IngredientsThe term glucan peptides — also rendered as glucan-peptide complexes, polysaccharide-peptide complexes, or glycopeptides of fungal origin — refers to a family of high-molecular-weight bioactive macromolecules in which a β-glucan polysaccharide backbone is covalently or tightly non-covalently associated with one or more peptide (protein) moieties. They are not a single discrete chemical compound but rather a class of structurally related conjugates whose precise architecture varies according to the biological source, strain, and extraction method employed.
The two most studied and commercially significant members of this class are:
PSK and PSP are two natural products extracted from Trametes versicolor, and their main components are a highly heterogeneous mixture of β-glucan macromolecules that possess a molecular weight of approximately 100 kDa and contain various moieties, including peptides, bound to β-glucan backbones.
A third, newer sub-class has emerged from more recent isolation efforts: Musarin, a novel 12 kDa polysaccharide peptide isolated from Trametes versicolor powder, was recently found and described. Earlier work had identified other small-molecule glycopeptides: In 1992, Yang et al. isolated a small polypeptide with a molecular weight of around 10 kDa from the crude extraction of Coriolus versicolor (Cov-1) polysaccharide peptide, and its anti-cancer activities were significantly higher than PSP and PSK. A polysaccharide–peptide complex with a molecular mass of approximately 15.5 kDa was discovered by Wang et al. in 1996, and it possessed the activities of inhibiting the growth of mice-implanted sarcoma 180 cells.
The term "Beta-glucan peptide (BGP)" is also used in the scientific literature more generically. Beta-glucan peptide (BGP) is described as a high molecular weight polysaccharide extracted from the macrofungus Trametes versicolor.
β-Glucans are a group of naturally occurring polysaccharides which are widely distributed in bacteria, fungi, algae, and cereals, in which they are part of the cell wall structure and have many other biological activities. Structurally, β-glucans are long or short-chain polymers of β-(1,3) or β-(1,4) linked glucose subunits which may be branched, with the side chains branching from the six-position of the backbone. In the context of glucan peptides, the glucan backbone is specifically β-1,3-linked with β-1,6 side-branching, covalently associated with peptide chains.
β-Glucans of mushrooms have short β-(1,6)-linked branches whereas those of yeast have β-(1,6)-side branches with additional β-(1,3) regions. This structural distinction is biologically consequential, as it influences receptor recognition and downstream immune signaling.
The peptide moiety of these complexes is an integral part of their identity. The peptide moiety of PSP contains 18 different amino acids, with aspartic and glutamic acid residues being most predominant. PSP consists of polysaccharide covalently linked to peptide, since the polysaccharides and peptides cannot be separated by either native PAGE or other chromatographic methods. The inseparability of the two moieties under standard analytical conditions distinguishes glucan peptides from simple polysaccharide–protein mixtures and defines them as true conjugate macromolecules.
PSK and PSP polymers are soluble in water. This water solubility, derived from the combined polysaccharide-peptide architecture, is critical to their bioavailability after oral ingestion and to their extraction via hot-water methods.
The primary organism from which glucan peptides are commercially extracted is Coriolus versicolor (L.) Quél., a higher fungi or mushroom now known by its accepted scientific name as Trametes versicolor (L.) Lloyd (family Polyporaceae).
Trametes versicolor belongs to the more advanced Basidiomycetes class of fungi. It grows on tree trunks throughout the world in many diverse climates, including North America. It is commonly known as "Turkey Tail" mushroom owing to the multicolored banding of its fan-shaped fruiting bodies.
β-Glucan peptides are also found, in varying structural configurations, across a broader range of fungal and non-fungal biological sources. Glucans are polysaccharides, specifically polymers of glucose, which are naturally occurring and may be found in cell walls of bacteria, yeast, fungi, and plants. Beta glucans (β-glucans) are themselves a diverse subset of glucose polymers, which are made up of chains of glucose monomers linked together via beta-type glycosidic bonds to form complex carbohydrates. β-1,3-glucans are carbohydrate polymers purified from, for example, yeast, mushroom, bacteria, algae, or cereals. However, the peptide-bound form characteristic of glucan peptides is most prominent and most clinically studied in the Trametes versicolor context.
