Polysaccharide Kureha
( PSK )

Polysaccharide kureha (PSK), also known as krestin, is an extract from the kawaratake mushroom. In Japanese, kawaratake means "mushroom on the riverbank." This mushroom is common in the woods of Japan, China, and the United States. It sports a fan-shaped fruiting body that resembles a turkey tail, which gave it the English common name turkey-tail mushroom. The fruiting body can be any of a variety of shades of blue, brown, gray, or white. In Japan, PSK is the most widely sold health food in the country.

PSK is a powerful antioxidant and immune stimulant. It contains complex polysaccharides that have demonstrated powerful anticancer activity in over twenty years of clinical use in Japan. It has also been used to increase resistance to viral skin infections in people with eczema. There have been over 200 scientific studies involving PSK. It is virtually nontoxic and readily bioavailable when taken orally.

The same active component in PSK can be purchased as coriolus extract. Studies have shown that healthy individuals who took a one-time dose of 1 gram of this extract had a significant improvement in cellular immune function within twelve hours. Coriolus is effective against hepatitis and is being tested as a treatment for hepatitis C.

Benefits of PSK for specific health conditions include the following:

• Atherosclerosis. PSK protects immune cells in the linings of artery walls from the action of harmful free radicals. This prevents the immune cells from attracting low-density lipoprotein (LDL, or "bad") cholesterol that gathers into artery-clogging plaques.
• Cancer. PSK's effectiveness against cancer is so widely recognized in Japan that in one year, purchases of PSK accounted for over 25 percent of the nations' entire expenditures for cancer treatment. It is especially beneficial when used together with standard chemotherapy or radiation therapy. PSK stops the spread of tumors by disabling enzymes that allow tumor cells to break out of the matrix that holds healthy cells in their proper places. This is especially useful in increasing the effectiveness of radiation therapy for endometrial cancer. In a study of patients at the National Cancer Center Hospital in Tokyo with fairly advanced endometrial and cervical cancer, some took 3 to 6 grams of PSK every day in conjunction with radiation therapy, while others received radiation alone. After the radiation treatment was completed, 36 percent of the patients who took PSK had no observable cancer cells, while that was true of only 11 percent of those who did not take PSK. The two-year survival rate was 94 percent for patients who took PSK and 74 percent for those who did not. The five-year survival rates were 79 percent arid 48 percent, respectively.
  Doctors have seen an increase in survival rates when PSK is used with either radiation therapy or chemotherapy for lung cancer. In one study of 185 patients with advanced (stage III) lung cancer, the five-year survival rate for people who received both radiation therapy and PSK exceeded that of those who received radiation alone by 400 percent. In another study involving 169 patients, PSK extended longevity in patients who received chemotherapy by an average of seven weeks.
  PSK also helps people with colorectal cancer. It checked the progress of the disease and increased survival rates in one trial involving 124 patients, all of whom were also treated with mitomycin (Mutamycin). PSK reduced the depth to which the cancer invaded the intestinal wall and curtailed the cancer's spread to both lymph nodes and blood vessels. In laboratory studies, PSK has been found to increase the effectiveness of the chemotherapy agent 5-fluorouracil (S-FU). It reduces the rate of cancer growth in the cecum, the place where the large intestine begins, and reduces the rate at which cancer enters the lymphatic system. PSK increases the effectiveness of immune-system components called T cells against colorectal tumors, and has also been found to prevent the spread of colon cancer to the liver. In one eighteen-year study, PSK reduced the spread of colon cancer to the peritoneum (the membrane lining the intestinal cavity) and the lungs in 60 percent of the people who took it.
  PSK is useful in treating several other cancers. In leukemia, it stops invasion of normal tissues by leukemia cells, and it reduces the likelihood of relapse in childhood acute lymphocytic leukemia after chemotherapy is discontinued. In melanoma, it reduces the rate at which cancer cells spread to the lungs and increases the effectiveness of chemotherapy treatment with cyclophosphamide (Cytoxan, Neosar) and interleukin-2 (IL-2), an immune-system chemical. In ovarian cancer, it helps maintain the body's production of IL-2. In prostate cancer, it reduces the rate of spread in those types of prostate cancer that can spread to the lungs.

PSK is available in tablet form. It should be used only under professional supervision.