Shiitake mushrooms are typically found growing naturally on the fallen and decaying broadleaf trees in Japan, China, and other Asian countries. Because of its medicinal applications, shiitake is now cultivated in the United States and throughout the world.
The key chemical ingredient found in the Shiitake mushroom is a polysaccharide known as lentinan. Shiitake mushrooms also contain complex carbohydrates, proteins, fats, soluble fiber, vitamins, and essential minerals. Commercial preparations employ the powdered mycelium which is extracted from the shiitake mushroom before the cap and stem grow. When shiitake is prepared in this manner it is called lentinus edodes mycelium extract (LEM). LEM is rich in polysaccharides and lignans.
Preliminary trails indicate that oral supplementation of shiitake may be useful for people suffering from hepatitis B. Lentinan, the most important constituent of shiitake, is used in Japan in a very purified, intravenous form. It has been reported to increase survival in people with recurrent stomach cancer, especially when used along with chemotherapy. It has also been somewhat useful for people suffering from pancreatic cancer and for people with HIV infection. However, there have not been any large-scale clinical trials to confirm these claims.Dosage Recommendation
Some medical professionals recommended taking 6-16 grams per day of pure shiitake mushroom compounds. It can be taken as a soup by boiling it for 10-20 minutes in water, cooled and strained, or as a decoction. If preferred, taking 1-3 grams of LEM two to three times a day will also provide the desired effect.
In Japan purified lentinan is considered a drug. LEM is unavailable as an herbal supplement in Northern America.