Medicinal Mushrooms and Cancer: What Trials Show About Turkey Tail, Shiitake, Reishi, and Eating Mushrooms

Can mushrooms help treat cancer? Some mushroom extracts may help when added to standard treatment. In Japan, PSK from turkey tail mushroom, given with chemotherapy after surgery, was linked to modestly longer survival in gastric and colorectal cancer trials, and lentinan from shiitake showed similar results in advanced gastric cancer. No study shows mushrooms can replace surgery, chemotherapy, or radiation, and supplements sold in the U.S. differ from these tested drugs.

Stories about mushrooms fighting cancer often begin with a striking image: fungi growing on tumors in a lab dish, or a patient who credits a mushroom supplement with recovery. Behind the headlines is a real field of research. Japan approved a turkey tail mushroom extract called PSK (Krestin) for use with cancer treatment decades ago, and researchers in Asia, Europe, and the United States have tested mushroom compounds in hundreds of studies. The results are more modest than online claims suggest, and they apply to specific, standardized extracts used alongside conventional care. This article explains which mushrooms have been studied, what clinical trials found, what eating mushrooms may do for cancer risk, and how to approach mushroom supplements safely.

Which Mushrooms Have Been Studied for Cancer?

The best-studied are turkey tail (Trametes versicolor, also called Coriolus versicolor), shiitake (Lentinula edodes), and reishi (Ganoderma lucidum). Much of the interest centers on beta-glucans and protein-bound polysaccharides, large sugar-based molecules in mushroom cell walls that can stimulate parts of the immune system in laboratory studies. Two mushroom-derived drugs have been used in cancer care in Japan for decades: PSK, also called polysaccharide-K or Krestin, extracted from turkey tail, and lentinan, extracted from shiitake. These are standardized pharmaceutical products, which is an important difference from the mushroom powders and capsules sold as supplements.

What Did Trials of PSK From Turkey Tail Find?

PSK has the largest body of clinical evidence among mushroom extracts, almost all from Japan. A 2007 meta-analysis in Cancer Immunology, Immunotherapy by Koji Oba and colleagues pooled eight centrally randomized trials with 8,009 patients who had surgery for gastric cancer. Adding PSK to chemotherapy reduced the risk of death by about 12 percent compared with chemotherapy alone. A 2006 meta-analysis in the same journal by Junichi Sakamoto and colleagues analyzed three trials with 1,094 patients after surgery for colorectal cancer and found about 29 percent lower risk of death and 28 percent lower risk of recurrence with PSK added to chemotherapy. These results are encouraging, but the trials were done decades ago with older chemotherapy regimens, and it is unclear whether PSK adds the same benefit to modern treatments.

What About Lentinan From Shiitake?

Lentinan is a purified beta-glucan from shiitake that has been given by injection with chemotherapy in Japan and China. A 2009 individual-patient meta-analysis in Anticancer Research by Oba and colleagues combined data from 650 patients with advanced or recurrent gastric cancer in five randomized trials. Adding lentinan to chemotherapy was associated with about 20 percent lower risk of death, with a possibly larger benefit in patients whose cancer had spread to lymph nodes. As with PSK, the trials used older chemotherapy combinations, and lentinan is an injected drug, not the same as eating shiitake mushrooms or taking shiitake capsules.

How Strong Is the Overall Evidence for Turkey Tail?

Weaker than single meta-analyses might suggest. A 2022 Cochrane review by Kathryn Pilkington and colleagues examined seven randomized trials with 1,569 people treated for colorectal cancer, six of them in Japan, all using turkey tail extracts, mainly PSK, alongside chemotherapy. The reviewers found very low-certainty evidence that turkey tail made little or no difference to stopping treatment because of side effects, uncertain effects on specific side effects such as low white blood cell counts, nausea, and fatigue, and low-certainty evidence of a small improvement in five-year survival. Most trials had methodological weaknesses. In the United States, a 2012 phase 1 trial in ISRN Oncology by Carolyn Torkelson and colleagues gave women who had completed breast cancer treatment up to 9 grams a day of turkey tail powder and found it was well tolerated, with signs of increased immune cell counts. That study was designed to test safety, not to show whether turkey tail improves survival.

Does Reishi Mushroom Help Cancer Patients?

