How It Works
Bottom Line: Shiitake mushroom has not been shown to treat or prevent cancer.
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.
Purported Uses
To prevent and treat cancer
Lentinan, when given intravenously, has been shown to be effective in extending the survival in patients with stomach or prostate cancer. However, shiitake extract alone is not an effective treatment for prostate cancer.
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
No scientific evidence supports this use.
Research Evidence
Few clinical studies have been performed with shiitake mushrooms. However, many researches have been performed on lentinan, the active compound present in shiitake mushrooms. See the lentinan monograph for more information.
Prostate cancer:
Patients with prostate cancer were given capsules of shiitake mushroom extract (SME) prepared from part of the shiitake mushroom for six months. At the end of the trial period, none of the patients showed a significant decrease in prostate-specific antigen (PSA) levels. Twenty-eight of the patients showed disease progression. Thus, researchers concluded that SME alone is not effective in the treatment of prostate cancer.
Warnings
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. This product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
Side Effects
Dermatitis (inflammation of the skin)
Increased skin sensitivity to sunlight
Eosinophilia (an abnormally high level of certain white blood cells)
Upset stomach
Special Point
Shiitake mushrooms are a common part of the diet in many cultures. It is unknown what dose of lentinan is absorbed through the gastrointestinal tract when shiitake mushrooms are consumed.
Scientific Name
Lentinula edodes
Common Name
Forest mushroom, lentinula, pasania fungus, lentinula, hua gu
Clinical Summary
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.
Lentinan (1,3 Beta-D-glucan), a polysaccharide isolated from Shiitake, has been well studied and is thought responsible for its beneficial effects.
It was shown to have anticancer effects in colon cancer cells
(1), which may be due to its ability to suppress cytochrome P450 1A enzymes that are known to metabolize pro-carcinogens to active forms
(2).
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). Studies conducted with Shiitake extracts in vitro and in mice revealed the mushroom's antiproliferative
(4), immunostimulatory
(4), hepatoprotective
(5), antimutagenic
(6), and anticaries
(7) properties, but a clinical trial failed to show effectiveness for Shiitake 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 in some patients; researchers also reported severe adverse effects in some patients
(9). It is not clear whether orally administered lentinan would exert similar effects.
Larger, well-designed studies are needed to confirm Shiitake's purported benefits.
Food Sources
Available as fresh or dried whole mushroom
Purported uses
- Cancer prevention
- Cancer treatment
- High cholesterol
- Immunostimulation
- Infections
Constituents
Polysaccharides: Lentinan, 1-3-beta-D-glucan
Protein: Lentin
Lipids: Linoleic Acid
Ergosterol
Amino Acids: Lysine, arginine, methionine and phenylalanine
Minerals and electrolytes: Potassium, calcium, magnesium, manganese, iron, copper, and zinc
Lignins
(3) (13)
Mechanism of Action
Lentinan possesses immune-regulatory, antimicrobial, anti viral, and cholesterol-lowering effects (13). The water extract of shiitake decreased IL-1 production and apoptosis in human neutrophils. However, it increased apoptosis in U937 monocytic cell line (14). Lentin, the protein component of shiitake, has strong antifungal effects. An in vitro study has shown lentin can inhibit the proliferation of leukemia cells and suppress the activity of human immunodeficiency virus-1 reverse transcriptase (3).
Adverse Reactions
None reported at normal doses.
Case Reports: Chronic hypersensitivity pneumonitis was observed in a lung cancer patient following exposure to Shiitake spores
(10).
Prolonged consumption of Shiitake powder resulted in dermatitis, photosensitivity
(11), eosinophilia, and gastrointestinal upset
(12).
Herb-Drug Interactions
None known.
Lab Interactions
Chronic consumption of Shiitake may increase eosinophil count.(12)
Literature Summary and Critique
Few significant clinical studies have been performed with the shiitake mushroom. However, lentinan, which is a polysaccharide component of the mushroom, has been studied extensively.
deVere RW. Effects of a Mushroom Mycelium Extract on the Treatment of Prostate Cancer. Urology 2002 ; 60(4):640-4.
Sixty-two eligible prostate cancer patients were administered shiitake mushroom extract (SME) in capsule form three times daily for six months in an open-label study. At completion, none of the patients had met the response criteria of a PSA level decrease greater than 50%. Twenty-three patients had disease progression and thirty-eight had stable PSA levels. Because of the lack of responders, this study shows SME alone to be ineffective in the treatment of prostate cancer.
References
1. Ng ML, Yap AT.
Inhibition of human colon carcinoma development by lentinan from shiitake mushrooms (Lentinus edodes). J Altern Complement Med 2002;8(5):581-589.
2. Okamoto T, Kodoi R, Nonaka Y, et al.
Lentinan from shiitake mushroom (Lentinus edodes) suppresses expression of cytochrome P450 1A subfamily in the mouse liver. Biofactors. 2004;21(1-4):407-409.
3. Ngai PH, Ng TB.
Lentin, a novel and potent antifungal protein from shitake mushroom with inhibitory effects on activity of human immunodeficiency virus-1 reverse transcriptase and proliferation of leukemia cells. Life Sci. Nov 14 2003;73(26):3363-3374.
4. Israilides C, Kletsas D, Arapoglou D, et al.
In vitro cytostatic and immunomodulatory properties of the medicinal mushroom Lentinula edodes.Phytomedicine 2008.
5. Akamatsu S, Watanabe A, Tamesada M, et al.
Hepatoprotective effect of extracts from Lentinus edodes mycelia on dimethylnitrosamine-induced liver injury.Biol Pharm Bull. 2004;27(12):1957-1960.
6. de Lima PL, Delmanto RD, Sugui MM, et al.
Letinula edodes (Berk.) Pegler (Shiitake) modulates genotoxic and mutagenic effects induced by alkylating agents in vivo. Mutat Res. 2001;496(1-2):23-32.
7. Shouji N, Takada K, Fukushima K, Hirasawa M.
Anticaries effect of a component from shiitake (an edible mushroom).Caries Res 2000;34(1):94-98.
8. deVere White RW, Hackman RM, Soares SE, Beckett LA, Sun B.
Effects of a mushroom mycelium extract on the treatment of prostate cancer. Urology 2002;60(4):640-644.
9. Gordon M, Bihari B, Goosby E, et al.
A placebo-controlled trial of the immune modulator, lentinan, in HIV-positive patients: a phase I/II trial.
J Med 1998;29(5-6):305-330.
10. Suzuki K, Tanaka H, Sugawara H, et al.
Chronic hypersensitivity pneumonitis induced by Shiitake mushroom spores associated with lung cancer. Intern Med 2001;40(11):1132-1135.
11. Hanada K, Hashimoto I. Flagellate mushroom (Shiitake) dermatitis and photosensitivity. Dermatology. 1998;197(3):255-257.
12. Levy AM, Kita H, Phillips SF, et al.
Eosinophilia and gastrointestinal symptoms after ingestion of shiitake mushrooms. J Allergy Clin Immunol 1998;101(5):613-620.
13. Hobbs C. Medicinal Mushrooms, 3
rd ed. Loveland (CO): Interweave Press; 1996.
14. Sia GM, Candish JK.
Effects of shiitake (Lentinus edodes) extract on human neutrophils and the U937 monocytic cell line. Phytother Res 1999;13(2):133-7.
