Mushrooms in Japanese Kampo Medicine: Formulations, Principles and Contemporary Evidence

Page updated October 8th, 2026

By MushroomHealthBenefits.com Research & Editorial Team

Kampo is Japan’s traditional system of herbal medicine, and several mushrooms have a long place inside it. The clearest example is turkey tail (called kawaratake in Japan), whose extract PSK (Krestin) has been used in Japan for decades alongside standard cancer treatment. Shiitake’s extract lentinan has a similar history. This article separates what traditional Japanese use claims from what modern human clinical trials actually show, so you can tell the difference before making any decision with a doctor.

Kampo Medicine: A Short, Honest Background

Kampo grew out of traditional Chinese medicine after it reached Japan more than a thousand years ago, then developed its own diagnostic style and formula tradition over centuries. Many Kampo formulas combine multiple herbs and, in some cases, fungi, chosen according to a practitioner’s assessment of a patient’s overall pattern rather than a single lab test.

Mushrooms are not the center of every Kampo formula. But a small number of species became closely tied to Japanese medical practice, especially once Japanese researchers began isolating specific compounds from them in the 20th century and testing those compounds in modern clinical trials. That history is what separates Kampo mushroom use from most other traditional mushroom use around the world: some of it was carried directly into regulated adjunctive cancer treatment in Japan.

The Mushrooms With the Strongest Kampo-to-Clinic History

According to the National Cancer Institute’s overview of medicinal mushrooms, a handful of species account for most of the traditional-to-modern bridge:

Turkey tail (Trametes versicolor, kawaratake). Its extract, PSK (also sold as Krestin), was approved in Japan more than 30 years ago as an add-on to chemotherapy for certain cancers. Our turkey tail human evidence and safety guide and our deep dive on PSK and PSP polysaccharides cover this in more detail.
Shiitake (Lentinula edodes). Its extract lentinan has also been studied and used in Japan alongside chemotherapy. See our shiitake human evidence and safety guide and our article on lentinan’s role in oncology research.
Reishi (Ganoderma lucidum). Reishi’s use is rooted more in Chinese tradition (where it is called Ling Zhi) but is also used in Japan, generally as an immune-supportive supplement rather than an approved drug.
Maitake (Grifola frondosa). Used traditionally in Japan and studied for its beta-glucan content; our maitake evidence and safety guide covers what human research exists.

A key point: PSK and lentinan are purified extracts studied as drugs in Japan, not the whole dried mushroom sold as a supplement in the United States. That distinction matters for anyone trying to compare a Kampo-based treatment history to a supplement bottle on a store shelf.

Separating Traditional Use From Human Clinical Evidence

These are three different kinds of evidence, and Kampo mushroom marketing often blurs them together. Here is how to tell them apart.

Traditional or historical use means a mushroom or extract has been used in Japanese medicine, sometimes for generations. It does not by itself prove the mushroom works for a specific modern condition.
Preclinical (lab or animal) evidence means a compound showed an effect in cells or animals. Animal results do not reliably predict human results.
Human clinical evidence means the compound was tested in people, ideally in randomized trials. Even positive human trials from Japan may not generalize to a different product, dose, or population.

According to the National Cancer Institute, PSK has the most human trial data of any Kampo-linked mushroom compound. Trials in gastric, colorectal, and lung cancer patients in Japan found that adding PSK to standard chemotherapy was associated with longer survival or fewer recurrences in some studies, and the treatment was generally well tolerated. Lentinan has a smaller but related body of human trial data in similar cancer settings. Reishi and maitake have far less human trial evidence, with most of their supportive data coming from smaller or non-randomized studies.

Read our full breakdown of how researchers grade this kind of evidence in In-Vitro, Animal and Human Studies: Understanding the Evidence Hierarchy, and our overview of what mushroom cancer research does and does not show.

What the Evidence Does Not Show

None of this evidence shows that any mushroom or mushroom extract supports cancer or replaces standard treatment. PSK and lentinan were studied and used in Japan as additions to chemotherapy, radiation, or surgery, not as substitutes for them. Neither PSK nor any other mushroom-derived compound is approved by the FDA as a cancer treatment in the United States. Study results from Japan, where PSK is a regulated pharmaceutical-grade extract, do not automatically apply to an over-the-counter supplement made by a different manufacturer with a different extraction process.

Extra-Caution Groups

Talk to a qualified clinician before using any Kampo-linked mushroom product if you fall into one of these groups:

You are currently undergoing chemotherapy, radiation, or another cancer treatment, since mushroom extracts may interact with these therapies.
You take immune-suppressing medication, such as after an organ transplant, since some mushroom compounds affect immune activity.
You take blood thinners or have an upcoming surgery, since some mushrooms may affect bleeding or blood clotting.
You are pregnant or breastfeeding, since safety data in these groups is limited.
You have a known mushroom or mold allergy.

A Quick Decision Path for Evaluating a Kampo-Linked Mushroom Product

Identify the exact compound or extract named on the label, such as PSK, PSP, or lentinan, not just the mushroom species.
Check whether that specific extract has human clinical trial data, or only traditional-use or animal data.
Note whether any trial you find used the same extract and dose form as the product in front of you.
Check the product for third-party testing or quality certification, since supplement manufacturing is not reviewed by the FDA the way drugs are.
Bring the product and any trial you found to a doctor or pharmacist before starting it, especially if you are being treated for a serious condition.

Frequently Asked Questions

Is Kampo medicine the same as Chinese medicine?
Kampo developed from traditional Chinese medicine after it reached Japan, but it evolved its own diagnostic approach and formula tradition over many centuries. They share roots but are not identical systems.

Are PSK and lentinan approved as cancer drugs in the United States?
No. According to the National Cancer Institute, PSK is approved in Japan as an add-on to standard cancer treatment, but neither PSK nor lentinan is FDA-approved as a cancer treatment in the United States.

Can I use a Kampo-linked mushroom supplement instead of chemotherapy?
No mushroom extract, including PSK or lentinan, has been shown to replace standard cancer treatment. In the studies with the most evidence, these extracts were used alongside chemotherapy or radiation, not instead of them, and always under medical supervision.

Why does the same mushroom show up in both Chinese and Japanese traditional medicine?
Traditional Japanese medicine developed out of Chinese medical traditions, so herbs and mushrooms like reishi carry a shared history across both systems, even though the two traditions later developed differently.

Educational Disclaimer

This article is for general education only. It is not medical advice, and it does not diagnose, treat, or promise any health outcome. Do not start, stop, or change any medicine or treatment, including a mushroom supplement, without talking to a qualified healthcare provider, especially if you are being treated for cancer or another serious condition.