The evidence is limited. A 2016 Cochrane review by Xingzhong Jin and colleagues found five randomized trials, mostly small and of poor methodological quality. Patients given reishi alongside chemotherapy or radiation were somewhat more likely to show tumor response than those on standard treatment alone, and several immune markers rose slightly, while reishi alone did not show similar effects. Four studies reported better quality of life. The reviewers concluded there was not enough evidence to justify reishi as a first-line cancer treatment and that it might be considered only as an add-on, given its generally tolerable safety profile in those trials.

How Are Mushroom Compounds Thought to Work?

Mostly through the immune system rather than by killing cancer cells directly. Beta-glucans and related polysaccharides are recognized by receptors on immune cells, such as dectin-1 and complement receptor 3, which are designed to detect fungi. When these receptors are activated, macrophages, natural killer cells, and other immune cells become more active and release signaling molecules. In theory, this could help the body respond to cancer cells or recover from the immune suppression caused by chemotherapy. Laboratory studies also suggest some mushroom compounds may slow cancer cell growth directly. How much these effects matter in patients depends on the specific compound, dose, and form, and on whether it is absorbed when taken by mouth, which is one reason results vary so much between products.

Could Mushroom Extracts Interfere With Immunotherapy?

That question has not been well studied. Modern immunotherapy drugs, such as checkpoint inhibitors, work by releasing brakes on the immune system, and adding other immune-active substances could in theory either help or cause unexpected effects, including more immune-related side effects. Because there are few clinical data on combining mushroom extracts with these newer drugs, oncologists generally advise caution and want to know about any immune-modulating supplement a patient takes. This is an area where research is ongoing, and patients should not assume that a supplement that “boosts immunity” will improve immunotherapy results.

Does Eating Mushrooms Lower Cancer Risk?

Observational studies suggest a link. A 2021 meta-analysis in Advances in Nutrition by Djibril Ba and colleagues at Penn State pooled 17 studies and found that people who ate the most mushrooms had a 34 percent lower risk of cancer overall than those who ate the least. The association was strongest for breast cancer, with about 35 percent lower risk; links with other specific cancers were weaker or based on too few studies. Eleven of the 17 studies were case-control designs, which rely on people remembering past diets after diagnosis and are prone to bias. Mushrooms are low in calories and provide fiber, B vitamins, selenium, and the antioxidant ergothioneine, so they are a healthy food regardless, but these findings do not show that mushrooms prevent cancer.

Are Mushroom Supplements the Same as the Tested Extracts?

Usually not. PSK and lentinan are standardized pharmaceutical products made with specific extraction methods and tested in clinical trials. Mushroom supplements sold in the United States are regulated as dietary supplements, which do not require proof of effectiveness before sale, and their content varies widely. Many products are made from mycelium grown on grain, which can contain a large share of starch from the grain rather than mushroom beta-glucans, while others use the fruiting body, the part that grows above ground. Independent testing has found that some products contain far less beta-glucan than their labels suggest. Choosing products with third-party testing and clear labeling of the mushroom part and beta-glucan content helps, but no supplement should be assumed to match the results of PSK trials.

Are Mushroom Supplements Safe During Cancer Treatment?

They are generally well tolerated in trials, but caution is warranted. Mushroom extracts can affect the immune system, which raises questions for people on immunotherapy, after organ or stem cell transplants, or taking immunosuppressive drugs. Reishi has been linked to rare reports of liver injury and may affect blood clotting, which matters for people on blood thinners or with low platelet counts during chemotherapy. Some supplements may interact with how the liver processes medicines. Contamination with heavy metals or other substances is possible in poorly controlled products. Anyone in cancer treatment should tell their oncology team about any mushroom supplement before starting it.

How Do Mushroom Options Compare?

Why Can’t Mushrooms Replace Cancer Treatment?

Because no study has shown that they can. Every positive clinical trial of PSK and lentinan tested the extracts as additions to surgery and chemotherapy, not as substitutes. Laboratory findings that mushroom compounds slow cancer cells in a dish or in mice often fail to translate into people. Choosing a mushroom regimen instead of proven treatment risks allowing a treatable cancer to grow, a danger also seen with other unproven remedies such as IV curcumin and cannabis oil. Integrative oncology programs at major cancer centers can help patients evaluate supplements safely alongside standard care.

Why Does Most Mushroom Cancer Research Come From Japan and China?