Other medicinal mushrooms also yield glucan-peptide type constituents. Turkey tail mushrooms (Trametes versicolor) are loaded with beta-glucans, notably polysaccharide-K (PSK) and polysaccharide-peptide (PSP). Both compounds have been studied for their major immune-modulating and anti-cancer properties and are even used as an adjunct therapy for cancer in Japan.
Medically used PSP is mostly obtained from the extraction of cultured Coriolus versicolor mycelia where β-glucan is the major component. Medically used PSP is mostly obtained from the extraction of Coriolus versicolor mycelia by batch fermentation.
As dietary supplements and pharmaceutical preparations, glucan peptides are available in multiple forms. Nutritional supplements may be manufactured by adding the β-glucan-peptide complex to a capsule, tablet or pill. As a health functional food, the β-glucan-peptide complex itself may be manufactured in the form of tea, juice and drink and thus ingested after liquefaction, granulation, encapsulation, and powdering. To use the β-glucan-peptide complex in the form of a food additive, the peptide complex may be manufactured in the form of a powder or concentrate.
Two proteoglycan fractions, polysaccharide-K (PSK) and Polysaccharide-peptide (PSP), are similar hot water extracts of Trametes versicolor with reported anticancer activity. The hot-water extraction process is the standard industrial method that releases soluble glucan-peptide conjugates while leaving behind insoluble cell-wall components. PSK is standardized to specific ratios of protein-bound polysaccharide and was registered as a pharmaceutical drug in Japan. PSP, developed in China, is available both as a pharmaceutical preparation and as a dietary supplement in various markets.
Traditional Chinese medicine uses Trametes versicolor (formerly Coriolus versicolor) for its longevity-enhancing and health-promoting properties. Coriolus versicolor is one of the most well-known traditional food and medicinal mushrooms in China for thousands of years.
The Trametes versicolor mushroom has a long history of treasured use in Asia as both a food and a medicine. In China, it is called yun zhi or "cloud fungus."
In the past few decades, Coriolus versicolor (taxonomic name, Trametes versicolor; Chinese name: Yun Zhi) and its related mushrooms recorded in traditional Chinese medicine (TCM) literature have found their way to the market in Asian countries as anticancer remedies, and potentially play an important role in the whole course of cancer treatment such as the recovery stage of post-operation, and the stages during and after radiotherapy or chemotherapy.
According to Kidd, the immunomodulatory activity of polysaccharide peptides in Trametes versicolor was discovered in 1965 in Japan by a chemical engineer who observed a case of cancer remission after ingesting yun zhi. Subsequent research led to identification of two closely related proteoglycan constituents of Trametes versicolor with anticancer activity: Krestin (PSK) and polysaccharide peptide (PSP).
Studies on the immunotherapeutic potential of the Coriolus versicolor polysaccharides in cancer started in the late 1970s and accelerated in the 1980s and 1990s. This systematic investigation built directly upon the centuries of traditional use by attempting to isolate and characterize the active constituents responsible for observed medicinal effects.
The historical use was broad in scope. PSP has proven beneficial to survival and quality of life not only for cancer patients but also shown efficacy in patients with hepatitis, hyperlipidemia, and other chronic diseases. These areas of traditional application — immunity, liver health, and metabolic regulation — correspond to the broad health categories attributed to yun zhi preparations in classical TCM texts.
An immunotherapeutic regime that employs polysaccharopeptide (PSP), a unique peptide-containing polysaccharide isolated from Coriolus versicolor, has already become routine clinical practice in Japan since 1977 and in China since 1987. This institutionalization represents a transition from traditional folk use to formally approved medical practice, an uncommon trajectory for any natural product. In Japan, PSK is prescribed to cancer patients routinely, both during and after radiation and chemotherapy.
The primary active structural unit of glucan peptides is the β-glucan polysaccharide backbone. The most-studied immunoactive structure of β-glucan is a β-1,3 backbone of D-glucose with β-1,6 branches of variable length and complexity. The degree of branching, molecular weight, and solution conformation (triple helix vs. random coil) all affect biological potency.
The chemical structure of β-1,3-glucan depends on the source of the β-1,3-glucan. Moreover, various physicochemical parameters, such as solubility, primary structure, molecular weight, and branching, play a role in biological activities of β-1,3-glucans.
