A collaborative Australian study has challenged the increasingly popular theory that gut health drives autism and rejected the use of fad diets and so-called therapies such as faecal transplants.
The research, published in the scientific journal Cell, was conducted by Autism CRC, Mater Research and the University of Queensland.
Lead author Chloe Yap – who is completing her medical degree and PhD – said children on the autism spectrum are more likely to have gut complaints including constipation, diarrhoea and abdominal pain.
But she said the study "didn't find that the microbiome causes autism".
"In fact, it looked almost the other way around, that the characteristics of autism contribute to microbiome differences.
"Specifically, it looks like autistic children often prefer to eat a narrow selection of foods, a less diverse diet — and that in turn affects the microbiome," Ms Yap said.
She said the microbiome is made up of "trillions" of microbes that live on skin and in the digestive tract.
"It is important for aspects of our metabolism, setting up our immune system and continuing development of our immune system," Ms Yap said.
"There are also some instances where disruption has been well documented to cause poor human health.
Ms Yap said in recent years "so-called therapies" have popped up that claimed to help children on the autism spectrum, including fad diets and faecal microbiota transfers, sometimes called "transpoosions."
Faecal transplants involve the transfer of stool from a healthy donor into the gastrointestinal tract of a recipient.
"With so many unknowns about autism and this generalised hype about the microbiome, parents really need clarity on what works and what doesn't to best help their child to thrive," Ms Yap said.
Research could help guide parents
Andrew Whitehouse — the professor of autism research at the Telethon Kids Institute and the research strategy director at Autism CRC (Cooperative Research Centre) — said about 2 per cent of Australians are on the autism spectrum.
"What this study shows is that the microbiome in and of itself is in no way a cause of why the brain develops differently and why children develop autism," Professor Whitehouse said.
"But what it also does urge us to do is to help promote healthy balanced diets in kids so they get all the nutritional intake they can get that can help promote their development."
He said when a child is diagnosed as being on the autism spectrum, families are often "inundated" with information about different therapies and potential treatments.
Professor Whitehouse said he had met families who had tried a variety of diets, including gluten and casein-free regimes and diets for different blood types.
"All of these have no evidence to support their use with children on the autism spectrum, but people try them because they are desperate to help support their child," he said.
He suggested families having trouble at mealtimes seek help from a speech pathologist or dietitian.
"[They] can certainly provide some tips, some therapies that can really help get the nutritional balanced diet that their children need."
The study involved 247 children, including 99 diagnosed with autism.
Ms Yap said researchers collected stool samples and profiled the bacteria contained in the samples.
She said they also collected clinical, psychometric, lifestyle, dietary and genetic data from participants "for a wholistic view of what's going on between autism and the microbiome".
Probiotics help with gut health, but 'not doing anything for the autism'
Brisbane mother Natalie Pollard, whose eldest son Ethan has severe autism, said she had given him daily probiotics for almost 10 years to improve his gut health.
While she said the probiotics improved his behaviour, she believed it was because it was making him feel better rather than treating his autism.
"The probiotics for him, from a physical point of view, are helping his gut, it's not doing anything for the autism," Ms Pollard said.
"He's always had a problem with his gut health. I was willing to try anything. It was like we had flicked a switch — he was so much calmer, so much less aggressive."
The mother of three boys welcomed the study, saying the results resonated with her, knowing Ethan's eating habits.
"He's got that autism thing going on where they need order and they need repetitiveness. He'll be like: 'I won't eat if different foods on the plate touch each other'," she said.
"It doesn't matter if I then try and fix it. He still won't go there."
At other times, Ethan, who turns 12 this Saturday, will only eat food in a particular order.
"That picky eating that they're talking about in the study, for us it's not that he doesn't like the food, or won't try it, it's because of this need for order, an obsessiveness and repetitiveness, that's where we have the problem," Ms Pollard said.
"If he's not getting the nutrients that he needs, then of course there's going to be problems."
