WARNING: Do not eat portobello, cremini, or button mushrooms without cooking them at high temperatures!

in health •  last year

First off, did you know that those 3 names are all the exact same kind of mushroom? All 3 of these (the most common mushrooms to be found in any grocery store in the western world), are actually just Agaricus bisporus, the only difference being their age. Buttons are the youngest, and portobellos are the oldest.

I was watching a recent Joe Rogan Experience recently (# with Paul Stamets), and towards the end, Paul mentioned something about portobellos being not that good to eat, the completely refused to explain why, stating that it would put his life at risk. After talking about his visits from black helicopters, and hassles with the patent office and FDA, you know he's already on quite a few folks' radar. I paused the episode at that point, talked to @dbroze about it a bit, then dove into the research, coming up with a few important safety facts for Agaricus bisporus mushrooms.

It's important to note that Agaricus b. is the most widely commercially produced mushroom on the market, with India exporting over 15,000 tonnes per year (mostly to the US)... Needless to say there are some vested interested who may not want anything questionable said about them.


(Image Source)

Make sure you cook your mushrooms!

These mushrooms contain agaritine & hydrazine, both of which have been found to be cancer-causing, but are luckily both heat-unstable. As Paul says in the video, you should cook all your mushrooms, but especially these ones. If you are boiling these mushrooms, be sure to toss out the water afterwards, as some of the agaritine will be extracted into it.

Cooking Types & Reduction of Agaritine:


  • 20-25% degraded after 5 minutes
  • 90% degraded after 2 hours

Dry Baking

  • ~25% degraded


  • 35-70% degraded

Never buy mushrooms from China

Studies have shown mushrooms (as well as rice) from China coming back with levels of arsenic, lead, mercury, and cadmium. Sometimes over the maximum amounts legally allowed, and for me personally and traceable amounts are too much. These mushrooms will often also be treated with sodium sulfite as an "anti-browning agent", which has been known to cause respiratory side effects.

The older mushrooms are better

The concentration of hydrazine in button mushrooms decreases with the age of the mushroom, meaning a portobello will have less in it than a cremini, and a cremini will have less than a button. No matter which you're going for, make sure to cook it. Maybe mention something to the people running that salad bar with raw mushrooms in it?

Only eat organic mushrooms

If you hadn't noticed, mushrooms are quite porous, they're almost like little sponges. While this makes them AMAZING to cook with, just soaking up flavors, it also makes them extremely good at absorbing whatever has been sprayed on them or around them. This means any of those wonderfully toxic Monsatan products they're getting sprayed with, are likely making it right to your dinner plate.

The JRE episode that spurred this

From Growing Gourmet and Medicinal Mushrooms by Paul Stamets

"This mushroom contains compounds that inhibit the enzyme aromatase. Aromatase is associated with tumor growth. Compounds inhibiting aromatase have potential for the treatment of breast cancer(Bankhead, 1999). A diet of mushrooms in mice with implanted tumors showed a decrease in aromatase as mushroom consumption increased. However, Agaricus brunnescens contains hydrazines, carcinogenic compounds that have been thought to dissipate only from prolonged, high temperature heating. More than 80 percent of known hydrazines are carcinogenic. The most notable carcinogenic hydrazine from this mushroom is agaritine, a powerful mutagen, which is activated by the mushroom enzyme tyrosinase, making it heat stable. Enzymes in the digestive system convert agaritine into carcinogenic by-products. The chemical culprits worthy of concern are: 4-(hydroxymethyl)phenylhydrazines and 4(hydroxymethyl)benzene diazonium ions(Walton et al. 1997). Free radicals can also activate Agaricus hydrazines into highly carcinogenic subconstituents (tomasi et al 1987) as well as catalytic processes in the kidneys (Price et al. 1996). Hence, there are several modes of activating agaritine into highly carcinogenic derivatives.