What distinguishes glucan peptides from simple β-glucans is the covalently associated peptide component. As noted above, the peptide component of PSP contains 18 different amino acids, with aspartate and glutamate predominating. This peptide moiety is not merely a contaminant of extraction; its covalent linkage to the glucan backbone appears to be integral to the molecule's pharmacological profile, though the precise contribution of the peptide to immunological activity versus that of the glucan alone remains an active area of research.
The mechanisms by which glucan peptides exert their biological effects are mediated through specific pattern-recognition receptors of the innate immune system. Based on in vitro studies, beta-glucans act on several immune receptors including Dectin-1, complement receptor (CR3) and TLR-2/6 and trigger a group of immune cells including macrophages, neutrophils, monocytes, natural killer cells and dendritic cells.
Recent discoveries, including identification of beta-glucan receptors, such as dectin-1, have started to shed some light on the mechanisms underlying the properties of these carbohydrates. The characterization of dectin-1 has revealed some of the processes involved in beta-glucan sensing, intracellular signaling, and induction of cellular responses and has provided new insights into the role of beta-glucans in immunity and disease.
Neutrophils, macrophages, and dendritic cells among others express several receptors capable of recognizing beta-glucan in its various forms. Special emphasis has been placed on Dectin-1, as we know the most about how this key beta-glucan receptor translates recognition into intracellular signaling, stimulates cellular responses, and participates in orchestrating the adaptive immune response.
Among the most important receptors that interact with β-glucans are Dectin-1, complement receptor type 3 (CR3), and Langerin. Dectin-1 is a type II transmembrane protein present in leukocytes, with the highest levels of expression in neutrophils, macrophages and dendritic cells.
Dectin-1 consists of an extracellular C-type lectin domain for β-(1,3)-glucan detection, linked via a transmembrane domain to an intracellular signaling tail. A stalk region linking the C-type lectin domain to the transmembrane domain is present in some isoforms. Upon recognition of β-glucan, Dectin-1 activates downstream signaling cascades including Syk kinase and the CARD9 adaptor pathway, leading to NF-κB activation and induction of cytokine responses.
Notably, receptor redundancy has been observed: in both a model of β-glucan-mediated protection against systemic Staphylococcus aureus infection and in zymosan-induced multiple organ dysfunction syndrome, β-glucan rich compounds had marked effects in vivo which were unaltered by Dectin-1 deficiency, suggesting that this receptor has a redundant role in these murine models. This implies that CR3, TLR-2/6, and other receptors can compensate for Dectin-1 in certain biological contexts.
The most well-characterized mechanism of β-glucan-mediated antitumor efficacy acts through the receptor for complement-component 3 (CR3) to induce neutrophil or NK cell cytotoxic activity against tumors opsonized with inactivated complement component 3b (iC3b).
β-Glucans are captured by macrophages via the Dectin-1 receptor with or without TLR-2/6. The large β-glucan molecules are then internalized and fragmented into smaller sized β-glucan fragments within the macrophages. They are carried to the marrow and endothelial reticular system and subsequently released. These small β-glucan fragments are eventually taken up by the circulating granulocytes, monocytes or macrophages via the complement receptor (CR)-3. The immune response will then be turned on, one of the actions being phagocytosis of the monoclonal antibody-tagged tumor cells.
β-1→3-D-glucans represent a pathogen-associated molecular pattern and are able to modify biological responses. In vitro studies using fungal β-1→3-D-glucan (glucan phosphate) have provided insight into the nuanced pro- and anti-inflammatory signaling balance: despite an activation of nuclear factor (NF)κB, NFinterleukin(IL)-6 and NFAT similar to LPS or TSST-1, no significant production of IL-1β, IL-6, tumor necrosis factor α or interferon γ was induced by glucan phosphate. This suggests that glucan peptides can activate innate immune surveillance pathways without triggering a full pro-inflammatory cytokine storm.
The proposed mechanisms involve a Th1 adaptive immune response via activation of dendritic cells, thus modulating the immunosuppressive tumor microenvironment to produce an inflammatory antitumor response.
