Thailand has officially stepped into the rainy season, which means it is mushroom season also. Unfortunately, every year there are reports of people dying after eating poisonous mushroom. This year is no exception.
A father and son in Tak province were found dead earlier this month even after being sent to Maesot Hospital due to excessive consumption of poisonous mushrooms. Two weeks ago, five locals in Chiang Mai's Mae Taeng district reportedly ate poisonous mushrooms. Fortunately, they were saved in time. But in Omkoi district also in Chiang Mai, a 40-year-old man was not as lucky after eating deadly mushrooms together with his son, who went into a coma.
Asst Prof Pharrunrat Tanaviyutpakdee from the Food and Nutrition Toxicology Division of Mahidol University's Institute of Nutrition warned people to never be careless when it comes to eating and picking mushrooms, especially types they are not used to. Even "mushroom experts" can be confused and mistaken when distinguishing between edible and lethal mushrooms.
"To be honest, there is no rule of thumb in terms of how to determine which mushroom is safe or unsafe to eat," Pharrunrat commented. "But roughly speaking, there are simple ways to assume whether or not they are poisonous by looking at their outer appearance. First, if the colours are very vibrant, avoid them. They are mostly poisonous. Second, if they are of odd shapes or the mushroom caps flake or look abnormally fluffy, do not eat them."
One mushroom that is most problematic in Thailand is death cap (Amanita phalloides or hed ra-ngok hin in Thai) which can mostly be found in the north and northeastern regions. Death cap is likely to kill and poison more Thais every year than any other mushroom species, explained Pharrunrat, because many find it difficult to differentiate this deadly mushroom with another edible type called Amanita vaginata, known in Thai as hed ra-ngok, which look very much alike.
To determine what's what, the food toxicology expert suggested we see if the mushroom has a ring on its stem. Amanita vaginata -- the safe type -- is a grey to greyish brown species with no ring on its stem. On the other hand, death cap has a skirt-like membrane or a ring on its stem. Death cap also has a cup-like structure (called volva) at its base. Sometimes mushroom pickers also fail to single out the edible hed ra-ngok from the deadly ones.
Oyster mushrooms (Pleurotus ostreatus).
"Sometimes they can appear very similar," she added. "Sometimes the dangerous hed ra-ngok hin is picked when it's still a button and its stem cannot therefore be seen. Or sometimes it blooms for so many days that its skirt or ring already falls. So when locals see there is no ring on its stem, they pick it and think it's safe to eat."
Mushrooms that grow in the forest pose higher health risks than those in man-made growing facilities, added Pharrunrat. This is because the latter is taken care of in a properly controlled environment and the mushroom species there can be quite specific based on what farmers want to grow. Forest mushrooms, conversely, are out in the open which might result in a mix of mushroom strains.
Mushroom poisoning or toxicology is the medical term that describes harmful effects which are consequences of the consumption of toxic mushrooms. According to the food toxicologist, symptoms can actually vary according to each individual and depend on so many factors including the quantity of mushrooms ingested, the preparation of mushroom (raw or cooked), source of mushroom (picked from forest or bought from supermarket) and so forth. The severity of mushroom poisoning can range from mild to even life-threatening.
"Certain types of mushrooms can trigger mild allergic reactions such as nausea, vomiting and stomachache. Some species might cause more serious symptoms especially on the nerve system like dizziness, hallucination, seizure and death," she explained.
What's worth noting is symptoms caused by the consumption of death cap are not necessarily acute -- the onset can be six to even 24 hours after eating. On average, symptoms caused by toxins from hed ra-ngok hin will develop around 10 hours after consumption. If consumed in a large amount, toxic substances will be absorbed by the liver and kidneys, leading to cell damage. The body will then not be able to rid poisons. There have been cases of people who died eight days after eating the deadly mushroom. So the first thing to do if a person happens to eat poisonous mushrooms is to try to make them throw up as much as possible. This is to remove the mushrooms from the stomach to reduce toxin absorption. Then send them to the nearest hospital immediately.
"It is also important to understand that some certain types of toxins in mushrooms, especially Amatoxins, are resistant to high temperature," Pharrunrat said. "This means even if you cook them through, they are still poisonous."
For safety reasons, it is highly recommended that consumers buy mushrooms from trustworthy sources and only opt for mushrooms they are familiar with.
"Pre-packaged mushrooms available in supermarkets might or might not go through pest control protocols but I would say that if you buy such products, chances of coming across poisonous species are zero," she stressed. "But if you are to buy forest mushrooms, you must be super super careful."
Also do not buy mushrooms in bulk. Some mushroom species such as hed kone (termite) and hed tub tao (bolete) are rich in proteins. But when stored for a long time, protein compounds might restructure, resulting in allergic reactions like rashes after consumption.
"Like other diets, mushrooms must also be consumed in moderation," Pharrunrat concluded. "Of course, they are high in fibre and can be a good substitute for vegetables. They also contain glutamic acid which enhances the taste of food. Some of them also have medicinal effects such as shiitake and lingzhi. But what to beware is that mushrooms are hard to digest. So do not eat them raw. And always eat them in a moderate proportion."
To know what’s what
Toxic mushrooms
- Grown in forest
- Stem is usually long and fat with skirt-like membrane or a ring on its stem
- Cap can be of various colours from lemon-green to orange or white to yellow
- Cap surface is usually flaky. There is usually a cup-like structure (called volva) at its base
Edible mushrooms
- Grown on grassland
- Stem is short and thin. Stem surface is smooth without flakes
- Cap is usually white an brown
- Cap surface is smooth
Information from the Toxicology Centre, the Ministry of Public Health's Department of Medical Sciences.
Barometer earthstars (Astraeus hygrometricus) or hed poh is in high demand this year. In early rainy season, the price can go up to 700 baht per kilo.
Death cap (Amanita phalloide) or hed ra-ngok hin.
