Educational information, not medical advice — ask your doctor or midwife.
Auricularia heimuer is an edible mushroom, sold dried as black wood ear or black fungus. It grows on dead hardwood and is a staple of Chinese cooking. People eat it as food, and it was also used as a folk medicine.
The real hazard with wood ear is not the mushroom. It is the soaking. Dried wood ear left in water for many hours, especially in a warm room, can grow a bacterium that makes bongkrekic acid.
That poison has caused deaths in China, and one near-fatal case in the United States in 2020. Cooking does not destroy it. Soaked mushroom that has sat out for hours should be thrown away, not rinsed and used.
As a food it is cheap, high in fibre and generally safe. As a medicine, the honest verdict is that human evidence is thin. Long use in Chinese kitchens and medicine texts is not proof that it treats any disease.
No one has shown clearly how it acts in the body. Almost all the work is in test tubes and animals.
The mushroom is rich in soluble fibre and polysaccharides (long sugar chains). In animals, these appear to bind fats in the gut and lower blood cholesterol. Soluble fibre does slow digestion in people, which is well accepted for fibre in general.
In animal studies, wood ear extracts have lowered blood sugar and blood fats. These results have not been repeated in good human trials.
The clotting effect has the most human backing. A 1980 report described less platelet clumping (blood cells sticking together) in a person who ate large amounts of the fungus. Adenosine-like compounds in the mushroom are the suspected cause.
In laboratory tests, extracts also mop up free radicals and stir immune cells. Whether any of that matters in a person who eats a bowl of wood ear salad is not established.
Most people meet it as food. The usual forms are:
- Dried whole ears or shredded strips, sold in Asian grocers. This is the most common form by far. - Fresh wood ear, sold in some markets and used quickly.
- Powder made from the dried mushroom, added to drinks or soups. - Capsules and tablets of mushroom powder or polysaccharide extract. - Liquid extracts, often sold in blends with other mushrooms.
Food-grade dried mushroom has a long track record. Concentrated extracts do not, and their strength is rarely stated in a way you can compare.
Wood ear has been recorded in Chinese food and medicine for well over a thousand years. Classical materia medica texts listed it among the useful fungi.
Writers described it as cooling and moistening. It was given for dry cough, bleeding piles and bowel complaints, and was thought to benefit the blood and circulation.
It also spread through Korean, Japanese and Southeast Asian cooking, mostly as a food rather than a remedy.
The name Auricularia heimuer is recent. Chinese cultivated wood ear was long filed under Auricularia auricula-judae, the European species.
Researchers separated it as its own species in 2014. Older studies may therefore sit under the old name.
Get emergency care straight away if, within a day of eating rehydrated wood ear, you have repeated vomiting, severe stomach pain, drowsiness, confusion, or yellow eyes or skin. These can be signs of bongkrekic acid poisoning, which can be fatal. Tell the medical team what you ate.
Call emergency services if you get swelling of the lips, face or throat, or trouble breathing after eating it.
Stop and see your doctor if you notice unusual bruising, nosebleeds, bleeding gums, or blood in your stool or urine.
See your doctor before using supplements if you take a blood thinner, diabetes medicine, or are due for surgery.
In the UK, EU, US, China and Australia it is an ordinary food, sold freely in grocers. Capsules and extracts are sold as food supplements. No medicines regulator has approved it to treat or prevent any disease.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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