Studies into the cellular and molecular mechanisms of action via fluorescence microscopy show that orally administered β-1,3/1,6-glucans are engulfed and processed by macrophages and dendritic cells that later travel to the different immune organs and release fragmented soluble β-1,3-glucan particles. This results in the priming of leukocytes via Dectin-1, CR3 and other collaborating receptors to enhance immuno-surveillance and counter pathogen attack by increasing the function of the complement system and innate immune cells, leading to improved antimicrobial and inflammatory responses.
More recent mechanistic research has proposed additional receptor interactions: beta-1,3 glucans may promote activation of T cells by a previously unknown mechanism. Treatment of a T lymphoblast cell line with beta-1,3 oligoglucan significantly increases mRNA levels of T cell activation-associated cytokines, especially in the presence of the agonistic anti-CD3 antibody. This immunostimulatory activity was observed in the absence of Dectin-1, a known receptor for beta-1,3 glucans.
This is the area with the most extensive human clinical evidence for glucan peptides. The body of evidence, while substantial in volume, carries significant limitations relating to study age, variable standardization of preparations, and predominantly Asian populations.
The most comprehensive pooled analyses to date cover both PSK and PSP preparations from Trametes versicolor. Randomized controlled trials were identified by systematic search over seven databases from inceptions to May 10, 2019. Two independent reviewers extracted data and assessed study quality. Meta-analyses were performed to pool hazard ratio (HR), risk ratio (RR), mean differences (MD), and 95% CI using random-effects models. Sources of heterogeneity were explored by subgroup analyses and sensitivity analyses. Publication bias was detected by Funnel plots, Begg's test, and Egger's test. Twenty-three trials involving 4,246 cancer patients were included.
Twenty-three trials involving 4,246 cancer patients were included in this work. C. versicolor and G. lucidum related natural products were significantly associated with lower risks of mortality (HR: 0.82; 95% CI: 0.72, 0.94) and higher total efficacy (RR: 1.30; 95% CI: 1.09, 1.55), but not associated with control rate compared with control treatment. There was no significant difference between C. versicolor related natural products and control treatment in the effect on relapse-free survival (HR: 1.19; 95% CI: 0.91, 1.55).
Compared with control treatment, C. versicolor and G. lucidum related natural products had a favorable effect on elevated levels of CD3 (MD: 9.03%; 95% CI: 2.10, 16.50) and CD4 (MD: 9.2%; 95% CI: 1.01, 17.39), but had no effect on the levels of CD8, CD4/CD8 ratio, or NK cells.
An earlier meta-analysis of PSK specifically in colorectal cancer reported: a systematic review and meta-analysis assessed the survival outcome in cancer patients from 13 clinical trials on C. versicolor. They reported a significant survival advantage when compared with standard conventional anti-cancer agents alone — a 9% absolute reduction in 5-year mortality was recorded, with one additional patient alive for every 11 patients treated.
A Cochrane-reviewed analysis of Coriolus versicolor in colorectal cancer found: a Cochrane review examining Coriolus (Trametes versicolor) extracts (primarily PSK) in colorectal cancer found very low-certainty evidence of a small survival benefit at 5 years when PSK was added to chemotherapy or radiotherapy compared to conventional treatment alone.
In 23 trials, 5 included non-small cell lung cancer (NSCLC) patients, 3 included breast cancer patients, 4 included gastric cancer patients, 4 included colorectal cancer patients, 3 included nasopharyngeal carcinoma patients, and the other 4 trials included esophageal cancer, rectal cancer, gastrointestinal cancer, and hepatocellular carcinoma patients, respectively. The range duration of therapy was 1 to 24 months.
A randomized, double-blind, placebo-controlled trial evaluated PSP in NSCLC: Non-small cell lung cancer is a leading cause of cancer deaths, and over 60% of patients present with advanced stages. Although polysaccharide peptides (PSP), isolated from the fungus Coriolus versicolor, have been reported to have anti-tumor effects, its clinical efficacy had not been properly evaluated. A double-blind placebo-controlled randomized study evaluated the effects of 28-day administration of PSP on patients who had completed conventional treatment for advanced NSCLC. Thirty-four patients with no significant difference in their baseline characteristics were recruited into each of the PSP and control arms. After 28-day treatment, there was a significant improvement in blood leukocyte and neutrophil counts, serum IgG and IgM, and percent of body fat among the PSP, but not the control, patients (P<0.05). PSP treatment appears to be associated with slower deterioration in patients with advanced NSCLC.
