Posted on 03/17/2013 7:22:25 PM PDT by neverdem
Can you tell the difference between a tasty paddy straw mushroom and a toxic death cap? Emma Shiells talks to the experts about the potentially deadly chemistry hidden in those gills
Death cap mushrooms are, as the name suggests, deadly © Science Photo Library
On a damp and drizzly autumnal morning you may think there are better places to be than foraging in the undergrowth of an orchard, but amateur mushroom hunters are sure to disagree with you. Martin Newcombe, an ecologist and fungi enthusiast, is one of those hooked.
‘The fact that fungi can grow so quickly makes them fascinating,’ says Newcombe; ‘they typically grow in two to three days depending on the environmental parameters.’ For some species like the stinkhorn ‘they can take just a matter of hours,’ he says. The fungal kingdom consists of a wide range of organisms that differ in their size, shape and colour, and in their means of reproduction and spore distribution. You could hold up two mushrooms that are identical to the naked eye, but on closer inspection find that they are two different species entirely – one edible, the other poisonous. It is only when you take a closer look at the spores using a microscope that you can identify the species accurately. ‘The spores are uniquely coloured, patterned and sculpted for each species, where some of them also undergo specific chemical reactions as well,’ explains Newcombe. ‘In the field there is often a limit to what you can do in terms of identification, as sometimes you can only recognise the genus until further tests can be carried out back in the lab. Only once you’ve looked at the spores in more detail and carried out some chemical tests, can you truly identify the species and determine its edibility,’ he adds.
No one really knows what mushroom colours are for, as they are not necessarily warnings. Contrary to popular belief, not all poisonous toadstools are bright red with white spots or warn you by their lurid yellow and green colours. Often poisonous mushrooms look like the edible varieties you might buy in a shop and therein lies the danger for the inexperienced forager.
‘Death cap is still the commonest cause of [mushroom] poisoning in Europe’ says Newcombe. A notorious fungus, it is part of the Amanita genus that contains around 600 species, some of which are the most highly toxic in the world. It is believed that this genus alone is responsible for approximately 95% of all mushroom poisonings, with 75% of fatal fungal poisonings attributed to death caps (Amanita phalloides) and the related destroying angel (A. virosa).1
The destroying angel is, you guessed it, also deadly © Science Photo Library
The toxicity of the Amanita species is due to the presence of two groups of toxins known as amatoxins and phallotoxins, both multicyclic peptides. It is believed that the death cap contains six related phallotoxins and five or more amatoxins.2 Geoffrey Kibby, a research associate at the Royal Botanic Gardens at Kew in the UK says that death cap ‘smells like gone-off, sickly sweet honey and they apparently taste really good. But you only need one cap to kill an adult; they are pretty nasty things to eat.’
After someone has eaten the deadly mushrooms, ‘there’s usually a delay between six to 30 hours from ingestion before the symptoms start to present themselves,’ explains Kibby. ‘Typically the person will experience food poisoning-type symptoms: severe abdominal pain, sickness and diarrhea, briefly followed by a day or so of apparent recovery,’ he says. ‘However, the patient will then relapse and deteriorate quite rapidly due to severe renal and liver failure’ often leading to death.
The less-harmful phallotoxins are responsible for the initial gastrointestinal symptoms, but it is the amatoxins that cause the most damage internally. In particular, α-amanitin has a high specificity for RNA polymerase II in the liver. By inhibiting this enzyme it prevents the formation of mRNA and stops protein synthesis, resulting in cell death and subsequent liver failure. When filtered through the kidneys, the toxin can then be reabsorbed into the bloodstream and re-circulated around the body, causing repeated liver and kidney damage.3
The amatoxin alpha-amanitin is responsible for death caps' deadliness
The death rate has certainly decreased over the years, thanks to the advances in treatments, according to Kibby. ‘In the US, they have more cases than we do [in the UK], so they’ve had more opportunity to try different treatments. Standard treatments usually involve large doses of penicillin and vitamin C, as well as keeping the liver and kidneys going,’ he says. Blood can be filtered using carbon-column haemodialysis units or attempting organ transplants in severe cases. ‘The latest chemical they are trialing is called Silibilin, which seems to have very effective results,’ says Kibby. Research shows that the drug works by preventing the uptake of the amatoxins by the liver cells and thereby protecting undamaged liver tissue. It also stimulates DNA-dependent RNA polymerases, resulting in an increase in RNA synthesis.4
But treatment is not always successful and it very much depends on how quickly people are diagnosed after ingestion. Victims who are hospitalised and given treatment almost immediately after ingestion have a mortality rate of around 10%, whereas those admitted 60 hours or more after ingestion have a 50–90% mortality rate.5 In spite of years of detailed research into its toxins, death cap is still the most deadly fungus known, and there’s still no known antidote for humans.
