New research suggests children with autism tend to have a less diverse population of gut microbes than other children. Scientists suspect modern practices, including eating processed foods and overuse of antibiotics, are feeding the problem.
Autism is a developmental disability that affects a person’s behavior as well as social and communication skills.
People with autism are also more prone to digestive upsets. Parker, a 14-year-old student at the Temple Grandin School in Boulder, Colorado, says his digestive problems improved when he gave up milk and wheat. Then his mood improved, too.
"I think I definitely got a little less grumpy all the time, and like less rigid and argumentative," he said. "Yeah. I think it definitely, definitely changed how I am like mood wise and neurologically, how I functioned in life.”
His classmate, Russell, who also has autism, suspects Parker's food choices affected the bacteria and microbes that live inside the human digestive tract.
“Per cell count you have got more bacteria in you and on you than you do cells," Russell said. "You want diversity in your gut. A lot of different things digesting your food for you.”
The human digestive tract is home to trillions of microbes and a growing number of studies indicate that promoting friendly gut microbes, like bacteroides fragilis, might be good.
“Bacteroides fragilis improves anxiety-like behavior, it improves repetitive behavior. It improves communication in the mouse models,” said Sarkis Mazmanian.
The UCLA scientist says feeding the microbe to mice specially-bred to exhibit autistic disorders improved their digestive health, and virtually eliminated their anxiety, a finding that has far-reaching implications for humans.
“It is very speculative, probably very controversial, that at least in a subset of autistic subjects, autism is not solely a disease of the brain, but perhaps the issues in the gut are contributing to autistic behavior, and if you can address the gastrointestinal symptoms, that you could have improvements in behavior,” Mazmanian said.
Autism rates in the United States have nearly tripled since 2000, according to the Centers for Disease Control, with severe forms leading to complete withdrawal from social contact, profound mental retardation, and overwhelming anxiety.
Scientists at Arizona State University hold another piece of the puzzle when it comes to bridging the gap between research in animals and results in humans. .
“Most of the people looking for microbes in the intestines in the kids with autism were looking for pathogens," said researcher Rosa Krajmalnik-Brown. "We are looking for if they are missing good microbes, and that is what we found.”
Krajmalnik-Brown's lab has documented that children with autism tend to have a less diverse population of gut microbes than a typical child. One of the many missing microbes is Prevotella, which may keep “bad bugs” from becoming bullies.
James Adams directs the school's Autism Asbergers Research Program.
"Our hypothesis is that it’s a lack of beneficial bacteria that make you more vulnerable to pathogenic bacteria, and kids with autism may have different pathogens," he said.
He says the autism epidemic may have roots in the many ways modern life harms a healthy gut community: too many processed foods, pesticides, plus a high use of antibiotics in livestock, and in kids.
"One of the major differences in medical histories of children with autism is that they have received two to three times as many oral antibiotics as typical children," Adams said.
All these researchers agree there is much more to solving the puzzle linking digestion, microbes and autism. But they believe they are on a promising path, and their discoveries might also help with other mood disorders, including depression and schizophrenia.