# PSK (Polysaccharide K / Krestin)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/psk-polysaccharide-k-krestin
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-18
**Evidence Score:** 8 / 10
**Category:** Mushroom/Fungi
**Also Known As:** Trametes versicolor, Coriolus versicolor, Turkey Tail, Yun Zhi, Kawaratake, Polysaccharopeptide, Cloud Mushroom, Many-colored Polypore

## Overview

PSK (Polysaccharide K) is a [beta-glucan](/ingredients/condition/immune-support) extract from Trametes versicolor mushrooms that activates immune cells through Toll-like receptor pathways. It enhances T-cell production and exhibits anti-tumor properties by modulating [cytokine](/ingredients/condition/inflammation) responses and inhibiting cancer cell proliferation.

## Health Benefits

- Enhances [immune system](/ingredients/condition/immune-support) function by increasing the production of T-cells, crucial for fighting infections. - Supports cancer therapy by inhibiting tumor growth and enhancing the efficacy of chemotherapy. - Reduces [inflammation](/ingredients/condition/inflammation) by modulating cytokine production, which helps in managing autoimmune disorders. - Promotes [liver health](/ingredients/condition/detox) by enhancing detoxification processes and protecting against liver damage. - Improves gut health by fostering beneficial gut microbiota, aiding in [digestion](/ingredients/condition/gut-health) and nutrient absorption. - Provides [antioxidant protection](/ingredients/condition/antioxidant) by neutralizing free radicals, reducing oxidative stress and cellular damage. - Supports [cardiovascular health](/ingredients/condition/heart-health) by lowering cholesterol levels, reducing the risk of heart disease.

## Mechanism of Action

PSK binds to Toll-like receptors (TLR-2 and TLR-4) on immune cells, triggering [NF-κB](/ingredients/condition/inflammation) signaling pathways that increase production of interferons and interleukins. The beta-1,3 and beta-1,6 glucan chains stimulate macrophage activation and enhance natural killer cell cytotoxicity. PSK also inhibits tumor angiogenesis by suppressing VEGF expression and promotes apoptosis in cancer cells through p53 pathway activation.

## Clinical Summary

Multiple randomized controlled trials involving over 8,000 cancer patients demonstrate PSK's adjuvant benefits in colorectal, gastric, and lung cancers when combined with chemotherapy. Studies show 10-15% improvement in 5-year survival rates with 3g daily PSK supplementation. Immunological studies confirm significant increases in T-helper cell counts and natural killer cell activity within 4-8 weeks. However, most research originates from Japan, and larger international trials are needed to confirm global applicability.

## Nutritional Profile

PSK (Polysaccharide K / Krestin) is a protein-bound polysaccharide extracted from the mycelium of Trametes versicolor (Coriolus versicolor, Turkey Tail mushroom). It is not a conventional food/nutrient source but a bioactive [immunomodulatory](/ingredients/condition/immune-support) compound. Key biochemical profile: **Primary bioactive compound:** β-glucan-protein complex with a molecular weight of approximately 94–100 kDa. The polysaccharide moiety (~75–80% by weight) consists primarily of β-1,4-linked glucose backbone with β-1,3 and β-1,6 branching. The protein component (~18–25% by weight) is rich in aspartic acid, glutamic acid, and leucine. **Bioactive compounds & concentrations (per gram of purified PSK):** β-D-glucan: ~620–750 mg; bound protein/peptides: ~180–250 mg; fucose: ~10–15 mg; mannose: ~8–12 mg; xylose: ~5–8 mg; galactose: ~5–10 mg. **Trace minerals (from fungal matrix):** selenium: ~0.5–2.0 µg/g; zinc: ~10–30 µg/g; copper: ~5–15 µg/g; manganese: ~3–10 µg/g; iron: ~15–40 µg/g. **Vitamins:** negligible quantities; trace amounts of B-vitamins (ergothioneine as a notable [antioxidant](/ingredients/condition/antioxidant) amino acid: ~1–5 mg/g in whole mushroom, lower in purified extract). **Fiber:** PSK itself is a soluble polysaccharide acting as a [prebiotic](/ingredients/condition/gut-health) dietary fiber analog; not a significant source of insoluble fiber. **Caloric/macronutrient value:** negligible at therapeutic doses (typically 1–3 g/day in clinical use). Fat content: essentially zero. **Bioavailability notes:** Oral bioavailability is moderate; the protein-bound nature of PSK enhances gastrointestinal absorption compared to unbound β-glucans. The β-glucan component is recognized by Dectin-1, CR3, and TLR-2 receptors on gut-associated lymphoid tissue (GALT), enabling immune activation even with partial systemic absorption. Peak immunological activity is observed 4–8 hours post-ingestion. The protein moiety protects against complete enzymatic degradation in the GI tract, improving functional delivery to Peyer's patches. Standard clinical dosing in Japanese oncology protocols is 3 g/day orally.

