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Toxic and Hallucinogenic Fungi

The query 'Can this be eaten?' is often heard when wild macrofungi are found. Early gatherers became familiar with macrofungi worth collecting for nourishment and which were harmful, by trial and error. Thus was generated the folklore that still surrounds fungi.

While the true nature of fungal reproduction was resolved by the middle of the 19thcentury, much of the folklore still gives fungi a sinister reputation. This reputation is partly deserved, since some species are so poisonous that the ingestion of even a small quantity can be fatal. While many wild mushroom species are safely edible (and leathery), edibility of many species is uncertain.

Not all cases of illness after consuming fungi can be attributed to poisoning. Differences in allergic response or sensitivity, different methods of preparation for cooking, the amounts of the fungi ingested, whether old or fresh, are some of the factors, which may influence the individual response.

The confusion caused by these many factors is best avoided, at least initially, by the mycophagist adopting a conservative approach. Obviously the safest means to avoid mycetismus (mushroom poisoning) is to be able to identify macrofungi in a careful and systematic way to the specific level. Then ask the question 'Is this species toxic?'.

While there is some agreement in regard to the general toxicity of many macrofungal species in the literature some authors assign a different emphasis. To clarify the uncertainty surrounding which species of macrofungi are reputedly toxic and their relative category of toxicity, some of the available literature was surveyed.

The books used for the survey were:

  1. Guide to Mushrooms, (1981), G. Pacioni, Edited G. H. Lincoff, Simon & Schuster Inc., New York. Includes the details of the 'edibility' of 420 species of macrofungi, reflecting mainly European opinion and some comments on Nth. American species.
  2. Common Australian Fungi, (1986), A.M.Young, New South Wales University Press, Sydney. Includes the details of the 'taste' (edibility) of 150 species of macrofungi.
  3. The Encyclopedia of Mushrooms (1979), Edited C.Dickinson & J. Lucas, Orbis Publishing Limited, London. Includes the details of the 'Culinary properties' (edibility) of 512 species of macrofungi reflecting mainly European opinion.
  4. Mushrooms and Toadstools of Australia (1988), C. J. Shepherd and C. J. Totterdell, Inkata Press Proprietary Limited, Sydney. Includes the details of the edibility of 228 species of macrofungi.

The fungi classified as toxic in the above literature were grouped, for the purposes of the survey, into three categories: -

D = Deadly (lethal cases have been reported)

P = Poisonous (usually non-lethal, symptoms severe)

C = Caution required (may cause unpleasant reaction, special preparations necessary, do not eat with alcohol, do not eat raw...etc.)

Publication
(number of species)
Deadly
(%)
Poisonous Caution
Guide to Mushrooms
(420)
6 (1.4%) 32 (7.6%) 17 (4%)
Encyclopaedia
(512)
8 (1.6%) 37 (7.2%) 30 (5.9%)
Common Australian Mushrooms
(150)
1 (0.7%) 13 (8.7%) 13 (8.7%)
Mushrooms and Toadstools
(228)
1 (0.4%) 27 (11.8%) 20 (8.8%)

Fortunately many of the organic compounds responsible for the toxicity of fungi have been isolated and identified, and for some we understand their mode of action. Many others need further work to better understand their effects.

Largely depending upon the type of toxin involved or symptoms displayed, there are four basic categories of fungal poisoning.

  1. Those that destroy cells with cellular poisons; such as amatin and phalloidin found in Amanita phalloides, muscarine in A. muscaria, Clitocybe dealbata, C. phyllophila and most species of Inocybe, amatin in Galerina spp., monomethylhydrazine in Gyromitra esculenta, orrellanine in Cortinarius orrellanus, C. gentiles and C. speciosissimus.
  2. Those that affect the central nervous system, in humans the brain and spinal cord, with nerve, or psychotropic or hallucinogenic poisons; such as the ibotenic acid-muscimol complex found in Amanita muscaria and psilocybin and psilocin in Psilocybe spp. and some species of Gymnopilusand Panaeolus.
  3. Those that affect the autonomic nervous system, the nerves and ganglia, not under voluntary control which enervate the heart, glands, visceral organs and smooth muscle; with toxins such as, muscarine found in A. muscaria, Clitocybe dealbata, C. phyllophila, and Inocybe spp. and coprine in Coprinus spp.
  4. Those that affect the gastrointestinal tract. Arguably most fungal poisonings are in this category typically causing stomach upsets.