The damaging effects of agaritine's derivatives may be partially suppressed by the mushroom's antioxidants, which, in turn help create host-generated superoxide dismutases (SODs), and the activity of aromatase inhibitors. Walton et al. 1998 asserted, however, that the mutagenic and pre-mutagenic compounds are not affected by quick cooking(10 minutes at 437F/225C) but are only slightly reduced by prolonged heat treatment in boiling water for 4 hours at 212F/100C). A study of blanched, canned mushrooms showed that the agaritine content was reduced tenfold in comparison to fresh mushrooms, from 229mg/kg to 15-18mg/kg(Andersson et al. 1999). However, this reduction may have been due to leaching of the hydrazines into the surrounding water used for blanching in combination with prolonged, high pressure steaming processing used for canning. Another report by Sharman et al. 1990, found most fresh samples of this mushroom had agaritine levels within the range of 80-225mg/kg but with one dried sample having 6,520 mg/kg, a comparatively high level. This result suggests that agaritine production may be a strain specific trait, as this one dried, sliced sample had more than 8 times the agaritine content of other samples in this same study. In contrast, dried Shiitake mushrooms, Lentinula edodes, have either undetectable or extremely low levels of agaritines, in the 0.082 mg/kg range (Stijve et al. 1986; Hashida et al. 1990). Hashida's study reported marked reduction of agaritines from boiling water at 212F(100C) for 10 minutes, a report in direct contradiction of Walton's 1998 study.

A Swiss report estimated that with the average consumption of 4 grams per day of Agaricus bisporus(=Agaricus brunnescens) the lifetime increase in cancer risk would be approximately two cases per hundred thousand lives(Shepard et al. 1995). In a metropolitan area of twenty million residents, approximately the size of Los Angeles, two hundred people would be expected to get cancer in their lifetime from eating Agaricus brunnescens mushrooms, all other factors being equal.

However, other investigations have questioned the cause and effect relationship of agaritine in Button mushrooms and its mutagenic properties(Pilegaard et al. 1997; Matsumoto eet al. 1991; Papaparaskeva et al. 1991; and Pool-Kobel 1990). Benjamin 1995 noted that early studies are controversial and potentially flawed. One study had the intravenous introduction of mushrooms into mice. Another study showed that mice implanted with cancer cells (Sarcoma 180) and then fed dried mushrooms showed inhibited tumor growth(Mori et al. 1986). More recent studies reconfirm that a diet of this mushroom, both raw and baked, induced tumors in mice(Toth et al. 1998)

The cited research is highly controversial and raises concerns about the human consumption of Agaricus brunnescens as a health food. For years, the conventional wisdom was that hydrazines would be destroyed with cooking. Anti-cancer polysaccharides, aromatase-inhibiting compounds, and antioxidants known from Agaricus brunnescens(Kweon 1998), may neutralize the carcinogenic effects of hydrazines, but in my opinion, the jury is still out on this issue. Eating this mushroom raw, especially with free radical inducing foods, is definitely not recommended. And yet, in the United States, up to 80 percent of all Button mushrooms consumed are eaten uncooked. I am disturbed that the most commonly cultivated mushroom in the world has few studies authenticating its beneficial medicinal properties, in stark contrast to the numerous studies on Shiitake, Maitake, Reishi, Yun Zhi, and others. The Portobello mushroom may be gourmet, but in absence of scientific studies, I doubt that, at this time, Agaricus brunnescens can be considered medicinally beneficial.

What to do? The financial future of the Button/Portobello industry may well depend on recognizing the risks, and aggressively developing low agaritine or agaritine-free strains. As analyses have shown more than an eight-fold difference in the concentrations of agaritine in Agaricus brunnescens mushrooms, clearly some strains already in cultivation are much lower in agaritine content than others. Pursuing low agaritine strains should be top research priority within the Agaricus industry, especially within the venue of the spawn producers. Given variations in agaritine levels in existing strains, a breeding program for creating agaritine free strains is a task preeminently achievable in the near future. Certainly the button mushroom industry has clear economic and ethical incentives for doing so."

