Doctor's Note

What else do mushrooms do for us? Check out:
Breast Cancer Prevention: Which Mushroom Is Best?
Why Do Asian Women Have Less Breast Cancer?

And check out my other “HHH” videos – Harmful, Harmless, or Helpful? – listed below the post, as well as my other videos on mushrooms

For more context, see my associated blog posts:  The Most Anti-Inflammatory MushroomMushrooms for Breast Cancer PreventionErgothioneine: A New Vitamin? and Mushrooms and Immunity.

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other “HHH” videos (Harmful, Harmless, or Helpful?) as well as these videos on mushrooms. Also, there are over a thousand subjects covered in the rest of my videos–please feel free to explore them as well!

    • I eat raw white mushrooms all the time. Switching to cooked would be easy enough. Sometimes I microwave them for 30 seconds to make them soft and juicy. Is that sufficient to kill the toxins? What’s the best method, and minimum length of time to cook them to kill the toxins?

      • Toxins

        Hello Eric,

        Taking a look at the study, when microwaving, it appears that if you microwave for 30 seconds you lose 51% of the agaritine and after 45 seconds 60% of the agaritine is lost.

        To answer your question about the absolute best method to reduce agaritine, if you boil in water for 1 hour you lose 88% of the agaritine and if you freeze them for 30 days then allow them to thaw out on their own for 1 hour without microwaving you lose 77% of the agaritine. These are by far the best 2 methods it seems to reduce this toxin.

        You should note that there is also no “safe” level of agaritine as it is known as a human carcinogen, the tolerance should be 0. Of course, one could assume that reducing as much agaritine as possible would be not nearly as destructive as full exposure.

        For more on some typically consumed toxins, check out this video on Blue-green algae and Spirulina

        Hope this helped!

        • signmanbob

          What about just buying canned mushrooms? These would already be cooked and could be rinsed off if they have any added salt.

          • Toxins

            I see no problem in that as long as the sodium content is low. If its very salty, we might be able to reduce the sodium, at best, by 30%.

          • Thea

            signmanbob: I have another thought for you concerning canned mushrooms – toxins leaching from the cans. I’m sure you’ve heard of the problems with BPA. But even if you can find a brand free of BPA, I have to wonder what else is in there that might be bad. What are they replacing the BPA with???? (That last part is just speculation on my part.)

            My tip on convenient mushrooms – get the pre-washed, pre-sliced mushrooms from the store. I know that Trader Joes and Market of Choice sell mushrooms this way. Then throw the mushrooms in the microwave (no oil or anything need be added) for a good 4-6 minutes. They come out perfect and you don’t have to deal with opening a can, draining, salt, BPA or anything else.

            Just a thought for you. Good luck.

          • signmanbob

            Thank you Thea! That does sound good. I’ll have to see if I can find those around here.
            So if microwaving 4-6 minutes will get rid of the toxins in the mushrooms, that won’t be much trouble at all.

          • Thea

            signmanbob: So glad the tip appeals to you.

            FYI: the reason I give such a large range of times is that cooking time depends on all these factors: your microwave power, how many mushrooms you are cooking, whether or not the mushrooms comes from the refrigerator or were sitting on your counter, and how thick/thin the store sliced them. (Trader Joes ones are thicker than Market of Choice. Depending on what I’m doing, both come in equally handy.)

            I just cook until it gets that cooked mushroom consistency. Once you get a brand you are familiar with, you will know exactly how long to cook them each time. It will be a snap.

            Another tip: The mushrooms naturally release their “water” into the cooking bowl. I scoop out the mushrooms, but leave the mushroom water. Then I add the chopped broccoli or cauliflower or whatever to the same bowl and cook it in the mushroom water. Yum! I usually do 3 minutes for broccoli. 4-5 minutes for cauliflower.

            Hope you can find those pre-sliced mushrooms I am talking about because it is so fast and comes out tasting so good. Good luck!

          • macrumpton

            I have been drying mushrooms in my oven at °250f for 2-3 hours. Is that enough cooking to reduce the agaritine to a safe level?

          • Thea

            macrumpton: I’m sorry, I have no idea.

  • Toxins

    What happens when eating raw mushrooms?

  • stacy

    If agaritine is so toxic and cooking mushrooms does not remove all of it, wouldn’t it be healthiest to not eat mushrooms at all?  
    It seems the exposure to agaritine is more dangerous than any health promoting effects of mushrooms, right?

