Doctor's Note

The bioavailability of some phytonutrients is increased by cooking. See my video, Best Cooking Method, to find out which vegetables are better cooked, and which are the best to eat raw. And check out my other videos on greens.

Also, note that the study I’m talking about here is published in an open access journal, so you can click on it in the Sources Cited section, above, and read it full-text for free.

For more context, check out my associated blog posts: Breast Cancer Stem Cells vs. BroccoliEating Green to Prevent CancerThe Anti-Wrinkle DietMushrooms and Immunity; and Probiotics During Cold Season?.

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  • Michael Greger M.D.

    The bioavailability of some phytonutrients is increased by cooking. See my Best Cooking Method video to find out which vegetables are better cooked and which are the best to eat raw. Check out my 33 other videos on greens and hundreds of other videos on more than a thousand subjects. And note that the study I’m talking about here is published in an open access journal, so you can click on it above in the Sources Cited section and read it full-text for free.

  • CapeBreton

    I’m curious about the In Vivo activity of these immune stimulating proteins. How do they make it through the digestive system and into the blood stream intact? You would expect them to be broken down by the HCl and proteolytic enzymes.

  • Eric Wags


    Did you read the study? There was also some animal testing done in vivo. Unfortunately not enough time for me to attempt to disseminate it.

  • paul3917

    I’m wondering if this effect, that cooked kale is more effective in stimulating the immune response isn’t related to Kouchakoff’s work in 1930 that foods heated above a “critical temperature,” 87 – 97 Celsius for most foods, resulted in increased production of white blood cells. Raw foodists take this as an indication that cooked food is unhealthy, however, interpreted in the light of this experiment, we might conclude that it is actually immune-stimulatory and salutary. If I read correctly, spinach and other green leaf vegetables containing rubisco, a protein used in photosynthesis, are also immune-enhancing. This might in part, explain the benefit of green leafy vegetables.

  • Thea

    I’m happy for these results since I like cooked kale way better than raw.

  • sarahharmony

    I juice the kale from my garden, then freeze it. Any idea what freezing does to it’s properties?

  • Anyone have some good kale recipes? Its rather gross tasting!

    • Thea

      mandy0678: re: kale recipes

      I personally would not go so far as to call kale “gross” (let’s talk amla powder for that), but I definitely agree that kale is not wonderful tasting. I especially did not like it when when I first started eating it. Luckily, at least for me, kale is an acquired taste and I’m working on acquiring it.

      Instead of eating kale by itself, I searched the web and my new vegan cookbooks for recipes which had kale in them, just not the only ingredient or main taste. I found a bunch of dishes – most of the recipes are free on-line. Look for “creamed” kale, pan-seared mushrooms with kale, and kale in bean soups. When you get more used to the taste, you can try kale chips or even the “cheasy” kale chips that I found on-line. The cashew cheese in this recipe is simply delish!

      I’ve also found that just about any recipe which calls for spinach (which is also very good for you, but which does not have the absorb-able calcium that kale has) can use kale instead. Sometimes you have to cook the kale longer than spinach.

      I hope this helps. I decided for myself that kale was worth the effort of trying to integrate into my diet. It has been quite the challenge, but I’m getting there. I hope you do too.

      Tip of the day: I have heard that Costco is now selling bags of *organic* baby kale that is already off the stem and for a decent price. I also heard that it is not as bitter as grown-up kale. I have no idea of the health differences between this baby kale and the grown up version, but based on other videos on this website, I would guess that baby kale is either just as healthy or maybe even healthier than the grown up kind.

      I hope you found this helpful. Good luck.

      • brian

        i eat my veggie burgers wrapped in kale leaves instead of bread since i like to steer clear of gluten, it works very well for that

    • Country heaven

      Heat up a sauté pan, add olive oil and crushed garlic, then chopped kale after you’ve rinsed it– strip the leafy part from any thick stems first– and add to the sautéing garlic. Add salt, to taste (or a small amount of umeboshi plum vinegar if you can find it in an Asian grocery) and enough water to cover the bottom of the pan to a quarter inch. Cover and cook until tender, but still bright green. The last part is essential. Healthy or not, over cooked kale is awful! This is delicious and healthy. Use much the same method to cook mustard greens and collard greens, all delicious and members of the cruciferous family of vegetables. So are broccoli, cauliflower, and Brussels sprouts. Spinach is not in the same family and despite being a leafy dark green vegetable, holds none of the extraordinary health giving properties of the others mentioned here. In fact, spinach can contribute to kidney stone formation.

