Where do get the impression mushrooms have no nutritional value?
I know from firsthand observations as well as reading resources, northern flying squirrels rely on arboreal fungi (along with lichen) to get them through the winter. Truffle feeding, here in the Pacific northwest, is such a common behavior of deer and squirrels, that I would find it hard to believe there is no value.
Also, there is quite a bit of new information (and old probably) about mushrooms’ ability to fight free radicals in our bodies. A great book to read is “Mycelium Running”. Paul Stamets quotes a study, which scientifically observed mycelium transferring sugars from a healthy tree to a stressed tree of a different species! I mean that’s real world Avatar stuff.
Anyway, I’m curious where you get that notion?