What is turkey tail?
Turkey tail is a type of mushroom that grows on dead logs worldwide. It's named turkey tail because its rings of brown and tan look like the tail feathers of a turkey. Its scientific name is Trametes versicolor or Coriolus versicolor. In traditional Chinese medicine, it is known as Yun Zhi. In Japan, it is known as kawaratake (roof tile fungus). There are many other types of Trametes mushrooms. It can be hard to tell the difference between turkey tail and other types of Trametes mushrooms without the use of special testing.
Turkey tail has been used in traditional Chinese medicine to treat lung diseases for many years. In Japan, turkey tail has been used to strengthen the immune system when given with standard cancer treatment.
What is PSK?
Polysaccharide K (PSK) is the best known active compound in turkey tail mushrooms. In Japan, PSK is an approved mushroom product used to treat cancer.
How is PSK given or taken?
PSK can be taken as a tea or in capsule form.
Have any laboratory or animal studies been done using PSK?
In laboratory studies, tumor cells are used to test a substance to find out if it is likely to have any anticancer effects. In animal studies, tests are done to see if a drug, procedure, or treatment is safe and effective in animals. Laboratory and animal studies are done before a substance is tested in people.
Laboratory and animal studies have tested the effects of PSK on the immune system, including immune cells called natural killer cells and T-cells. For more information on laboratory and animal studies done using PSK, see the Laboratory/Animal/Preclinical Studies section of the health professional version of Medicinal Mushrooms.
Have any studies of PSK been done in people?
PSK has been studied in patients with gastric cancer, breast cancer, colorectal cancer, and lung cancer. It has been used as adjuvant therapy in thousands of cancer patients since the mid-1970s. PSK has been safely used in people for a long time in Japan and few side effects have been reported.
Gastric cancer
Studies show that the use of PSK as adjuvant therapy in patients with gastric (stomach) cancer may help repair immune cell damage caused by chemotherapy and strengthen the immune system.
Studies of PSK as adjuvant therapy for gastric cancer include the following:
- A randomized clinical trial in Japan done between 1978 and 1981 included 751 patients who had surgery for gastric cancer. After surgery, patients received chemotherapy with or without PSK. On average, the patients who received chemotherapy and PSK lived longer than those who received chemotherapy alone. The researchers believe it might be possible to predict which patients would benefit the most from PSK depending on the numbers of granulocytes and lymphocytes in the patient's blood.
- In 1994, a study in Japan followed 262 patients who had successful surgery for gastric cancer and were given chemotherapy with or without PSK. Patients who received chemotherapy and PSK were less likely to have recurrent cancer and lived longer than those who did not. Treatment with PSK caused few side effects. The researchers thought the study showed that PSK and chemotherapy should be given to gastric cancer patients after surgery to remove the cancer.
- A review published in 2007 combined results from 8 randomized controlled trials in 8,009 patients who had surgery to remove gastric cancers. After surgery, patients in the trials were given chemotherapy with or without PSK. The results suggest that receiving chemotherapy and PSK helped patients live longer after surgery.
Breast cancer
To date, PSK studies in patients with breast cancer have focused on changes in the immune system (T-cell and B-cell levels in the blood) rather than on clinical results (patient survival, symptoms, side effects, and quality of life).
Colorectal cancer
Studies of PSK as adjuvant therapy for colorectal cancer include the following:
- PSK was studied in a randomized clinical trial for its effect on the immune system in patients with stage II or stage III rectal cancer. Patients received chemotherapy and radiation therapy, with or without PSK. This study found that PSK increased the number of cancer-killing immune cells and had anticancer effects in tissue that received radiation therapy.
- A review that combined results from 3 studies in 1,094 patients with colorectal cancer found that patients who received PSK were less likely to have recurrent cancer and lived longer than those who did not.
- Two groups from Japan studied patients with colorectal cancer who received adjuvant chemotherapy with or without PSK after surgery. In the first study, patients who were treated with both chemotherapy and PSK had markedly better 10-year survival rates. In the second study of patients who were older than 70 years, 3-year survival rates were markedly higher in the group treated with both chemotherapy and PSK.
Lung cancer
Studies of PSK as adjuvant therapy for patients with lung cancer include the following:
- Five nonrandomized clinical trials reported that patients treated with PSK and radiation therapy with or without chemotherapy lived longer.
- Six randomized clinical trials in patients with lung cancer studied chemotherapy with or without PSK. The studies showed that patients who received PSK improved in one or more ways, including immune function, body weight, well-being, tumor-related symptoms, or longer survival.
Have any side effects or risks been reported from turkey tail or PSK?
There have been few side effects reported in studies of PSK in Japan.
Is turkey tail or PSK approved by the FDA for use as a cancer treatment in the United States?
The FDA has not approved the use of turkey tail or its active compound PSK as a treatment for cancer or any other medical condition.
The FDA regulates dietary supplements separately from foods, cosmetics, and drugs. The FDA's Good Manufacturing Practices require that every finished batch of supplements is safe and that the claims on the label are true and do not mislead the consumer. However, the FDA does not regularly review the way that supplements are made, so all batches and brands of mushroom supplements may not be the same.