Given that we are physically capable of detecting a single photon there’s some possibility that in fact we could do something along those lines.
Some vitamins are quite volatile, having a shelf-life of days if not stored properly, and most minerals are as well to some degree, ever take a whiff of an unpainted hot metal roof?
Again, hate to disagree, but if your skin cells are lacking that nutrient and suddenly they get to absorb a few molecules, then there’s no reason to assume there wouldn’t be a reaction, (a microscopic sigh of relief as it were).
And if he were standing in the store in front of that produce that might well be the case.
To clarify, I’m not really arguing against any of your points here, (and I fully agree with the self-medication), but at the same time there’s equal argument in the other direction. Perhaps @Mister44 can oblige us with a double-blind test? 
