|The person most responsible for stimulating the current medicinal interest in shiitake was Japan's Kisaku Mori, Ph.D. In 1936, Dr. Mori established the Institute of Mushroom Research in Tokyo. Until his death in 1977, Dr. Mori worked with scientists from around the world to document the medicinal effects of shiitake. Using analytical techniques, Mori found shiitake high in many enzymes and vitamins that were not usually found in plants. His findings, published in Mushrooms as Health Foods, were extensive. Working for years with human subjects, he discovered that shiitake is effective in treating a long list of ailments including high cholesterol, gallstones, hyperacidity, stomach ulcers, diabetes, vitamin deficiency, anemia, and even the common cold.
Mori's work gained notoriety, particularly in Japanese medicinal circles, and, beginning in the 1960s, scientists launched an extensive search to uncover the secret of shiitake's legendary healing powers. Their studies - over one hundred in all - have focused on shiitake's ability to rapidly lower serum cholesterol, as well as this mushroom's potent antitumor, antiviral, and antibiotic properties.
High levels of cholesterol in the blood has been linked to serious diseases such as arteriosclerosis and strokes, so investigators were excited in 1966 when they isolated a substance from shiitake that dramatically lowered blood cholesterol. This substance, now called eritadenine, was given to rats on a high-cholesterol diet. In just a few days, as reported in The Journal of Nutrition, the blood cholesterol level of the rats dropped 25 to 45 percent. Eritadenine has been associated with the water-soluble fiber of shiitake, but its action is even stronger when the whole mushroom is consumed. Studies with humans have shown that only three ounces of shiitake (5-6 mushrooms) a day can lower cholesterol by twelve percent in a week.
"Many of the human diseases currently increasing throughout the world have no specific cures," notes mycologist John Donoghue, co-author of Shiitake Growers Handbook. "Immune system failure or dysfunction is a common element in cancer, viruses, and immune-deficiency diseases," says Donoghue. He and other scientists around the world contend that there is increasing evidence that the health-promoting compounds found in medicinal and edible fungi, including shiitake, stimulate the immune system.
Scientists now believe that a polysaccharide called lentinan and virus-like particles found in shiitake trigger the increased production of various serum factors associated with immunity and inflammation. These so-called lymphokines, such as interferon and interleukin, stimulate the defense system, spurring the proliferation of phagocytes, including macrophages and other immune fighters that attack cancer cells, bacteria, and viruses.
The most dramatic experiment demonstrating shiitake's antitumor effect was performed on animals. At the National Cancer Research Center in Tokyo, mice suffering from sarcoma, a type of virally-induced cancer, were treated with small doses of shiitake extract over short periods of time. In 1970, the results, published in the journal Cancer Research, showed that six out of ten mice had complete tumor regression. At slightly higher concentrations, shiitake was 100 percent effective - all mice showed tumor regression.
In a 1996 study at Drew University, a protein-bound polysaccharide extracted from shiitake was found to have strong anti-tumor properties. In the study ten cancer patients were treated with the compound and all showed significant improvement.
Similar studies have shown that shiitake extract helps prevent transplanted tumors from taking hold, and "excellent results" were obtained by Japanese scientists in a four-year follow-up study of patients with advanced and recurrent stomach and colon cancer. Shiitake extract is even being tested for use with modern chemotherapy drugs to lessen their toxic effects on healthy tissue and the immune system.
The most recent development in shiitake medical research involves the use of shiitake extract to inhibit the reproduction of human immunodeficiency virus (HIV) in tissue culture. Researchers working at Japan's Yamaguchi University School of Medicine have reported that shiitake extract has a "protective effect" that inhibits the usual cell-destroying effects of the HIV virus. Researchers have noted that substances such as shiitake, which both enhance the immune response and have anti-viral effects, should be further evaluated for the treatment of AIDS.
In addition to fighting cancer, inhibiting the growth of viruses, and lowering cholesterol, shiitake have potent antibiotic effects against other organisms. A substance called cortinelin, a broad-spectrum antibacterial agent, which has been isolated from shiitake, kills a wide range of pathogenic bacteria. A sulfide compound extracted from shiitake has been found to have an effect against the fungus that causes ringworm and other skin diseases.