Reishi
Best evidence: Human trials, weak or mixed
Ganoderma lucidum
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: trials exist and disagree, or are too small and too poorly designed to conclude anything from.
What is actually being talked about
Triterpenes, which give the intense bitterness, and beta-glucans.
Claim by claim
Fatigue and quality of life in illness
Human trials, weak or mixed
Several small trials with modest results. Cochrane has reviewed reishi for cancer treatment and concluded the evidence does not support it as a first-line treatment, while noting possible adjunct effects worth further study.
Sleep and calm
Animal and cell studies only
Sedative effects in rodents. Human evidence is essentially absent.
Immune modulation
Human trials, weak or mixed
Changes in immune markers in small studies, with no clear clinical outcome attached.
The honest summary
Two thousand years of recorded use, a great deal of laboratory work, and human evidence that stays stubbornly thin. It is the mushroom where the gap between reputation and demonstration is widest.
Who should be careful
May increase bleeding risk and is a genuine concern alongside anticoagulants. Also lowers blood pressure in some people. Both are worth raising with a doctor rather than discovering.
What is actually in the jar
Dual extraction matters here more than for any other species. The triterpenes are alcohol-soluble and the beta-glucans are water-soluble, so a water-only extract is missing half of what the species is taken for.
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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
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.