Maitake (Grifola frondosa) is found mainly in temperate mountainous regions of Japan, North America, and Europe. The fruiting body of this mushroom is one of the largest of any mushroom, approaching the size of a basketball. Maitake fruiting bodies grow with a distinctive overlapping pattern, which has been described as looking like dancing butterflies. Maitake is prized for its culinary benefits; its medicinal effects have only recently been emphasized although some of them have been known for many years. The mushroom was used medicinally as a general tonic to promote wellness and vitality, and is now considered to be an adaptogenic medicine. Historically, maitake was also used for lowering high blood pressure and treating cancer; these uses are two foci of current research. This mushroom has been a staple in Asian diets for thousands of years. Once difficult to cultivate, maitake is now grown relatively easily in Japan, increasing the mushroom's availability as a medicine.
Maitake can benefit circulation in a number of ways, one of which is to prevent cardiovascular conditions caused by elevated blood lipids. Maitake changes the metabolism of lipids in the body by inhibiting their accumulation in the liver and in the serum. The exact mechanisms of these actions are not yet fully known.20 Other actions of maitake include its ability to lower blood glucose, thereby decreasing the insulin burden on the micro- and macrovasculature. Mounting evidence shows a correlation between elevated insulin levels and cardiovascular morbidity.21 Maitake is thought to lower blood glucose levels by activating insulin receptors.22,23 Another effect of this mushroom on vascular health may be an ability to lower blood pressure. Two preliminary studies demonstrated that maitake lowered blood pressure in laboratory animals significantly.24,25
Other significant health effects of maitake include its immune-enhancing properties. One of the active ingredients of the fungus is beta-glucan. Found in several plants, beta-glucan is a polysaccharide molecule that can support the body's defenses against tumors. Maitake's beta-glucan content may be responsible for its immunostimulatory actions, including regulation of interleukin-1, NK cells, cytotoxic T-cells, and superoxide anions.26 Several preliminary studies on the effects of maitake on certain cancers were performed in the mid-1990s.27-29 However, no follow-up studies have yet been done. Promising studies on beta-glucan as an immune stimulant suggest that maitake is a viable choice for treating conditions that involve impaired immunity. Other immunostimulatory principles of this fungus should be examined in future research.
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