Ella thought on the five exceptions to Gamp's Law, trying to figure out which one she wanted to try and explain. Food came to mind immediately, probably because Ella was quite hungry at the moment. Pity you couldn't transfigure something into food! As for why it is an exception to the rule, Ella tried hard to put her thoughts into words. "Professor, I was thinking that maybe transfigured food wouldn't be as good as the real thing. I mean real food gives you all the vitamins and stuff that you need to grow healthy and strong. If you used magic to just transfigure food, it might not provide you with what you needed to live and therefore is forbidden. It might look and even taste like the real thing, but it might not have all the good stuff, you know?"