A new study may shed new insights into links between the gut microbiome and autism spectrum disorder (ASD).
Content Outline
- Results at a glance
-
Autistic children showed a stronger diet–microbiome “network”
-
Emulsifiers drive the destruction of microbial ecological networks in ASD
Introduction
It’s estimated that around 1 in 100 children across the world are diagnosed with autism spectrum disorder (ASD) [1]. ASD describes a diverse group of lifelong conditions that can influence a person’s social interaction, behavior, and language development [2]. The needs of individuals can vary and change over time – no two people with ASD are the same.
A complex interplay between environmental and genetic factors is thought to be involved in the cause of ASD. Because it is not a disease, ASD cannot be cured, but there are certain interventions that can help individuals manage challenges, develop skills, and thrive. New research is finding that certain lifestyle factors, like diet, could have a big influence on some of the ASD symptoms, such as emotions and behaviours.
Here, we explore recent research that could help link diet, the gut microbiome, and autism spectrum disorder outcomes.
Investigating the gut and brain in ASD
In recent decades, scientists have focused their attention on the bidirectional communication pathway between the gut and the brain, known as the gut-brain axis. In ASD, disruptions in the gut-brain axis have been found [3], while dysbiosis, an imbalance of gut microbiota, has also been associated with behavioral and gastrointestinal symptoms in ASD individuals [4]. This has led researchers to investigate the gut microbiota in people with ASD more closely to understand how it may be influencing the condition and whether it could be targeted for better outcomes.
In a study by Wu and Colleagues, 818 children (462 with ASD and 356 without), with a mean age of 8.4 years and 27.3% female. The overall food choices and quality, as well as nutrient intake and exposure to food additives, were assessed.
The size of this study is important because earlier research investigating the link between ASD and the gut microbiome has been limited by smaller cohorts or less detailed dietary data. Here, the researchers aimed to map how dietary indices (overall diet quality), nutrient intake, and exposure to food additives relate to microbiome patterns—and whether those relationships differ in autism.
Results at a glance
|
Children with ASD |
Non-ASD children |
|
|
Overall diet quality |
More likely to have lower diet quality scores |
Generally higher or more balanced diet quality |
|
Diet quality and symptoms |
More severe core symptoms, GI issues, and atypical eating behaviors |
Weaker or no strong correlation observed |
|
Diet-microbiome interaction strength |
Strong, highly interconnected diet–microbiome network |
The microbiome appeared more stable in response to diet |
|
High starch intake |
Linked to reduced microbial vitamin K2 synthesis pathways |
Less clear or attenuated association |
|
Dietary emulsifier effects |
Associated with disrupted microbial connectivity |
Weaker effects |
|
Key mediating microbes |
Faecalibacterium prausnitzii and Coprococcus eutactus showed strong mediation effects |
Mediation effects less pronounced |
Diet quality tracked with autism-related challenges
One of the clear results of the study was that poorer diet quality was linked to greater challenges in children with ASD. For example, those with poorer dietary patterns had more severe ASD symptoms, higher medication use, gastrointestinal complications, and challenges across many eating behaviours, including fussy eating, desire to drink, appetite regulation, and food enjoyment.
This does not mean the parents were doing anything wrong or that diet causes autism. Eating differences in ASD are often deeply rooted in sensory processing [5], preference for sameness, anxiety, and communication needs. For some children, foods with mixed textures, strong smells, or unpredictable flavors can feel genuinely aversive. For others, mealtime routines help create a sense of control and safety.
Alongside previous research, this study demonstrated significant differences in gut microbiome alpha diversity and dysbiosis scores between ASD and non-ASD individuals (Fig 1). Using the Chinese Children Healthy Dietary Index (CCDI) to characterise diet quality, the CCDI was found to be associated with microbial dysbiosis in the ASD group.
Figure 1. The gut dysbiosis score is markedly different between non-ASD and ASD individuals.
What these findings suggest is something more nuanced: when diet quality is low—regardless of why—there may be downstream effects on the gut ecosystem, and those effects could relate to GI symptoms and other difficulties that often co-occur with autism.
Autistic children showed a stronger diet–microbiome “network”
The study showed that there was stronger diet-microbe association in children with ASD compared to their non-ASD peers. The gut microbiota in ASD individuals were more responsive to dietary variables, especially:
-
protein intake
-
CCDI scores
-
bean consumption
Children with higher-quality diets, as reflected in stronger CCDI scores, were more likely to have higher Firmicutes abundance, a group of bacteria commonly linked to healthier eating patterns. Many of these microbes ferment dietary fiber and produce short-chain fatty acids (SCFAs), like butyrate. SCFAs are critical for a strong gut barrier, regulating immunity, and influencing the gut-brain axis. This could mean that a better quality diet could lead to improved gastrointestinal and even behavioural outcomes in ASD children.
