a lot, actually! yinglets are resistant to a wide range of common natural toxins, owing to their home swamps in canon being so full of toxic flora and fauna. they apparently adapt to new toxins of those types fairly rapidly, as well, and sequester what their bodies can't process, making them toxic to most things that'd try to eat them
this is partly the result of their immune systems, toxin-processing organs, and the "hell microbes" (as Val often put it) that are in their guts, which help to break down toxins in their food, as well as breaking down most things they eat. think of it like the microbiome we have in our own guts, but way more powerful, and as far as I can tell, present before their small intestines (since otherwise it's unlikely they'd be protected against toxins they eat, so easily)
it'd be easier to list what they can't eat. and that's... anything that contains glutens!
devestating news for my baking career
i mean i got zhe good genes i can eat grains, but everyone else is gonna explode


