Japan uses mushroom extracts in cancer care, while immune blends rest on far less

Key takeaways

• Mushroom extracts have been approved as add-ons to cancer treatment in Japan and China for more than 30 years, but the FDA hasn’t approved any medicinal mushroom for any condition⁴⁵.
• In a pooled analysis of five Japanese trials, adding lentinan, a shiitake compound, to chemotherapy for advanced stomach cancer raised median survival from 114 to 139 days³.
• In an industry-funded study, 52 healthy adults who ate shiitake daily for four weeks showed livelier immune cells in lab tests, but nobody counted infections¹⁰¹¹¹².
• In a 2021 review of 34 trials of fungal beta-glucans, most found fewer or milder respiratory infections, but 26 of the trials used yeast or a yeast-like fungus, not mushrooms¹³.
• Raw or undercooked shiitake can cause an itchy rash of whip-like streaks, and 9 of 519 Japanese patients given lentinan by IV developed it¹.

In August 2015, a 44-year-old man arrived at an Australian hospital with a two-day-old rash that looked like whip marks. While cooking dinner, he had eaten some raw shiitake mushrooms, and by the next morning red streaks ran across his arms¹.

Steroid pills and a steroid cream didn’t stop it. The streaks spread over his torso, down his shins and onto his scalp¹. His wife, who ate the same cooked meal, had no rash, and he’d eaten cooked shiitake before with no problems¹. Ten days later the rash was clearing fast, leaving slightly darker skin¹.

Doctors call it shiitake dermatitis. Most blame lentinan, a large sugar molecule in the mushroom that heat breaks down¹.

This is the twist. In Japan, purified lentinan is a cancer medicine, given by vein alongside chemotherapy¹³. In one Japanese trial of 519 patients receiving it, 9 developed the same streaky rash¹.

That’s the medicinal mushroom story in miniature. Mushrooms hold compounds strong enough to stir the immune system. But the forms that have been tested are mostly purified extracts, given to cancer patients in Asia. The “immune blends” sold to healthy Americans are a different product.

Our article on mushroom supplements covers labels, grain fillers and the chaga and reishi safety cases. This one covers what has been tested, in whom, and what it means for you.

The tested forms are cancer medicines abroad, not shelf supplements

Medicinal mushroom extracts have been approved in Japan and China as add-ons to standard cancer treatment for more than 30 years, according to the National Cancer Institute (NCI)⁵. Japanese doctors were already testing PSK, an extract of turkey tail mushroom (Trametes versicolor), in stomach cancer patients from 1978 to 1981⁵.

China makes its own turkey tail extract, called PSP⁴. In the U.S., PSP and a related extract are sold as dietary supplements, according to integrative medicine specialists at Memorial Sloan Kettering Cancer Center (MSK) writing in The ASCO Post⁶.

The U.S. Food and Drug Administration (FDA) hasn’t approved any medicinal mushroom to treat cancer or any other condition⁴. Supplements aren’t reviewed for effectiveness before they’re sold, NCI notes, and their contents can vary from batch to batch⁴.

Most of the immune interest centers on beta-glucans, large sugar-chain molecules made by mushrooms and yeasts¹³. Our mushroom supplement article explains why a label’s “polysaccharides” number can include starch from grain.

Turkey tail’s PSK: decades of trials, mostly in Japan

Of the mushrooms NCI reviews, PSK has by far the most human trials. NCI’s summary for health professionals, last updated in November 2024, walks through them⁴.

Stomach cancer. In a 1994 Japanese trial of 262 patients who’d had surgery, 73.0% of those given PSK with chemotherapy were alive at five years, compared with 60.0% given chemotherapy alone⁴. By our math, that’s 13 more people alive out of every 100.

A 2007 pooled analysis of eight randomized trials with 8,009 patients found a modest survival edge, a hazard ratio of 0.88⁴. By our math, that’s about a 12% lower risk of death at any point during follow-up. Not every trial agreed. In one with 751 patients, five-year survival was 67.9% with PSK and 61.8% without, a gap that fell just short of statistical significance⁴.

Colorectal and lung cancer. A pooled analysis of three trials with 1,094 colorectal cancer patients found better five-year survival with PSK⁴. In lung cancer, six randomized trials of 3 grams of PSK a day with chemotherapy each reported a benefit on at least one measure, from immune tests to weight, symptoms or survival⁴.

