The researchers found changes in the gut microbiome of people on the autism spectrum appear to be due to “fussy eating”, which is more common among autistic children due to sensory sensitivities or restricted and repetitive interests.
The collaborative study was funded by the Autism CRC and involved more than 40 researchers from Mater Research, The University of Queensland, Telethon Kids Institute, University of New South Wales, Children’s Health Queensland, La Trobe University, Queensland University of Technology and Microba Life Sciences. The findings are being published in the scientific journal Cell.
First-author, Chloe Yap from Mater Research and The University of Queensland said the team examined genetic material from stool samples of 247 children, including 99 children diagnosed with autism.
“While it’s a popular idea that the microbiome affects behaviour, our findings flip that causality on its head,” said Ms Yap who is completing her medical degree and PhD at The University of Queensland.
“We found that children with an autism diagnosis tended to be pickier eaters, which led them to have a less-diverse microbiome. This in turn was linked to more-watery stools. So, our data suggests that behaviour and dietary preferences affect the microbiome, rather than the other way around.”
Senior study investigator and the head of Mater Research’s Cognitive Health Genomics Group, Dr Jake Gratten said that out of more than 600 bacterial species identified in the gut-microbiomes of study participants, only one was associated with a diagnosis of ASD.
“There’s been a lot of hype around the gut microbiome in autism in recent years, driven by reports that autistic children have high rates of gut problems. But that hype has outstripped the evidence,” Dr Gratten said.
“We are already seeing early clinical trials involving faecal microbiota transplants from non-autistic donors to autistic people, despite not actually having evidence that the microbiome drives autism. Our results suggest that these studies are premature.”
The researchers performed a large autism stool metagenomics study (n=247) based on participants from the Australian Autism Biobank and the Queensland Twin Adolescent Brain project.
The wrote that they found negligible direct associations between ASD diagnosis and the gut microbiome.
“Instead, our data support a model whereby ASD-related restricted interests are associated with less-diverse diet, less-diverse microbial taxonomic diversity, and looser stool consistency. In contrast to ASD diagnosis, our dataset was well powered to detect microbiome associations with traits such as age, dietary intake, and stool consistency.
“Overall, microbiome differences in ASD may reflect dietary preferences that relate to diagnostic Q2 features, and we caution against claims that the microbiome has a driving role in ASD.”
Autism CRC Research Strategy Director, Professor Andrew Whitehouse, from the Telethon Kids Institute and University of Western Australia, said the findings provide clarity to an area that has been shrouded in mystery and controversy.
“Families are desperately seeking new ways to support their child’s development and wellbeing. Sometimes that strong desire can lead them to diet or biological therapies that have no basis in scientific evidence,” Professor Whitehouse said.
“The findings of this study provide clear evidence that we need to help support families at mealtimes, rather than trying fad diets. This is a hugely important finding.”
The study is one of the largest to date to examine what organisms are in the stool microbiome and what those organisms have the potential to do.
Autism spectrum disorder (ASD) is a neurodevelopmental condition characterised by social and communication difficulties, restricted and repetitive behaviours, and unusual sensory responsiveness.
The researchers concluded: “Our results are consistent with an upstream role for autism-related behaviours and dietary preferences on the gut microbiome and are contrary to claims of the microbiome having a major (or causal) role in ASD.”
“Autism-related dietary preferences mediate autismgut microbiome associations”
Authors: Jacob Gratten, et al.