In the first study to examine how effective Ontario-grown onions are at killing cancer cells, U of G researchers have found that not all onions are created equal.

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

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 boasts particularly high levels of the compound compared to some parts of the world.

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, said Murayyan, study’s lead author.

“Anthocyanin is instrumental in providing colour to fruits and vegetables so it makes sense that the red onions, which are darkest in colour, 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.

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Dr. Stegall’s Comments: As an onion lover, this study is great news! We know that quercetin has anti-cancer properties, based on lab studies showing that it kills cancer. We are less certain about the extent of this effect in the body, but because quercetin seems to have a positive benefit without any significant side effects, I frequently use it in my protocols. Capsules remain the best way to get enough of it, as it is impossible to eat enough onions to get a therapeutic amount of quercetin. But I still believe that we get medicinal benefits from the foods we eat, and there is probably some value in getting cancer fighters like quercetin in their native state in addition to obtaining through supplements.