Grifola frondosa (MaitakeMushroom)
In China and Japan, maitake mushrooms have been consumed for 3,000 years, valued for their legendary properties. Maitake's scientific name, Grifola frondosa, is derived from an Italian mushroom name referring to a mythological beast, half lion and half eagle. Years ago in Japan, the maitake had monetary value and was worth its weight in silver. In the late 1980s, Japanese scientists determined that the maitake was more potent than shiitake, suehirotake, and kawaratake mushrooms, all of which are used in traditional Asian medicine for immune function enhancement.
In the US, maitake extracts are commercially available as dietary supplements marketed to “enhance immune function” and to treat HIV and cancer. Beta 1,6-glucan, a protein bound polysaccharide, has been identified as the active constituent. Maitake extracts exhibited hypoglycemic effects in a few studies.
In other studies, maitake demonstrated antitumor effects, enhanced bone marrow colony formation, reduced doxorubicin toxicity, and inhibited tumor metastasis in vitro. In a study done in mice, an orally administered extract promoted maturation of hematopoietic cells to functionally active myeloid cells and enhanced peripheral blood leukocyte recovery following chemotoxic bone marrow injury. A novel polysaccharide, MZF, was shown to induce dendritic cell maturation and enhanced antitumor response. Maitake also enhanced interferon activity against bladder cancer cells and alleviated inflammation associated with inflammatory bowel disease.
In a small non-controlled study, tumor regression or significant improvements in symptoms were observed in half of the subjects who took Maitake extract. In a trial of postmenopausal breast cancer patients, oral administration of a maitake extract was shown to have immunomodulatory effects; and to enhance neutrophil and monocyte function in patients with myelodysplastic syndrome. More studies are underway to establish maitake’s anticancer potential.
Mechanisms of Action
Maitake is thought to exert its effects through its ability to activate various effector cells, such as macrophages, natural killer cells, and T cells, as well as interleukin-1 and superoxide anions. Studies also suggest possible hypoglycemic activity. The antidiabetic effect of alpha-glucan may be due to its effects on insulin receptors by increasing insulin sensitivity and ameliorating insulin resistance of peripheral target tissues.
Maitake extract enhanced the growth and differentiation of mouse bone marrow cells treated with doxorubicin, a chemotherapeutic agent. In addition, maitake extract may modulate antigen presentation as evidenced by protection of mice against tumor implantation following transfer of dendritic cells from tumor-bearing mice that were treated with maitake extract.
In other studies, maitake D fraction demonstrated antitumor activity by upregulating expression of a proapoptotic gene, BAK-1; and prevented breast carcinogenesis, blocked tumor invasiveness, reduced angiogenesis, and increased overall survival in a murine model. In addition, maitake polysaccharides were found to induce apoptosis GFPs induced via the mitochondrial-dependent apoptotic pathway in human breast cancer cells; the beta glucan GFPBW1 also showed antitumor effects that are thought in part due to activation of macrophages via the Dectin-1/Syk/NF-κB signaling pathway; and an orally administered maitake alpha-glucan was found to activate dendritic cells and macrophages in Peyer’s patches, resulting in induction of systemic antitumor T-cell response.
Maitake also exerted antidepressant effects in mice, involving activation of the α-Amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, which are important mediators for the treatment of depression.
Dosage
In studies doses 6 g/day whole powder or 20 mg purified extract have been used. For general immuno-support and cancer prevention, a formula containing several mushroom species (which may contain 12 to 25 mg of Maitake extract) may be reasonable.
Safety
Maitake may not be appropriate for those taking hypoglycemic medications (blood glucose lowering medications) because it can have additive effects. Maitake may interact with anticoagulants such as warfarin resulting in an elevated international normalized ratio (INR).