These trials paired PSK with chemotherapy drugs such as mitomycin and tegafur⁶. The sources we reviewed don’t show whether it adds the same benefit to today’s treatments.

PSK has caused few reported side effects in Japan⁵. With chemotherapy, MSK lists dark stools that aren’t from bleeding, darkened fingernails and mild blood and stomach problems⁶.

A lab warning sign. In mice, a turkey tail extract called VPS increased intestinal tumor growth, MSK reports, adding that more research is needed⁶. Animal results don’t predict people reliably, as our animal-studies article explains, but they’re a reason for caution.

Shiitake’s lentinan bought weeks, not years

Lentinan is used in Japan for stomach cancer that can’t be removed by surgery or has come back, usually with the chemotherapy drug tegafur³.

In 2009, researchers at Kyoto and Nagoya universities and other Japanese centers pooled patient-level data from five randomized trials³. They had records for 650 people with advanced stomach cancer.

Median survival, the point at which half the patients had died, was 139 days with lentinan and chemotherapy, compared with 114 days with chemotherapy alone³. By our math, that’s about 25 more days. Over a median of six months of follow-up, 82.6% of the lentinan group and 84.2% of the comparison group died³.

Lentinan lowered white blood cell counts in 5.6% of patients, compared with 1.6% without it³. The pages we opened didn’t state funding or conflicts of interest.

That’s a real but small gain, in very sick people, from a purified drug. It says nothing about eating shiitake or swallowing a capsule for a cold.

Maitake. At MSK, a small early trial gave 34 women who’d had breast cancer an oral maitake extract for three weeks⁸⁹. The extract both stimulated and suppressed different immune measures, and MSK’s experts warn that maitake can push the immune system in both directions⁸. A small study in people with myelodysplastic syndrome, a bone marrow disorder, found better function in two kinds of white blood cells⁸. Both reported immune measures, not survival or infections⁸.

Reishi, chaga, cordyceps and lion’s mane. In a Japanese study, 123 people with colon polyps took 1.5 grams a day of a reishi extract for a year⁴. Their polyps shrank slightly in number and size, while those in 102 untreated people grew⁴. That’s a hint, not proof. NCI’s summary doesn’t cover chaga or cordyceps, and we found no immune trials of either in the sources we checked⁴; our supplement article covers what’s known. Lion’s mane belongs to a later article on brain supplements.

Immune markers rise, but infections are rarely counted

When mushroom products are tested in people without cancer, researchers usually measure immune cells in a blood or saliva sample. That’s useful science, but it isn’t the same as catching fewer colds.

Shiitake on the plate. In a study published in 2015, University of Florida researchers had 52 healthy adults ages 21 to 41 eat shiitake every day for four weeks¹⁰¹¹. A summary of the published paper puts the dose at 5 or 10 grams of dried mushroom a day¹¹.

Afterward, one type of T cell multiplied about 60% more in lab tests, and natural killer T cells roughly doubled their growth¹¹. Saliva antibodies rose and a blood marker of inflammation fell¹¹.

But both groups ate shiitake, and participants knew it, according to the trial’s registry entry¹². There was no comparison group without mushrooms, and no one tracked infections¹⁰¹². The U.S. Mushroom Council and the Australian Mushroom Growers Association, two industry groups, paid for the study¹¹.

Turkey tail after breast cancer. In a phase 1 safety trial at the University of Minnesota and Bastyr University, women who’d finished radiation for breast cancer took 3, 6 or 9 grams of turkey tail powder a day for six weeks⁷. Eleven enrolled and nine finished. The powder was supplied by Paul Stamets’s company, Fungi Perfecti⁷.

Lymphocyte counts bounced back sooner at the higher doses, and some immune cells rose⁷. The authors called these trends worth a larger trial. NIH and the Gateway for Cancer Research funded it, and the authors declared no conflicts⁷.

Beta-glucan pills for colds. A 2021 review in the journal Food & Function, paid for by European and Greek public funds, gathered 34 placebo-controlled trials of fungal beta-glucans¹³. Only 8 used mushrooms; the other 26 used baker’s yeast or a related fungus¹³.

Most found fewer or milder respiratory infections, but some found no difference, and immune-cell results were inconsistent¹³. The trials were too different to combine into one number¹³.