Thiamine metabolism
Further analysis using the KEGG pathway, a series of maps or networks of gene products, suggested that dietary microbial changes were functional as well as compositional. Microbial genes associated with higher CCDI scores were enriched in pathways related to cofactor biosynthesis, including vitamin B1 (thiamine) metabolism.
Thiamine supplementation is commonly used in ASD. Studies have found that 11% of ASD patients have thiamine levels below a healthy range, and thiamine deficiency is also associated with obesity. It has been proposed that self-imposed dietary restrictions could lead to an inadequate thiamine intake in ASD individuals [6]. Thiamine is essential for energy production and neurological function, suggesting that diet-driven microbial shifts could influence metabolic processes relevant to ASD.
▶ Try our Brain Performance capsules to support your cognition and brain health, packed with HMOs and a B vitamin complex.
Higher starch intakes and the effects in ASD
A higher starch intake, commonly observed in children with restrictive or highly repetitive eating patterns, was associated with reduced activity in microbial pathways involved in vitamin K2 production.
Vitamin K2 is important for mitochondrial function and the regulation of inflammation, and deficiency is associated with neuroinflammatory and metabolic disturbances [7], both of which are classic hallmarks of ASD. This finding suggests one potential mechanism by which heavily starch-based dietary patterns could influence microbial metabolism in ways that may be less supportive of neurological health.
▶ Did you know? Not all starch is created equal. Resistant starch can have major benefits for your gut microbiota and metabolism.
Specific microbes, diet, and ASD outcomes
Wu et al also identified specific microbes that could shed some light on how diet influences ASD-related outcomes. They were:
-
Faecalibacterium prausnitzii – A next-generation probiotic [8] that is known for its anti-inflammatory benefits and butyrate-producing qualities. In this study, it was found to mediate some of the beneficial effects of higher protein and zinc intakes on ASD symptoms.
-
Coprococcus eutactus – In this study, this bacterium had the strongest mediation effect and was identified as having a key role in gut-brain communication. This means it could be a potential probiotic target for future dietary interventions in ASD.
Emulsifiers drive the destruction of microbial ecological networks in ASD
One finding from the study that was particularly important was the discovery that dietary emulsifiers could disrupt microbial networks and facilitate the loss of keystone taxa. Two main synthetic emulsifiers were identified: polysorbate-80 and carrageenan.
Emulsifiers are additives that help foods maintain their texture and consistency, keep ingredients combined, improve how they feel in your mouth, and prolong their shelf life. They are commonly found in many ultra-processed foods and are found in foods, such as:
-
ice creams and frozen desserts
-
sauces, dressings, and spreads
-
flavored dairy products and dairy alternatives
-
packaged baked goods
-
some convenience foods and ready meals
Recent research has shown that emulsifiers can change the diversity of the gut microbiome, induce dysbiosis, and could even lead to metabolic disorders [9]. In the study by Wu and Co, exposure to polysorbate-80 and carrageenan was linked to disrupted microbial connectivity in autistic children. That is how microbes relate to each other, including how they interact, co-exist, and work together to form a stable and resilient gut environment.
These disruptions are also commonly found in inflammatory bowel disease (IBD), where emulsifiers can reduce the integrity of the gut barrier and promote dysbiosis [10]. When microbial connectivity pathways are disrupted, the gut microbiota may become less stable and less able to withstand stressors, which in ASD could manifest into amplification of gastrointestinal and neuroimmune dysfunction. Interestingly, these changes were not seen or were not seen as strongly in the children without ASD (Fig 2). This means that children with ASD may have distinct microbiomes and different microbiome-mediated responses to certain dietary components.
Figure 2. Microbial network connections are disrupted in ASD (right) compared to non-ASD individuals (left), with polysorbate-80 and carrageenan.
Summary: What does this mean?
Overall, this study suggests that the gut microbiome in ASD is associated with diet and associated diet responses. Diet quality and specific ingredients can directly influence the colonic ecosystem, potentially affecting behaviour, gastrointestinal symptoms, and atypical eating behaviours. Ultimately, ASD-specific microbial biomarkers could be useful for diagnostic purposes in the future, while an overhaul of dietary guidelines could help mitigate some digestive symptoms in individuals with ASD and improve their quality of life.
Nourishing your gut with prebiotics, like fiber and human milk oligosaccharides (HMOs), is the perfect way to keep your colonic ecosystem happy and thriving. Check out our range of scientifically backed PureHMO® products, including our SuperHMO for kids powder.
Written by: Leanne Edermaniger, M.Sc. Leanne is a professional science writer who specializes in human health and enjoys writing about all things related to the gut microbiome.
