What Are Postbiotics?
What Are Postbiotics? A Comprehensive Guide to the New Frontier in Gut Health In the world of gut health, most ...
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Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterised by challenges in social interaction, communication, and repetitive behaviours. Increasing evidence suggests that the gut microbiome—the collection of microorganisms living in the human gastrointestinal tract—may play a significant role in the development and management of ASD. This blog explores the research linking the gut microbiome to ASD, including potential mechanisms, therapeutic approaches, and actionable insights.
“The gastrointestinal symptoms of individuals with ASD seem to correlate strongly with the severity of their ASD” (source)
Research consistently shows that children with ASD have differences in gut microbiome composition compared to neurotypical individuals. Studies have reported:
These imbalances may contribute to gastrointestinal symptoms common in ASD, such as constipation, diarrhoea, and abdominal pain.
Gut imbalances have also shown to correlate with other autism co-morbidities, such as sleep difficulties, abnormal mood, and social deficits. In comparison with ASD patients without GI symptoms, it has been discovered that GI comorbidity in patients with ASD was associated with increased sleep issues, abnormal mood, argumentative, oppositional, defiant, or destructive behavior, anxiety, sensory responsiveness, rigid compulsive behaviours, self-injury, aggression, lack of expressive language, and social impairment (source).
Research has found that 36.7% of children with ASD had abnormal intestinal permeability, compared to less than 5% of children in the control group. Similarly, another study reported that 43% of ASD children experiencing gastrointestinal symptoms showed signs of impaired intestinal permeability (source).
More recently, a study explored the link between leaky gut and behaviour. The researchers measured levels of intestinal fatty acid-binding protein (a marker of leaky gut) in the blood of children with ASD. Their findings revealed that higher levels of this protein were associated with more severe challenges in communication, social interaction, and maladaptive behaviours (source).
Emerging evidence suggests a link between SIBO and ASD. In one study (source) SIBO was significantly associated with worse symptoms of autism.
Some studies have proposed that yeast overgrowth, particularly Candida albicans, could contribute to symptoms (source).
Candida can releases ammonia and toxins that can induce autistic behaviours (source).
Overall the research is mixed on candida and autism but this should come as no surprise – candida isn’t the sole cause of autism and thus not everyone being investigated would have a candida overgrowth. The important thing to appreciate is that it can be connected, and when is, needs treating.
You may like to read our blog on Candida albicans.
It’s important to note that recent research (source) has argued that at least some of the imbalances in the gut microbiome are due to the decrease dietary diversity of neurodivergent children. So there’s a chicken and egg debate happening here.
The gut-brain axis is a complex communication network between the gut and the brain, mediated by the vagus nerve, immune system, and microbial metabolites like short chain fatty acids. Dysbiosis in ASD may disrupt this axis, leading to:
Probiotic therapy has been described as an additional and alternative treatment for ASD (source) They may help by:
A meta-analysis, published in 2024 (source), which looked at eight studies with a total of 318 samples from autistic patients aged 1.5-20 years, concluded that the probiotic intervention group had significantly better behavioural symptoms compared to the control group.
In another paper, children with ASD aged 5–9 years who received probiotic supplements for 3 months showed improvements in their gut microbiome, gut symptoms, and the severity of their symptoms, behaviours, and functioning (source). Similarly, a multi-strain combination of 10 probiotics administered for 4 weeks to a 12-year-old child with ASD decreased gut symptoms and improved ASD core symptoms.
A 2019 review by Sanctuary et al. highlighted that probiotic supplementation improved both gastrointestinal and behavioural symptoms in children with ASD (source).
Recommended Products: Various lactobacillus and bifidobacteria strains have been investigated. One of these is VSL#3. The yeast probiotic Saccharomyces Boulardii has also been shown to be helpful.
In this large cohort study (source), antibiotic exposure during pregnancy or early infancy was not associated with an increased risk of autism spectrum disorder, intellectual disorder, or language disorder in children. However, elevated risks were observed in several subgroups such as children using antibiotics during very early life and those with long term antibiotic use, which warrants attention and further investigation.
Diet plays a critical role in shaping the gut microbiome.
Nutritional interventions that may benefit individuals with ASD include:
It is incredibly important to work with an experienced health professional when considering any dietary restriction/regime. It is very common for these diets to result in nutrient deficiencies that could actually exacerbate certain symptoms.
Prebiotics are non-digestible fibers that fuel beneficial gut bacteria. Supplementing with prebiotics like PHGG and GOS may support microbial balance. However the research has suggested this doesn’t always lead to improvement in behaviour. (source) The evidence is mixed here, as it is in many areas. I see prebiotics being important as we know they are effective in modulating the gut microbiome which is an important consideration for those with autism.
The growing body of research highlights a strong connection between the gut microbiome and ASD. While dysbiosis, leaky gut, and SIBO may contribute to symptoms, interventions like probiotics, dietary changes, and potentially FMT offer promising avenues for support. By addressing gut health, caregivers and clinicians can improve not only gastrointestinal symptoms but also quality of life and behavioural outcomes for individuals with ASD.