Lentinus edodes (Shiitake) Mushroom Health Benefits

What is SHIITAKE? - is the mushroom that the Chinese affectionately named "Xiang-gu" (or "Shiang-gu"), "the fragrant mushroom". They are a treasured and traditional delicacy at dinner tables in China, Japan and Korea. Shiitake also contains a material well known for its medicinal benefits: Lentinan, a water soluble polysaccharide produced and extracted from shiitake, is an aproved anti-cancer drug in Japan [source: Mushroom Growers Handbook 2 -Shiitake Cultivation].

History - This mushroom has been renowned in China and Japan for thousands of years both as a food and as a medicine. It has an exotic and delicious taste and is a central part of many Oriental dishes and is increasingly adopted in the West. In the Oriental folk medicine it was used for a wide range of health problems. It has particularly valuable in treating high blood pressure and lowering blood cholesterol. [source: Medicinal Mushrooms by S. Sulliwan and S. Rowan].

Cultivated for over 1000 years in Asia, shiitake is a highly prized mushroom not only for its excellent taste and culinary usage but also for its important therapeutical effect. From this point of view this mushroom is considered a functional food (food with important medicinal value). It's name 'shiitake' derives from the 'shii' tree (Castanopsis cuspidata) on which it grows and 'take' which is the Japanese word for 'mushroom'.

Shiitake is on the third place among cultivated mushroom species in the world (after white button and oyster mushrooms) and Japan is the major producer of shiitake. First written record on shiitake cultivation comes from China during the Sung Dynasty (960-1127). Shiitake it is grown mainly in East Asia but in the past decades a growing worldwide interest may be observed (especially in USA and Europe where is considered an exotic mushroom).

Ecology: shiitake is native to Southeast Asia where grows on a wide variety of deciduous wood in a warm and moist climate.

Nutritional value: the shiitake raw fruitbodies include 88-92% water, protein, lipids, carbohydrates, vitamins and minerals. Dry shiitake contains 58-60% carbohydrates, 20-23% protein, 9-10% fiber, 3-4% lipids, and 4-5% ash. Shiitake is also a good source of vitamins: D2, B (B1, B2, B12) and pantothenic acid, while minerals include: Fe, Mn, K, Ca, Mg, Cd, Cu, P, and Zn.  Polyssacharides some of the major active substance responsible for the therapeutic effect amount 1-5% of the dry weight of shiitake.

Active Constituents: The major active constituents isolated from shiitake are: Lentinan (a cell-wall constituent from the fruitbodies or mycelium of shiitake -a polysaccharide), LEM (a protein-bound polysaccahride), KS-2 (a polysaccharide containing alpha-linked mannose and a small amount of peptide), JLS (a compound derived from the mycelium), Eritadenine (a nucleic acid derivative), EPS and EPS4 (water soluble lignins) [source: Mushroom Growers Handbook 2 -Shiitake Cultivation].

Shiitake is one of the medicinally most studied mushroom along with Reishi (Ganoderma lucidum), Maitake (Grifola frondosa), Kawaratake (Trametes versicolor) or Chaga (Inonotus obliquus).  A unique active compound found in shiitake was named 'lentinan' which is a water-soluble polyssacharide isolated from fruiting bodies which has been observed to have a powerful anti-tumor effect.

Side effects: consumption of raw shiitake can cause dermatitis but generally depends from a person to another (it was rarely  encountered: 1 to 50 people); the consumption of shiitake in excess can cause diarrhea. Alergic reactions to the spores of shiitake have been reported in workers picking mushrooms indoors (symptoms include fever, headache, congestion, coughing, sneezing, or nausea).

Availability: shiitake is available on the market as fresh, or dried fruiting bodies, or as extracts (capsules, tablets, injections, tinctures, etc), syrup, wine, bear, tea, or as medicinal dish. The most effective are the so called 'LEM tablets' (Lentinus edodes mycelium extract). The precipitate obtained from a water solution of the mycelium by adding four volumes of ethanol was named 'LAP'. Both LEM and LAP demonstrated strong antitumor activities orally and by injection to animal and humans.
 The quantity of shiitake that one should consume in order to feel any health effects is huge and probably would cause diarrhea or stomach upset, this is the reason why extracts work best. If you would like to prepare your own shiitake extract check out instructions on how to Make Your Own Medicinal Mushroom Extract.

References:

Kuhn, M. and Winston, D. 2001. Herbal therapy and supplements: a scientific and traditional approach. Philadelphia: JB Lippincott.

Wasser, S.P. 2005. Shiitake (Lentinus edodes). In: Encyclopedia of Dietary Supplements DOI: 10.1081/E-EDS-120024880. Marcel Dekker: New York, Pp. 653-664.

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