The safety evidence is clean, and it is all in rats
A commercial lion's mane powder passed guideline animal toxicology at up to 2000 mg per kilogram of body weight a day, with no DNA damage. No human measure was taken.
What the study found
No toxic effect in rats at the highest dose anyone tested
A commercial lion's mane powder went through guideline animal toxicology: no acute toxicity, no harm over repeated feeding at up to 2000mg of powder per kilogram of body weight a day, and no DNA damage in any test. That is the best safety evidence on lion's mane, and it is all in rats.
The caveat · Rat no-harm dose, not a human limit
2000mg per kilogram was the highest dose tried, not a limit anyone established, and a rat no-harm level is not a human intake limit. No human safety measure was taken. The company selling the powder ran and wrote it. An expert panel review records one anaphylactic reaction to fresh lion's mane.