Shiitake
Best evidence: Approved as a drug
Lentinula edodes
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
Lentinan, a beta-glucan, plus eritadenine.
Claim by claim
As an adjunct in gastric cancer treatment
Approved as a drug
Lentinan is licensed in Japan as an injectable adjunct to chemotherapy in gastric cancer. Injected, prescribed, and unrelated to eating shiitake or taking a capsule.
Cholesterol
Human trials, weak or mixed
Eritadenine lowers cholesterol convincingly in rodents. The human evidence is old, thin and inconsistent.
The honest summary
The most sensible entry on this page, because you can simply cook and eat it. Shiitake is genuinely nutritious food with a licensed pharmaceutical derived from one of its compounds, and those two facts are not the same fact.
Who should be careful
Raw or undercooked shiitake causes a striking whip-mark rash in a small proportion of people, called shiitake dermatitis. Cooking it properly destroys the compound responsible.
What is actually in the jar
Buy it as food, fresh or dried, and grow it on a log if you want a supply. There is no good argument for a shiitake capsule when the mushroom is in every supermarket.
You can also just eat it. Which is a better argument than any capsule on this page. The shiitake sheet
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The others, graded the same way
Lion's mane
Hericium erinaceus
Human trials, promising
Turkey tail
Trametes versicolor
Approved as a drug
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
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.