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Grifola Frondosa: Hen of the Woods

Ecology

The Grifola frondosa, or maitake mushroom is a polypore that grows in northern temperate forests, and has a long history of medicinal use. In the western hemisphere, it grows in Canada, and the northeastern and mid-Atlantic US. It is not unheard of, however, to see it in the northwestern or southeastern states.  In the eastern hemisphere, it is found in China, northeastern Japan, and Europe. This mushroom is found on dead or dying trees or stumps, usually around the base. It can also be found growing from submerged, rotting roots. It prefers oaks, though it will also grow on other deciduous hardwoods such as elm, maple, blackgum, and beech (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000). It has also been reported to grow uncommonly on Douglas fir (R. L. Gilbertson, 1986). It tends to prefer the boundary between wooded areas and open fields (Stamets, Mycelium Running, 2005). Maitakes are generally classified as saprophytes, feeding on dead wood. Though they are sometimes found on dying trees, the maitake is rarely the initial pathogen, and will consume already weakened by another organism (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000).

Morphology

            This fungus is a large, soft-fleshed polypore that goes from dark gray-brown when young to lighter gray with age. The fruiting body is a dense cluster of fan-shaped, wavy-margined caps that are 2-10 cm in diameter and extend radially from a common base. Clusters can be anywhere from several to over a hundred pounds in weight. The underside of the caps is covered in 5 mm deep, maze-like pores that extend far down the stem. There are approximately 2 to 4 pores per mm (Kuo, 2010). Hyphal growth is described as fluffy, and non-rhizomorphic, extending in uneven circles when grown on agar. When grown on sawdust or woodchips, hyphae form dense mats that exude orange or rusty fluids (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000). When suspended in liquid culture, growth is a “feather-like mycelial clump” (Bum Chun Lee, 2004). The spores are white, smooth, and elliptical. Cystidia are absent (Kuo, 2010).

History

            Though known and used by many cultures around the world, this mushroom first entered formal Western literature in 1785 under the name Boletus frondosus in James Dickson’s publication Fasciculus Plantarum Cryptogamicarum Britanniae (Harvard University, 2009) . The name was then changed to Grifola frondosa in 1821 by Dickson and fellow British mycologist Samuel Frederick Grey (Index Fungorum Partnership, 2013). The fungus was described in Gray’s textbook, A natural arrangement of British plants as being “eatable, but requir[ing] thorough dressing”, having a “much branched thallus”, and “numerous, halved, smoke grey caps” (Gray, 1821). It currently has many synonyms, including Boletus frondosus, Agaricus frondosus, and Polyporus frondosus (IMA, 2013). Because of its edibility and widely-accepted medicinal uses, the maitake mushroom has many names spanning several languages. It is known as “Laubporling” (or “Ram’s head”) in Germany, the “signorina” (or “lady”) mushroom in Italy, and both as maitake (“dancing mushroom”) and kumotake (“cloud mushroom”) in Japan. In the US it is known as hen-of-the-woods, the dancing butterfly mushroom, or as maitake (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000).

Look-alikes

            The maitake mushroom is often confused with several other species. Its lookalike Grifola umbellata can be distinguished from frondosa by its “multiple caps arising from one stem, a lighter color, and a more fragile texture.” In addition, the spores of G. umbellata are “larger and more cylindrically shaped” (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000). Another misconception is with the mushroom Laetiporus sulphureus because of its similar common name, “chicken-of-the-woods.” The similarity ends there, however, as chicken-of-the-woods is anywhere from bright orange to yellowish-white (Alan E. Bessette, 2007), compared with the light brownish-grey of the maitake.

Cultivation

            Though known by many cultures for many years, efforts have begun only recently to produce it artificially, on a large scale.  Prior to the late 1979, when the first cultivation techniques were developed, maitake mushrooms were available only in the wild (Hobbs, 1996). The first large-scale commercial production began in Japan in 1981, at a modest scale of 325 tons (F. Takama, 1981). For about 10 years, Japan held the monopoly on production, until US and China began producing. Between 1991 and 1997, worldwide production increased around 40-fold, arriving at 331,000 tons produced annually (Chang, 1997).

Medicinal Value

            Traditional medicine systems in countries such as China and Japan have long touted the health benefits of maitake.  One of the earliest mentions of this mushroom is in the Chinese medical text the Shen Nong Ben Cao Jing, from the Han Dynasty (206 BC. – 220 AD.).  Here it is said to be able to “improve the spleen, assuage stomach ailments, treat hemorrhoids, and calm the mind and nerves” (Jones, 1998).  However, modern medicine has only recently begun investigating these claims. While human studies are rare, a single survey of non-human studies showed that studies have been conducted assessing maitake as an anti-diabetic, anti-hypertensive, antineoplastic, antiviral, immunosuppressant, and interferon (Catherine Ulbricht, 2009). A study by the National Cancer Institute agrees with the National Institute of Health of Japan in saying that the powdered fruiting bodies of maitake show significant activity against the HIV virus (Stamets, Growing Gourmet and Medicinal Mushrooms, 2000).

            A study was conducted assessing maitake as a weight-loss aid where mice were either fed a high-cholesterol diet or the same diet supplemented with maitake. After 12 days, the mice given maitake had cholesterol levels 43% lower than those fed the control. By day 24, body weight and body fat were significantly lower as well (K. Kubo, 1996).

            Much of the attention on maitakes is focused on a polysaccharide D-fraction that contains the glucan grifolan (Ohno, 1984). This acid-insoluble, alkali-soluble, hot-water extractable fraction (Konno, 2001) was found to have extreme anti-cancer activity in countless studies. The first was a study where the D-fraction was administered to cancerous mice, and caused complete tumor regression in more than one-third of the trials (Ohno, 1984).  A similar study found that a water extract of maitake inhibited the reproduction of leukemia cells grown in culture (Lovy, 1999). It appears that maitakes have a potential two-fold effect of causing direct apoptosis to cancer cells as well as stimulating the immune system of the host (Konno, 2001). Today, vitamin and supplement companies provide these compounds in the form of “maitake D-fraction” capsules or extracts.

            Another claim often made about maitakes are their ability to reduce blood pressure. A study was conducted where rats were fed either a control diet or one supplemented with 5% maitake powder. The blood pressure of the rats eating the maitakes, after 63 days, was significantly lower than that of the control (Yearul Kabir, 1987).

            Regardless of medical benefits, maitake is widely accepted as a nutritious food. One analysis of 100 grams of dried maitakes contains 377 calories, 26 grams of protein, 19 grams of sugar, and 29 grams of fiber. It is also high in vitamin D, potassium, and niacin (Stamets, Mycelium Running, 2005).

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