But, why?
Except for a few periods of a few months, when I chose to go off caffeine or limited my intake for other reasons, I've been drinking several liters a day of aspartame-and-caffeine-containing drinks since 1996. I've yet to identify any related effects: my teeth aren't great, but haven't been eaten away by acid; I'm overweight, but less than I have been at times since 1990; I don't find dehydration to be a problem. Some of my friends drink similarly large quantities, and none of them have shown any apparent effects, either. This, of course, is mere anecdote, but surely if there were really a serious problem then there'd be an epidemic of some problem easily traced to aspartame, given that millions of people drink liters per day of diet colas and other drinks?