- Forest mushroom
- Pasania fungus
- Hua gu
For Patients & Caregivers
Lentinan, a polysaccharide extracted from Shiitake, may help extend the survival of patients with some cancers when used with chemotherapy.
The medicinal properties of Shiitake mushroom are attributed to a polysaccharide (sugar molecule) named lentinan, on which extensive research has been done. Lentinan is a polysaccharide called a 1,3 beta glucan. In laboratory tests, lentinan does not kill cancer cells directly, but enhances a number of aspects of the immune system, which may aid in the slowing of tumor growth. Lentinan also kills viruses and microbes directly in laboratory studies. Most studies involving lentinan involve intravenous or intramuscular injections. It is uncertain whether ingestion of shiitake mushrooms provides similar effects. One clinical trial has shown shiitake extract alone is not an effective treatment for prostate cancer. More studies are needed.
- To prevent and treat cancer
A Shiitake extract was found ineffective for the treatment of prostate cancer. However, an oral formulation of lentinan was shown effective in extending the survival in patients with stomach, colorectal, pancreatic cancers and hepatocellular carcinoma. Larger studies are needed to confirm this effect.
- To lower high cholesterol
Lentinan has a cholesterol-lowering effect in lab studies, but there is no proof from clinical trials that either lentinan or shiitake mushrooms can lower cholesterol in people.
- To stimulate the immune system
Lentinan stimulates the activity of certain immune cells in lab studies and in people. However, it is unclear if lentinan or shiitake are effective in treating diseases such as AIDS and cancer.
- To treat infections
There is no scientific evidence to support this use.
For Healthcare Professionals
Shiitake mushroom, native 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 an anticancer agent.
Studies conducted with shiitake extracts in vitro and in animal models reveal antiproliferative (4), cytotoxic (21), immunostimulatory (4), hepatoprotective (5), antimutagenic (6), and anticaries (7) properties, but a clinical trial failed to show effectiveness in the treatment of prostate cancer (8).
Results from two small studies of HIV-positive patients who were administered intravenous lentinan showed a statistically insignificant increase in CD4 cells and neutrophil activity, but researchers also reported severe adverse effects in some patients (9).
Improvements in quality of life and survival were seen with an oral formulation of superfine dispersed lentinan in patients with hepatocellular carcinoma (15), gastric (16), colorectal (17), and pancreatic (18) cancers. An orally administered shiitake mycelial extract decreased the incidence of adverse effects associated with chemotherapy in a small study of patients with advanced gastrointestinal cancer (22).
Large-scale studies are needed to establish shiitake as a useful adjunct to cancer treatment.
Shiitake mushroom supplementation enhanced gut immunity by up-regulating interleukin (IL-23) secretion in a mice model of acute dextran sodium sulfate-colitis (29). In another study, high-doses of shiitake mushroom were found to prevent obesity in rats by increasing the plasma triacylglycerol (TAG) accumulation in the liver, rather than adipose tissue (30).
Shiitake also exerts antiviral and antifungal effects. Both acqueous and alcoholic extracts of the mushroom, and the polysaccharide lentinan, inhibited replication of poliovirus type 1 (PV-1) and bovine herpes virus type 1 (BoHV-1) (31). Another polysaccharide isolated from shiitake was shown effective against bacterial infection in mice by increasing T-helper (Th1) cell immunity, resulting in activation of macrophage-mediated immune response (32). Lentin, the protein component, has strong antifungal properties, inhibits proliferation of leukemic cells, and suppresses the activity of human immunodeficiency virus-1 reverse transcriptase (3).
The anticancer effects of the polysaccharide lentinan (1,3 beta-D-glucan) may be due to its ability to suppress cytochrome P450 1A enzymes that are known to metabolize pro-carcinogens to active forms (2). Dried shiitake extract caused apoptosis in human hepatocellular carcinoma (HepG2) cells by mediating the pathway of caspases 3 and 8 (21). Polysaccharides SLNT1 and JLNT1 isolated from the mushroom also demonstrated antitumor effects by increasing serum levels of interleukin 2 (IL-2) and tumor necrosis factor (TNF-α) production, and by inducing apoptosis in tumor cells in mice (33).
Chronic hypersensitivity pneumonitis: In a lung cancer patient following exposure to shiitake spores (10).
Dermatitis, photosensitivity, eosinophilia, and gastrointestinal upset: Following prolonged consumption of shiitake powder (11)(12).
Intermittent dermatitis over a 16-year period: Linked to consumption of shiitake mushrooms in a 45-year-old male (19).
Esophageal symptoms: Linked to a food allergy in a 37-year-old man following consumption of shiitake mushroom (20).
Hypersensitivity pneumonia: In a 37-year-old man following inhalation of Shiitake mushroom spores (23).
Dermatitis: After consumption of raw or cooked shiitake mushroom (24)(25)(26).
Flagellate erythema: Characterized by pruritic, erythematous eruption of multiple linear streaks on the trunk and extremities associated with consumption of raw shiitake mushrooms (27).
Small bowel obstruction: Caused by ingestion of a whole shiitake mushroom, resulting in necrosis and mucosal damage in the small intestine (28).