Morchella Punctipes, Courtesy T. Lockwood
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Morchella punctipes, courtesy T. Lockwood. 16 FUNGI Volume 14:2 Spring 2021 North American Mushroom Poisonings and Adverse Reactions to Mushrooms 2018–2020 Michael W. Beug Toxicology Chair, North American Mycological Association n his article “World Mushroom reported involve consumption of raw contain heat-labile carcinogens. However, Production: An Overview” (FUNGI or only lightly cooked mushrooms. some toxins, like amanitins, are not 14[1]: 8–13) Dr. Britt Bunyard The culprit is lentinan, a chemical that decomposed on heating and so species Ireported that there has been a 30-fold receives broad use in cancer therapy in containing amanitins (notably Amanita increase in commercial mushroom Japan and some other Asian nations. species in the Section Phalloideae, like production since 1978. World per capita However, about 4% of all people have Amanita phalloides and the Amanita mushroom consumption has grown to an adverse reaction to lentinan, which bisporigera group remain toxic even after 4.7 kg/year from 1 kg/year in 1997. Over in susceptible individuals, can cause cooking). half of all mushrooms consumed are rupture of the microcapillary blood Mushrooms may also be contaminated cultivated edibles, 38% are medicinals, vessels. The result is a very painful rash by bacteria which would be killed on and 8% are wild harvested. that can last for a week or more. The cooking. I was curious about how these changes rash is known as “shiitake flagellate Pleurotus species (oyster and king might be reflected in mushroom- dermatitis.” Lentinan is destroyed by oyster mushrooms) are the second most poisoning data. I had not summarized heating, so cooking the mushrooms widely cultivated edible mushrooms, the poisonings reported to NAMA prevents the painful rash. A very tiny occupying 19% of the cultivated sales since 2017 and it was time for me to percentage of people have an adverse market. While most people tolerate update the mushroom poisoning case reaction even to well-cooked shiitake, cooked oyster mushrooms, consumption registry. The full update, “Summary of typically suffering diarrhea, vomiting, of raw and undercooked oyster the Poisoning Reports in the NAMA intestinal cramps, and nausea. There mushrooms is a very significant cause Mushroom Poisoning Case Registry: are no mushrooms, indeed no foods of of gastrointestinal upset, sometimes 2018 through 2020” was published in any kind, that do not cause problems for leading to hallucinations. On rare McIlvainea vol. 30 (2021) and is available some sensitive individuals. Shiitake is occasions, someone will have a bad free online at www.namyco.org. In this possibly the most widely tolerated of all reaction even to well-cooked oyster note, I highlight findings from the full foods—if it is well cooked. mushrooms if they drink alcohol with report. Tables I and II are reproduced Thorough cooking is important for all their meal. However, most people from McIlvainea vol. 30. edible fungi. The exception is truffles. can eat oyster mushrooms and drink It is noteworthy that the NAMA data The cell walls of fungi are chitin, which alcohol with no problem. One woman is a result of voluntary reporting and is very indigestible, but is made more who consumed several raw stipes of only captures a small fraction of the digestible on cooking. Though I have not cultivated blue oyster mushrooms adverse events in any one year. Most seen it reported recently, consumption suffered chills, flushing, diarrhea, adverse reactions (to any mushroom) go of raw and undercooked mushrooms intestinal cramps, sweating, muscle unreported to NAMA. can lead to a bezoar, a serious blockage spasms, vomiting, drowsiness, weakness, Globally, Lentinula edodes (shiitake) of the stomach or intestines due to headache, and blotchy skin on her face. is the dominant cultivated mushroom the formation of a bolus of undigested I no longer eat any oyster mushrooms at 22% of world cultivated mushroom material. Several edible mushrooms, because 1) there are many other species production. Prior to 10 years ago, I had most notably morels (indeed, all that I like far better and 2) I have seen never seen a reported adverse reaction species of edible ascomycetes, except too high a percentage of bad experiences to shiitake in North America. Now culinary truffles), are poisonous raw, with Pleurotus species. adverse reactions to shiitake are one of containing unknown compounds that Auricularia species (wood ears, also the 10 most common events reported are decomposed upon heating. Other called black fungus), a flavorless jelly to NAMA. Most of the adverse cases species, including Agaricus species, mushroom with great texture, are third Spring 2021 FUNGI Volume 14:2 17 Flammulina velutipes, courtesy N. Craig. in annual production. I had expected poisonings reported to NAMA over or winter mushroom), at 11%, ranks them to also be prominent in the toxicity the past three years (8 cases). This is fifth in global production. I