The intake amount for maitake varies according to the metabolic type and condition of the patient. Dried and fresh shiitake mushrooms are available at most Asian markets. Krestin is available only from the manufacturer, Kureha Chemical Industry Limited, Tokyo, Japan. The shiitake mushroom has been used in traditional Chinese medicine to strengthen immune resistance to disease. The Chinese regard shiitake mushrooms as one of the most beneficial botanical medicines.
Chinese legends refer to it as a plant that gives eternal youth and longevity.
In Japan, the dried mushroom was hung in the home or its entranceway as a talisman to ward off evil. The main research on maitake has centered on its antitumor activity and its activity with regard to cholesterol, diabetes, and hypertension. These kinds of studies were previously done on reishi and shiitake mushrooms. They claim shiitake mushrooms contain large amounts of protein, fibre, B vitamins, vitamin D and minerals such as calcium, phosphorous and iron. Lentinan, a compound made from shiitake mushrooms, has been approved in Japan for the treatment of stomach cancer.