I'm not a Doctor but I would guess since the paint is on the outside of the can it won't get in your food. You should aviod breathing the fumes from your camp stove, paint or no paint.
I think aluminium is bad in general. If you are worried about it you should switch to an inert metal pot like titanium or stainless steel. My personel opinoin. I aviod aluminium at home too, including deorderant, bottles, pots….. though sometimes I drink beer from cans. Just get a Ti pot.
uuuug, I know stainless steel is not an inert metal, you know what I mean.