## Dosage & Preparation

Dosages for [immune support](/ingredients/condition/immune-support) typically range from 1 to 3 grams per day. Consult a healthcare provider before use.

## Safety & Drug Interactions

PSK is generally well-tolerated with mild side effects including darkened fingernails, nausea, and occasional diarrhea in 5-10% of users. It may enhance immune responses and could theoretically interact with immunosuppressive medications like cyclosporine or corticosteroids. PSK should be used cautiously in autoimmune conditions as it may overstimulate [immune function](/ingredients/condition/immune-support). Safety during pregnancy and lactation has not been established, so use is not recommended for pregnant or nursing women.

## Scientific Research

PSK has been extensively studied, with numerous clinical trials supporting its use as an adjunct in cancer therapy, particularly in Japan.

## Historical & Cultural Context

In traditional Chinese medicine, Coriolus versicolor has been used for centuries to strengthen the [immune system](/ingredients/condition/immune-support) and treat infections.

## Synergistic Combinations

PSP, Erinacine C, [Hericenone](/ingredients/condition/cognitive) B, Reishi, Maitake

## Frequently Asked Questions

### What is the typical PSK dosage for immune support?

Clinical studies typically use 3 grams of PSK daily, divided into three 1-gram doses taken with meals. This dosage has shown immune-enhancing effects in trials lasting 3-12 months.

### Can PSK be taken with chemotherapy?

Yes, PSK has been safely combined with chemotherapy in numerous clinical trials, often enhancing treatment effectiveness. However, patients should consult their oncologist before adding PSK to ensure proper timing and monitoring.

### How long does it take for PSK to show immune benefits?

Measurable increases in immune cell activity typically occur within 2-4 weeks of consistent PSK supplementation. Maximum immune enhancement effects are generally observed after 6-8 weeks of continuous use at therapeutic doses.

### Is PSK the same as turkey tail mushroom extract?

PSK is a specific standardized extract from turkey tail mushrooms (Trametes versicolor) containing concentrated beta-glucans. While turkey tail extracts may contain PSK, not all turkey tail products are standardized to PSK's specific polysaccharide profile.

### What foods naturally contain PSK?

PSK is not found naturally in common foods but must be extracted from turkey tail mushrooms through specialized processing. Fresh turkey tail mushrooms contain the precursor compounds but not the concentrated, bioactive PSK form used in supplements and research.

### Does PSK interact with common medications like immunosuppressants or blood thinners?

PSK may interact with immunosuppressant medications since it enhances immune function, potentially reducing their effectiveness in transplant or autoimmune disease management. Additionally, PSK has mild anticoagulant properties, so concurrent use with blood thinners like warfarin or aspirin should be discussed with a healthcare provider. Always inform your doctor about PSK supplementation before starting new medications.

### Is PSK safe for children, pregnant women, or the elderly?

PSK is generally considered safe for the elderly and children at appropriate dosages, though research in these populations is limited. Pregnant and breastfeeding women should avoid PSK due to insufficient safety data and its immune-stimulating effects on the developing fetus. Consult a healthcare provider before giving PSK to children or using it during pregnancy or lactation.

### What is the difference between PSK (Krestin) and other turkey tail extracts available as supplements?

PSK is a standardized, pharmaceutical-grade polysaccharide extract from turkey tail mushroom developed in Japan, while commercial turkey tail supplements vary widely in processing methods and polysaccharide content. PSK typically contains higher concentrations of beta-glucans and has stronger clinical evidence from cancer research compared to generic turkey tail extracts. The standardization and bioavailability of PSK make it more clinically reliable, though it may be more expensive than non-standardized alternatives.

---

*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
*License: CC BY-NC-SA 4.0 — Attribution required. Commercial use: admin@hermeticasuperfoods.com*