Turkey tail (Trametes or Coriolus versicolor) is a mushroom whose extracts are used by people with cancer, mostly alongside chemotherapy. The most studied extract is PSK (polysaccharide-Krestin), tested mostly in Japan.
Also known as: Trametes versicolor, Coriolus versicolor, PSK, polysaccharide-K, Krestin.
There is no intake value. In the colorectal cancer trials, an extract (PSK) was taken for 4 weeks to 3 years alongside chemotherapy (Pilkington 2022).
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
What studies show: a 2022 Cochrane review of 7 trials (1,569 people with colorectal cancer, 6 of them in Japan) found very low-certainty evidence on whether PSK reduced chemotherapy side effects such as low white cells, mouth sores, nausea and fatigue, and low-certainty evidence of a small improvement in 5-year survival. The reviewers note the chemotherapy used in these trials does not reflect current practice (Pilkington 2022). A 2023 review of mushroom studies in cancer care found PSK linked with better survival in 4 gastric cancer studies, but called the evidence inconclusive for routine use, as many studies were small and not randomized (Narayanan 2023).
Safety: across mushroom supplements in cancer studies, most reported side effects were mild, mainly nausea, vomiting, diarrhea and muscle pain (Narayanan 2023).
We could not find a single published half-life or time to peak for turkey tail that applies to a supplement dose, so we do not list one. Plant and mushroom products are mixtures of many compounds, so no single figure would describe them.
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