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.