Mushrooms are a fascinating class of life form: vast underground mycelia that push up strange fruiting bodies when climatic conditions are right, and a vast range of forms–from common fairy rings and puffballs to strange, unearthly, pale violet discs; from tiny pinheads to hubcap-sized saucers. Of an estimated 100,000 species of mushrooms, most are edible and very nutritious, containing large amounts of protein, fiber, minerals (including calcium), B vitamins, and vitamin C.
Shiitake (shee-TAH-kee) mushrooms are a culinary rage in the United States today (you can even buy kits for growing your own), but have been important in Chinese culture for thousands of years. One of the earliest recorded uses of shiitake (Lentinula edodes) dates as far back as the fourteenth century, when the Chinese physician Wu-Rui described it as a food that accelerates vital or “spirit” energy (known as Qi in Chinese), staves off hunger, “cures cold, and penetrates into the blood circulatory system.” Today, these attributes are collectively taken to mean that shiitake makes a person more lively. Wu also stated that shiitake was “good for treatment of Heart Troubles . . . beneficial to [all forms of] Malignancy, likewise certainly [good for] Snake’s poison.” For the past thirty years, scientists have been investigating some of these uses and have amassed evidence that shiitake can help the body fight heart disease, cancer, and viral diseases. Most of the research has been carried out in Japan. Some of the studies are discussed below.
The body could not function without cholesterol, which helps the body break down fats, or lipids, in the small intestine so that they can be absorbed into the bloodstream. In the liver, cholesterol combines with lipids and proteins in the blood to form various complexes called lipoproteins. A large proportion of low-density lipoproteins (LDL or “bad” cholesterol) in the blood has been linked to clogged artery walls, which can lead to heart attack or stroke. High-density lipoproteins (HDL or “good” cholesterol), on the other hand, have been shown to scavenge excess LDL from the bloodstream and carry it to the liver for excretion or processing into good cholesterol.
According to studies performed in Japan during the 1970s, shiitake contains an amino acid called eritadenine that accelerates cholesterol’s processing in the liver. In addition, shiitake’s high dietary fiber helps the body process cholesterol.
In a 1974 study, 40 elderly people and 420 young women ate 9 g of dried shiitake or the equivalent amount of fresh shiitake (90 g) daily. After seven days, total cholesterol level (the types of cholesterol affected were not distinguished) had decreased 7 to 15 percent in the elderly and 6 to 12 percent in the young women.
Another 1974 study involved thirty young women. Ten added 90 g of fresh shiitake and 60 g of butter to their daily diet, ten added only the butter, and ten added only the shiitake. After seven days, the total cholesterol level of the shiitake and butter group decreased an average of 4 percent, while that of the butter group increased an average of 14 percent and that of the shiitake group declined an average of 12 percent. The researchers concluded that shiitake had “completely nullified” the effect of the butter on the cholesterol level of the first group of participants.
In 1969, researchers at Tokyo’s National Cancer Center Research Institute isolated a polysaccharide compound from shiitake that they named lentinan. Doses of 0.5 to 1 mg lentinan per kg of body weight caused tumors in laboratory mice to regress or disappear in 80 to 100 percent of the subjects. Researchers have since demonstrated that lentinan works by stimulating immune-system cells to rid the body of tumor cells. In clinical trials, lentinan administered with chemotherapy has increased the life span of cancer patients, improved the effectiveness of chemotherapy, and kept tumors from growing. In Japan, lentinan is approved for use as a drug to prolong the lives of patients undergoing chemotherapy for stomach cancer.
Additional studies have shown that when shiitake mushrooms make up 10 percent of the daily diet of cancerous mice, tumor growth is inhibited by nearly 40 percent. When shiitake constitutes 30 percent of the diet, tumor growth is inhibited by nearly 78 percent. Researchers have concluded that the entire mushroom stimulates immune cells such as macrophages and T cells, as well as natural killer cells, and contains compounds that block the formation of carcinogens from nitrates that are found in many processed meats and some vegetables.
The plague of modern humankind has been the common cold. In current times, however, more serious viral infections, some leading to certain death, have plagued society, including hepatitis B (a liver disease transmitted through transfusions, the use of unsterile needles, or other blood-to-blood contact) and HIV (the virus that causes AIDS). Whether shiitake can cure the common cold is doubtful, but an extract of its mycelium shows promise as a treatment for these more serious viral infections, including hepatitis B and HIV.
You may have encountered mushroom mycelium while digging in rich soil; it is a stringy, weblike material that looks like a rotted root system. When temperature, moisture, and other conditions are right, the mycelium develops fruiting bodies, or the portions we call mushrooms. In Japan, an extract called LEM (short for Lentinula edodes mycelium) has been the focus of many studies.
Hepatitis B: Trials of LEM at sixteen clinics in Japan during the 1980s involved an unspecified number of patients with chronic hepatitis B, the use of unsterile needles, or other blood-to-blood contact. The studies showed that LEM may cause the body to produce protective antibodies, so a follow-up study was conducted. Forty people with chronic hepatitis B took 6 g of LEM orally each day for four months. Hepatitis B symptoms were alleviated in all of the patients, and the virus was inactivated in fifteen.