Medicinal mushrooms have a long history in East Asian traditional medicine, and Japan approved PSK and lentinan as cancer-related drugs in the late 1970s and 1980s, which led to many clinical trials there. Health systems in Japan and China have covered these products, so researchers had both cultural and practical reasons to study them. Western research has been more limited, partly because mushroom extracts are hard to patent and partly because regulators require modern trials with current treatments. This geographic concentration matters: results from Japanese patients receiving older oral chemotherapy may not apply to patients elsewhere receiving today’s regimens, which is why reviewers call for new, well-designed trials.

What Nutrients Do Everyday Mushrooms Provide?

Common culinary mushrooms, such as white button, cremini, portobello, shiitake, and oyster, are low in calories and provide fiber, B vitamins such as riboflavin and niacin, potassium, selenium, and copper. They are among the richest dietary sources of ergothioneine, an antioxidant compound researchers are studying for links to healthy aging. Mushrooms exposed to ultraviolet light can be a meaningful source of vitamin D. Using mushrooms to replace some meat in dishes lowers saturated fat and calories while keeping a savory flavor. Whatever their effect on cancer, they fit well into the kind of plant-rich diet linked to lower risk of many chronic diseases.

How Should Patients Talk to Their Oncologist About Mushrooms?

Bring the specific product, including its label, to an appointment and ask whether it could interact with your treatment. Ask whether your cancer center has an integrative oncology service, which can review supplements for safety and evidence. Be honest about what you are taking, since many patients do not tell their doctors about supplements, which can lead to unrecognized interactions. Ask what outcome you hope the mushroom will improve, such as fatigue, appetite, or immune recovery, and whether there are treatments with better evidence for that goal. Eating mushrooms as food is almost always fine and can be part of a healthy diet during and after treatment, unless your team advises otherwise, for example during periods of very low white blood cell counts when food safety precautions apply.

What About Chaga, Maitake, and Lion’s Mane?

These popular mushrooms have even less clinical evidence for cancer. Maitake extracts have been tested in small early-phase studies, including at U.S. cancer centers, mainly to measure safety and immune effects rather than survival. Lion’s mane is marketed mostly for brain health, and its cancer research is almost entirely laboratory-based. Chaga, a fungus that grows on birch trees, is high in oxalates, and case reports have linked heavy chaga use to kidney damage from oxalate buildup. For all three, there is not enough human evidence to recommend them for cancer prevention or treatment, and the same cautions about product quality and interactions apply.

How Can You Spot Misleading Mushroom Cancer Claims?

Be skeptical of products or posts that promise to cure, shrink, or reverse cancer, rely on personal testimonials rather than trials, cite only laboratory or animal studies, or suggest stopping conventional treatment. Watch for claims that a supplement contains “the same compound as” PSK or lentinan without evidence of equivalent dose and preparation. Legitimate sources describe which specific extract was tested, in which cancer, alongside which treatment, and how large the effect was. Under U.S. law, supplement makers are not allowed to claim their products treat or cure diseases, so such claims are themselves a warning sign.

What Is Integrative Oncology?

Integrative oncology combines evidence-based complementary approaches, such as exercise, nutrition, mind-body practices, acupuncture, and carefully selected supplements, with standard cancer treatment to manage symptoms and improve quality of life. Many major cancer centers have integrative medicine services staffed by physicians, pharmacists, and dietitians who can review supplements for interactions and evidence. Professional groups such as the Society for Integrative Oncology publish guidelines on which approaches have support for specific symptoms. For patients interested in medicinal mushrooms, these services offer a way to explore them without risking harmful interactions or delays in proven care.

Common Myths

“Mushrooms cure cancer.” No trial has shown mushrooms can replace standard treatment.

“Any turkey tail supplement equals PSK.” PSK is a standardized drug; supplements vary widely.

“Natural means safe during chemotherapy.” Some extracts may affect immunity, clotting, or drug processing.

“Lab results prove benefit in people.” Effects in cells and mice often do not hold up in human trials.

“Eating mushrooms has been proven to prevent cancer.” The link comes from observational studies that cannot prove cause and effect.

Key Terms

PSK (polysaccharide-K): A protein-bound polysaccharide drug extracted from turkey tail mushroom.

Lentinan: A beta-glucan drug extracted from shiitake mushroom.

