- Oyster Mushroom
- Oyster Shelf
- Tree Oyster
The oyster mushroom (scientific name Pleurotus ostreatus), also known simply as pleurotus, is one of the most common edible mushroom varieties. Oyster mushroom was initially cultivated as food in Germany during the First World War, as an emergency measure. It later become popular all around the world and it is cultivated today in many countries. The king oyster mushroom, another cultivated variety, is a close relative.
The name of the mushroom comes from the distinctive shape of the cap, which spans broadly, resembling an oyster. Oyster mushroom grows on dead hardwood trees, in temperate and sub-temperate forests. Besides their value as food, they can also be used for industrial purposes in mycoremediation tasks. Pleurotus ostreatus is cultivated all around the world, especially in Europe, India, South East Asia and Africa.
Due to the presence of gills underneath the cap, oyster mushrooms were initially included in the Agarius family by Joseph Freiherr von Jacquin in the 18th century. They were moved to the Pleurotus family by German mycologist Paul Kummar in 1871. During the First World War, oyster mushrooms were cultivated for the first time in Germany as food. The antibiotic effects of the species were also discovered at that time.
This species can easily be cultivated on decaying wood or straw but it is also one of the most popular mushrooms for harvesting from the wild. Its taste is said to resemble the one of bitter almonds, a bittersweet flavour of benzaldehyde.
Not only has the common name of the mushrooms come from the specific shape of the fruiting body, but the Latin one as well. Pleurotus is a Latin word meaning “sideways”, due to the stem that is located on the side of the cap. Both the common English name oyster and the Latin ostreatus are connected to the shape of the cap, which looks like the mollusk with that name. Since the aroma is also similar to an oyster, the name is even better suited.
Due to the specific shape, other varieties of Pleurotus are also named oyster mushrooms. In order to avoid confusions with its relatives, Pleurotus ostreatus is sometimes named the grey oyster mushroom or the tree oyster mushroom.
The broad cap of this species has a diameter between 5 and 25 cm and looks like an oyster or a fan. It can have a wide range of colors in the wild, which can be white, gray, brown or tan. Young specimens have edges that roll inwards, later they can develop waves or lobes, with a smooth surface. The firm flesh has a white color and the stipe pattern influences its thickness. Gills go down on the stalk and have mild colors, such as white or cream. The stipe is not always present but it usually attached to the wood surface, at an angle from the cap. It tends to be very short and quite thick. The spore print is best visible on a dark background and can be white or lilac-grey.
A type of natural compounds known as statins is found in generous amounts in oyster mushrooms. These activate some receptors in the liver that make it eliminate LDL (bad) cholesterol from the body, reducing its overall level.
The connection between consuming oyster mushrooms and a reduction in the level of dangerous cholesterol has been validated by scientific studies. This is due to the statins in their compositions but it is not yet known what quantity of mushrooms must be eaten to trigger this effect.
Oyster mushrooms are also rich in polysaccharides and modern research has found that these bioactive compounds might be effective against cancer. Their chemical structure consists of small sugar molecules combined into a complex carbohydrate.
Of all polysaccharides, the beta-D-glucans are thought to be the most effective. These boost the reaction of the immune system and stimulate it to fight tumours. Pleuran is the name of the beta-D-glucan that was found in oyster mushrooms.
Diabetes is one of the most serious diseases of the modern world, caused by a lack of insulin in the body. In order to produce insulin, we need a good supply of calcium. Oyster mushrooms are rich in both calcium and vitamin D, which is normally produced inside the body and rarely found in food sources. Vitamin D boosts insulin sensitivity, reduces general inflammation and reduces the risk of both type 1 and type 2 diabetes.
Vitamin D plays other roles in the body as well; it increases the replication factor of healthy cells, fights common cold or flu and prevents autoimmune conditions. It stops the strong inflammatory responses that are the trigger of many serious diseases of either a chronic or an autoimmune nature, such as multiple sclerosis, irritable bowel syndrome, rheumatoid arthritis, digestive problems and high blood pressure.
Oyster mushrooms supply vitamin B3, which prevents the dangerous hardening of arteries, or atherosclerosis, which can cause lethal heart diseases. It also provides a reduction on the levels of cholesterol and triglycerides. Other benefits of this vitamin are better circulation, reduced inflammation and a lower histamine production. People who have experienced a cardiac arrest or another serious heart condition can greatly benefit from an increase intake of vitamin B3.
Niacinamide is a form of vitamin B3 that can be applied externally on the skin in order to heal the small infections known as acne. It can treat redness, irritation, flare ups and skin inflammation. Granuloma annulare and bullous pemphigoid are some more serious skin diseases that form skin blisters, leading to infections and pain. They can both be treated with vitamin B3.