In human studies, non-small cell lung cancer patients have increased leukocyte and neutrophil counts after PSP consumption, as well as increased serum IgG and IgM.
Morimoto and colleagues conducted a 5-year postoperative randomized controlled trial comparing chemotherapy with Krestin (PSK) immune therapy in 376 women with stage II ER-negative breast cancer who received either a prodrug of 5-fluorouracil or 3,000 mg/d Krestin (PSK). The 5-year overall and relapse-free survival rates for ER-negative patients were the same regardless of whether they had received chemotherapy alone or Krestin (PSK) alone.
A comprehensive study of PSK in gastric cancer found: a comprehensive study with 349 gastric cancer patients receiving PSK (3 g/day) as adjuvant immunotherapy revealed a greatly improved 3-year recurrence-free survival (RFS) rates when patients were MHC class I-negative.
Clinical trial data for PSP in breast cancer further showed: clinical trial data for Krestin (PSK) from China and PSP from Japan suggest that PSP immunomodulation improves disease-free and overall survival in breast cancer.
In a randomized study of 158 esophageal cancer patients, the survival of the radiochemotherapy plus Krestin (PSK) (3,000 mg/d for 12 weeks) group was significantly better than that in the group receiving radiochemotherapy alone.
PSP has previously been shown to have immuno-stimulatory, anti-tumour and analgesic effects in animal models. When used as an adjunct in cancer chemotherapy in clinical trials carried out in China, PSP improved the quality of life in the patients by improving appetite and alleviating symptoms associated with cancer chemotherapy.
TNF-alpha and IL-8 gene expression were significantly induced after PSK administration in healthy volunteers and gastric cancer patients, although individual response varied.
Healthy volunteers and breast cancer patients who used a formula containing Coriolus and Salvia had elevated CD4+ counts, a high CD4+/CD8+ ratio, and elevated absolute counts of B-lymphocytes.
Most trials predate modern oncology standards, with variable randomization, blinding, and control conditions. Extracts and dosages are heterogeneous across studies. Many trials were conducted prior to contemporary chemotherapy regimens. The complexity and high molecular weight of PSK and PSP make it difficult to study their mechanism of action, and for a long time, they have only been used as adjuvant to supplement chemotherapy and radiation therapy rather than as an anti-cancer drug for clinical treatment.
The intricacy and high molecular weight make mechanistic research difficult, which restricts their further application as a medication in clinical cancer treatment.
Studies provide evidence on the potential immunomodulatory effects of yeast β-glucans: On one hand, the substances elicit/amplify the immune reaction as shown in the prevention of infections; on the other hand, they are capable of reducing the inflammatory reaction by inducing anti-inflammatory processes.
In preclinical (animal) models, PSP has demonstrated immunopotentiating effects specifically under conditions of immune suppression: PSP possessed immunopotentiating effects, being effective in restoring CPA-induced immunosuppression such as depressed lymphocyte proliferation, Natural Killer cell function, production of white blood cells. Effects of PSP (2 g/kg/day) on cyclophosphamide-induced immunosuppression were investigated by determining lymphocyte proliferation, Natural Killer (NK) cell formation, IgG and IL-2 concentration, WBC count and the weight of organs.
A cross-over study investigated the humoral immune and inflammatory response in participants aged 65 years or older after consuming 2.5 mg of Lentinex each day for 6 weeks, and showed a significant increase in circulating B cell number.
Pre-clinical studies have revealed major insights in relation to β-1,3/1,6-glucan signaling pathways and toxicological parameters; however, further research involving large randomized controlled trials with a clear immunological target need to be undertaken before the association of β-glucan and immuno-stimulation in humans can be more clearly understood. This characterizes the current state of the human clinical evidence as promising but insufficiently confirmed at a high evidentiary standard.
