I know from personal experience that Aspartame, NutraSweet etc. gives me horrible, and I mean dreadful, migraines. Aspartame also stimulates appetite, I don’t know where I read this, but I have read it in a paper or something.
I have heard anecdotal that when Aspartame heats up, it can become toxic to your body (like when the truck delivering bottles of Diet Coke gets hot). I have also heard, on some TV program that it is causing serious eye problems.
I will never touch the stuff again.