Study: Kids with Autism Have Fewer Kinds of Gut Bacteria

Researchers using high-tech DNA analysis found that children with autism have fewer kinds of intestinal bacteria than do children without autism. However, this reduced “biodiversity” did not relate to the severity of gastrointestinal problems.

The study appears today in the journal PLOS ONE. Rosa Krajmalnik-Brown and Jin Gyoon Park, of Arizona State University’s Biodesign Institute, led the investigation.

Among children with autism, GI problems such as constipation and gut pain are common. Some have suspected that imbalances in intestinal bacterial are to blame. Other research has suggested that problematic gut bacteria might contribute to autism symptoms by triggering inflammation that reaches the brain. Considerable research has shown that intestinal bacteria play important roles in both digestion and regulation of the immune system in all persons.

“While the precise links between the gut microbiome, the brain and autism are not yet clear, we’re certain there’s a strong relationship that affects outcomes and quality of life for people living with autism,” says Autism Speaks Senior Director of Discovery Neuroscience Daniel Smith, PhD. “This study brings us one step closer to understanding this relationship. It also highlights the need to take a ‘whole body view’ to develop autism treatments.”

Autism Speaks is actively funding research aimed at understanding how the gut “talks” to the brain, Dr. Smith adds. “We're trying to reveal how the gut-to-brain conversation might cause autism symptoms and related health issues.”

Analyzing the ‘microbiome’ in children with or without autism
In this study, researchers used high-throughput DNA analysis to take a complete census of the bacteria in fecal samples from 20 children with autism. For comparison, they did the same with 20 children without autism. A typical person has up to a quadrillion (1014) intestinal bacteria, they note. These bacteria aid in digestion, produce vitamins and generally promote GI health. All the children in the study had some gastrointestinal symptoms.

The researchers found significantly decreased microbial diversity (fewer types of bacteria) in the children with autism. However, they were  surprised to find no link between this lowered diversity and the severity of GI symptoms. Nor did they find links to differences in the children’s diets.

Among the types of bacteria reduced in those with autism, Prevotella was the most conspicuous. It occurred only in very low levels in the children with autism. By contrast, it was common in those not affected by autism – who altogether had more diverse and robust communities of intestinal bacteria.

“Recent research has reinforced the need to study GI bacteria not just as individual organisms, but as communities in the GI system,” comments Alycia Halladay, PhD, Autism Speaks senior director of environmental and clinical sciences. “This is such an important topic that the NIH is supporting a human microbiome mapping project similar to the human genome project.” Environmental influences on GI bacteria remain an important target of study for Autism Speaks and others.

“With the study just published in PLOS-ONE, autism spectrum disorders join the list of complex disorders linked to changes in microbiota,” adds gastroenterologist Alessio Fasano, M.D. The number of subjects was limited, and the findings did not prove that changes in microbiota were involved in the onset of autism, he notes. “Still, this study suggests that a more in-depth analysis may lead to breakthrough findings. Ongoing studies, including those sponsored by Autism Speaks, are likely to open a new paradigm of autism diagnosis and management.”