    • james

      steamed shredded Kale with Mashed sweet potatoes with sauteed red onion, garlic, oil(your choice) and balsamic vinegar. Mix it all up, done,tasty!

    • Abigale

      I put a whole bag of roughly shredded kale into vegetable curries… can’t taste it then lol I put it in last, on the top of the curry when its more or less cooked, then put the lid on to steam the kale, then mix it into the curry gently..

    • so far, this is my favorite kale recipe
      I also just sautee them in a tbs. of vegan butter until they are crisp. i use dino/lacinato kale, or young lacinato kale. REALLY GOOD recipe. i personally LOVE crisp cooked kale though and eat it everday, so dont be surprised if you still dont like it. I actually have not tried boiled or soft cooked kale, so maybe those aren’t as good?

      ALSO, kale needs to be kept cold, exposure to a room temp. or warm environment for too long makes kale taste bitter, so always keep it refrigerated(this is what i read online somewhere anyway).

    • VegEater

      We cook chopped kale briefly in the microwave to steam it, then add pressed or chopped garlic and a tsp of olive oil. We love it.
      We also add 2-3 bunches of chopped kale to nearly every soup we make at the end of cooking time.
      I was brought up to value vegetables, especially leafy greens, but I really have trouble seeing kale as gross in any way. I like lacinato kale best.

  • ChrisH

    Thanx Mandy & Thea, for making me think I’m weird – I like kale, taste ‘n all, raw or cooked. Luckily I’m living by myself, in a house at the edge of town, because the odor of cooking this life saver of a vegetable has been known to be upsetting some haters…

    • I love kale as well, raw and cooked, so I guess we’re both weird.

  • veggiechick

    I love dinosaur kale to me it has a better taste. I love it in stir fry’s.

  • Melanie

    Surprising results! I enjoy the flatter-leafed versions of kale rather than curly kale. I enjoy it steamed with mushrooms and eggplant, served over rice with some soya sauce. There was an excellent recipe for kale and tomato soup with garlic and almonds in the book Vegan of $4 a Day. Dr. G., I hope you get to do some lectures for pharmacology students. They’d love your presentations.

  • Michael Greger M.D.

    For some context, please also check out my associated blog post Breast Cancer Stem Cells vs. Broccoli!

  • Coach Mac

    No Kale in France. What is the closest to kale here?

    • Toxins

       Try consuming any dark green leefy vegetable such as collards, spinach, bok choy, arugula and Swiss chard.

    • Euclidean2

      swiss chard is super-nutritious as well. Be sure to consume both cooked and raw (juice or whole leaf) forms of kale and swiss chard.

    • Adrien

      I live in Paris and we can find Kale now thanks to Kristten who started
      the Kale Project. And guess what, the season just started !

      I just had my first Kale chips, and it’s awesome !

    • Adrien

      I live in Paris and we can find Kale now thanks to Kristten who started
      the Kale Project. And guess what, the season just started !

      I just had my first Kale chips, and it’s awesome !

  • Do you know if it’s okay to drink kale juice if you’ve got fructose malabsorption.
    I have it, and got told to stay away from most fruits. (Except grape, lemons, those kinda things).

    But i really want to be as healthy as I possible can, but I feel really limited.
    I take what I can, in vegetables, and nuts. But hardly any fruit, since that makes me fully constipated.

    You seem awfully smart, got any suggestions, ideas xD?

  • rasil

    I consume raw kale daily and often twice a day as the basis for my salad.  Here is a healthy and absolutely delicious recipe for using kale as one uses any kind of lettuce.

    kale, onion, red bell pepper, Persian cucumbers ( or baby cukes), plum tomatoes, jalpenos (optional, I prefer the tamed style as they are not as “hot” but add a bit of zing to the salad), garlic & onion powders, and “good” Italian dressing.

    Wash, dry, and de-stem kale.
    Roll and cut both length and width wise into small pieces.
    Slice or dice onions, peppers, cukes, & jalapenos. (**do not add tomatoes yet)
    Add garlic & onion powders and place kale in a plastic bag and shake until powders and all ingredients are blended well.
    Store and refrigerate in a zip lock bag for the same amount of time you would store lettuce.
    Retrieve the kale and use as you would any kind of lettuce.
    Add tomatoes and Italian salad dressing only when ready to serve or it will become soggy.  Delicous and soooo nutritious.  Provides more and a better quality of calcium than Boneva :)

    *N.B. It seems to be much work initially but once the kale is prepared, it is a pleasure to reach into the bag and retrieve only what you need without going through the preparation each time you want a salad.  Enjoy!

