Compounds produced in the digestive system have been linked to autistic-type behaviour in laboratory settings, potentially demonstrating that what autistic children eat can alter their brain function, say scientists from the University of Western Ontario.

They announced their findings Thursday in Ottawa.

UWO researchers investigated the "gut-brain" connection after many parents of autistic children reported significant improvements in the behaviour of their autistic children when they modified their diet, eliminating dairy and wheat products, Dr. Derrick MacFabe, the director of a research group at UWO in London, Ont., told CBC News Thursday.

Researchers were particularly interested in one dietary characteristic the autistic children seemed to exhibit, he said.

"Certainly, a lot of these children had peculiar cravings for high-carbohydrate foods that caused their behaviours," he said.

"We were interested in finding a link between certain compounds that are produced by bacteria in the digestive system — particularly those occurring with early childhood infections."

The bacteria produce propionic acid, a short chain fatty acid, which in addition to existing in the gut, is commonly found in bread and dairy products, MacFabe said.

To test their hypothesis thatdiet plays a part in generating autistic behaviour, UWO scientistsadministered the compound to rats' brains.

"They immediately engaged in bouts of repetitive behaviour, hyperactivity and impaired social behaviours which had close similarity to what parents are seeing with autism," MacFabe said.

When the rats' brains were examined later, they were found to have inflammatory processes similar to those in the brains of autistic children, he said.

"We found, looking at the rats' brains under the microscope, changes that looked a lot like what's occurred from autopsy cases of patients who had autism."

It's remarkable that a simple compound like propionic acid would have such a dramatic effect on "normal" animals, he said.

MacFabe said his research team, and scientists at Queen's University in Kingston, Ont., and Harvard University, are now conducting screening studies looking at effects of dietary changes in the general population.

New way of approaching autism

Dr. Martha Herbert, assistant professor in neurology atHarvard Medical School, told CBC News that the study opens up a new way of thinking about the disorder.

"Now we're learning that the brain and body can influence each other," she said.

Autistic children are increasingly being seen as "oversensitized," meaning "things may bother them that don't bother other people," she said. "We need to pay attention to this."

Treating a child's health should be the first step in addressing autism, Herbert said, rather than solely focusing on behavioural therapy, currently a mainline approach.

"Behaviour therapy is certainly important. But the child's health controls the bandwidth that the child has for being able to benefit from behavioural therapy. If a child is sick, they won't be able to focus."

Parents should watch their children closely to determine what foods trigger reactions and to consider removing those triggers, she said.

Herbert strongly advocatesa balanced diet, consisting of all food groups, not just "bread and cheese."

"If you have foods that child is sensitive to in their immune system, that can set up processes that can impact brain function, and it can do so in a negative way. And if you remove those foods, that negative impact can stop."