Turkey tail
Best evidence: Approved as a drug
Trametes versicolor
Nothing here is medical advice and nothing here treats or prevents any disease. The grade on each claim describes the strength of the published evidence, not how well the mushroom works. The strongest grade on this page means: a regulator somewhere has assessed a specific preparation for a specific use and licensed it. this is a different thing from a supplement containing the same species.
What is actually being talked about
Polysaccharide-K, known as PSK or krestin, and polysaccharide peptide, PSP. Both are protein-bound beta-glucans.
Claim by claim
As an adjunct to chemotherapy in specific cancers
Approved as a drug
PSK has been an approved adjunct cancer therapy in Japan since 1977 and is among the most-used such agents there, with meta-analyses in gastric and colorectal cancer showing a survival benefit. That is an approved pharmaceutical preparation used alongside conventional treatment under medical supervision. It is not a capsule bought online, and it is not a treatment for anything on its own.
General immune support in healthy people
Human trials, weak or mixed
Some measurable changes in immune cell counts in small studies. Whether that translates into a healthy person being less ill is not shown.
The honest summary
The strongest evidence base of any mushroom here, and the widest gap between what the evidence supports and what is sold. A regulated drug used alongside chemotherapy in Japanese hospitals is a completely different product from a supermarket capsule, and the marketing relies on you not noticing.
Who should be careful
Anyone in cancer treatment should raise this with their oncology team rather than adding it independently. Interactions with treatment are a real question and not one to guess at.
What is actually in the jar
Look for extract standardised to beta-glucan content. Turkey tail is thin and leathery, so a whole-mushroom powder is largely indigestible fibre; the active fractions are hot-water extracted for a reason.
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The others, graded the same way
Lion's mane
Hericium erinaceus
Human trials, promising
Reishi
Ganoderma lucidum
Human trials, weak or mixed
Chaga
Inonotus obliquus
Animal and cell studies only
Cordyceps
Cordyceps militaris, Ophiocordyceps sinensis
Human trials, weak or mixed
Shiitake
Lentinula edodes
Approved as a drug
Maitake
Grifola frondosa
Human trials, weak or mixed
Several of these interact with real medication. Reishi and cordyceps affect bleeding and blood sugar, chaga is high enough in oxalates to have caused kidney damage in heavy users, and anyone in cancer treatment should raise turkey tail with their oncology team rather than adding it independently. Tell your doctor what you are taking.