Could Red Onions Be Used to Prevent Cancer?


A common ingredient found in guacamole or sitting atop your burger may help stave off cancer.

Onions — in particular, red onions — contain some mighty cancer-destroying power, according to a new study from researchers at the University of Guelph in Ontario, Canada.

While the research is preliminary and still limited to cell cultures, the study holds significant promise for cancer-prevention treatments down the line.

Credit: Sharon Mollerus/Flickr, CC BY 2.0

Previously, scientists knew that onions were packed full of antioxidant properties, which can neutralize damaging molecules known as free radicals and reduce the chances one has of developing many types of cancer.

Yet little research had been devoted exclusively to the humble root vegetable and its impact on long-term health. For the new study, Guelph researchers assessed five types of onions and how the onion extracts interacted with cancer cells.

Among the five types of onions they tested, the researchers discovered that a variety of onion known as the Ruby Ring, a type of red onion, was the most adept at destroying cancer cells in a lab culture.

The researchers believe that high levels of antioxidant molecules in the Ruby Ring onion may be the reason behind the success at hindering cancer growth. Specifically, the researchers found that red onions grown in Ontario contain “particularly high levels” of quercetin, a flavonoid that is already known for disease-fighting ability.

Also abundant in the red onions is something called anthocyanin, which boosts the “scavenging” ability of quercetin in rooting out and destroying free radicals.

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“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,” said lead author Abdulmonem Murayyan, a doctoral candidate at the University of Guelph.

To test the onion extracts, the researchers mixed quercetin from the five types of onions directly with colon cancer cells. The results, so far, were highly promising.

Credit: Damian Gadal/Flickr, CC BY 2.0

“We found onions are excellent at killing cancer cells,” said Murayyan.

The researchers say their findings shed light on the mechanism of disease prevention and that the onion extracts essentially suck the life out of cancer cells by negating growth potential.

“Onions activate pathways that encourage cancer cells to undergo cell death,” described Murayyan. “They promote an unfavorable environment for cancer cells and they disrupt communication between cancer cells, which inhibits growth.”

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Critically, the new study employed a technique that can extract quercetin without the use of harmful chemicals, which may make human consumption free of chemical traces.

“This new method that we tested to be effective only uses super-heated water in a pressurized container,” said Suresh Neethirajan, a professor of Engineering. “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.”

Looking ahead, the researchers hold out promise that the cancer-destroying quercetin translates successfully to real-life human trials. Eventually, they foresee quercetin as an additive to foods as a natural treatment method.

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