These effects may be attributed to the presence of irritating substances, which in some instances may be degraded to harmless compounds by heating.

The confusion surrounding the toxicity of macrofungi may be due to regional variations. Amanita muscaria, a cosmopolitan fungi, commonly found in large numbers in pine plantations, which contains the intoxicants ibotenic acid and muscimol, and a small quantity of the toxin muscarine, has in North America some colour variations. Yellow is common in the northern states, becoming more salmon-like in the southern states while in the west the colour is more typically red. The significance of the colour variation has not been determined. However, it is well established for plants that many species that are widespread and occupy a variety of habitats may be composed of several genetically distinct subspecies. That is, environmental gradients are usually accompanied by genetic gradients in the species of inhabitating organisms. It may be that the same clinal argument could account for some of the reported confusion concerning the toxicity of apparently the same species of macrofungi.

Nevertheless, other factors contribute to the confusion related to macrofungal toxicity. The ingestion of large quantities of A. muscaria may be fatal suggesting that high doses of the toxin muscarine may for some sensitive people, be lethal. Noteworthy, A.muscaria when dried allows the unstable ibotenic acid, to convert to muscimol, thereby increasing the concentration of this highly active hallucinogen, which may be a factor in some reported fatalities.

Some authors suggest that A. pantherina is not deadly; rather it contains a greater quantity of the intoxicants ibotenic acid and muscimol than does A.muscaria. Cortinarius gentiles, C. orellanus and C. speciosissmus, Claviceps purpurea, Gyromitra esculenta and Hygrocybe conica are also considered deadly, although the report relating fatalities to H. conica is considered doubtful.

C. purpurea is the cause of ergot of rye. While not a macrofungi and not gathered as food, the sclerotia of the fungus contain powerful alkaloids (ergotamine, ergometrin, ergonovine and lysergic acid amongst others) that have in the past caused many human deaths after eating contaminated rye products.

Gyromitra esculenta, commonly called the 'False Morel' contains the poison monomethylhydrazine (MMH: sometimes called Hellvelic acid or Gyrometrin). MMH is used in the aerospace industry where exposed workers suffer the same symptoms as people who have eaten the fungus.

Yet all is not doom and gloom. While there appears to be a large number of wild fungi that are harmful if eaten, it has been suggested that of the known species of macrofungi perhaps 10% are harmful with about 3-5% considered lethal. In addition many people having an Anglo-Saxon and Celtic heritage regard anything other than the commercial mushroom with suspicion. Other people, whose origin is one where wild macrofungi are gathered, are at a greater risk of poisoning if they eat unfamiliar wild Australian mushrooms.

On a cautionary note, Milk Caps (Lactarius spp.) must be identified to specific level as some species are poisonous. Morel (Morchella esculenta) should not be eaten raw as stomach upset is likely, the fungi needs to be parboiled before cooking. Honey Fungus (Armillaria mellea) should be parboiled, the water discarded, before eating. It has a bitter taste, which may upset some people. (Some suggest that A. mellea does not exist in Australia, rather it is A. leuteobubalina, which is a common cause of disease in eucalypts.) Puffballs (Lycoperdon spp.) should only be eaten when the inside is white and the fungi are young and fresh. Mature and old specimens have been reported to be bitter and there are some reports of narcotic and hallucinogenic affects. Finally, Coprinus comatus while edible before autodigestion begins should not be consumed with alcohol, although it is reported to be less toxic than C. atramentarius.

So, even sometimes the best advice needs to be examined in depth, lest we face the perils of mycetismus.

This page was prepared by the Sydney Fungal Studies Group.

LINK to table of toxins and their associate symptoms.

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