Mushrooms' Toxic Tricks: How Do They Make Poisons?

Mushrooms are the fruiting bodies of fungi that have evolved contemporaneously with plants for millions of years. They are widely distributed throughout the world, with thousands of species, but only about 100 are toxic. Mushrooms produce toxins for various reasons, one of which is to protect themselves from being eaten so they can reproduce. These toxins can have varying levels of toxicity and can lead to different symptoms, from slight gastrointestinal discomfort to organ failure and even death. While some mushrooms are poisonous, others are healthy and delicious, and it is important to obtain them from a reliable source or an expert. This article will delve into the fascinating world of mushrooms, exploring how they produce toxins and the potential dangers they pose.

Toxins as a defence mechanism

Mushrooms are the fruiting bodies of fungi that have evolved alongside plants over millions of years. They are widely distributed globally, and while many mushrooms are safe and edible, some are toxic and can cause poisoning, sometimes leading to death.

It is believed that mushrooms produce toxins as a defence mechanism to prevent themselves from being eaten, allowing them to protect their spores and reproduce. This theory is supported by the observation that insects and snails, which are known to feed on mushrooms, avoid consuming poisonous varieties. The toxins act as a deterrent, making the consumer sick enough to avoid that species in the future or even causing fatal consequences.

The toxins in mushrooms can vary, with some species containing gastrointestinal irritants that cause vomiting and diarrhoea, while others have more deadly effects, such as liver or kidney failure. The specific symptoms and severity of mushroom poisoning depend on the type of toxin ingested. For example, amatoxin, found in species like Galerina and Lepiota, can lead to liver toxicity, while orellanine, produced by members of the Cortinarius genus, is a nephrotoxic agent.

It is important to note that the colour of mushroom caps does not seem to be a reliable indicator of toxicity. While some theories suggest that poisonous mushrooms may emit an unpleasant smell that discourages consumption, it is unclear if this is a direct result of toxin production or an intentional warning signal. To avoid mushroom poisoning, it is crucial to properly identify mushrooms before consumption and be aware of similar-looking toxic species.

Additionally, while cooking or processing can render some otherwise inedible mushrooms safe, it is important to remember that many toxic mushrooms cannot be made toxin-free through these methods. Certain toxins, like amatoxins, are thermostable and resistant to heat, so cooking will not eliminate their harmful effects. Familiarising oneself with both edible and toxic mushroom species is essential for safe consumption.

The role of colour

While the colour of a mushroom may not be a reliable indicator of its toxicity, some studies suggest that poisonous mushrooms emit an unpleasant smell that discourages consumption. The role of colour in mushroom toxicity is a complex topic that involves various factors, including the evolutionary advantages of toxin production, the mechanisms of toxin transmission, and the diverse strategies employed by mushrooms for survival and propagation.

Mushrooms, the fruiting bodies of higher fungi, have evolved alongside plants for millions of years. They produce toxins for defence, protecting themselves from being eaten by predators such as rodents, slugs, and insects. This defence mechanism allows them to survive long enough to reproduce by spreading their spores. The gills, pores, or tooth-like structures on mushrooms facilitate spore production and dispersal.

The colour of a mushroom's cap has been a subject of discussion in determining its toxicity. However, studies suggest that cap colour is not a reliable warning sign to deter predators. This may be because many mushroom predators are nocturnal and have poor vision, making it challenging to distinguish between different colours accurately. As a result, relying solely on colour to determine edibility can lead to inaccurate consumption.

Additionally, the toxicity of mushrooms is not limited to a specific colour group. Poisonous mushrooms, such as Amanita (reds and whites), Galerina (yellows), and Lepiota (browns and whites), exhibit a diverse range of colours. This variation in colour among toxic species further reinforces the idea that colour is not a reliable indicator of mushroom toxicity.

While colour may not be a definitive factor in determining mushroom toxicity, it is crucial to approach wild mushrooms with caution. Misidentification of toxic mushrooms as edible species is a common reason for mushroom poisoning. To ensure safety, it is essential to familiarise oneself with the characteristics of both edible and toxic mushroom species before consuming any wild mushrooms.

Poisonous mushrooms and smell

Mushrooms are the above-ground part of a fungus. They are typically made up of a stem and a cap with gills on the underside, though some have pores or tooth-like structures. The gills, pores, and tooth-like structures produce spores, which aid in the propagation of the fungus.

Some mushrooms are poisonous, and this is thought to be a defence mechanism to prevent consumption by predators such as rodents, slugs, and insects. Poisonous mushrooms contain a variety of toxins, including amatoxin, psilocybin, muscarine, coprine, allenic norleucine, and gyromitrin. The most common consequence of mushroom poisoning is gastrointestinal upset, which can lead to vomiting, diarrhoea, and abdominal pain. More severe cases of mushroom poisoning can result in organ failure and even death.

