I was glad to find this thread. I've been enjoying fresh maitakes purchased through a CSA, which sources them from Hokto Kinoko Company in southern California. I sautee them in ghee, olive oil, or a mixture, and I think I'm cooking them plenty. After they're cooked, I generally add them to eggs or soups.
But I've started to notice a correlation, that I seem to have some diarrhea after eating them -- more so when I eat a larger amount at once. It does not seem serious, and I plan to continue eating them in small quantities. I don't know how these cultivated maitakes might differ from wild ones as far as this effect.
Just one person's experience. I was glad to discover this thread to help figure out whether I'm alone in this reaction. This site also mentions that fresh maitakes can cause diarrhea: https://www.botanical-online.com/en/mushrooms/maitake-mushroom-properties
