Anti-Cancer Recipes: Should you Cook Onions?

anti-cancer onion artNow that your anti-cancer kitchen is brimming with small red and yellow onions, the obvious question is: Should you cook them or eat them raw?

The short answer: 

Both, but cook them lightly. 

Like garlic and crucifers, onions contain enzymes that get activated when you cut the vegetables. In a cascade of actions, the enzymes produce sulfur-based compounds that fight cancer and protect your DNA.  This chemical reaction is the plant’s protection from predators, explains Dr. Irwin Goldman, an onion expert and professor at the University of Wisconsin. When insects bite into the plant’s leaves, the enzymes get to work and generate pungent chemical warriors. 

But the enzymes are very sensitive to heat.

As you know from previous posts, you have to first cut alliums (the onion and garlic family) to break their cell walls and release the enzymes. Then you have to let the vegetables sit for a while so that the sulfur compounds have time to develop.

How long? Nobody really knows for sure, but Goldman suggests leaving onions for 30 minutes. (A garlic researcher I spoke with suggested about 15 minutes for garlic, and another sulfur expert thought both times were too long. Until science has a full answer, I’m hedging my bets and cutting well in advance.) 

Then, either eat the veggies raw—probably the best choice in the case of garlic. Or quickly cook onions.

Eating onion raw will maximize the sulfur compounds, but onions have another trait going for them that its garlic cousin appears to lack:  Onions are rich in quercetin, which acts as an antioxidant and anti-inflammatory, inhibits estrogen and according to recent studies, inhibits cancer cells from metabolizing glucose and fatty acids as fuel. 

Like many phytonutrients, quercetin concentrates in the plant’s outer layers.  (That’s why you must peel onions ever so gently.)

And quercetin, it turns out, may get concentrated with a little cooking, depending on how you cook it, although again scientists aren’t yet sure.  In one study, baking onions at 350F for 15 minutes slightly increased the quercetin. Sauteeing at 200F for 5 minutes increased it even more. But let’s say you want to make a miso soup and boil the onions for a few minutes instead? Good idea or not? Boiling onions for 5 minutes decreased the quercetin, but the good news is that it leeched into the cooking water–meaning you could just lap it up.

That’s the quercetin quotient. So now let’s get back to the sulfur in onions. How long does it take before heat destroys their ability to make sulfur compounds? Goldman says that if you cook onions, you should cook them quickly–4 to 5 minutes at most–to preserve the enzymes. If fact, if you cook them longer, his research has shown that they cause your blood to become sticky, increasing your risk of cardiovascular disease and of cancer spreading. 

Ready to try the recipe for Indalian onions

Because some sulfur compounds are soluble in water and some in fat, a saute-steam seems ideal.  Cut the onions small enough so that they cook quickly; saute for a minute of so on low to moderate heat along with anti-inflammatory spices (such as this turmeric mix), then add a little liquid and cover and quickly steam. (If you want to cook garlic a bit for flavor,  throw in some crushed raw garlic or its juice at the end.)

BOTTOM LINE: Putting this together with all the other anti-cancer cooking tips in this blog, what’s the bottom line?

Eat onions raw AND lightly cooked. Choose the small red and yellow onions grown in northern soils, peel them lightly, cut them small enough so that they cook quickly (but not too finely or the enzymes may evaporate) and let them sit.  Then eat them raw or do a quick saute-steam, cooking them on low to moderate heat for 4- 5 minutes max. For an extra bolus of sulfur, throw in some raw garlic or onion once the dish has cooked.  

p.s. “But raw onions give me heartburn,” you might be thinking. In some people, they trigger the valve between the stomach and esophagus to open and close erratically. I’ve heard the chlorophyll in green plants is a good antidote. Let our 3000 readers know if that trick works for you.

onion art courtesy and copyright of New York artist Rachel Chodorov    If you’d like to submit your original work to be used along with our anti-cancer recipes, just leave a reply below along with your email address.  


14 thoughts on “Anti-Cancer Recipes: Should you Cook Onions?

  1. Pingback: From Harriet Sugar-Miller- Should you Cook Onions? | Nutritional Boot Camp

  2. Great post and website! My best friend Kay was diagnosed with cancer not long ago and since she was given the bad news, her outlook on life has completely changed; especially how and what she eats. We always hear about clean eating, and cooking light, but sometimes I don’t think it really registers until we’re faced with something like cancer. Tips like this post are wonderful for those with cancer, fighting it, or supporting someone who has cancer. I recently bought a cook book for Kay called “Kicking Cancer in the Kitchen” by Annette Ramke & Kendall Scott. She absolutely loves it and the recipes are delicious! Their website,, is an amazing reference and has a bunch of information; definitely worth checking out! Thanks for this post, I think I’m going to forward it on to Kay!

    Liked by 1 person

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    • Thanks, Sam, for that study. Yes, if you’re making soup, go ahead and cook the onion in a lot of water to release the quercetin into the liquid. But then you should discard the onion and just drink the liquid. The reason is that when onions are cooked for a long time, they make the blood sticky. How long? This study suggests boiling for more than 20 minutes will do that.


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  7. How many medium small onions do you need to eat a day or a week to make any real difference.. are these enzymes and nutrients and things in granulated garlic and granulated onion..


    • How many? Nobody really knows–and everything else that you eat or don’t eat also figures into the equation. Sorry, but I don’t know anything about granulated garlic or onion. Their health impact may be dependent, at least in part, on the process used for drying them. With dried berries, those that are freeze dried retain phytonutrients but those that are spray dried, don’t.


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