Almost all poisoning cases that Kibby has been involved in have been due to misidentification, where immigrants have picked what they thought they recognised from their native country, or based on knowledge passed down from older generations. Recently, Australian news channels reported a case where four people in Canberra accidently poisoned themselves after consuming death cap at a New Year’s Eve party. Two of them later died. They were of Asian descent, and it is believed that they may have mistaken the death caps for edible paddy straw mushrooms (Volvariella volvacea) – a common ingredient used in Asian cuisines.
Paddy straw mushrooms are edible... © Geoffrey Kibby
Brett Summerell, a fungi expert from the Royal Botanic Gardens in Sydney, Australia, told ABC News shortly after the deaths that ‘mushrooms that are poisonous in Australia have very close relatives to those that are quite safe to eat and have a very similar appearance to the straw mushroom.’ Newcombe agrees: ‘They’ve come from a culture where mushrooms like that are eaten and so probably thought they recognized them, rather than identified them.’
Since these deaths, the Australian government and the Australian National Botanical Gardens have released a factsheet on death caps.6 It provides detailed descriptions and photographs, as well as possible locations in southern Australia and what symptoms to expect. They emphasise the importance of not confusing death caps with the edible straw mushrooms that are grown and eaten in Asia. Even though the straw mushrooms are not native to Australia, a related species V. speciosa is and looks very similar to straw mushrooms. They have even been found to grow side-by-side with the death caps in some areas of Australia. Each species in the Volvariella genus has a volva at the base of the steam and gills that do not reach the stem – just like the death cap. As the guidebook3 says, ‘great care should be taken in identification to avoid confusion with the deadly white-spored Amanitas’.
...but they closely resemble V. speciosa (right), which can grow next to death caps (left) © Heino Lepp/Australian National Botanical Gardens
‘The greenish form of death cap does look like the paddy straw mushroom,’ says Kibby. ‘Even the bulbous bag at the base of the stem can be present on the paddy straw mushroom so that wouldn’t have alerted them initially.’ The only way to tell them apart is by looking at their spores, according to Kibby: ‘The paddy straw mushrooms have pink spores whereas the death cap have white spores.’ There are also chemical tests that can be carried out: adding sulfuric acid to the mushroom’s stem or gills will turn black if it is a death cap. The Meixner test uses concentrated hydrochloric acid and newspaper to determine the presence of the deadly toxin α-amanitin.7
As an experienced mycologist, Kibby is often called upon to help with mushroom poisonings via the National Poisons Information Service (NPIS), which is a clinical toxicology service available for healthcare professionals in the UK. In 2011, the NPIS saw 257 poisoning cases linked to eating mushrooms in the UK, but without any deaths in over four years. That was until last year, when Kibby’s expertise was urgently needed as a married couple were hospitalised after eating mushrooms suspected to be death caps. ‘They [NPIS] got the son to go down to the bottom of the garden and photograph the mushrooms for me, they also packaged some up and sent them to me in London that same afternoon,’ explains Kibby. ‘As soon as I opened the package I could smell that gone-off honey smell that is so typical for A. phalloides [death cap].’
Sadly the woman died from multiple organ failure, but her husband survived having only consumed a very small amount of the fungi. ‘She was doubly unlucky, as it was the end of the year so they shouldn’t have been there in the first place, and they were albino in colour; the least typical colour form [for death caps],’ says Kibby. ‘Apparently, she had identified them as edible mushrooms using a field guide,’ he adds.
Unfortunately, even non-poisonous fungi can be pretty bad for you, because they are very good at recycling. They are non-photosynthetic organisms, gaining energy and nutrients for their biosynthetic pathways through the degradation of other plants and matter, which means they can easily absorb trace elements from their local environment.
Fungi collected near former smelters, landfill sites and land treated with sewage sludge can accumulate significant quantities of metal ions, such as cadmium, mercury, lead, copper and chromium. Even worse, high levels of radioactive caesium-137 isotope have been found in mushrooms. ‘It was only a few years ago that the British government stopped monitoring toadstools generally from the fallout at Chernobyl,’ says Newcombe. Kibby believes that there are still some areas of far eastern Scandinavia where picking mushrooms is not advisable, due to the radiation found in them.
