I've got in-world poisons, often with real-world analogues (like belladonna) but in building the social structure of the back-stabbing nobility, I began looking at poison resistances and antidotes.
Basically, those who protect royalty also try and find a way to up their poison resistance, and during especially troubled times, put anti-toxins in their foods.
I already know about Mithridatism, "the practice of protecting oneself against a poison by gradually self-administering non-lethal amounts." But this is not what I am wanting to do.
I am looking to gradually dose the king with a general anti-toxin that's proof against most poisons. My question here is, are there real-life analogues that would be that broad? And if not, what combinations of things would be best?
EDIT: Don't worry about tech level--can be anything through to today's science--this is set in a Renaissance-type world, but I can adjust anything to fit because the world is pretty flexible and not entirely Renaissance, I just need some jumping off points to create what's needed.
Right now, I am finding that many things which wipe out poison aren't actually good to ingest on the regular (like charcoal)--and I am looking for things that will. Stuff that's close is ok, because I can use it as a starting point at least in building that bit of my world.