Doctor's Note

There is a level at which sulforaphane may become toxic, but that appears to be only at extremely high doses (see Liver Toxicity Due to Broccoli Juice?, and How Much Broccoli Is Too Much?). Watch my other videos on liver health.

Note that most of the sources for this video are open access, so you can download them by clicking on the links in the Sources Cited section, above.

For more context, check out my associated blog posts: Fighting Inflammation With Food SynergyAntioxidants in a Pinch: Dried Herbs and SpicesStool Size and Breast Cancer RiskBreast Cancer Survival and Soy; Breast Cancer Stem Cells vs. BroccoliThe Best DetoxTreating PMS with SaffronEating Green to Prevent Cancer; and Are Microgreens Healthier?

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  • Michael Greger M.D.

    This “glow stick” reaction is similar to what happens in garlic. I talked about it in #14 of my Ask the Doctor Q&A blog. There is a level at which sulforaphane may become toxic, but that appears to be only at extremely high doses (see Liver Toxicity Due to Broccoli Juice and How Much Broccoli Is Too Much?). Watch my 18 other videos on liver health, as well as hundreds of other videos on more than a thousand subjects. Note that most of the sources for this video are open access, so you can download them by clicking on the links above in the Sources Cited section.

  • Elvin

    ‘Chew it or lose it’? But it sounds as though putting it in a blender would be just fine, no?

    • p

      does the blender work as good as chewing?

    • Richard Hachem

      If not, masticating juicers should do the trick.

    • barbarabrussels

      I don’t think so. As I understood it, it’s the reaction with the saliva. But I may be wrong.

      • Mike

        Just spit in the blender

      • sf_jeff

        Saliva breaks down starches and helps with nitrites. I am not aware of interactions with sulforaphanes.

        • name

          You’ve not even hear of sulforaphane until now…

          • Ryan

            Is that really called for? Play nice please.

    • Kent Nauman

      Will this process release the sulforaphane? Freezing fresh broccoli to use the ice crystals to tear the broccoli cells apart then thaw the broccoli to room temperature for several hours before cooking?

  • AuntyVal

    In all these studies using broccoli sprouts, can we just assume the same results using broccoli instead?

  • yuli.90

    hello! i’ve been a huge fan of your videos ever since i saw you speak at the nyc veg fest. thank you for bringing so much information into my life!

    i have a question regarding detox. this pas year i’ve been trying to do a raw food diet to try to cure my asthma, allergies, and just feel generally happier. i want to experience a full detox and get the detox phase over with, i have read about “monofruit island” and that eating only one type of fruit for a short period of time is the best and purest way to do a detox. i was considering doing bananas for two weeks. i was wondering if you had any input or suggestions on this.
    MUCH appreciated!!! thank you.

    • Toxins

      Do not follow the “detox plan” myths. The best detox is drinking LOTS of water and eating totally whole foods plant based. Including a lot of broccoli in your diet will be highly beneficial for cleaning up your body.

      • Ivy

        l agreed with whole foods→unrefined! Thank you

      • Kartoffelmao

        Yes, and also avoiding the crap the needs detoxification in the first place. :)

    • Tiago Cartageno

      Hello yuli.90, it looks like we have similar problems. I´m answering a two years old comment but I hope in the meantime you have found the perfect detox for you.
      I am 32 years old and all my life I had severe problems with allergies and asthma. I took all the pills that the doctors told me to take. That cured indeed my allergies but didn´t prevent them from happening again.
      2 years ago I definitely got upset for can´t control it and I have started to change my diet to a vegan one ( no animals, no dairy ). In the beginning I have made a lot of errors but I have learned from it. After two years, more precisely these Spring I had the final test for my diet.
      Every Spring my body reacts VER BADLY to pollen, so before Spring came I watched a lot of Dr Greger´s Antioxidant videos. That said I started to eat EVERYDAY red fruits ( mainly cherries, blueberries and açaí ), watercress and red cabbage. All foods full packaged with the best antioxidants. Also, and very important, I ´ve started to put a pinch of oreganos and cloves in every food I took. No doubt my antioxidant levels raised!

      This Spring, for the first time in my life, I didn´t have any problems so far! I can´t explain how happy I am for that and It is really exciting to know that I could took a major change in my body and that definitely happened with the help of the great DrGreger.

      If you want detox, you want antioxidants.

  • LynnCS

    Love when you talk science! Ooooh! :-)

  • Emily

    Hi Dr. Greger,
    Do you have any research on broccolini or broccolette (cross between broccoli and chinese broccoli – gai lan)?
    Emily :)

  • Barbara Keene

    good news is I love these veggies, bad news is your Dad hates them.  Just got out of the hospital with my heart, his mind is going and my overall health is going,
     we make a heck of a combination, hope you are well!

  • Michael Greger M.D.

    For some context, please check out my associated blog post The Best Detox!

