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The Dangers of Gyromitra esculenta

or, What’s good for the goose, isn’t necessarily good for the gander.

By Jim Dunham

        Gyromitra esculenta, also called the beefsteak, or brain, mushroom contains ethylidene gyromitrin.  Ethylidene gyromitrin may be converted to N-methyl-N-formylhydrazine (MFH) after the mushroom is eaten.  MFH may then be converted to the toxic monomethylhydrazine (MMH) or into a much safer metabolic form, called 1-acetyl-2-methy-2-formylhydrazine (Ac-MFH).       What’s important to note is that certain people’s systems convert MFH into Ac-MFH fairly rapidly.  These are the geese.       What about the ganders?  Well, they convert MFH into Ac-MFH much more slowly.  This means that their systems end up with a much larger amount of much more of the highly toxic MMH.  Now the gander wishes that he hadn’t come to the picnic after all.      It’s also important to note that if there are young geese and ganders at the picnic, then they are in greater danger than the oldsters.  Because their body weight is less than the adults, if they eat the same number of mushrooms then the percentage of toxins in their systems is much higher.  This is true regardless of their ability to convert MFH into Ac-MFH.      Because this example is greatly over-simplified, interested readers are referred to A Morel Hunter’s Companion, by Nancy Weber, pages 64-69.

Spores Afield - May 2000


More on Gyromitra

by Marilyn Shaw,
Toxicology chairperson

     The accompanying discussion of the development of various toxins associated with Gyromitra esculenta is interesting, but it should not effect your decision to on whether or not to eat any gyromitra.  Dr. Weber prefaces this discussion with, “With this background, we can TRY (emphasis mine) to explain some of the apparent peculiarities of poisoning by the beefsteak morel.”  She ends the paragraph with, “There is no convenient way to tell whether one is “fast” or “slow” acetylator and thus no way to judge tolerances for toxins in the beefsteak morel.”  It should be understood that, just because one has eaten these mushrooms without ill effect in the past does not settle the question one way or the other.  It is well known that people can eat them for years, then, for no apparent reason, get sick and even die.  The mortality rate among those who become ill is about 14%.

     Dr Weber goes on to state, “We cannot in good conscience, however, recommend eating any species of Gyromitra until more detailed information on fruiting body composition is available.  McIlvaine and Macadam (1902) were perhaps ahead of their time when they wrote of the beefsteak morel: “It is not probable that in our great food-giving country anyone will be narrowed to G. esculenta for a meal.  Until such an emergency arrives, the species would be better left alone.”  Their advice could well be extended to cover the entire genus.”  Considering that Charles McIlvaine, the professor of the quintessential “cast iron stomach”, was reported to have personally tested (by eating) something well over 700 species, it would seem wise to follow his advice.

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