and social behavior difficulties.
- At the end of the study, only 17% had severe autism compared to 83% during the beginning. Around 44% no longer fit the criteria for mild autism.
One can never talk about gut health and, by extension, autism microbiome without touching on diet. In a 2011 research study, researchers noted that prebiotics and probiotics may help alleviate the symptoms of ASD by improving the diversity or composition of the gut flora.
The science behind autism microbiome may be still in its infancy, but the studies are both enlightening and promising.
Looking for more materials to read? Parents and adults with ASD can read Total Gut Balance.
Hopefully, with these developments, it won’t be long before we can figure out what causes ASD. From this, we can find solutions to treat and eventually cure ASD.
What do you think about the recent studies about autism gut microbiome? Share your thoughts in the comments section below!
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- Characterization of the Oral Fungal Microbiome (Mycobiome) in Healthy Individuals