  • Michael Greger M.D.

    Please also check out my associated blog post Fighting Inflammation with Food Synergy

  • Deb

    Is broccoli’s detoxifying benefit lost when consumed pureed into soup rather than chewed? Thank you.

  • Deb

    Is broccoli’s detoxifying benefit lost when consumed pureed into soup rather than chewed? Thank you.

    • Toxins

      If u puree it beforehand and let it sit for 10 min, then apply heat and put it in the soup, you will probably get more of the sulphorophane, which “cleanses” you.

  • geekay

    Does it matter if the broccoli is cooked?

  • Timt

    Dear Michael Greger M.D. , Is broccoli’s detoxifying benefit lost when consumed blended into a juice rather than chewed? Thank you.

  • Michael

    Hi Dr,

    What happens to the body on the inside if we do a 10 day Master Cleanse (lemon diet), or a 20 day or 30 day? Is it safe? Are there risks?


  • hahaha….”the herbivore says ‘EWWWW, it tastes like broccoli’ and runs away.” LOLZ, Doc you crack me up…awesome information too! ♥!

  • One study says to cook the broccoli for ten minutes at 140 degrees to melt away a spoiler chemical that stops the formation of sulforaphane. Cooked that way brings big results.

  • Suzanne

    Million dollar question.. can it be cooked, steamed or must it be eaten raw to receive the optimal benefits?

    • Toxins

      Sulphorophane production is heat sensitive so yes, raw would be best.

      • Hollywood Resident

        How confusing to see another video on this site stating that boiling greatly magnifies the protective effects of broccoli and other greens such as chard and kale. I detest ALL raw greens and vegetables (except lettuce), but LOVE them ALL cooked. Broccoli sprouts are particularly nasty tasting. And now here’s this issue with the Sulphurophane. I am obviously not chewing the broccoli before I boil it, only afterward. But I need clarification, if in order to get the benefits I must grind it into a smoothie, I will, please advise!

        • Toxins

          Chopping the broccoli before hand should provide similar benefits. Leave it for 30 min. before cooking.

          • Hollywood Resident

            Thanks. It may be immaterial since I like (lightly boiled) broccoli and usually eat about 1 cup a day, in addition to other things like brussel sprouts, swiss chard, romaine lettuce, chick peas, bell peppers etcetera, making it likely that even less than optimal sulfurophane in my broccoli is not a problem. But the confusion comes from the research on the ‘muddling’ or chewing/cutting/crushing of garlic and broccoli in order to activate it chemically. Garlic cloves are easy to crush and leave for 10 minutes before cooking, or better yet, buy in pre-chopped form. Whereas broccoli comes in a bunch on a stalk, and is not easy to ‘crush’ unless you’re chopping or blending it. Since I prefer whole florets lightly boiled or well steamed, theres a limit to how much ‘chopping’ I’d like to do to it. I wonder if the research looked at how much of the sulfurophane in the entire broccoli head is activated by 1)cutting it in the fields 2)chopping off the florets 3)semi crushing it on a hard surface, etc. For all we know, cutting a 4 inch floret from the stalk fully activates the phytonutrients in the entire length of that floret. With broccoli the distance that the cutting effect travels from the point of trauma is important to know if you prefer it in traditional floret form. Unless in my case, as I said, eating plenty of it daily in concert with other vegetables already provides adequate sulfurophane. Thats the thing about these research nuggets, you always want a little more clarity.

          • Toxins

            There is indeed sulphorophane activity from consuming a whole un-chewed piece of broccoli. I forget which video Dr. Greger demonstrates this in. In the big picture it doesn’t really matter. We should consume broccoli in which ever way entices us to eat them as long as they are not doused in butter or bacon wrapped.

          • Marie

            Agreed. But he ends the above video with the suggestion to “chew it or lose it” referring to the study showing increased sulphorane release when the broccoli was chewed. For practical reasons I’m not sure why or when you’d want to eat a whole un-chewed piece of broccoli but it seems worth it to do some gnawing on the healthy green veg before swallowing. Having said that I’ve gone through medical issues and known others who have had medical issues which made pre-blending or breaking down all food (a pre-digestion) before ingesting during the healing/ treatment time. As others have commented I wonder if this would serve same purpose, i.e. is it the mechanical action of chewing that releases the increased sulphoraphane and or chemical action of saliva? As you said, big picture doesn’t matter really (its all good) but it would be nice to have this clarified.

          • Marie

            Sorry, should have finished sentence about pre-blending food. Im sure you understood I was trying to explain that in some cases breaking down food before eating (as in blending etc.) is advised as part of certain treatment plans for serious GI issues (alone or secondary). I know for me and others it was…and we werent really worried about the detox process at the time but that’s life. All is well now.