Beta-glucans: Polysaccharides in mushroom cell walls that can stimulate immune activity.

Mycelium: The root-like network of a fungus, often grown on grain for supplements.

Adjuvant therapy: Treatment given after the main treatment, such as surgery, to lower the risk of recurrence.

The Bottom Line

Mushroom extracts have real but modest evidence in cancer care. In Japanese trials, PSK from turkey tail added to chemotherapy after surgery was linked to longer survival in gastric and colorectal cancer, and lentinan from shiitake showed similar results in advanced gastric cancer, though these studies used older treatments and newer reviews rate much of the evidence as low certainty. Reishi lacks good evidence. Eating more mushrooms is associated with lower cancer risk in observational studies. No research supports using mushrooms instead of standard treatment, and supplements should be discussed with an oncology team before use.

Frequently Asked Questions

Does turkey tail mushroom help fight cancer?

PSK, a standardized extract of turkey tail, was linked to modestly longer survival when added to chemotherapy after surgery for gastric and colorectal cancer in Japanese trials, with about 12 and 29 percent lower risk of death, respectively. A 2022 Cochrane review rated much of this evidence as low certainty. Turkey tail supplements sold in the U.S. are not the same as PSK.

Can mushrooms cure cancer?

No. Every positive clinical trial tested mushroom extracts alongside surgery and chemotherapy, not as replacements. Laboratory studies showing mushroom compounds slowing cancer cells do not prove effects in people. Relying on mushrooms instead of proven treatment can allow cancer to progress. Mushroom extracts should be viewed, at most, as possible additions discussed with an oncologist.

Is it safe to take mushroom supplements during chemotherapy?

Mushroom extracts were generally well tolerated in trials, but they can affect immune function and, in the case of reishi, possibly blood clotting and the liver. Product quality varies widely. People in cancer treatment, especially those on immunotherapy or with low blood counts, should talk with their oncology team before taking any mushroom supplement.

Does eating mushrooms reduce cancer risk?

A 2021 meta-analysis of 17 observational studies found people who ate the most mushrooms had 34 percent lower cancer risk overall and about 35 percent lower breast cancer risk than those who ate the least. Most studies were case-control designs prone to bias, so the findings show an association, not proof that mushrooms prevent cancer.

What is the difference between PSK and lentinan?

PSK is a protein-bound polysaccharide extracted from turkey tail mushroom and taken by mouth, studied mainly with chemotherapy after cancer surgery. Lentinan is a purified beta-glucan from shiitake given by injection, studied mainly in advanced gastric cancer. Both are standardized drugs used in Japan and differ from mushroom supplements sold in stores.

References

1. Oba K, Teramukai S, Kobayashi M, et al. Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curative resections of gastric cancer. Cancer Immunology, Immunotherapy. 2007;56(6):905–911. PMID 17106715
2. Sakamoto J, Morita S, Oba K, et al. Efficacy of adjuvant immunochemotherapy with polysaccharide K for patients with curatively resected colorectal cancer: a meta-analysis of centrally randomized controlled clinical trials. Cancer Immunology, Immunotherapy. 2006;55(4):404–411. PMID 16133112
3. Oba K, Kobayashi M, Matsui T, et al. Individual patient based meta-analysis of lentinan for unresectable/recurrent gastric cancer. Anticancer Research. 2009;29(7):2739–2745. PMID 19596954
4. Pilkington K, Wieland LS, Teng L, et al. Coriolus (Trametes) versicolor mushroom to reduce adverse effects from chemotherapy or radiotherapy in people with colorectal cancer. Cochrane Database of Systematic Reviews. 2022;11:CD012053. PMID 36445793
5. Torkelson CJ, Sweet E, Martzen MR, et al. Phase 1 clinical trial of Trametes versicolor in women with breast cancer. ISRN Oncology. 2012;2012:251632. PMID 22701186
6. Jin X, Ruiz Beguerie J, Sze DM, et al. Ganoderma lucidum (Reishi mushroom) for cancer treatment. Cochrane Database of Systematic Reviews. 2016;4:CD007731. PMID 27045603
7. Ba DM, Ssentongo P, Beelman RB, et al. Higher mushroom consumption is associated with lower risk of cancer: a systematic review and meta-analysis of observational studies. Advances in Nutrition. 2021;12(5):1691–1704. PMID 33724299

Last updated: October 10, 2026