If you take a supplement with minerals, there’s often different forms but when it comes to actual food, its always just the isolated mineral.
How do you figure out what form each mineral takes? Like, foods that have a bunch of magnesium in it, what form of Mg is it usually? Oxide?
It’s not that that’s a stupid question, it’s just so broad as to be largely unanswerable. Every mineral and constituent nutrient is going to come in a variety of forms depending on the type of food and the specific nutrient. For magnesium, sure, some may be in oxide form, but also magnesiums salts, permanganates, constituent parts of various enzyme complexes, receptor binding sites… the number of permutations is nearly indescribable.