We can now add autism to the many health problems associated with eating too much processed foods.

Scientists at the University of Central Florida (UCF) have discovered how high levels of propionic acid (PPA), which is used to increase the shelf life of packaged foods and inhibit mold in commercially processed cheese and bread, reduces the development of neurons in fetal brains.

The study published June 19 in Scientific Reports also found exposing neural stem cells to excessive PPA damages brain cells in several ways. It identified the molecular changes that occur when neuro stem cells are exposed to high levels of PPA.

The 18-month study was self-funded by UCF and was conducted by Dr. Saleh Naser and Dr. Latifa Abdelli and UCF undergraduate research assistant Aseela Samsam.

Autism is a developmental disorder characterized by difficulties with social interaction and communication and by restricted and repetitive behavior. There is no cure for autism, which affects about 1 in 59 children worldwide.

Common symptoms of autism can include repetitive movements, self-abusive behavior like head-banging, intense focus on one item, inability to interact with others and unresponsiveness. Along with Asperger’s syndrome, autism is classified as part of what’s called “autism spectrum disorder” (ASD). This syndrome consists of a range of mental disorders of the neurodevelopmental type.

Naser began the study after reports showed autistic children often suffer from gastric issues such as irritable bowel syndrome. He wondered about a possible link between the gut and the brain.

He then began examining how the microbiome (or gut bacteria) differed between people with autism and those without the condition.

"Studies have shown a higher level of PPA in stool samples from children with autism and the gut microbiome in autistic children is different," said Naser. "I wanted to know what the underlying cause was."

Laboratory experiments showed that exposing neural stem cells to excessive PPA damages brain cells. PPA disrupts the natural balance between brain cells by reducing the number of neurons and over-producing glial cell that help develop and protect neuron function.

Too many glial cells disturb connectivity between neurons, however. They can also cause inflammation, which has been found in the brains of autistic children.

Excessive amounts of PPA also shorten and damage pathways neurons use to communicate with the rest of the body. This combination of reduced neurons and damaged pathways impede the brain's ability to communicate. It results in behaviors often found in children with autism.

PPA occurs naturally in the gut and a mother's microbiome changes during pregnancy and can cause an increment in the acid. Naser and Abdelli said eating packaged foods containing PPA can further increase the amount of this acid already in a woman's gut, which then crosses to the fetus.

The study authors claimed theirs is the first to discover the molecular link between elevated levels of PPA, the proliferation of glial cells, disturbed neural circuitry and autism.

The research team will attempt to validate their findings in mice models by seeing if a high PPA maternal diet causes autism in mice genetically predisposed to the condition.

Autism Rising
Autism is "difficult to track," given the lack of medical tests to diagnose the disorder, according to Michael Kogan, author of the new report. Kelly Sikkema/Unsplash