Newcombe once harvested mushrooms growing near a disused factory that was an old iron smelter. ‘You could taste the iron in them,’ he says. ‘I sent samples off to be tested and, sure enough, there was more iron in them than there should have been.’ And mushrooms that grow near roadside edges can absorb lead from passing vehicles. The mushrooms themselves might be edible, but once they have absorbed metals from their surrounding environment they can become poisonous due to the high concentration of heavy metals found inside them.
In the UK, collecting mushrooms is more of an occasional pastime, whereas in other cultures people pick them for everyday consumption. In mainland Europe, pharmacists can be asked to help identify them. ‘Problems arise when people try to identify edible mushrooms using only a guidebook. If you want to eat wild mushrooms, you’ve got to go on organized forays with someone that knows what they are doing,’ says Kibby. ‘No matter how good the field guide is, it can’t possibly cover all colour variations and eventualities. It seems silly to risk your life when you can go to your local deli and buy exotic mushrooms there,’ he says.
Kibby says that, contrary to what you might expect, most poisonings happen not from picking really weird-looking mushroom, but from the most normal looking ones, such as paddy straw mushrooms. ‘If only people would stick to really weird and wonderful mushrooms like some Boletus,’ he says. ‘Then you can’t go wrong as you can’t mistake them for anything else.’
Caesar's mushroom is an edible Amanita variety © Francesco Carta/Alamy
Not all mushrooms from the Amanita genus are bad for your health; some of its species are edible, like the glorious Amanita caesarea with its orange cap and yellow stem and gills. Known in English as Caesar’s mushroom, it has been prized since Roman times and is not easily confused with other Amanita species, thanks to its vibrant colouring. It has yet to be found in the UK, but grows in warmer climates like southern Europe and North Africa. It was said to be a favorite of the Roman emperor Claudius and has been found growing along old Roman roads. Many ancient historians believe that Claudius died from mushroom poisoning, murdered by his own wife Agrippina in 54 AD. It has been widely speculated that death caps were used as the poison, but it is now considered to be unlikely given the short timeframe reported between him getting sick and dying.8
Kibby has tried some edible Amanitas, ‘but even then my heart was in my mouth,’ he adds. He has eaten A. rubescens, which although edible after cooking, are poisonous if eaten raw. ‘It did taste delicious although I couldn’t help but watch for symptoms over the next few hours,’ he says.
1 J R Hanson, The chemistry of fungi, RSC Publishing, Cambridge, 2008
2 G Kibby, Guide to mushrooms of Britain and Europe, Octopus Publishing, 2006
3 R Phillip, Mushrooms and other fungi of Great Britain and Europe, Pan, London, 1981
4 K Hruby, G. Csomos, M Fuhrmann and H Thaler, Human Toxicology 1983, 2, 183 (DOI: 10.1177/096032718300200203)
5 The Bad Bug Book, US Food and Drug Administration, 2nd edn, 2012, p200 http://1.usa.gov/XO6DF6
6 Australian National Botanical Gardens http://bit.ly/10gSeRl
7 M Beuhler, DC Lee and R Gerkin, Ann. Emerg. Med., 2004, 44, 114 (DOI: 10.1016/j.annemergmed.2004.03.017)
8 V J Marmion and T E J Wiedemann, J. R. Soc. Med., 2002, 95, 260 (DOI: 10.1258/jrsm.95.5.260)
It can be a decent area, but so much depends on the weather, which can be screwy! Last spring was terrible . Last winter, the fallen leaves didn’t get enough moisture to compress. So in the Spring, there was a very think fallen leaf bed. Nothing poked through! Couldn’t find ‘em!
The thing is a fungus, it’s decaying plant matter. Why eat a food that is in effect a natural poison?
“Hills Angles’’ GRRROWL!! The BBC did a number on the guy. Political correctness run amok basically just tossed him off the air. Broke his heart.
I don't know how much chance you want to take with something that irreversibly destroys the liver and kidneys.
All boletes stain blue if you bruise them. I have never heard of any poisonous boletes either.
Morels are not a poisonous mushroom........Sorry I didn't clarify that.
Boletus Satanas (AKA - "The Devil's Bolete") is one of the most common poisonous mushrooms in my part of Europe.
Morels contain small amounts of hydrazine toxins that are removed by thorough cooking; morel mushrooms should never be eaten raw.