The colour of a mushroom's cap is not an indicator of its toxicity, as poisonous mushrooms can come in various colours, including reds, yellows, browns, and whites. While some sources suggest that poisonous mushrooms emit a smell, there is no evidence that this is a reliable indicator of toxicity. However, it is important to note that the smell of a mushroom can be a helpful factor in identifying its species, especially when combined with other characteristics such as its appearance and the environment in which it is found.

It is crucial to correctly identify mushrooms before consumption, as misidentification can lead to poisoning. Unless one is an expert, it is recommended to only eat mushrooms purchased from a reputable source, such as a supermarket or greengrocer. If you suspect that you or someone else has ingested a poisonous mushroom, seek medical attention immediately, even if symptoms have not yet appeared.

Toxins and cooking

Mushrooms are the above-ground part of a fungus. They are short-lived and produce toxins as a defence mechanism to discourage consumption by predators, allowing them to protect themselves long enough to reproduce. There are many different mushroom poisons, and some are toxic enough to be fatal. Poisoning from ingestion of toxic mushrooms is not uncommon, with around 100 out of thousands of mushroom species being toxic, and poison control centres recording around 1,000 cases of mushroom poisoning per year between 2010 and 2017.

The symptoms of mushroom poisoning depend on the toxin ingested and can vary from slight gastrointestinal discomfort to organ failure and death. The onset of symptoms also varies, with some taking days to manifest. Amatoxin, for example, shows no symptoms for 6-12 hours post-ingestion, followed by a quiescent interval of 24-36 hours, during which laboratory signs of hepatotoxicity may be observed. After 48 hours, hepatic damage intensifies, leading to liver failure and possibly death within a week. Other common toxins found in mushrooms include psilocybin, muscarine, coprine, allenic norleucine, and gyromitrin.

When it comes to cooking mushrooms, it is important to note that not all toxic mushrooms can be rendered safe for consumption through cooking. Some mushroom toxins, such as amatoxins, are thermostable and are not broken down by heat. For example, α-Amanitin, the poison produced by the death cap (Amanita phalloides), is not denatured by heat. Other mushrooms, such as Devil's bolete, can lead to strong gastrointestinal symptoms even when cooked, while lurid bolete requires thorough cooking to break down its toxins. On the other hand, true morels, a type of mushroom that can cause gastrointestinal upset when eaten raw, are typically cooked before consumption.

To prevent mushroom poisoning, it is crucial to properly identify mushrooms before consumption. Mushroom gatherers should familiarize themselves with both edible and toxic mushroom species, as misidentification can have severe consequences. While some folklore rules, such as "poisonous mushrooms will turn rice red when boiled," exist to determine the safety of wild mushrooms, these misconceptions can be dangerous and even life-threatening.

How toxins affect the body

Mushrooms are the fruiting bodies of a group of higher fungi that have evolved with plants for millions of years. They are widely distributed throughout the world, with thousands of species. However, only about 100 species are toxic to humans, and only 15-20 species are potentially lethal when ingested.

The toxins in mushrooms are thought to have evolved as a defence mechanism to prevent consumption by predators such as rodents, slugs, and insects. This mechanism allows the mushrooms to protect their spores, survive, and reproduce. While some poisons may only make the consumer sick enough to avoid that mushroom species in the future, others can be fatal.

The effects of mushroom toxins on the body depend on the specific toxin ingested and the amount consumed. Amatoxin, for example, blocks the replication of DNA, leading to cell death. This can affect cells that replicate frequently, such as those in the kidneys, liver, and eventually the central nervous system. Amatoxin poisoning can cause loss of muscle contraction, liver failure, and even death if not treated quickly. Other toxins, such as coprine, cause a disulfiram-like reaction, leading to headaches, nausea, vomiting, flushing, tachycardia, and rarely, hypotension.

Some toxins, like muscarine, stimulate the muscarinic receptors of nerves and muscles, causing symptoms such as sweating, salivation, tears, blurred vision, palpitations, and respiratory failure in high doses. Gyromitrin, on the other hand, affects multiple body systems. It is converted by stomach acids into monomethylhydrazine (MMH), which is toxic to humans and affects various hepatic systems, leading to hepatocellular damage and potentially, renal failure.

The symptoms of mushroom poisoning can vary widely, from slight gastrointestinal discomfort to organ failure and death. They may range from benign symptoms such as nausea, vomiting, and diarrhoea to more severe manifestations like liver failure, kidney failure, and neurological issues. The onset of symptoms also differs depending on the toxin, with some toxins taking days to show identifiable symptoms of mushroom poisoning.

Frequently asked questions