Oyster mushroom is rich in copper, an essential mineral that plays several key roles. It is needed for the maintenance of galactose, dopamine and other brain pathways that have a direct impact on our energy, ability to focus and overall mood. Without enough copper, we can’t concentrate properly and we have a low metabolic activity that causes fatigue. Superoxide dismutase, vitamin C, tyrosinase, ascorbate oxidase and other antioxidants need copper in order to function properly. They can neutralize the dangerous free radicals that are the trigger of aging, cancer or neuro-degenerative diseases.
Anemia is a condition that starts when not enough oxygen reaches the cells. There can be several causes: the body doesn’t produce enough red blood cells, there is not enough oxygen in the blood or blood is lost in some way. Vitamin B2 is essential against anemia because it is needed for the production of both red blood cells and steroid hormones. It plays a vital role in the metabolism of iron and the transport of oxygen. Anemia and sickle cell anemia are usually associated with low amounts of vitamin B2. This critical compound also decreases the amount of homocysteine in the blood.
Another key role of B vitamins is the conversion of sugars and carbohydrates into glucose, which can be burned by cells to generate energy. They are also involved in the metabolism of fats, proteins and other nutrients. Of all the B complex, vitamin B5 is the most important in balancing the metabolism and speeds up the healing of tissues, organs and muscles.
Healthy teeth need a constant supply of minerals calcium and phosphorous, as well as vitamin D. They improve the mineral density of tooth enamel and of the jaw, which actually supports the teeth. This is why kids who are developing their teeth need diets rich in phosphorous and calcium. Vitamin D acts as a balance between calcium and phosphorous and boosts the absorption of both minerals. It can also prevent periodontal gum disease by reducing overall gum inflammation. Including oyster mushrooms to your diet will help with these issues.
A good supply of iron is required for a balanced mood, which is influenced by a number of neurotransmitter functions. Mood is also affected by the level of serotonin, dopamine and other hormones. As a result, a lack of iron leads to bad mood, insomnia, low energy and a general lack of motivation.
The Wernicke-Korsakoff syndrome is a serious brain disease that damages nerve structure, causing lethargy, muscular problems and even the inability to move. Increased amounts of vitamin B1 can prevent this condition, which is usually reported by alcoholics or people who have a low level of thiamine (vitamin B1) due to improper diets. As a result, thiamine can relieve some of the effects of alcohol withdrawal.
Chinese cuisine makes heavy use of oyster mushrooms, which are found in many recipes. However, they are popular all over the world due to the high content of nutrients. A very simple but delicious recipe is to prepare a sauté with olive oil and garlic. They are a great choice for a healthy diet due to the high content of vitamins or nutrients and the low amount of calories, sodium, fat, cholesterol and gluten. Oyster mushrooms are some of the best vegetal sources of iron.
Oyster mushrooms can be consumed raw but this is not recommended, since it is estimated that one in then people has minor allergic reactions after consuming them. They should be cooked instead; you can discard the stem and the tougher parts and just use the tender pieces. Oyster mushrooms are best added as the final ingredients, since they cook quite fast. They have a meaty texture that is excellent for stir-frying, regular frying or braising.
Oyster mushroom pairs very well with white meat or seafood and can even replace real oysters in some dishes. In wild mushroom pastas or risottos they can be mixed with chanterelle or shiitake mushrooms.
Oyster mushrooms have a short shelf life and should be consumed as fast as possible. In order to preserve their texture and flavour for as long as possible, wash them only immediately before cooking. It is possible to preserve them by freezing or as a sauté with oil or butter. They dry up fast and can be used in dried form in most recipes.
Oyster mushrooms are considered a delicacy in Asian cuisine, especially in China, Japan or Korea. They are sometimes consumed as such, or as an ingredient in stuffed dishes, stir-fried mixes with soy sauce or other recipes. It is also possible to use them to prepare a sauce similar to the real oyster sauce, which is a key ingredient in Asian cuisine. Oyster mushrooms have a mild taste that has been compared with the one of anise. They taste better when young, since elder mushrooms develop an acrid taste and the texture becomes too tough.
Vitamin D is normally produced inside the body and only rarely found in plant foods. Oyster mushrooms are an exception and a cup supplies about 4% of the daily required dose of this essential vitamin. The cap is the richest in nutrients and young specimens are healthier than old ones. Oyster mushroom is one of the best sources of ergothioneine, a strong antioxidant compound typical to mushrooms that can reduce overall body inflammation. This compound was found to prevent the build-up of plaque in the arteries, which reduces the risk of cardiovascular disease, according to the results of recent studies. Oyster mushrooms supply generous amounts of fiber, potassium, folate, protein and vitamin B6.
Side effects and cautions
Oyster mushrooms include a small dose of a sugar alcohol named arabitol, which can cause digestive issues to some sensitive people.