It has been reported that even cooked morels can sometimes cause mild intoxication symptoms when consumed with alcohol.
When eating this mushroom for the first time it is wise to consume a small amount to minimize any allergic reaction. Morels for consumption must be clean and free of decay.
Morels growing in old apple orchards that had been treated with the insecticide lead arsenate may accumulate levels of toxic lead and arsenic that are unhealthy for human consumption.
Boletus Satanas (AKA - "The Devil's Bolete") don't always look so scary, they can even look very much like the much sought after Cep.
Read about it on wikipedia:http://en.wikipedia.org/wiki/Boletus_satanas
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Red-mouth Bolete (Boletus subvelutipes)
Looks like there isn't much danger of The Devil's Bolete being eaten.
Yeast in considered a fungus.
And you brush your teeth with algae and consume the same every time you eat jello.
I hear that it is eaten in parts of Italy and the Czech Republic - but never fried as that does not kill the toxins.
I remembered reading about a mycologist living in rural France seeing people eat all kinds of poisonous mushrooms and he was stunned. It turned out that the local practice involved boiling all mushrooms twice and twice draining off teh water prior to cooking.
I also just found out my girlfriend has a mushroom allergy - she was never able to put a finger on her occasional stomach aches until one day when she had shitake mushrooms and had a bad reaction - we then realized what it was.
Shitake mushrooms can give some people a severe reaction akin to food poisoning.
Read up on the French doctor I mentioned above. I read the story in another language and it was fascinating - he ate the deadliest mushrooms THREE TIMES to demonstrate his cure and cured himself.
As soon as the poisoning effects are noticed 1200mg of Nifuroksazyd and 1500mg of Dihydrostreptomycin should be administered orally and daily application of 3 grams of vitamin C intravenously. If the vomiting is frequent and not weakening during the therapy then Metoclopramid should be administered intravenously. All drugs have to be administered during the 3 day period in the same quantities and during that period only carrot soup should be eaten. This method was first published in 1970. and didn't get a green light. On 1971. Dr. Bastien ate a 10 gram mushroom and administered only half of the aforementioned dose without the C vitamin. He got hepatitis. He cured 82 people with the full dosage from 1971 to 1974. In 1974 he repeated the experiment on himself, but this time with 60 grams of fresh mushrooms and a full dosage of the aforementioned drugs and only sympthoms he had was diarrhea wihout vomiting or hepatitis. With that experiment he drew some interest on his method and since then many people in France were successfully cured. He ate mushrooms again in 1981 without consequences. Many people were cured with this method since then. I thought that it would be good to have such information on the boards. Not that anyone would need it, but just in case ;)
Also... check out this link:
OLD ARTICLE IN ENGLISH ABOUT THE BASTIEN TREATMENT
I eat the Parasol Mushroom.
Yuck! I can't imagine a mushroom being worth eating after turning it to mush. Unless you're making soup with it. I love King Boletes, Aspen Scabers and Puffball mushrooms and almost always saute them in butter with a little black pepper and salt.
...- he ate the deadliest mushrooms THREE TIMES to demonstrate his cure and cured himself.
Considering the danger that just sounds nutty to me. I'm not sure his treatment is considered the state of the art either. France has pioneered the use of Milk Thistle extracts combined with antibiotics and dialysis for the treatment of Death Cap and Destroying Angel poisoning. Milk Thistle has amazing properties of liver protection and toxin removal from liver hepatocytes.
The Death Cap Amanita phalloides
Info on toxicity and treatment down the page.
I stick to the ones I know, but there is one risky one that I MUST eat each September.
It is far too good to pass up.
The Saffron Milk Cap.
I cannot resist them.
I have Destroying Angels in my yard almost every year. I also had three excellent specimens of Aspen Scabers in the yard last summer. First time ever. Also some recurring Puffball Mushrooms.
Yeah but can you die of eating yeast?
Where ever that soil is I get a nice crop of Suillus bovinus. Easy to recognize and edible, I don't eat them as the best ones grow next to the road and who knows what's under my yard! WWII was fought in this neighborhood.
I have puffballs every year in the same place. Once found a giant edible bolete in the backyard and I get a ton of crap mushrooms.
About two or three years ago I injected spores in my yard to see what would happen, but thus far there seem to be no results.
Puffball spores are supposed to be a blood coagulant so I was saving it. Last year I decided to 'seed' my yard with it and spread those spores and the broken pieces of the shell all around. We'll see if they take this year.
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