    • Toxins

      Although yes agaratine is toxic and yes agaratine is not completely eliminated, mushrooms are still higihly nutritious and the minute amounts we are exposed to when eating cooked mushrooms is not of a concern.

      • DvoraChesed

        On the other hand many foods are also highly nutritious, and they have no agaritine at all.

        • Toxins

          Mushrooms are special, in that they are more beneficial in certain ways then other plant foods.

          • DvoraChesed

            Vitamin C counteracts the carcinogen acrylamide produced by roasting coffee beans. I wonder if Vit C or another antioxidant would counteract agaritine?

          • Toxins

            I have not seen this evidence, please share.

          • DvoraChesed

            Please Google acrylamide+Vitamin C.

          • Toxins

            Articles, blog posts, and news stories are not evidence, as this is what you will find when google searching. I need you to link an actual study so we can examine whether this claim you made is true or false.

          • DvoraChesed

            Google past page one.
            Several of the hits do reference actual studies.

            P.S. the “approval” came from me by accident :)

  • thissal

    The kicker with Agaricus species, including the buttons, is
    that one of their primary hydrazine components, along with
    gyromitrin, is “agaritine,” a substance somewhat resistant
    to cooking heat, with a significant percentage (25–75%) of
    agaratine material typically remaining after being subjected to
    various methods of cooking. So, the question as far as avoiding
    hydrazines in Agaricus is concerned, actually becomes whether
    to eat members of this genus at all.

    We need to keep in mind that lab tests and subsequent
    conclusions drawn concerning carcinogenic or mutagenic
    health hazards of hydrazine involve massive doses of isolated
    extracts administered to mice in a concentrated time frame.
    Similarly disturbing test results are likely to be found with many
    substances present in many, many foods humans commonly
    eat without suffering or even worrying about any particular
    health concern. The relatively unblemished human history of
    consuming edible Agaricus species suggests we may continue to
    do so.

  • pamela

    are the white muahrooma harmful raw? ive been eating them for 35 years!

  • Worth noting that the initial toxicological studies fingering agaritine in mice (but not rats) used rather extreme protocols.

    “Feeding studies using mushrooms and mushroom extracts have in general provided no evidence of toxicological effects of agaritine or mushroom consumption, in contrast to results of studies which have administered non-physiologically relevant concentrations of chemically synthesized hydrazine derivatives to mice. The available evidence to date suggests that agaritine from consumption of cultivated A. bisporus mushrooms poses no known toxicological risk to healthy humans.”

    Roupas, Peter, et al. “Mushrooms and agaritine: A mini-review.” Journal of Functional Foods 2.2 (2010): 91-98.

    • cohorts are wrong

      I think we can conclude that we have to take Dr Greger advice with a pinch of salt :). He also seems to be demonizing coconuts but very pro soy. Go figure!

      • jn

        Not the old “soy is bad for you” propaganda again…

      • Toxins

        Dr. Greger does not demonize coconuts, he doesn’t advocate coconut oil or coconut milk.

      • Greg_X

        Dried coconut is 57% saturated fat. Fresh raw coconut is 30% saturated fat.

      • Lisa

        Ah – I see you’re a LCHF troll.

  • Curious

    Hello. I love you Dr. Greger!

    Yesterday I ate several raw white button mushrooms (even after viewing your mushroom video) so I was a little concerned. I went to “sources cited”, and saw evidence of the agaritine content, but I wanted to know why agaritine from mushrooms was considered so toxic.

    I found this 2010 “mini review” from Australia that concluded there was no evidence of toxic effects from eating raw mushrooms:

    Roupasa P, Keoghb J, Noakesb M, Margettsa C, Taylorb P. Mushrooms and agaritine: A mini-review. Journal of functional foods. 2010;2(2):91-98.
    According to the conclusion:

    “Direct administration of chemically synthesized hydrazine compounds, including agaritine, to mice has been reported to be associated with potential carcinogenic effects in some studies, but contradicted by other studies. No carcinogenic effects have been scientifically validated in studies with mice, rats or humans where mushrooms have been consumed…A critical analysis of the studies to date leads to the conclusion that consumption of A. bisporus and other edible
    mushrooms does not result in any known toxicological or carcinogenic
    effects in healthy humans.”

    Please note that the review was funded by Mushroom and Health Global
    Initiative (MHGI).

    Do you happen to know if there are any studies on consumption of edible mushrooms that have found toxic effects?
    Thanks for being a fantastic resource!

