Background of Lentinula Edodes (Shiitake) Mushroom

Shiitake, an edible mushroom indigenous to East Asia, is cultivated worldwide for its purported health benefits. The fresh and dried forms of the mushroom are commonly used in East Asian cooking. It is also valued as a medicinal mushroom. Shiitake is popular in many countries around the world and is commonly found in supermarkets and Asian grocery stores.

Lentinan ([1,3] beta-D-glucan), a polysaccharide isolated from shiitake, is thought to be responsible for many of the mushroom’s beneficial effects. An injectable form of lentinan is used for cancer treatment in some countries, but it has not been evaluated in large studies.

RESEARCH: In vitro studies conducted with lentinan have indicated its anticancer effects in colon cancer cells¹³; these effects may result from its ability to suppress cytochrome P450 1A enzymes that are known to metabolize pro-carcinogens to active forms¹⁴.

Lentin, the protein component of shiitake, has been shown to exert antifungal properties, as well as inhibiting the proliferation of leukemic cells, and suppressing the activity of HIV-1 reverse transcriptase¹⁵.

Studies of shiitake extracts suggest antiproliferative¹⁶, immunostimulatory¹⁷, hepatoprotective¹⁸, antimutagenic¹⁹, and anticaries²⁰ effects in vitro and in mice. But a clinical trial failed to show any benefit of an oral shiitake extract in the treatment of prostate cancer²¹.

More recently, however, improvements were reported in quality of life and survival with an oral formulation of superfine dispersed lentinan in patients with hepatocellular carcinoma²², gastric cancer²³, colorectal cancer²⁴, and pancreatic cancer²⁵. Larger, well-designed studies are needed to determine whether oral lentinan is superior to the injectable form.