May 28, 2026, 4:11 pm | Read time: 6 minutes
Autism spectrum disorders have been increasing significantly for years, while researchers worldwide are searching for ways to identify affected children earlier. A new study from the U.S. now focuses on an organ that many have barely considered: the gut. Scientists found unusual chemical traces in the urine of many children with autism. The findings could provide clues as to why some children are affected—and how risks might be identified earlier.
Unusual Gut Substances Much More Common in Children With Autism
A new study is shaking up research on autism and gut health. The central finding: Children with autism had significantly higher levels of certain metabolic products in their urine than children without autism. On average, children with autism had more than three unusual metabolic products in their urine, which were not found at these levels in any of the children without autism.
Why Researchers Are Suddenly Focusing on the Gut
Autism spectrum disorders (ASD) usually begin in early childhood. Affected children often have difficulties with social communication and exhibit repetitive behaviors or very rigid routines. Many also suffer from digestive issues such as constipation, diarrhea, stomach pain, or bloating.
For this reason, research has increasingly focused on the gut microbiome—the billions of bacteria, fungi, and other microorganisms in the gut. The hypothesis is that changes in this gut flora could play a role in some children with autism.
Previous Studies Already Provided Initial Clues to a Gut Connection
Several previous studies had already provided evidence that certain bacterial byproducts are more common in people with autism.1,2, 3
Digestive problems also occur much more frequently in affected individuals than in other children. The new study builds directly on these observations. The researchers therefore examined certain chemical substances in the urine. These are produced when gut bacteria or yeast break down food. Some of these substances had already been noted in previous studies of children with autism.4
The researchers were particularly interested in whether a simple screening test could be developed from this. Autism is often diagnosed relatively late, even though early intervention is considered particularly important.
What Exactly the Researchers Studied
The study involved 52 children diagnosed with autism spectrum disorder and 47 children without autism. All were between two and eleven years old. The study was conducted at four locations in the U.S. Researchers analyzed urine samples from the children using a highly sensitive laboratory method, specifically looking for metabolic products from gut bacteria and yeasts.
One substance that stood out was p-cresol sulfate. It is produced when certain gut bacteria break down protein components from food. Previous studies had repeatedly linked this substance to autism.5,6
Additionally, the researchers examined other bacterial byproducts and substances that could indicate a higher presence of yeast in the gut. They then developed their own evaluation system, counting how many of these unusual substances were elevated in a child.
One Substance Particularly Stood Out to the Researchers
Children with autism had significantly higher levels of certain bacterial metabolic products in their urine than the comparison group. Some of these substances were 100 to 1,000 times higher than in children without autism. Particularly affected were byproducts of the protein building blocks phenylalanine and tryptophan, which are normally needed for important neurotransmitters in the brain like dopamine, serotonin, or melatonin.
One Specific Byproduct Stood Out
One substance that repeatedly stood out was p-cresol sulfate. This byproduct of certain gut bacteria was significantly elevated in many children with autism. On average, researchers found more than three different unusual substances in the urine of children with autism, which were not present at these levels in any of the children without autism. The children without autism were within the normal range.
In the first analysis, the researchers’ test system correctly identified about 90 percent of the affected children. No child from the control group was incorrectly classified as affected. However, in a second, stricter analysis, the detection rate dropped to 78 percent. Even among the few children with autism whose tests were inconspicuous, researchers often found other rare metabolic peculiarities unrelated to the gut.
Is Autism Not Just a “Brain Issue”?
The study challenges the widespread notion that autism originates solely in the brain. Instead, it highlights the so-called gut-brain axis, referring to the close connection between the gut, metabolism, immune system, and brain.
Researchers suspect that certain metabolic products from gut bacteria could reach the brain via the bloodstream, potentially influencing the development of nerve cells or important neurotransmitters.
To make this more understandable, the researchers themselves draw an unusual comparison: alcohol. Ethanol is also produced by microorganisms—specifically by yeasts. Alcohol can significantly alter speech, thinking, mood, and movements. Similarly, the researchers believe some of the discovered bacterial substances could affect the brain.
However, a direct proof of this is still lacking. The study only shows that these substances were unusually elevated in many children with autism.
Researchers Even Propose a New Form of Autism
The study provides further evidence that gut flora and brain development may be more closely linked than long assumed. At the same time, researchers hope that a simple early test could be developed from this, perhaps through a urine sample. This could allow children at higher risk to be identified earlier and receive quicker support.
Additionally, researchers suspect that there could be different biological subgroups within the autism spectrum. For this specific group, they even propose a new name: “ASD-MDM”—autism closely associated with unusual metabolic products from gut bacteria.
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Why Experts Remain Cautious
The study provides intriguing insights but also has clear limitations. Only 99 children were studied in total. Much larger studies would be needed for a reliable diagnostic test.
Moreover, the researchers did not account for the children’s diet, medication intake, or body weight. All these factors can influence the gut flora.
However, it is important to note: The study does not prove that gut bacteria cause autism. While researchers found unusual metabolic products in many affected children, whether these changes actually contribute to the development of autism or are merely side effects remains open.
It should also be noted that several authors are involved with companies or hold patents related to the developed test. Such conflicts of interest do not automatically mean the results are incorrect, but they play an important role in the scientific evaluation.
The researchers themselves explicitly describe their work as a pilot study. Larger investigations are already underway.
Conclusion: The Gut Is Increasingly in Focus for Autism
Many children with autism had unusual metabolic products from gut bacteria or yeasts in their urine—particularly elevated levels of the bacterial byproduct p-cresol sulfate. Researchers, therefore, suspect that there could be a specific form of autism closely linked to changes in the gut. Whether this will eventually lead to a reliable early test will now need to be shown by larger studies.