HIV: Test-tube studies in Japan have shown that LEM was less toxic to normal cells and more toxic to cells infected with HIV than AZT, a drug that slows the progress of AIDS. Researchers also found that LEM contained substances that increased cell formation in bone marrow, the site where most immune system cells are born; other researchers discovered that lignins–a main constituent of dietary fiber–in LEM were causing the increases. In test tubes, LEM lignins have been shown to prevent HIV cells from proliferating and damaging T cells, as well as preventing cell damage from herpes simplex I and II, two viral infections that often accompany HIV infection. The test-tube studies are promising, but clinical studies are needed to determine the effect of the LEM lignins on HIV in the body.
As for lentinan, the shiitake polysaccharide drug, it alone has shown no effect against HIV in test-tube experiments, but a combination of lentinan and AZT has been shown to be twenty-four times as effective at inhibiting HIV as AZT alone. Trials of lentinan in combination with anti-HIV drugs were approved in Japan in the late 1980s and have shown positive results. A long-term, carefully controlled study at several hospitals in the United States used a similar strategy of giving AIDS patients lentinan in combination with an anti-HIV drug and found the therapy superior to the anti-HIV drug alone.
More Research, More Mushrooms
In addition to shiitake, many other kinds of mushrooms are under scientific scrutiny. Some of them, used for centuries as medicine in the Orient, have made their way to the United States, where interest in using them both as food and medicine has been increasing. Although there have been few studies of these mushrooms in the West as yet, reports from other countries may encourage Western researchers to begin exploring their medicinal benefits.
A Chinese Tribute
Nearly 1,000 years ago in China, a delicious mushroom known as hsiang ku, or “fragrant mushroom”, became one of the first edible fungi to be cultivated when a farmer named Wu San Kwung mimicked nature by infecting notches he cut into logs with pieces of the mushroom; these eventually produced whole mushrooms. Wu San was immortalized in 1265 when in a small mountain village near the city of Qingyuan in Zhejiang Province on the Pacific Coast, a statue of the inventor was erected in the Temple of Xiyangdian, or “Temple of the Mushroom God”.
A Rich Harvest
Before its cultivation began in Japan, the shiitake mushroom (Lentinula edodes) was harvested from the wild, mainly from an evergreen tree resembling a chestnut (Castanopsis cuspidata). The name for the mushroom combines the Japanese name for the tree, shiia, with the Japanese word for mushroom, take.
The exportation of shiitake brings more money into Japan than any other agricultural export; the mushroom is also cultivated in Canada, Europe, the United States, and many other countries. It is grown on sawdust from hardwood trees such as alder, oak, chestnut, and maple, or on logs studded with wooden plugs that have been infected with the mushroom culture. Log cultivation is slow but produces a firmer, thicker mushroom, which many hold to be superior in flavor to those cultivated on sawdust. In Japan, the thicker mushroom is called donko, whereas the thinner-capped, cheaper grade is called koshin.
Shiitake mushrooms are a good source of digestible protein, which consists of more than 40 percent essential amino acids.
Dried shiitake contains a large amount of vitamin D (3.25 mg/g), protein (22.7 percent), amino acids (14 percent), potassium (33 mg/g), and as much as 55 percent polysaccharides.
• Chang, S. T., et al., editors. Mushroom Biology and Mushroom Products. Hong Kong: The Chinese University Press, 1994.
• Chihara, G., et al. “Fractionation and Purification of the Polysaccharides with Marked Antitumor Activity, Especially Lentinan, from Lentinus edodes (Berk.) Sing. (An Edible Mushroom)”. Cancer Research 1970, 30:2776-2781.
• Gordon M., et al. “A Phase II Controlled Study of a Combination of the Immune Modulator, Lentinan, with Didanosine (DDI) in HIV Patients with CD4 Cells of 200-500/mm3”. Journal of Medicine 1995, 26:193-207.
• Han, S. International Symposium on Production and Products of Lentinus Mushroom, ISMS Committee on Science Asian Region, Qingyuan County Government, Zhejiang Province, China, November 1-3, 1994, Program and Abstracts. 44-45, 77.
• Suzuki, S., and S. Ohshima. Mushroom Science IX (Part 1), Proceedings of the Ninth International Scientific Congress on the Cultivation of Edible Fungi, Tokyo, 1974. Kiryu, Japan: Mushroom Research Institute, 1976.
• Yan, X.-M. International Symposium on Production and Products of Lentinus Mushroom, ISMS Committee on Science Asian Region, Qingyuan County Government, Zhejiang Province, China, November 1-3, 1994, Program and Abstracts. 42.
Kenneth Jones is president of Armana Research Inc., a bibliographic research and science writing service in Gibsons, British Columbia. He is the author of Shiitake, The Healing Mushroom (Rochester, Vermont: Healing Arts Press, 1995).