Turkey Tail (PSK/PSP)
Trametes versicolor
Immune-modulating mushroom polysaccharides used as a chemotherapy adjuvant in Asia.
Evidence tier
Preliminary
Research weight
Citations
13 verified / 13
Classification
Gut & Immune
❝
What the evidence says. Early or small human trials; promising but not yet conclusive.
What is Turkey Tail (PSK/PSP)?
Turkey Tail (PSK/PSP) (Trametes versicolor) is a gut and immune supplement used for may modulate immune and hematological function (nk-cell activity, lymphocyte and white-cell counts), mostly shown in cancer-adjuvant settings rather than healthy users. NutriDex grades the human evidence as Preliminary. Turkey Tail (Trametes versicolor, formerly Coriolus versicolor) is a common bracket fungus whose protein-bound polysaccharides PSK (Krestin) and PSP have been used for decades as immune-adjuvant agents alongside chemotherapy and surgery in Japan and China. The strongest human evidence is in oncology: pooled analyses and a 2022 Cochrane review suggest PSK, added to conventional treatment in cancers such as gastric, colorectal and lung, is associated with a small improvement in long-term survival, though the certainty of evidence is low and older trials used chemotherapy regimens no longer in standard use. Mechanistically it acts as a non-specific immunomodulator, increasing markers such as NK-cell activity and lymphocyte counts, and PSP shows prebiotic-like effects on the gut microbiome. Evidence for the over-the-counter supplement as a standalone immune booster or longevity aid in healthy people is preliminary and rests mainly on immunologic surrogate markers rather than clinical outcomes. It is generally well tolerated, but it should be viewed as an adjunct studied under medical supervision, not a proven self-care therapy.
Purported Benefits
✓May modulate immune and hematological function (NK-cell activity, lymphocyte and white-cell counts), mostly shown in cancer-adjuvant settings rather than healthy users
✓As an adjuvant to chemotherapy/surgery in gastric, colorectal and lung cancers, PSK is associated with modestly improved survival and reduced tumor-related symptoms (low-certainty evidence)
✓PSP behaves like a prebiotic and may shift the gut microbiome in small healthy-volunteer studies
✓Standalone over-the-counter immune-boosting claims for healthy people are largely unproven and rest on immunologic surrogate markers, not clinical outcomes
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Survival as adjuvant to cancer chemo/surgery (GI cancers)Cochrane (low certainty) and pooled RCTs show modest 5-year survival gains in colorectal/gastric cancer; many trials use outdated regimens. | Moderate | ↑ benefit · small | 5 |
| Immune / hematological markers (NK activity, lymphocytes)Small phase I trials show trends in lymphocyte counts and NK activity; surrogate markers, not clinical outcomes. | Preliminary | ↑ benefit | 2 |
| Gut microbiome (prebiotic-like shift) in healthy adultsSingle small RCT (n=24) found PSP produced prebiotic-like microbiome shifts in healthy volunteers. | Preliminary | ↑ benefit | 1 |
Dosing & Compounds
Typical Dose
PSK 3 g/day or PSP ~1–3 g/day, typically as an adjuvant to conventional cancer therapy; whole-mushroom extracts have been studied at 3–9 g/day. No established dose for general immune support in healthy adults.
Active Compounds
Safety & Cautions
Generally well tolerated; the most common side effects are mild gastrointestinal upset, nausea, and darkening of the stool or nails. Because it stimulates immune activity, people with autoimmune conditions (e.g., rheumatoid arthritis, lupus, multiple sclerosis) and organ-transplant recipients on immunosuppressants should use caution or avoid it, as it may theoretically counteract immunosuppressive therapy. It may have additive effects with anticoagulant/antiplatelet drugs and could interact with immunosuppressants and certain chemotherapy agents, so cancer patients should only use it under oncologist supervision rather than self-prescribing. Safety has not been established in pregnancy or breastfeeding, and these groups should avoid it. As with all supplements, product quality, polysaccharide content, and contamination vary widely, and "turkey tail" supplements are not equivalent to the pharmaceutical-grade PSK/PSP used in clinical trials. Anyone with a serious illness should consult a clinician before use and should not substitute it for proven medical treatment. Educational only — always check with your doctor or pharmacist before combining Turkey Tail (PSK/PSP) with any medicine.