A randomized clinical trial directly investigated the prebiotic potential of PSP from Trametes versicolor: PSP led to clear and consistent microbiome changes consistent with its activity as a prebiotic. Despite the diversity of the human microbiome, strong microbiome clustering was noted among subjects. The microbiomes of healthy individuals show substantial diversity but remain stable over time; the antibiotic amoxicillin alters the microbiome and recovery from this disruption can take several weeks. PSP from T. versicolor acts as a prebiotic to modulate human intestinal microbiome composition.
This evidence is from a small randomized human trial and should be considered preliminary but specifically mechanistically plausible given that the β-glucan component of glucan peptides is a known substrate for certain beneficial colonic bacteria.
Clinical trials into the effects of β-glucan on the immune system have demonstrated that β-glucans not only affect the immune system but may also reduce cholesterol levels. It has been demonstrated that β-glucans not only affect the immune system but may also reduce cholesterol levels. Different types of β-glucans, not only β-glucans found in oats, are able to reduce cholesterol levels.
In the context of glucan peptides specifically, Chinese clinical data referenced in the literature indicate PSP has been used in patients with hyperlipidemia, though the peer-reviewed primary clinical trial literature on this endpoint for PSP/PSK specifically is limited. The more robust cholesterol-reduction evidence applies to cereal-derived oat β-glucans, which have different structural properties (β-1,3/1,4 linkages vs. β-1,3/1,6 in fungal sources) and are not glucan peptide conjugates.
PSK was found to have an inhibitory effect on colon cancer cell lines (HT29 and SW480) by Hirahara et al. According to Roca's results, LoVo and HT-29 human colon cancer cells were prevented from proliferation, migration, and invasion by treatment of polysaccharide-rich extracts from Trametes versicolor. They suggested that the antitumor activity may be caused by elevating the expression of E-cadherin protein and suppressing the activity of MMP-2.
Regarding the broader pattern of colorectal cancer clinical research: Almost all of these studies were done in Japan and focused on cancers of the esophagus, stomach, colon, or breast. Most of them found that people with cancer were helped by PSK. People who received PSK along with other treatments, such as surgery, chemotherapy, or radiation therapy, generally had longer disease-free periods and increased survival rates compared with patients who got only standard treatment.
PSP inhibits the growth and metastasis of various tumors in animal models in addition to preventing tumor formation brought on by different chemical carcinogens. PSP inhibited cancer cell migration and significantly reduced the production of matrix metalloproteinase MMP-9 in a time- and dose-dependent manner, according to in vitro cell migration assays of breast cancer cells from 4T1 mice. When given PSP therapy in vivo, mice injected with 4T1 cells showed inhibited proliferation in the lung, preventing the development of liver metastases. These are preclinical animal findings and have not been confirmed in human trials.
β-Glucan is active in all species from earthworms to humans, and is able to stimulate humoral and cellular immunity, metabolically regulate diabetes, stimulate wound healing, reduce psychophysical stress, attenuate chronic fatigue syndrome and inhibit the development of cancer. These findings arise from a broad literature spanning multiple β-glucan types and sources; the degree to which each of these effects applies specifically to the peptide-conjugated fungal forms requires differentiation in interpreting the literature.
The following dosages are reported strictly as they appear in cited peer-reviewed and clinical sources, and are not prescriptive recommendations.
Doses of PSK most commonly used have been between 1 g and 3.6 g daily.
In the phase I breast cancer trial at the University of Minnesota / Bastyr University, doses of whole Trametes versicolor preparation were escalated: A phase I, two-center, dose escalation study determined the maximum tolerated dose of a Tv preparation when taken daily in divided doses for 6 weeks after recent completion of radiotherapy. Eleven participants were recruited and nine women completed the study. Each cohort was comprised of three participants given one of three doses of Tv (3, 6, or 9 grams).
In a randomized study of 158 esophageal cancer patients, Krestin (PSK) was administered at 3,000 mg/d for 12 weeks.
The randomized placebo-controlled trial using 2.4 g as a daily treatment for approximately 5.9 weeks showed a better quality of life without a significant difference in the primary endpoint measure of the median time to progression.
In the NSCLC randomized trial, PSP was administered over 28 days; the specific per-day dose was not reported in the cited abstract.
The gastric cancer adjuvant study used: PSK at 3 g/day as adjuvant immunotherapy in 349 gastric cancer patients.