have no category, but have not had a single counting both “edible” and “poisonous” recent reports of adverse reactions report of a bad reaction for several years species! The problem is typically from the mushroom itself, which is now. They are very popular in Chinese gastrointestinal upset accompanied by prized both for its healthy properties cuisine and are used medicinally for flu-like symptoms. In some cases, there is (low cholesterol, etc.) and for a range purported antitumor, hypoglycemic, a clear allergic reaction accompanied by of purported medicinal benefits. anticoagulant, and cholesterol-lowering rash. A good way to tempt fate is to help However, contamination by Listeria properties. The anticoagulant properties yourself to some of the raw sliced button monocytogenes, found growing on are very real and lead to a poisoning mushrooms typically found in salad imported enoki mushrooms, led to 31 known as Chinese restaurant syndrome. bars. Pass on them and do the restaurant people hospitalized plus four deaths The blood-thinning properties can owner a favor and tell them not to serve in 17 states in June of 2020. When lead to excess bruising and horrendous raw or only lightly cooked mushrooms. purchasing cultivated mushrooms, I only menstrual periods. Unwary diners on From the wild, I place Agaricus species buy American. While problems with blood thinners are in danger of too much in one of two camps. The prized almond imported mushrooms are not common, blood thinning and excess bleeding. or anise-smelling species (all edible for I see such reports often enough to be Agaricus species, mainly Agaricus most people) and the ones that smell wary of imported mushrooms, even bisporus (the common button a bit like wet asphalt (poisonous for dried mushrooms. Cultivation practices mushroom, also known as baby bellas, most people). I have never tried one in North America mean that mushrooms crimini, and portobellos) occupy of the foul-smelling species, but even from North America are far less likely to fourth place in global production. Until the choice almond-smelling species be contaminated. this most recent three-year period, like Agaricus augustus will give me I have also seen a recent surge in Agaricus bisporus rarely showed up in gastrointestinal distress. One consumer reports of people becoming ill from mushroom poisoning reports. However, of a foul-smelling Agaricus species, when bags of imported dried mushrooms with the huge increase in mushroom presenting at the hospital for treatment, containing a mixture of species. If you consumption, Agaricus bisporus noted that they tasted “a bit off.” suffer gastrointestinal distress, how has climbed to number one in total Flammulina species (enoki, enokitake, are you to know which species in the 18 FUNGI Volume 14:2 Spring 2021 mixture caused your problem? When different properties than the fruitbody purchasing dried mushrooms, stick to and both can be beneficial. single species. You can mix your own Among the medicinal mushrooms, later once you have safely eaten each I see the most problems with Inonotus species separately. obliquus (chaga). Chaga forms a black Cultivation of medicinal mushrooms canker typically on birch trees in accounts for about 38% of global northern latitudes. I have case reports production. I regularly consume a few of people harvesting a black growth on species of “medicinal mushrooms.” conifers and a different black growth My number one favorite is Hericium on cherry trees that were not chaga, erinaceus (lion’s mane). Cultivated and both caused severe gastrointestinal species have a great texture and a distress. Just because something is a very nice flavor. Wild lion’s mane in polypore does not necessarily mean my area tastes like lobster. I prefer it that it is not poisonous. Even when to every other edible species. In Asia correctly identified, things do not one important use is in slowing the always go well. In one case involving progression of dementia. In vitro study unspecified preparation, an individual evidence indicates that it has powerful suffered hepatitis and renal failure from neurogenerative properties. Maybe it “chaga.” In a second case, consumption will slow my own growing dementia; of “chaga” tea led to three days of it certainly cannot hurt. It certainly is vomiting and confusion, elevated liver delicious. Another powerful, but little enzymes, elevated serum creatinine, and appreciated, medicinal mushroom is coagulopathy. In a third case a person Boletus edulis. The stipes are loaded with drank “chaga” tea for two weeks and beta glucans, which many people believe then his trunk and legs turned purple. are very good for you. I eat as many king Another kept a container of “chaga” tea, boletes as I can find. Just don’t mess drinking from it regularly, winding up up and consume an East Coast look- hospitalized after the tea turned moldy. alike, Boletus huronensis. It can cause Among other polypores, I have four nasty and long-lasting gastrointestinal recent reports of gastrointestinal distress distress.