Flour may hold clue to ALS rise, says researcher

by Hilary Thomson
Staff writer

A chemical once produced in the manufacture of white bread may play a role in the increased incidence of some neurological diseases, according to the preliminary findings of a team of UBC researchers.

"We think we've found a smoking gun," says Christopher Shaw, an associate professor of Ophthalmology. "There is a very suspicious correlation between the characteristics of this substance and those known to be toxic to the nervous system."

The incidence of neurological diseases, notably amyotrophic lateral sclerosis (ALS), has been on the upswing during the last 50 years.

Shaw and fellow researchers think the culprit may be methionine sulfoximine (MSO), a toxic byproduct of nitrogen trichloride, which was used to bleach unprocessed wheat flour. By 1950 the process was banned in the United Kingdom and the United States. Canada stopped using it in 1968.

In the late 1940s, scientists discovered that dog biscuits made from bleached flour produced canine epilepsy. A risk for humans via white bread was suspected, but the exact toxic effects of MSO had not been investigated until neuroscientist Shaw and colleagues from the University of Tampere in Finland and Dalhousie University began their investigation last month.

Scientists have known since 1976 that MSO acts to inhibit the production of two molecules critical to the healthy functioning of the nervous system, glutathione and glutamine. Cells in the nervous system are particularly sensitive to a decline in either of these two molecules.

It was not known, however, if the compound had a direct effect on neurons. Shaw, research associate Jaswinder Bains and Physiology PhD candidate Bryce Pasqualotto have found that MSO over-stimulates neurons. In a phenomenon known as excitotoxicity, MSO directly turns on a toxic cascade of events which can lead to neuron death, says Shaw.

"This appears to be the worst possible toxin you can imagine for the nervous system because it strikes in so many different ways at the same time," he says.

Because it is eliminated from the body over time, MSO cannot be detected in patients now suffering from neurological disease.

"We know people have been exposed to a toxin but we're still uncertain of the impact," says Shaw. "My main concern is what the MSO story tells us about the presence of other toxins in processed foods. It's probably not the only thing out there."

Shaw became interested in MSO while researching the effect on neurons of other chemical compounds which can be excitotoxic. Similarities between them and MSO sparked his curiosity in the decades-old story.

"I think this is the tip of an iceberg," says Shaw. "Many products in the supermarket have been processed with chemicals that are not listed on the package."

The team's preliminary findings have been accepted for publication in the journal Medical Hypotheses.

Their work is funded by the Amyotrophic Lateral Sclerosis Association. UBC spin-off Precision Biochemicals Inc. provided chemicals used in the research.