Maitake (Grifola frondosa) is the Japanese name for an edible fungus with a large fruiting body characterized by overlapping caps. It is a premier culinary as well as medicinal mushroom.
Maitake is increasingly being recognized as a potent source of polysaccharide compounds with dramatic health-promoting potential. The most recent development is the MD-fraction, a proprietary maitake extract its Japanese inventors consider to be a notable advance upon the preceding D-fraction. The D-fraction, the MD-fraction, and other extracts, often in combination with whole maitake powder, have shown particular promise as immunomodulating agents, and as an adjunct to cancer and HIV therapy. They may also provide some benefit in the treatment of hyperlipidemia, hypertension, and hepatitis.
The scientific name Grifola frondosa is derived from the griffin, the beast from Greek mythology with the head and wings of an eagle and the body of a lion, and frondosa, meaning leaflike. In Japanese, mai means dance and take means mushroom, thus “dancing mushroom.” Maitake often occurs as a heavy mass (clumps may weigh many pounds) at the base of stumps and on the roots of oaks, elms, persimmons, and other trees. Like many other fungi, maitake’s optimal growing conditions exist within a limited range for temperature, moisture, humidity, and other environmental factors. While relatively rare in the wild in Japan, maitake is not an uncommon forest mushroom in the United States and Canada, where it is known as hen of the woods (because the shape and color of its clusters bear a likeness to the tail feathers of a hen)  and sheep’s head. The most important constituents of Maitake are certain polysaccharides, known as beta-glucans, which are bound to proteins. PSK, Lentinan, and Shizophyllan are all forms of beta-glucan.
Maitake’s prominent immuneboosting effects are thought to be due predominantly to these polysaccharides. Polysaccharides such as beta-glucans found in a number of medicinal mushrooms are increasingly being recognized for their non-specific immunomodulatory effects. These so-called biological response modifiers can be potent antiviral and antitumor agents, not by killing viruses or cancer cells directly but by stimulating the body’s innate ability to marshal cellular defenses.
The Immunopotentiating Maitake Fractions
In the early 1980s Japanese mycologist Hiroaki Nanba of the Pharmaceutical University at Kobe was studying various medicinal mushrooms, especially shiitake. He gradually came to the conclusion, however, that the polysaccharides in maitake have a unique structure and were among the most powerful to be studied to date, demonstrating more pronounced antitumor activity in animal tests than other mushroom extracts. 
Maitake also demonstrated the most promise as an orally effective immunomodulator. In 1984 Nanba identified a fraction found in both the mycelia and the fruit body of maitake with the ability to stimulate macrophages. Nanba noted that various betaglucans differ and that the beta-glucans found in the maitake D-fraction have a unique and complex structure, containing both a 1,6 main chain having a greater degree of 1,3 branches, and a 1,3 main chain having 1,6 branches. The D-fraction’s high molecular weight may also be a factor in its immunomodulating effects, according to research into antitumor activity and glucose consumption by macrophages. One investigation concluded, “These results suggest that an antitumor glucan is not always a multiple enhancer of host defense mechanisms and that a large molecular weight is required to augment multiple immunological activities.” 
Numerous studies have confirmed that maitake has prominent beneficial effects on immune function. [4,5-6] It promotes the action of not only macrophages, but also a variety of other immune-related cells, such as natural killer (NK) cells and cytotoxic T-cells (Tc) that can attack tumor cells. Maitake also increases the immune-related efficiency of these cells by increasing interleukin-1, interleukin-2, and lymphokines. Maitake researchers have identified several ways maitake can counter cancer:[7-8]
- By protecting healthy cells from becoming cancerous
- By helping to prevent cancer metastasis.
- By slowing or stopping the growth of tumors.
Studies have confirmed all three of these potential benefits.
Maitake is among the most promising natural sources of immunotherapeutic products. Standardized beta-glucan extracts such as the D- and MD-fraction show particular potential as carcinostatic agents that can be used in conjunction with conventional medical treatments to treat cancer. The fraction extracts have an important ease-of-use advantage over similar anticancer mushroom derivatives, such as Lentinan and Shizophyllan, by being better absorbed when administered orally. Extracts have also been shown effective in studies on HIV, diabetes, hypertension, liver ailments, and weight control.
1. Jones K. Maitake: a potent medicinal food. Alt Comp Ther 1998;4:420-429.
2. Nanba H, Hamaguchi A, Kuroda H. The chemical structure of an antitumor polysaccharide in fruit bodies of Grifola frondosa (maitake). Chem Pharm Bull 1987;35:1162-1168.
3. Adachi Y, Ohno N, Ohsawa M, et al. Change of biological activities of (1-3)-beta-D-glucan from Grifola frondosa upon molecular weight reduction by heat treatment. Chem Pharm Bull 1990;38:477-481.
4. Borchers AT, Stern JS, Hackman RM, et al. Mushrooms, tumors, and immunity. Proc Soc Exp Biol Med 1999;221:281-293.
5. Adachi Y, Okazaki M, Ohno N, Yadomae T. Enhancement of cytokine production by macrophages stimulated with (1—>3)-beta-Dglucan, grifolan (GRN), isolated from Grifola frondosa. Biol Pharm Bull 1994;17:1554-1560.
6. Kubo K, Nanba H. Modification of cellular immune responses in experimental autoimmune hepatitis in mice by maitake (Grifola frondosa). Mycoscience 1998;39:351-360.
7. Yamada Y, Nanba H, Kuroda H. Antitumor effect of orally administered extracts from fruit body of Grifola frondosa (maitake). Chemotherapy 1990;38:790-796.
8. Suzuki I, Takeyama T, Ohno N, et al. Antitumor effect of polysaccharide grifolan NMF-5N on syngeneic tumor in mice. J Pharmacobiodyn 1987;10:72-77.