Have you heard of this?
I’ve used raw shiitake mushrooms in my food preparations for a number of years now (I do marinate my shiitakes in soy sauce and oil before I use them). I have never had an issue with them.
A while back, however, it was reported that uncooked shiitake could have a toxic effect.
Uncooked shiitake have a starch-like substance, lentinan, which is used as an anti-cancer agent. Sloan Kettering research showed the protein in lentinan, lentin, has anti-fungal properties, reduces the growth of leukemia cess, and suppresses HIV viral enzyme activity.
The lentinan, which is only broken down by cooking, and can apparently cause some people to have a toxic reaction to it.
This is not going to stop me from using shiitake, because I have never had an issue with them, and I like the health producing qualities they have. Perhaps the marination in soy sauce prevents the problem – I don’t know. I just know that I eat up to a quarter-pound of shiitake mushrooms a month because I like them quite a bit, and I can get them at a reasonable price.