People have been known to eat shoes, tree bark and grass during famines. I imagine most would be surprised at what they’d consider eating if they’d been without food long enough.
The really interesting cases are the foods that used to be all but inedible, but aren’t now. For example who was it that thought that the banana might be a good candidate for selective gardening? The original “banana” is tiny, full of seeds, and just about inedibly bitter. Ditto citrus, which also used to be small, tough, full of seeds, and horribly sour.
Ever eat a pine tree? Many parts are edible.