Polysaccharide peptide (PSP), primarily extracted from the mushroom Coriolus versicolor (also known as Turkey Tail), has been researched for its potential to support cancer patients undergoing chemotherapy. The scientific interest stems from PSP's purported immunomodulatory properties, including stimulation of various immune cells such as T-lymphocytes and natural killer (NK) cells. Some clinical studies, primarily conducted in China and Japan, have evaluated PSP as an adjunct to conventional cancer therapies, including chemotherapy.

Several trials suggest that PSP may help reduce the severity of chemotherapy-induced side effects, particularly by improving immune function and reducing fatigue or infection rates. However, the quality of evidence is generally low to moderate. Many studies suffer from methodological limitations, small sample sizes, or lack of rigorous controls. Systematic reviews and meta-analyses have concluded that while PSP appears to be safe and may offer modest benefits in quality of life and immune status, the evidence is insufficient to recommend its widespread use for reducing chemotherapy side effects. More robust, large-scale randomized controlled trials are needed to confirm these findings.

In summary, there is some scientific evidence—mainly preliminary and not yet definitive—to support the use of polysaccharide peptide for reducing certain chemotherapy side effects, but the current level of evidence is not strong.