11/03/2026
In 1977, Japan approved a compound derived from the Turkey Tail mushroom (Trametes versicolor) for use alongside conventional cancer treatment.
The compound is called PSK (Polysaccharide Krestin). It was approved by Japan’s national health authorities as a prescription therapy used together with standard medical care.
Over the years, PSK was examined in many clinical studies involving more than 10,000 patients across different types of cancer, including stomach, colon, lung, and breast cancers.
Researchers observed that PSK appeared to support immune system activity during treatment. Studies reported that the compound could stimulate certain immune cells, including natural killer cells and dendritic cells, which help the body recognize abnormal cells.
Because of its widespread medical use, PSK became one of Japan’s most commonly prescribed supportive cancer therapies. At its peak, researchers estimate it represented around 25 percent of Japan’s national spending on supportive cancer treatments.
Scientists emphasize that PSK was used within regulated healthcare systems and studied in controlled clinical trials together with standard medical treatment.
Source: Kidd PM., “The Use of Mushroom Glucans and Proteoglycans in Cancer Treatment,” Alternative Medicine Review (2000); Ikuzawa M. et al., clinical studies on PSK from Trametes versicolor.
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