Other common name(s): Japanese mushroom, Black Forest mushroom, golden oak mushroom, oakwood mushroom
Scientific/medical name(s): Lentinus edodes, Lentinula edodes
A shiitake mushroom is an edible fungus native to Asia and grown in forests. Shiitake mushrooms are the second most commonly cultivated edible mushrooms in the world. Extracts from the mushroom, and sometimes the whole dried mushroom, are used in herbal remedies.
Studies in animals have found antitumor, cholesterol-lowering, and virus-inhibiting effects in compounds in shiitake mushrooms. However, clinical studies are needed to determine whether these properties can help people with cancer and other diseases. It is reasonable to include shiitake mushrooms as part of a balanced diet.
How is it promoted for use?
Shiitake mushrooms are promoted to fight the development and progression of cancer and AIDS by boosting the body's immune system. These mushrooms are also said to help prevent heart disease by lowering cholesterol levels and to help treat infections such as hepatitis by producing interferon, a group of natural proteins that stops viruses from multiplying. Promoters claim that eating both the cap and stem of the mushroom may be helpful, but they do not say how much must be eaten to have an effect. They say the strength and effects of the mushroom depend on how it is prepared and consumed.
Promoters claim that shiitake mushrooms contain several compounds with health benefits. A compound called lentinan is believed to stop or slow tumor growth. Another component, activated hexose-containing compound (also known as 1,3-beta glucan), is also said to reduce tumor activity and lessen the side effects of cancer treatment. The mushrooms also contain the compound eritadenine, which is thought to lower cholesterol by blocking the way cholesterol is absorbed into the bloodstream. These claims are currently being studied.
What does it involve?
The fresh or dried whole mushroom is widely available in grocery stores, while extracts of the mushroom are sold in capsule form in health food stores and on the Internet. Kits for growing shiitake mushrooms indoors at home are available from some Internet sellers.
For medicinal purposes, the extracts of compounds in shiitake mushrooms would usually be recommended, rather than the mushroom itself. For example, some Japanese researchers give lentinan along with chemotherapy to treat patients with lung, nose, throat, and stomach cancer. Extracts of the active compounds, such as lentinan and eritadenine, are mainly sold in Japan. Activated hexose-containing compound is sold as a nutritional supplement in the United States, Europe, and Japan.
What is the history behind it?
Medicinal use of shiitake mushrooms dates at least to 100 AD in China (see Chinese Herbal Medicine). The mushrooms have been widely consumed as a food for thousands of years in the East and more recently in the West. Today, shiitake mushrooms are very popular in the United States as well. Research into the anticancer properties of shiitake mushrooms has been going on since at least the 1960s.
What is the evidence?
Animal studies have shown some positive results regarding the antitumor, cholesterol-lowering, and virus-inhibiting effects of several active compounds in shiitake mushrooms.
There have been some studies in humans. At least one randomized clinical trial of lentinan has shown it to prolong life of patients with advanced and recurrent stomach and colorectal cancer who were also given chemotherapy. Lentinan is a beta glucan (sometimes called beta glycan) that is found in several mushrooms, yeasts, and other foods. Beta glucan is a polysaccharide, a large and complex molecule made up of smaller sugar molecules. The beta glucan polysaccharide is believed to stimulate the immune system and activate certain cells and proteins that attack cancer, including macrophages, T-cells, and natural killer cells. In laboratory studies, beta glucan appears to slow the growth of cancer in some cell cultures.
Several potential cancer-fighting substances have been found in shiitake mushrooms, and purified forms of these compounds are being studied as treatment for stomach and colorectal cancer. It is not known whether any of these results will apply to the mushrooms bought in supermarkets or the extracts that are sold as supplements. One nonrandomized study published in 2002 looked at use of shiitake mushroom extract by men with prostate cancer but did not find any positive effect. Sixty-two men took the extract 3 times a day. After 6 months, they did not have any significant decrease in their level of prostate-specific antigen (PSA), a protein in the body that typically increases as prostate cancer grows, and nearly a quarter of them had increases in their PSA level. More human clinical trials are under way to understand which, if any, compounds in shiitake mushrooms may be effective for which types of cancers.
To reduce cancer risk, the American Cancer Society's nutrition guidelines recommend eating a balanced diet that includes five or more servings a day of vegetables and fruit, choosing whole grains over processed and refined foods, and limiting red meats and animal fats. Choosing foods from a variety of fruits, vegetables and other plant sources such as nuts, seeds, whole grain cereals, and beans is healthier than consuming large amounts of one particular food. (For more information, see American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention).
Are there any possible problems or complications?
Shiitake mushrooms and their extracts are generally considered safe, although there are reports of diarrhea or bloating. In some people, allergic reactions have developed affecting the skin, nose, throat, or lungs. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.
More information from your American Cancer Society
The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).
The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management
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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.
Last Revised: 11/01/2008