          • dogulas

            All that has to happen is the cells need to be broken up sufficiently for the enzyme and the precursors to find one another and bind to form the product sulforaphane. Chewing, blending, chopping, and possibly head-banging, running over, and dueling with raw broccoli does that, to varying degrees based on how well the cells are crushed and broken. There does need to be some time for the enzyme to do its work on enough precursor molecules though, so there must be some waiting before cooking if you’re going to cook it. Once there has been sufficient time (I’d say 30-40 minutes is plenty), the sulforaphane has been created in good quantities, and it is not destroyed by cooking once it is created. So you can then cook it all you like if desired.

            If you’re just eating raw broccoli, there is apparently enough time for the enzyme to do its work in the mush you have swallowed into your stomach, at least somewhat, before your stomach acids destroy the enzyme. Bottom line is eat broccoli however you like besides swallowing it whole (sounds rather difficult anyway), and if you’re going to cook it, great, but crush the cells up in some mechanical fashion first and give it 40 minutes before applying the heat.

    • Ronald Chavin

      The entire Brassica family (which includes cabbage, Chinese cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, mustard greens, red radishes, giant white turnips, watercress, etc.) needs to be eaten raw and chewed well for maximum health benefit. About half of the glucosinolates are destroyed by boiling, about half are destroyed by freezing, and about three-quarters are destroyed by freezing-then-boiling.

      However, other families of vegetables are not as severely damaged by cooking. For example, eating cooked/canned tomatoes has some health advantages and some health disadvantages when compared to eating raw tomatoes. Legumes (including foods made from soybeans) tend to retain the vast majority of their health benefits even after cooking or factory processing. The beneficial chemicals in allium vegetables (garlic, onions, scallions, leeks, and chives) are moderately damaged by drying or cooking but not as severely damaged as in cabbage family vegetables.

  • Ronald Chavin

    Here’s an interesting study from Lithuania which indicates that cabbage eaters have a lower death rate from stomach cancer than broccoli eaters:

    Pesticides are less of a problem for cabbage eaters than broccoli eaters because the outer layers of the cabbage are almost always thrown away both by the farmer and the consumer.

    The fungus (black mold) which infects most cabbage family vegetables can more easily be removed by cabbage eaters than by broccoli eaters.

    As a result, head cabbage has a longer shelf life than broccoli.

    However, broccoli contains substantially more lutein, which is a carotenoid that is beneficial for preventing age-related eye diseases.

  • Amy Sullivan

    If you juice broccoli, do you still get the enzyme?

    • dogulas

      Definitely, but why give up the fiber?

  • dynamicjoe

    Do Broccoli sprouts as a supplement help?

  • kabocha

    For people who are hypothyroid, how much cooking will render broccoli harmless to the thyroid gland?

    • dogulas

      Not sure about how much cooking is needed. I would assume that after it is at boiling tempuratures, 6+ minutes would surely do the trick. Otherwise though, getting the right amount of iodine should do its job just fine. Don’t take my word for it though. I’m no thyroid expert. I just know what I’ve heard in the videos on this site :)

  • acepex

    Wouldn’t juicing Broccoli work even better for getting the most out of it in terms of nutrition and sulforaphane?

    • Marie

      He lists a video above on juicing it and if you watch it I think you’ll see it doesn’t note any negative impact but neither does it point out any benefit, i.e. increased sulphorophane. I believe it needs to be clarified whether the increased enzyme was from the mechanical breakdown action of chewing and or the salivary or bio-chemical action. Maybe somebody knows and will comment.

      • dogulas

        It’s definitely produced at least from the mechanical breakdown alone. Because in other videos it is demonstrated that blending up or chopping raw broccoli, letting it sit for awhile (to make the sulforaphane), then cooking it (destroying all enzymes), and after all that finally eating it…still has the effect. The blended up, un-chewed broccoli has also had its sulforaphane content analyzed and it has the full amount expected.

    • Wade Patton

      Whole juice, where you retain the fiber would work, but you’ll always reduced the quality of your food when removing fiber as conventional juicing does.

  • Bettie Page

    Love your graphic example of the lite stic!

  • ayon

    shld try morn bloosom available at optm health care.

  • Bill Young

    Hi, the question I always had and could not find an answer to is the possibility of harmful oxidation of the food being blended. Just like the homoginization process oxidizes the fat in milk. Doesn’t that happen to the particles of food also?

  • nodome

    Excellent website-a lot of good information on nutrition–Thankyou, Nutritionfacts! One thing I will add from my own experience when it comes to cleansing/detoxing. The cleanse that Dr. Schulze at developed totally changed my life many years ago. If you have any type of terminal disease then please check him out.

  • Anthony

    Do you have any information on diatomaceous earth?

  • Jeffrey

    Raw or cooked, Dr. Greger? Please let us know. Thanks!

    • sh

      Yes, Raw or Steamed/Cooked?

  • Bat Marty

    if we slow juice Kale or broccoli, is sulforaphane present in the juice?