Key Studies ★ 13 studies
Meta-analysis
Ma 2017 (network meta-analysis)
✓ PubMed
Systematic review and network meta-analysis of 23 RCTs (10,684 GI-cancer patients) found adjuvant PSK significantly increased 1-5 year overall survival and 1-7 year disease-free survival without added side effects; benefit was clearest in colorectal and gastric cancer, and PSK plus chemotherapy was the superior arm (significantly improved 3- and 5-year OS).
Cochrane systematic review
7 RCTs, 1,569 patients
✓ PubMed
This Cochrane systematic review found low-certainty evidence that adjunctive Coriolus (PSK) modestly improved 5-year survival in colorectal cancer (RR 1.08, 95% CI 1.01–1.15; ~16 needed to treat for one to benefit), with very-low-certainty, uncertain effects on chemotherapy adverse events.
Systematic review and meta-analysis
23 RCTs, 4,246 patients
✓ Full text
A meta-analysis of Coriolus versicolor- and Ganoderma-related products as adjunct cancer therapy found a lower mortality risk (HR 0.82, 95% CI 0.72–0.94, ~18% reduction) and higher treatment efficacy, but no significant effect on disease control rate.
Systematic review
28 studies (6 RCTs)
✓ PubMed
A systematic review of PSK and Coriolus versicolor in lung cancer concluded most RCTs supported improved immune function, reduced tumor-related symptoms, and better 1-, 2-, and 5-year survival, while calling for larger rigorous trials.
Meta-analysis
Oba 2007 (meta-analysis of central-randomization RCTs)
✓ PubMed
Pooled analysis of 8,009 patients from 8 centrally randomized RCTs showed adjuvant PSK immunochemotherapy after curative gastric cancer resection reduced mortality with an overall hazard ratio of 0.88 (95% CI 0.79-0.98; P=0.018), no significant heterogeneity.
Agency / regulator
NCI PDQ Medicinal Mushrooms
✓ Source
NCI's PDQ Health Professional summary reviews Trametes versicolor (PSK/PSP) clinical evidence in gastric, colorectal and other cancers, characterizing trial data as mostly older Japanese adjuvant studies of variable quality.
RCT
Pierce/Standish 2012 (Phase 1)
✓ Full text
Phase 1 dose-escalation trial of Trametes versicolor (up to 9 g/day) in 9 women after breast cancer radiotherapy found it well tolerated, with trends toward increased lymphocyte counts and dose-related increases in CD8+ T cells and CD19+ B cells.
RCT
Akagi 2010 (mechanistic RCT)
✓ PubMed
Randomized trial in stage III gastric cancer (n=21): PSK + UFT vs UFT alone yielded 3-year overall survival of 62.2% vs 12.5% (P=0.038); PSK significantly reduced poor-prognosis CD57+ T cells, suggesting an immunological mechanism.
Phase I clinical trial
9 women completed
✓ PubMed
A phase I dose-escalation trial (3, 6, 9 g/day for 6 weeks) of Trametes versicolor in breast cancer patients post-treatment found it well tolerated, with trends toward increased lymphocyte counts at higher doses and increased NK-cell activity at 6 g/day.
Randomized clinical trial
24 healthy volunteers
✓ PubMed
A randomized trial found PSP from Trametes versicolor produced consistent prebiotic-like shifts in the gut microbiome of healthy volunteers, in contrast to the disruptive effects of amoxicillin.
RCT
Nakazato 1994 (Lancet RCT)
✓ PubMed
Multicenter RCT (n=262) after curative gastrectomy: adding PSK to mitomycin + fluorouracil improved 5-year disease-free rate (70.7% vs 59.4%, P=0.047) and 5-year survival (73.0% vs 60.0%, P=0.044), with only slight toxicity.
RCT
Ohwada 2004 (BJC RCT)
✓ PubMed
RCT in stage II/III colorectal cancer (n=205): oral PSK + UFT vs UFT alone improved 5-year DFS (73.0% vs 58.8%, P=0.016) and reduced recurrence by 43.6%; in stage III, PSK significantly increased DFS (60.0% vs 32.1%, P=0.002) and OS (74.6% vs 46.4%, P=0.003).
Observational
Wang 2022 (Medicine)
✓ Full text
In a Taiwan retrospective cohort of gastric cancer patients after gastrectomy plus adjuvant chemotherapy, adding PSK was associated with longer median overall survival (6.49 vs 3.59 years; adjusted HR 0.76, P<0.0001).