A cross-over study used 2.5 mg of Lentinex (a soluble β-1,3/1,6-glucan from Lentinus edodes) each day for 6 weeks.
For PSP pharmacokinetics: PSK is rapidly absorbed and partly metabolised in the gastrointestinal tract. Peak plasma levels occur between 0.5 to 2 hours for small molecules and 4 to 24 hours for large molecules. Excretion is primarily through the lungs with 70% excreted in expired air after 24 hours. Radiolabelled PSK or its metabolites are also excreted in the urine and faeces with 86% excreted within 24 hours.
Toxicological assessments indicate that PSK and PSP have low toxicity with no reports of abnormalities in animals or humans following acute and chronic toxicity tests.
PSK and PSP have been used as adjuvant therapy for cancer in Japan and China and are commonly considered nontoxic in addition to having no adverse effects.
Turkey Tail extracts like PSK and PSP are generally well tolerated, with few serious adverse events reported. Common mild effects include gastrointestinal discomfort. Multiyear dosing at 3 g/day has been documented in cancer patients without serious toxicity.
The phase I breast cancer trial found: Nine adverse events were reported (7 mild, 1 moderate, and 1 severe), suggesting that Tv was well tolerated. These findings show that up to 9 grams/day of a Tv preparation is safe and tolerable in women with breast cancer in the postprimary treatment setting.
Side effects from PSK in these studies were very mild.
Adverse interactions between Coriolus versicolor mushroom and herbs or drugs have not been reported except for a potential interaction with cyclophosphamide. This is pharmacologically plausible given that PSP has been shown in preclinical data to modulate the plasma half-life and clearance of cyclophosphamide: PSP enhanced the plasma half-life of anti-cancer drugs and decreased the clearance rate of cyclophosphamide, while increasing the cytotoxic effect of cyclophosphamide on the HepG2 cancer cell line. This interaction is consequential in oncology settings where cyclophosphamide dose-intensity matters.
A rat study examined the effects of PSP on phase I drug metabolism: The effects of non-toxic doses of PSP on phase I metabolism was investigated in the rat using the conventional probe antipyrine. Acute PSP (3–5 micromol/kg, i.p.) treatment did not produce significant changes in antipyrine clearance. This suggests limited acute effects on cytochrome P450-mediated metabolism at the doses studied, though these are animal data and do not fully characterize human drug interaction potential.
High doses of a hot water extract of Coriolus enhanced development of large intestinal tumors in mice. However, this is not clinically relevant as the dosage was 10–13x higher than what is used in human studies and the mice were injected with known potent carcinogens.
Until safety data become available, pregnant or breastfeeding women should avoid taking Coriolus. This reflects an absence of safety data rather than identified harm.
Because glucan peptides exert immunostimulatory effects, their use in individuals with autoimmune conditions or those receiving immunosuppressive therapy represents a theoretical concern not yet formally evaluated in dedicated clinical trials. All sufficiently-purified polysaccharidic immunomodulators distinguish themselves by very low toxicity (e.g., lentinan has an LD50 (mouse) >1600 mg/kg). However, low acute toxicity does not address chronic immunological consequences in susceptible populations.
A practical consideration in evaluating the safety profile of commercially available glucan peptide supplements is that the term "Turkey Tail extract" or "PSP supplement" does not guarantee standardization. The safety data from clinical trials pertain to specific characterized preparations (PSK from Kureha Corporation, Japan; COV-1 derived PSP from specific mycelia fermentation). Commercial dietary supplement products may differ substantially in glucan content, peptide fraction, molecular weight distribution, and purity.
The evidence for glucan peptides — primarily as PSK and PSP from Trametes versicolor — is strongest for oncological adjuvant applications (Level: moderate, based on multiple RCTs and meta-analyses, though largely from older Asian trials with methodological limitations), moderate for immune modulation (Level: emerging, supported by human clinical data but requiring larger, better-controlled trials), and preliminary for gut microbiome and metabolic effects. Mechanistic understanding at the receptor and signaling level is well-developed in preclinical science. The fundamental challenge remains the structural complexity and heterogeneity of these macromolecules, which makes rigorous dose-response and mechanism attribution difficult compared with small-molecule drugs.
Health conditions that Glucan peptides may help support.
Body systems that Glucan peptides may help support.
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