This article discusses the connection between gut health and autism. There is evidence that the gut microbiome may be different among people on the autism spectrum than the wider population, and that there are links between gut health and ASD symptoms[0]. There is also research indicating that gut health may be improved by microbiota transfer therapy. Some scientists have disputed the significance of the gut microbiome, arguing that it cannot cause autism.
However, there is mounting evidence to suggest a link between the gut and autism spectrum disorders. The gut-brain connection, or the gut-brain axis, has been researched for decades, but in recent years there has been an exploded growing interest in targeting the gut for potential treatments of autism. Investigating researchers have identified a potential link between gut health and autism due to the occurrence of gastrointestinal symptoms in those on the autistic spectrum. This has opened up new directions for investigating the implications of the gut microbiome on behaviour and easing behavioural issues associated with autism. [Sources: 0, 7, 8]
Gut Microbiome Composition In Autistic VS Non-autistic People
Many studies have found differences in the gut microbiome composition between autistic and non-autistic people, suggesting abnormal development of the gut microbiome in those on the autism spectrum. Much speculation has arisen about how these differences could be linked to symptoms of autism. Researchers are now looking at how early life factors such as diet and antibiotics affect the gut microbiomes of children with autism, as well as wider population associations between microbial composition and autism. [Sources: 1, 4, 10]
Germ-free Mice Exposed to Autistic Fecal Samples Exhibited Autism-like Behaviour
In a recent study, researchers reported that a group of germ-free mice exhibited autism-like behaviour when exposed to fecal samples from autistic subjects. This suggests that the lack of normal gut microbiomes in the mice may be related to the behavioural symptoms they exhibited. The findings support previous research linking autism and gut health, including studies that have shown that children without autism have different microbial compositions in their guts than those with autism. According to one microbiologist, inherited microbiome differences could also be driving some cases of autism. To test this hypothesis, researchers put fecal samples from children with and without autism into germ-free mice. They found that those pups exposed to fecal samples from autistic subjects had reduced social behaviours compared to control mice – suggesting an underlying connection between their gut microbiome and their behaviour. [Sources: 3, 10, 12]
Fecal Microbiota Transplant (FMT)
In a separate study, 18 autistic children were transplanted with fecal samples from healthy donors and experienced significant improvements in their autism symptoms. The researchers suggested that the changes in microbiome diversity triggered by the transplant were responsible for these improvements. Furthermore, when pregnant mice exposed to other inflammatory stimuli such as lipopolysaccharide (LPS) had their offspring examined, it was found that they exhibited higher rates of intestinal inflammation as well as altered microbiome diversity which showed their offspring increased anxiety-like behaviours and impaired social interactions – similar to those seen in autism. [Sources: 3, 9, 12]
Microbiota Transfer Therapy (MTT)
The connection between gut health and autism is becoming increasingly clear. Following microbiota transfer therapy (MTT) to improve the faecal microbiota transplant, researchers have been able to identify specific microbial species that are associated with autism spectrum disorder (ASD). Through genome sequencing technology, they were able to detect improved microbial taxa and microbial pathways in the microbiome of these individuals. This suggests further follow-up studies are needed to explore future research and determine which specific microbial species, their functional gene expression and taxa genes, may be linked to ASD. Recent studies suggest that up to 1,000 bacterial species can be found within the human gut microbiome; this is why it is important for us to consider whole genome shotgun metagenomics in order to extract detailed data from the microbiome. [Sources: 6, 12]
Researchers have found a strong correlation between gut health and autism. This connection has been suggested by numerous studies and is further evidenced by the use of microbiota transfer therapy (MTT) in autistic children. Gut bacteria can influence the brain axis and have an impact on behaviour, as well as cognitive issues in autistic children. These bacteria can also affect sensory sensitivities and fussy eating habits, which are common issues seen in people with autism spectrum disorder (ASD). A study published online reported that microbiota transfer therapy had a positive effect on the gastrointestinal dysfunction associated with ASD. The connection between gut health and autism is now being studied extensively. Researchers are exploring how microbiomics, the study of microorganisms within the body, can be used to better understand this connection. They are also looking at how changes to the gut microbiome may be beneficial for autistic children; from improving their behavioural issues to helping them regulate their emotions. [Sources: 1, 2, 5, 6]
