Two bananas to a potato (I assume we’re talking something like a russet, not a little red potato?) sounds generous to the potato, if we’re talking volume equivalence.
you can most definitely change the levels of components in a fried food.
the oil gets 'dirty' from extended use in frying. Why is it dirty? It's not dirt, and it's not oil breakdown (in most cases).
The oil is drawing components from the food into itself.
Forget the frying for a second; most fries are parboiled or blanched -- this also leeches material away from the vegetable, this time it leaves with the water used for blanching.
A french fry is delicious, but it's different than a potato -- even if it's made from one.
I don't know about the case of potassium specifically, but in general I thought that the bioavailability of elements can vary with different types of cooking?
There would still be potassium in there, unless it’s pulled out by the frying oil.
Elements can’t get lost in a chemical reaction. You can only change the molecule they’re part of, so it might not be processable by the human body, but the potassium isn’t going to disappear.
> Why would something being an element mean that heating it as part of a food wouldn’t act as a catalyst for some chemical interaction?
It sounds like the person thinks that chemical reactions can make elements change/disappear, which is not the case. And I specifically mentioned the Oil removing the potassium as an option.
A temperature so hot that the atoms of the potato would violently collide into each other, probably at least tens of millions of degrees and you would need something to confine the potato plasma!