Food News

Do Red Onions Really Have Super Powers?

June 14, 2017

Red onions are capable of fighting off cancer more effectively than their lighter counterparts, according to a study from the University of Guelph in Ontario, Canada.

In particular, red onions contain high levels of quercetin—a flavonoid with strong clinical evidence as an anticancer compound—along with anthocyanin, the pigment that gives red onions, as well as berries, grapes, eggplant, and purple corn, their dark color. Working together, anthocyanin increases the ability of quercetin to destroy cancer cells.

In the study, researchers placed colorectal adenocarcinoma (colon cancer) cells in direct contact with quercetin from five different types of onions.

Shop the Story

"We found onions are excellent at killing cancer cells," said Abdulmonem Murayyan, a PhD student involved in the study. "Onions activate pathways that encourage cancer cells to undergo cell death. They promote an unfavourable environment for cancer cells and they disrupt communication between cancer cells, which inhibits growth."Follow-up trials also indicated that onions can activate the same response in breast cancer cells.

We love all onions equally, but researchers found that Ontario-grown red onions killed off more breast and colon cancer cells than four other varieties of onion, which is maybe something to keep that in mind this summer as you’re building burgers, mixing salads, and grilling vegetables.

And if you're among the red onion-avoidant (like Chopped's Scott Conant, whose fierce hatred of red onions has spawned its own Tumblr universe), it's possible you're just eating them wrong. Even raw onions become less intense after soaking them in cold water, and every stir-fry gets infinitely better when you start by tossing onions over high heat. Eventually, you'll become one of those impressive kitchen pros who can flip food in the pan like it's nothing. Do it for your health, of course.

See what other Food52 readers are saying.

  • Mary Frances
    Mary Frances
  • AntoniaJames
  • Dona
  • emcsull
Karen Lo

Written by: Karen Lo

lunch lady


Mary F. June 19, 2017
Being from Ontario (Toronto, about an hour away from the University of Guelph) and a red onion lover, I am very pleased to hear about the health benefits of red onions. But I'm sure that these benefits are found in red onions grown in other places too - I really hope this doesn't cause a vastly increased demand for "Ontario-grown red onions"! I want to still be able to eat our local produce affordably! :)
And I'm definitely going to follow AntoniaJames' recommendation for keeping quick pickled red onions in the fridge!
AntoniaJames June 19, 2017
Mary Frances, those quick pickled onions give you a great ROI of time, rewarding you with a versatile, cost-effective, super-tasty ingredient - especially during the summer. I've been making them every week, re-using the brine once -- adding an extra pinch of salt and sugar, because the brine is diluted with the juice of the onions sitting in it. Hope you try them. ;o)
P.S. I also use the leftover brine to pickle chard stems that I've blanched for about a minute, before blanching the leaves for other uses. They add a nice bit of crunch and great flavor to salads of all kinds and grain bowls.
AntoniaJames June 14, 2017
I was a raw-onion-of-any-kind avoider until I tried the quick pickled red onions in this recipe: Now I have at least a pint, and usually more, in my fridge at all times. Great for quesadillas, sandwiches of any kind (especially panini), on any kind of tacos, on tartines, or chopped and added to Gjelina style roast vegetables (tossed with garlic confit, red wine vinegar and chopped parsley), or chopped and added to quick corn and bean salad with cilantro citrus dressing (using charred corn, including Trader Joe's frozen when corn is not in season), etc. See my comment in the link above for ways to make those pickled onions even better. Everyone loves them! ;o)
Dona June 15, 2017
A-J, you've sold me on pickled onions. I read your comments on the link, are you saying you don't microwave the onions as directed in the recipe? You Heat the liquid and pour over the onions? Thanks
AntoniaJames June 19, 2017
Dona, I always heat the vinegar + herbs / spices for a few minutes first, to infuse the vinegar with the flavor as much as possible. Lately, I've been doing this in a wide-mouth pint jar. Then I add the onions to the jar, pouring off any excess vinegar into another container and using for another/the next batch, and then I heat the onions in the jar in the microwave for about a minute. It's kind of imprecise but the reason for doing this is to keep the herbs and spices from getting too mixed up with the onions, as they're not particularly attractive when serving, and not good to eat. They sit on the bottom and stay there.
Also, while we're on this topic . . . . here are two other ideas for pickled onions, from Yotam Ottolenghi, from "The Guardian" food pages a few weeks ago:
I made both over the weekend. Ottolenghi doesn't add water - you just massage the vinegar and spices into the onions and let them sit. The salt causes the onions to release plenty of water. These are good!! I served the ones flavored simply with lime peel on roti wraps with cod pieces (TJ's frozen - best fish bargain around) sauteed quickly after patting dry and sprinkling with cumin and coriander, with a few coriander leaves, sliced cucumbers and avocado, for a different kind of fish taco. Outstanding. ;o)
emcsull June 21, 2017
great tip ! Now, what spices do you like to use ?