Many studies, with scientific designs, have been done on mice studies to analyze data. Unfortunately, the sample size meant to be included in these studies was small, which can make it difficult to draw definitive conclusions. Despite this, there is evidence linking a change in the microbiome to Autism Spectrum Disorders (ASD). However, the study design and data analysis issues meant that recent studies are weighing findings with caution. [Sources: 4, 7, 12]
A recent study casts doubt on the connection between gut health and autism. The study suggests that a possible causal involvement of gut microbiota in autism is not supported by current evidence. Previous animal studies had suggested that atypical gut bacteria may influence the cause of autism, but this recent study did not find any evidence to suggest this. Although emerging animal research has found a role for microbiome in ASD causes dysbiosis, disputed scientists have suggested that several studies may have been misinterpreted, or lack sufficient data for accurate conclusion. Suggesting researchers have also pointed to other potential causes of autism such as environmental toxins, inflammation and immune system dysfunction. [Sources: 7, 11, 12]
Researchers have explored the gut microbiome of people with autism and the connections between various gastrointestinal problems and autism. The findings of limited research suggest that children with autism are more likely to suffer from a wide range of gastrointestinal problems such as constipation, diarrhea, bloating and flatulence. This relatively under-researched aspect of autism is an interesting area for further exploration. Our own research into the presence of microbial biomarkers in children with autism has indicated anecdotal evidence that a subset of those with autism may have underlying gut health problems. [Sources: 11]
Recent research from Dr. Jake Gratten, a researcher in molecular bioscience at the University of Melbourne’s Genomics Group, took Swedish researchers’ findings one step further by identifying the genetic basis for the gastrointestinal problems experienced by some children without autism. Dr. Gratten’s research indicates that individuals with autism spectrum disorders (ASDs) may experience unusual gastrointestinal inflammation that could be associated with their condition. He also discovered that people with autism have significantly fewer bacteria in their gut microbiomes than those without autism, which can lead to inflammation and other problems. The research conducted by Dr. Gratten and his team reveals that those with autism may have 600 bacterial species fewer than their brothers and sisters without the condition, indicating an underlying biological cause for their significant gastrointestinal problems. This finding suggests a possible link between gut health and cognitive development in those with Autism Spectrum Disorders (ASDs). Further research into this phenomenon is ongoing, but it appears clear that there is a connection between gut health and autism spectrum disorders (ASDs) 0 1, 3, 5]
Recent studies have revealed that a gene mutation, known as the ‘velcro’ gene, affects neuron communication and can develop autism-like behaviours in those with this mutation. Previous animal studies have shown that the same velcro gene mutation can cause dysfunction of the gut-brain axis team, which is thought to be responsible for this connection. A study conducted by researchers at RMIT University has built on this work and revealed that an increased risk of developing offspring with autism can occur when pregnant mice are exposed to certain environmental factors. [Sources: 0, 9]
The researchers found that when pregnant mice with the Velcro gene mutation were exposed to environmental triggers such as stress or infection, their offspring were more likely to exhibit autism-like behaviours. This suggests that environmental factors may interact with genetic mutations to increase the risk of developing autism.
The study also found that the offspring of mice with the Velcro gene mutation had alterations in their gut microbiota, which is known to play a role in brain development and behaviour. This further supports the idea that dysfunction of the gut-brain axis may be involved in the development of autism.
These findings have important implications for understanding the complex interplay between genetic and environmental factors in the development of autism. Further research is needed to better understand how these factors interact and to develop potential interventions to prevent or treat autism.
Sources
[0]: https://www.sciencedaily.com/releases/2019/05/190530101143.htm
[1]: https://www.bmj.com/company/newsroom/distinctive-gut-microbiome-unrelated-to-diet-may-characterise-children-with-autism/
[2]: https://trayt.health/trayt-community-perspective-autism-and-the-brain-gut-connection/
[3]: https://hms.harvard.edu/news/gut-brain-connection-autism
[4]: https://www.uwa.edu.au/news/Article/2021/November/Gut-bacteria-doesnt-cause-autism
[5]: https://imb.uq.edu.au/article/2021/11/new-study-starves-link-between-gut-microbiome-and-autism
[6]: https://news.asu.edu/20221214-discoveries-study-finds-microbiota-transfer-therapy-provides-longterm-improvement-gut
[7]: https://www.gutmicrobiotaforhealth.com/a-study-casts-doubt-on-the-contribution-of-altered-gut-microbiota-in-autism-spectrum-disorder-related-behaviors/
[8]: https://www.autism.org/nutrition-gut-brain-connection/
[9]: https://www.autismspeaks.org/science-news/spotlight-gut-bacteria-brain-connection-autism
[10]: https://www.science.org/content/article/gut-bacteria-may-contribute-autism-symptoms-mouse-study-finds
[11]: https://www.thehindu.com/sci-tech/science/explained-how-does-the-gut-microbiome-link-to-autism-spectrum-disorders/article66528560.ece
[12]: https://atlasbiomed.com/blog/the-microbiome-autism-link/
