In the wild, this light amber fungus is found on fallen hardwood trees. The caps have nearly ragged gills and an inrolled margin when young, and they are covered with a delicate white flocking. The stem may be central or off center. Indigenous to temperate Asia, they are not found in the wild in the United States but are widely cultivated. A similar species occurs wild in Costa Rica.
Medical uses: A vast amount of research into shiitake’s medicinal properties has been completed and shows that it has the ability to fight tumors and viruses and enhance the immune system. For more details, refer to the accompanying story.
Precautions: Shiitake is nonpoisonous, but researchers have observed cases of shiitake-induced skin rashes, and some people who work indoors cultivating shiitake experience “mushroom worker’s lung”, an immune reaction to shiitake spores. A watery extract of the whole mushroom is reported to hinder blood coagulation, so people who bleed easily or who are taking blood thinners should check with their health-care provider before using shiitake or its derivatives for a long period.
LEM has shown no evidence of acute toxicity in more than seventeen years of use in Japan, even in massive doses (more than 50 mg a day for one week), though mild side effects such as diarrhea and skin rashes have been reported. Likewise, lentinan has no known serious side effects. People with allergies may experience adverse reactions due to its histamine-sensitizing properties.
Taking shiitake: The traditional dose is 1 or 2 fresh shiitake mushrooms daily for preventive care or 6 to 16 g of dried shiitake in tea, soup, or other dishes. Commercial preparations (extracts in capsule form) of shiitake are available in the United States in health-food stores but may be expensive. Dried shiitake mushrooms are available in Asian food stores in the United States, usually at more affordable prices. To avert possible digestive upset from eating large quantities of fresh shiitake, LEM, which is concentrated and easily absorbed, is preferred as medicine.
Christopher Hobbs is a member of the Herbs for Health Editorial Advisory Board. He is author of Medicinal Mushrooms: An Exploration of Tradition, Healing, and Culture (Botanica Press, 1995) and many other books. He is a fourth-generation herbalist and botanist with more than twenty years of experience.
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