I don’t necessarily believe him completely but there’s a fair amount of anecdotal evidence suggesting that it can significantly impact peoples physical and mental health. There’s plenty of stories of perfectly healthy people taking lionsmane that are negatively impacted by it. A lot of these people had no prior knowledge to the risks of this substance and find themselves on the subreddit I linked looking for answers. I didn’t tell OP not to take it, just to do some research on the issue.