Well HCL (hydrochloric acid) can dissolve a lot, and given enough time I’m sure it can break down nearly anything but the reason our digest tract is shaped the way it is, is so that we can get as much food through our body and effectively as possible!
So for instance, say you swallowed your locker key. You’re going to poop that out and it’s going to look exactly the same way as it went in. But DO NOT DO THIS! So many things go wrong, like the key puncturing your digestive tract and letting digested material get into the rest of your body and this can kill you….and it’s really painful! So, promise me you won’t try it?
So other stuff we can’t digest are chewing gum and parts of sweet corn! Well we can’t digest the resin in chewing gum, that’s why you’re always told not to swallow gum! And we only digest a bit of the sweet corn kernel so the outside bit is always pooped out!
The acid HCl (hydrochloric acid) is quite a strong acid, but it is only really active in the stomach! Your whole digestive system is adapted for digesting (and dissolving) any good food sources and usually is very good at taking everything available from what you eat!
So, yes some metals would survive, and some big chemicals. If you think of fibre in the diet and many compounds which make plants and vegetables, often they can’t be dissolved and digested very well. It sounds like a bad thing but actually that is a good thing, and its important to eat them!
Generally though, most things are digested completely by the digestive tract, even if the HCl acid in the stomach doesn’t do this job on its own. Pretty much the only thing you can control is how much you chew your food. Did you know that in your mouth there are enzymes in your spit which begin dissolving the food as soon as you chew? That is part of the reason why you should completely chew food before swallowing, because some things are only really dissolved in the mouth!
I hope this helps answer your question!
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