The newest example shows the pattern. In a 2026 Japanese trial, 40 cold-prone adults took 180 milligrams a day of yeast beta-glucan or a placebo for 12 weeks¹⁴. The beta-glucan group kept more antibody in the nose and reported fewer days with cold symptoms, but natural killer cell activity didn’t change¹⁴. One author worked for Kobayashi Pharmaceutical¹⁴.

So if beta-glucans do trim colds, most of that evidence comes from yeast, not the mushroom in your blend.

Shiitake dermatitis: a rash that looks like whip marks

Doctors in Japan first described the rash in 1977. It was reported in Europe in 2006 and in the U.S. in 2010¹.

In the published cases we read, the streaks appeared within about a day of eating raw or lightly cooked shiitake, and they may itch¹². They took about 10 days to three weeks to clear, and one man’s rash came back after another shiitake meal five months later¹.

Why some people react isn’t settled. Researchers first called it a toxic reaction to lentinan, and newer reports point to a delayed allergy². By our math, the Japanese lentinan trial’s rate works out to about 1.7%. From that trial, the authors of the 2016 report extrapolated that up to 2% of people may be vulnerable¹.

Cooking helps, but sources differ on how much. Doctors at St Vincent’s Hospital in Melbourne note that thorough cooking breaks down lentinan, and they told their patient to avoid undercooked shiitake². Doctors writing in the Medical Journal of Australia in 2016 noted cases after boiled, baked, grilled and fried shiitake, and advised cooking at 150 degrees Celsius (about 300 degrees Fahrenheit) or more, or avoiding shiitake if you’ve reacted¹.

Cautions for blood thinners, diabetes drugs and cancer care

Blood thinners and diabetes medicines. MSK experts note that maitake may raise the INR, a clotting test, in people taking warfarin, based on a case report⁸. It may also add to the effect of blood-sugar-lowering drugs⁸⁹. MSK advises talking with your physician about both⁸.

Turkey tail. MSK’s specialists say no interactions with prescription drugs have been reported⁶. That isn’t the same as proof of safety, given the mouse tumor finding above⁶.

Immune drugs and autoimmune disease. Maitake’s two-way immune effects are one reason for caution⁸. Our mushroom supplement article covers MSK’s warning for people on immune-suppressing drugs, and a later article covers supplement cautions for autoimmune conditions.

Pregnancy. Drugs.com, a commercial drug-information database, says safety data on maitake in pregnancy and breastfeeding are lacking⁹.

Cancer treatment. NCI advises people with cancer to talk with their doctor, nurse or pharmacist before trying complementary products, because some can interfere with standard treatment⁵. If you’re in cancer care, talk with your oncologist before adding any mushroom product, and ask whether a product is PSK or simply turkey tail powder.

The mushroom claim ladder

Use this to place any mushroom claim. “In whom” matters as much as “what.”

Mushroom or product	Strongest human evidence	In whom	Rating	Caution
PSK (turkey tail extract)	Randomized trials with chemotherapy; better survival in some4	Stomach, colorectal and lung cancer patients, mostly Japan	Promising but early	Not FDA-approved; a store capsule isn’t PSK46
Lentinan (shiitake extract by IV)	Pooled trials: about 25 more days of median survival3	Advanced stomach cancer, Japan	Promising but early	Rash in about 2 in 100; low white cells13
Turkey tail powder	Phase 1 safety trial; immune trends7	11 women after breast cancer radiation	Not enough evidence	Mouse tumor signal; ask your oncologist56
Maitake extract	Small early trials; immune markers only8	Breast cancer and bone marrow disorder patients	Not enough evidence	Warfarin, diabetes drugs89
Reishi extract	One polyp study; no cancer-outcome trials4	Japanese adults with colon polyps	Not enough evidence	Liver cases (see our supplement article)
Chaga, cordyceps	Not covered in NCI’s summary4	None tested for immunity in our sources	Not enough evidence	Chaga oxalate (see our supplement article)
Shiitake as food, for immunity	Four-week marker study, no infections tracked1112	52 healthy adults	Not enough evidence	Cook well12
Beta-glucan pills for colds	Mixed trials, mostly yeast1314	Healthy adults	Promising but early	A marker isn’t an infection
Mushroom “immune blend”	No trials of blends in the sources we reviewed	Healthy adults	Not enough evidence	Check species, part and dose

Respecting the tradition, and the dose

Turkey tail has a long place in traditional Asian medicine as a remedy, not a food, MSK notes⁶. Japanese researchers turned that tradition into a purified extract and ran trials, which is why PSK has the record it has.