  • barbarabrussels

    The source cited seems to be about the agaritine content not about its level of harm. Also, agaritine doesn’t seem to be all bad, e.g. the article “Agaritine purified from Agaricus blazei Murrill exerts anti-tumor activity against leukemic cells.”

    Which states “The results indicate that agaritine from ABM has direct anti-tumor activity against leukemic tumor cells in vitro. This is in contrast to the carcinogenic activity previously ascribed to this compound.”
    Is there conclusive evidence that agaritine is harmful if consumed in raw mushrooms? I couldn’t find it.

  • Mark

    Is there a difference between “Fresh Cooked” and Canned Mushrooms? In other words is the efficacy of the mushroom diminished by the canning process? Or are canned and cooked on par?

  • zapp7

    This review found that there is no evidence that consumption of agaritine in mushrooms leads to any toxicological effects.

    Most of the animal studies that found toxic effects resulting from agaritine used an isolated form in very high doses that are not representative of whole mushroom consumption. Given that agaritine is a known toxin, it’s a decent precaution to cook mushrooms. But given the lack of evidence of any real toxic effect from human consumption of whole raw mushroom, I’m not going to lose any sleep over it.

  • John Tiffany

    Garcinia kola or bitter kola nut—not to be confused with the regular kola or cola
    nut–is traditionally used by African medicinemen who believe that it
    has purgative, antiparasitic, and antimicrobial properties. The seeds
    are used for bronchitis, throat infections, colic, head or chest
    colds, and cough. It is also used for liver disorders and as a chewing stick. Reports
    say it cures viruses—Even Ebola. What does Dr. Greger say about it?

  • bryan

    Is there a target internal temperature when most of the toxic stuff is gone?

  • I’m reading How Not to Die (amazing book, I want to buy it for everyone I know) and have a question about mushrooms. As an avid mushroom hunter, I am wondering why you would say “all wild-foraged mushrooms should be on the red light list” – are you punishing chanterelles for the sins of the morel?

  • Danilo

    How long do you cook button mushrooms?

    • Thea

      Danilo: Until the mushroom has the texture of a cooked mushroom as opposed to a raw mushroom.
      I’ve got this down to a science for my needs. I like to buy the pre-sliced button mushrooms. It takes 5.5 minutes in the microwave for one 8 to 10 ounce package. If I’m cooking two packages, it takes 8.5 minutes. These times are for mushrooms that have been in refrigerator.
      I find that mushrooms are pretty forgiving, so over cooking a bit might make them a bit tougher, but they still work great and sometimes tougher is exactly what you want for an application.
      Good luck.

      • Danuta

        doesn’t microwaving kill enzymes in food? would it not be the same with the beneficial nutrient properties of the mushroom – especially if you don’t use the low power setting?

        • Thea

          Danuta: Microwaving does not kill enzymes any more than regular cooking does. And your original question was about how long to cook mushrooms.
          As for “killing enzymes”, that’s not something I usually worry about. (The following video talks about an enzyme that matters, but note the video description “There are a few examples of plant enzymes having physiologically relevant impacts on the human diet…” ) Plenty of studies show a great deal of healthy outcomes from eating cooked food. So, I eat some cooked food and some raw food. That seems to be a good approach in general. Though when it comes to mushrooms, as explained in the above video, the general advice would be to eat only on cooked mushrooms.
          There are a lot of myths about microwaves out there. Here is a great article for dispelling those myths: So, this is good news! Enjoy your microwave!! :-)

      • Joy Dancer

        I had this same question just now. Thank you so much for your help!

  • Leanne Sands

    Is it true that people with kidney disease can’t eat mushrooms because of the phosphorus in it? Ailing kidneys can’t filter it out of the blood hence raising the person’s potassium level causing heart issues and blood pressure issues.

  • Stephen Lonefeather

    I steam mine in a basket steamer
    and toss out the water.

  • ronroberts

    Perhaps just as nutrients are better sourced in whole foods, the negative effects of toxins are rendered more harmless in whole foods. Does reductionism apply to both? I would like to see studies that show the negative health effects of eating mushrooms rather than agaraitine, (although I do not support poisoning mice for research). Perhaps it is impossible to feed mice enough mushrooms cause problems.

  • Susie

    Gosh, I have been eating a very delicious marinated mushroom dish for many years! A bit concerned, now, or does marinating them in lemon juice/vinegar sort of cook them?