  • Reklaw

    Dr. Greger, what foods have you know to be helpful for someone that is HIV positive?

    • Healthy

      Raw organic extra virgin coconut oil. Ref: Dr. Mercola.

  • Kale is really awesome stuff…I prefer the dino kale too but am now growing my own curly kale! Love to dip it raw in hummus for a snack…also love to add it torn up into lentil soup. Let’s not forget kale chips…wow, great stuff if you don’t add a lot of gunky stuff to it! I do also love it sauteed with garlic & onions and put over black rice.

  • nyxdeity

    KALE CHIPS!! I am not a fan of just chewing on kale but I love kale chips, I even saw a recipe for chocolate covered kale chips YUMM

  • Wow! Pretty amazing.

  • Андрей Ханевский
  • BB

    Kale is the crack of the Hamptons…

  • Have you done this experiment with BLENDED kale? I consume green smoothies on a regular basis, and like to include a couple of large kale leaves in each one. I’d love to know if blending it (or even juicing, but I like to keep the fiber by blending) makes as much difference as cooking it does?

    • Dr Connie Sanchez, ND

      For the immuno-stimulatory effects of kale eating kale cooked appears to be better; however, eating it raw is good too. Putting a couple of kale leaves into your smoothie each morning is most definately a good idea, however, make sure to add cooked kale to your daily menu as well for even better results. The combination of cooked and raw in the diet covers all the bases.

  • lovestobevegan

    Working Out the Knots Kale

    – 1 bunch de-stemmed green/red curly kale
    – pinch black pepper
    – pinch sea salt
    – juice of half a lemon
    – 3 cloves garlic, minced

    Remove the bulk of the stems from the kale by holding the thick end of the stem and sliding your hand toward the skinny end. Shred the kale into pieces with your hands and place kale in a large bowl. Top kale with remaining ingredients and massage everything together until kale turns bright green, about 1-2 minutes. Serve cold.

    Bookmark my new Plant-Based Emporium Facebook page for all my latest recipes.

    ~Complements of lovestobevegan

  • Soymoon

    I have been juicing and smoothing kale for about 6 months now, but here’s my question: The Doctor has put me on methotrexate to fight RA. Do I want to be boosting my immune system if I am taking that? They say I can’t take echinacea because it boosts the immune system. Should I stop eating Kale? Please advise!

  • why isn’t a photograph of kale used? seems silly to me. lacinato (dinosaur) kale is beautiful!

    • Wade Patton

      that really threw me off too.

  • Wade Patton

    Eating kale for my very first time (knowingly) right now. That and beet greens (also first), a beet, black beans, corn tortillas (toasted) and salsa. Whoops, there’s some broccoli and garlic on the plate too…how’d that happen? Came here to check up on kale’s specific greatness. Looks like another WIN WIN!


    Why do doctors tell people who take blood thinning medicine to not eat kale and other green leafy veggies b/c the Vit K in kale etc counteracts blood thinning properties of say, plavix, xarelto, etc ?

  • Katy

    I’m curious about the thallium levels in kale. Does organic kale have this problem. Mother Jones has an interesting article on too much kale but they don’t go into the levels that are too much.

  • In that kale stimulates the immune system, should kale be avoided by someone with lupus?

  • Marco

    Here in Italy it’s impossible to find Kale (curly). An alternative is Tuscan Kale (dino) but it’s hard to find in some places and periods.
    Which is the difference in oxalates between Kale and Tuscan Kale?
    Anyone knows another kale/lettuce high in calcium but lower in oxalates?

  • Mery Daae

    could we have a simplified chart “to find out which vegetables are better cooked, and which are the best to eat raw. “?? I’ve been working on optimizing my health (Hashimoto’s, chronic fatigue, IBS) via a plantbased diet and I think I’m hitting the sweet spot at High raw (as much as I can), plantbased diet (no gluten, no oil) and fasting some days. I really don’t want to miss out on boosted nutrients and I’ve heard betacarotens and others actually increase via cooking (thanks to your helpful info) but then all the separate info just clutters up. I would love to see a chart to make sure to include certain cooked plant foods. Also (less crucial though), what is your opinion on fasting? I’ve done a search and I don’t seem to find anything.

  • 4Baccurate

    The question of kale is confusing. For example, if someone has an overactive autoimmune syndrome (for example, lupus and/or antiphospholipid antibody syndrome, , but at the same time wants to lessen the chance of developing breast cancer—-Would kale worsen the autoimmune disorder but at the same time lessen the breast cancer risk? Thanks.