09 Jun 2017 --- In the first study to examine how effective Ontario-grown onions are at killing cancer cells, University of Guelph researchers have found that not all onions are created equal and that red onions have the strongest cancer-fighting power. Onions as a superfood are still not well known. But they contain one of the highest concentrations of quercetin, a type of flavonoid, and Ontario onions boast particularly high levels of the compound compared to some parts of the world.

Engineering professor Suresh Neethirajan and Ph.D. student Abdulmonem Murayyan tested five onion types grown in Ontario and discovered the Ruby Ring onion variety came out on top.

The Guelph study revealed that the red onion not only has high levels of quercetin, but also high amounts of anthocyanin, which enriches the scavenging properties of quercetin molecules, says Murayyan, study's lead author.

“Anthocyanin is instrumental in providing color to fruits and vegetables so it makes sense that the red onions, which are darkest in color, would have the most cancer-fighting power.”

Published recently in Food Research International, the study involved placing colon cancer cells in direct contact with quercetin extracted from the five different onion varieties.

“We found onions are excellent at killing cancer cells," says Murayyan. "Onions activate pathways that encourage cancer cells to undergo cell death. They promote an unfavorable environment for cancer cells, and they disrupt communication between cancer cells, which inhibits growth.”

The researchers have also recently determined onions are effective at killing breast cancer cells.

“The next step will be to test the vegetable's cancer-fighting powers in human trials,” says Murayyan.

These findings follow a recent study by the researchers on new extraction technique that eliminates the use of chemicals, making the quercetin found in onions more suitable for consumption.

Other extraction methods use solvents that can leave a toxic residue which is then ingested in food, says Neethirajan.
“This new method that we tested to be effective only uses super-heated water in a pressurized container,” he says. “Developing a chemical-free extraction method is important because it means we can use onion's cancer-fighting properties in nutraceuticals and in pill form.”

While we can currently include this superfood in salads and on burgers as a preventative measure, the researchers expect onion extract will eventually be added to food products such as juice or baked goods and be sold in pill form as a type of natural cancer treatment.