Research Links: 1, 2, 3, 4, 5, 6, 7

If you enjoyed this post, please up-vote & re-steem it, and follow me to make sure you catch all my travels, vegan recipes, philosophy, and videos!



I'm always open to and grateful for any & all gifts and support from the universe, and it all goes towards my many projects to make the world a more peaceful, loving, free, and well-fed place :-)


Authors get paid when people like you upvote their post.
If you enjoyed what you read here, create your account today and start earning FREE STEEM!
Sort Order:  

I love mushrooms but I am always suspicious of them. The last several times I had portobellos I felt there was a weird taste. I now eat oyster mushrooms as a vegan meaty substitute because I'm here in Mexico and they are reasonably priced but they look so beautiful, it makes me slightly uncomfortable.

Great post thanks.

So what mushrooms should you eat?
I know someone who's brother owns a mushroom farm and he doesn't eat mushroom... Maybe because they're grown in poo.


The best mushrooms to eat are lion's mane, maitake, and shiitake, with chaga & reishi being great for making teas. There are plenty of others that are healthy as well like oyster, lobster, morel, chantrel, etc.

Most mushrooms are not grown on waste, only a few are actually.

That was an interesting post. I had no idea button and portobello mushrooms were the same. It's also good to know that they're not safe to eat raw, because I much prefer them cooked!


Yep, exact same fungus :-) Sometimes our personal tastes already know what we need to do/not do to protect ourselves it seems like.

A very useful article. Thank you so much for sharing this information. I have been eating raw mushrooms, but I will not eat raw mushrooms any longer, and will definitely try to get the organic ones when I do buy mushrooms. I was not aware at all of the tumor risks of certain mushrooms, and appreciate the cooking recommendations provided in the article.


You're very welcome!


Great post! Thanks for sharing.

I love mushrooms; but, after this post will take a few minutes to sauté them in a little butter, or as my favorite…roast them until they take on the flavor of bacon.

Again, many thanks.


This post has received a 7.39 % upvote from @buildawhale thanks to: @dbroze. Send at least 1 SBD to @buildawhale with a post link in the memo field for a portion of the next vote.

To support our daily curation initiative, please vote on my owner, @themarkymark, as a Steem Witness

wonderful article ,i like it so much

Wonderful post brother, I was wondering if you were going to ever put it up ;-P



Thanks brother! It definitely got lost in the tornado a bit, but I did it haha.


The @OriginalWorks BETA V2 bot has upvoted(0.5%) and checked this post!
Some similarity seems to be present here:
This is an early BETA version. If you cited this source, then ignore this message! Reply if you feel this is an error.


That source is cited, and what I pulled from there is also all shown as a quote in the post itself.

This post has received a 16.51 % upvote from @upmyvote thanks to: @dbroze. Send at least 1 SBD to @upmyvote with a post link in the memo field to promote a post! Sorry, we can't upvote comments.

That's interesting, When I am cooking with mushrooms I always have a nibble of raw mushroom, not sure I will do now


It's all about quantity, and most of what I read said that tiny amounts will not really have an effect.


Phew That's good, I only have a little, still think I will give them a miss now :)

I heard this podcast too and was wondering the same. Thanks for checking!
Those mushrooms suck anyways. If you're reading this and don't like mushrooms it's probably 'cause your eating portobellos or criminis. Never understood why they include the white ones at salad bars. Especially since they are raw and bad for you. Morels, chanterelle, lions mane: worth checking out.

Great article , I will be sharing this on my social media for more people to read.


Thanks! It's always so wonderful when someone discovers an old post, especially since Steemit is such a new-or-forget-it place.

Love the new info, I had wondered about the history of these store bought shrooms. Totally agree - only buy organic as they absorb absolutely everything which is why they are so amazing and nutrient dense. I love picking wild morels and matsutake. These little power-houses are mineral dense and really add satiation factor to any green leafy meal!
Thanks for the info about the common grocery forages.

OMG ty for sharing this.

love 'shrooms, but raw are gross :P