Grifola frondosa is a polypore mushroom that grows in clusters at the base of trees, particularly oaks. The mushroom is commonly known among English speakers as hen-of-the-woods, ram's head and sheep's head. In the United States' supplement market, as well as in Asian grocery stores, the mushroom is known by its Japanese name maitake (舞茸), which means "dancing mushroom". Throughout Italian American communities in the northeastern United States, it is commonly known as the signorina mushroom. G. frondosa should not be confused with Laetiporus sulphureus, another edible bracket fungus that is commonly called chicken of the woods or "sulphur shelf". The fungus becomes inedible like all polypores when they are older, because it is too tough to eat.
The fungus is native to the northeastern part of Japan and North America, and is prized in traditional Chinese and Japanese herbology as a medicinal mushroom, an aid to balance out altered body systems to a normal level. Due to the taste and texture of the mushroom, it is widely eaten in Japan, although the mushroom has been alleged to cause allergic reactions in rare cases.
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Like the sulphur shelf mushroom, G. frondosa is a perennial fungus that often grows in the same place for a number of years in succession. It occurs most prolifically in the northeastern regions of the United States, but has been found as far west as Idaho.
G. frondosa grows from an underground tuber-like structure known as a sclerotium, about the size of a potato. The fruiting body, occurring as large as 100 cm, is a cluster consisting of multiple grayish-brown caps which are often curled or spoon-shaped, with wavy margins and 2–7 cm broad. The undersurface of each cap bears approximately one to three pores per millimeter, with the tubes rarely deeper than 3 mm. The milky-white stipe (stalk) has a branchy structure and becomes tough as the mushroom matures.
In Japan, the Maitake can grow to more than 50 pounds (20 kilograms), earning this giant mushroom the title "King of Mushrooms". Maitake is one of the major culinary mushrooms used in Japan, the others being shiitake, shimeji and enoki. They are used in a wide variety of dishes, often being a key ingredient in nabemono or cooked in foil with butter.
Use in traditional Eastern medicine 
The sclerotia from which hen of the woods arises have been used in traditional Chinese and Japanese medicine to enhance the immune system. Researchers have also indicated that whole maitake has the ability to regulate blood pressure, glucose, insulin, and both serum and liver lipids, such as cholesterol, triglycerides, and phospholipids, and may also be useful for weight loss.
Maitake is rich in minerals (such as potassium, calcium, and magnesium), various vitamins (B2, D2 and niacin), fibers and amino acids. One active constituent in Maitake for enhancing the immune activity was identified in the late 1980s as a protein-bound beta-glucan compound.
Maitake research 
In 2009, a phase I/II human trial, conducted by Memorial Sloan–Kettering Cancer Center, showed Maitake could stimulate the immune systems of breast cancer patients. Small experiments with human cancer patients, have shown Maitake can stimulate immune system cells, like NK cells. In vitro research has also shown Maitake can stimulate immune system cells. An in vivo experiment showed that Maitake could stimulate both the innate immune system and adaptive immune system.
In vitro research has shown Maitake can induce apoptosis in cancer cell lines (human prostatic cancer cells, Hep 3B cells, SGC-7901 cells, murine skin carcinoma cells) as well as inhibit the growth of various types of cancer cells (canine cancer cells, bladder cancer cells). Small studies with human cancer patients, revealed a portion of the Maitake mushroom, known as the "Maitake D-fraction", possess anti-cancer activity. In vitro research demonstrated the mushroom has potential anti-metastatic properties. In 1997, the U.S. Food and Drug Administration (FDA) approved an Investigational New Drug Application for a portion of the mushroom.
Research has shown Maitake has a hypoglycemic effect, and may be beneficial for the management of diabetes. The reason Maitake lowers blood sugar is due to the fact the mushroom naturally contains an alpha glucosidase inhibitor.
Maitake contains antioxidants and may partially inhibit the enzyme cyclooxygenase. An experiment showed that an extract of Maitake inhibited angiogenesis via inhibition of the vascular endothelial growth factor (VEGF).
Maitake gallery 
See also 
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