Can Gut Bacteria Shape Autism Traits? New Evidence Links the Gut

Autism spectrum disorder (ASD) is usually discussed in terms of brain development and behaviour—but growing research suggests the story may also begin in the gut. Many autistic individuals experience digestive problems such as constipation, abdominal pain, or food sensitivities. Researchers now believe this is more than a coincidence (1^✔ ✔Trusted Source
Identifying gut microbiota composition disparities in autistic individuals and their unaffected siblings: correlations with clinical characteristics

Go to source). Our gut is home to trillions of bacteria that help digest food, regulate immunity, and even communicate with the brain through what is called the gut–brain axis. The study from Nature explored whether differences in gut bacteria might be linked to autism by comparing three closely related groups: 239 autistic individuals, 102 unaffected siblings, and 81 growing children without autism aged 4 to 25 years.

By studying siblings with similar genes, diets, and environments, researchers hoped to discover gut bacteria that could be beneficial rather than harmful to non-autistic siblings.

What Makes Siblings' Guts Unique?

Among various other things, one of the most surprising results was that unaffected siblings had the most prosperous and diverse gut microbiome of all groups. In the simplest terms, their intestinal bacteria were more varied and evenly distributed.

Why does this matter? The variety of the gut microbiome is regarded as a healthier and stronger one. It is also more helpful for digestion, inflammation and balancing the body in general. It is thought that this diversity can serve as a form of buffer, aiding in the ability of the siblings not to be affected even though they have genetic vulnerability to their autistic siblings or peers.

This observation indicates that the gut diversity on its own might be protective, a notion that may redefine the current understanding of autism risk.

The Good Gut Bacteria and What They Do

The study identified certain beneficial gut bacteria that were more common in typically developing children and siblings but lower in autistic individuals.

1. Blautia
(Main Function: Gut balance & inflammation control)

• Synthesises short-chain fatty acids (SCFA) which feeds gut cells
• Helps keep the gut lining healthy
• Related to decreased inflammation
• Cited as a factor of improved metabolism and immunity

Why is it important for autism?

Lower levels have been observed in several brain–gut disorders, including autism.

2. Eubacterium hallii Group
(Main Function: Energy metabolism & gut repair)

• Transforms dietary fibres into butyrate, which is a major gut-cell energy source
• Enhances the integrity of the intestinal barrier
• Helps to control the metabolism of fat and sugar in the blood

Why is it important for autism?

Butyrate is also known to influence brain function via the gut–brain axis.

3. Anaerostipes
(Main Function: Gut–brain communication & anti-inflammatory action)

• A powerful butyrate-producing bacterium
• Reduces gut inflammation
• Supports immune balance

Why is it important for autism?

Considered one of the most important “beneficial” bacteria in autism research.

4. Erysipelotrichaceae UCG 003
(Main Function: Lipid metabolism & gut structure support)

• Part of the fat digestion and absorption
• Contributes to the balance of microbes of the gut
• Its changes in level are associated with metabolic and inflammatory disorders

Why is it important for autism?

More abundant in typically developing individuals in this study.

5. Parasutterella
(Main Function: Gut chemistry regulation)

• Helps control digestion by regulating the bile acid metabolism
• Modulates the gut acidity and intestinal absorption
• Related to stable gut-ecosystems

Why is it important for autism?

Often seen as a marker of a well-regulated gut environment.

6. Ruminococcaceae UCG 013
(Main Function: Fibre digestion & gut strength)

• Hydrolyses complex plant fibres
• Produces beneficial SCFAs
• Promotes colon integrity and bowel consistency
• Associated with enhanced gut resilience

Why is it important for autism?

Lower levels may weaken gut integrity and gut–brain signalling.

These bacteria contribute to the digestion process, a healthy gut lining, the reduction of inflammation, and the healthy communication of the brain. Their levels go low, then gut health and the brain-related processes, such as mood and social behaviour, can also be compromised.

Of these, Anaerostipes was the most significant bacterium, as it decreased inflammation and promoted the health of the gut lining.

Why is Anaerostipes Gut Bacteria Important for Autism?

• Better social communication was associated with higher levels of Anaerostipes
• Reduced emotional distress and anxiety-like behaviours
• Fewer behavioural issues, e.g., withdrawal or sadness

That is, individuals who had more of these beneficial bacteria would have milder symptoms that were related to autism. This reinforces the notion that the gut microbes are not only involved in digestion, but they can also be involved in mood, feelings and even social behaviour as well.

Higher levels of bacteria of the Prevotellaceae family, namely Prevotella and Alloprevotella, were also observed in unaffected siblings. The significance of these bacteria is that they degrade complex carbohydrates, synthesise vitamins and aid in anti-inflammatory processes.

Previous research has also shown a consistent low Prevotella in autistic people. It is more prevalent in siblings, which implies that it might be beneficial to keep the gut and brain balanced. Other researchers think these microorganisms contribute to healthier chemical signalling between the gut and the brain by potentially reducing the risk of autism-related characteristics developing.

This leads to a thrilling prospect: some gut bacteria might silently guard vulnerable children.

Why Digestion and Behaviour Are Linked In Autism

The researchers also discovered that the general gut bacteria were correlated with:

• Social communication problems.
• Repetitive behaviors
• GIT symptoms such as abdominal discomfort and bowel.

This strengthens the fact that the gut and the brain are constantly talking to each other. This communication can be disrupted when gut bacteria are not in balance, and this may interfere with behaviour and emotional control.

Remarkably, although the digestive symptoms were widespread, they did not comprehensively describe the gut variations, i.e., the microbiome might be the cause of autism attributes beyond gut irritations.

Why A Gut Check Is Essential For Autism?

The present study has solid evidence that gut bacteria are different in an important way among autistic individuals, their unaffected siblings, and their normally developing peers. Most importantly, it identifies certain microbes that can be beneficial in protection against more serious forms of autism and, most of all, bacteria that can maintain gut health and decrease inflammation.

Though this does not imply that autism may be treated by modifying gut bacteria so much alone, it provides an opportunity in the future, which can be in the form of:

• Selective probiotics or prebiotics.
• Diet-based interventions
• Individualised gut-health interventions and behavioural interventions

The takeaway is hopeful: the gut may be an unexpected ally in understanding and supporting autism. By learning more about these tiny microbes, researchers are uncovering new pathways toward better health and quality of life!

Reference:

1. Identifying gut microbiota composition disparities in autistic individuals and their unaffected siblings: correlations with clinical characteristics - (https://www.nature.com/articles/s41398-025-03768-8)

Source-Medindia