That’s the respectful way to read the evidence. The tradition pointed somewhere real, and testing showed where the benefit is (modest, in specific cancers, with a specific extract) and where it hasn’t been found (preventing colds in healthy people with a capsule).

For everyday immune health, mushrooms belong on the plate. Cook shiitake well, enjoy the variety, and save extracts for situations where they’ve been tested, with a clinician who knows what else you take.

Questions readers ask

The bottom line

Medicinal mushrooms aren’t folklore. Purified extracts from turkey tail and shiitake have decades of trials in Japanese cancer patients, with modest survival gains in some stomach and colorectal cancers.

For healthy people, the story is thinner. Mushroom foods and supplements nudge immune markers in small studies, but trials haven’t shown that a mushroom blend prevents infections. Cook shiitake well, check with your clinician about blood thinners and diabetes drugs, and if you have cancer, bring any mushroom product to your oncologist before you start.

Related reading

• A Mushroom Capsule May Hold More Grain Than Mushroom. Here’s How to Tell
• Only 1 in 20 treatments tested in animals wins approval for people
• Your immune system works more like a team than a volume knob, and some habits help it
• Memory, Immune and Stress Formulas Sell a Result. Here’s How to Test One
• Zinc shortfalls weaken immune cells, yet extra zinc hasn’t proved a shield

Sources

1. McNally A, Ross C, Wayte J. “Shiitake Dermatitis: The Tale of an Under-Recognised, Undercooked Fungus.” Medical Journal of Australia, 2016;204(3):124-126. mja.com.au
2. Wu K, de Menezes S, Robinson A. “Flagellate Erythema: A Case of Shiitake Dermatitis and Review of Pathogenesis.” EMJ Allergy & Immunology, 2022. emjreviews.com
3. Oba K, Kobayashi M, Matsui T, Kodera Y, Sakamoto J. “Individual Patient Based Meta-analysis of Lentinan for Unresectable/Recurrent Gastric Cancer.” Anticancer Research, 2009;29(7):2739-2745. pubmed.ncbi.nlm.nih.gov
4. National Cancer Institute. “Medicinal Mushrooms (PDQ), Health Professional Version.” NCI, updated November 6, 2024. cancer.gov
5. National Cancer Institute. “Medicinal Mushrooms (PDQ), Patient Version.” NCI, updated July 11, 2024. cancer.gov
6. Bao T, Gubili J (Memorial Sloan Kettering Cancer Center). “Coriolus versicolor.” The ASCO Post, Integrative Oncology, September 10, 2018. ascopost.com
7. Torkelson CJ, et al. “Phase 1 Clinical Trial of Trametes versicolor in Women with Breast Cancer.” ISRN Oncology, 2012. doi.org
8. Deng G, Gubili J (Memorial Sloan Kettering Cancer Center). “Maitake Mushroom.” The ASCO Post, Integrative Oncology, April 10, 2019. ascopost.com
9. Drugs.com. “Maitake.” Natural Products monograph, updated March 23, 2026. drugs.com
10. University of Florida Institute of Food and Agricultural Sciences. “UF/IFAS Study: Mushrooms Boost Immunity.” UF/IFAS News, April 16, 2015. blogs.ifas.ufl.edu
11. HealthDay. “Shiitake Mushroom Intake Tied to Improved Human Immunity” (on Dai X, et al., Journal of the American College of Nutrition, published online April 11, 2015). HealthDay, 2015. healthday.com
12. ClinicalTrials.gov record NCT01398176, “Immune Benefits From Mushroom Consumption” (University of Florida), via Veeva CTV registry copy. ctv.veeva.com
13. Vlassopoulou M, Yannakoulia M, Pletsa V, Zervakis GI, Kyriacou A. “Effects of Fungal Beta-Glucans on Health: A Systematic Review of Randomized Controlled Trials.” Food & Function, 2021;12:3366-3380. pubmed.ncbi.nlm.nih.gov
14. Kanno T, Ishibashi K-I, Kajiyama S, et al. “Dietary Beta-1,3/1,6-Glucan from Baker’s Yeast Supports Upper Respiratory Mucosal Immune Health in Healthy Adults: Evidence from a Randomized, Double-Blind, Placebo-Controlled Trial.” Nutrients, 2026;18(6) (abstract record). nutrition-evidence.com