It appears as though there may be a risk to drinking diet soda after all, although it has nothing to do with the alleged risk of obesity. Rather, there is evidence to suggest that drinking dark-colored diet cola (and dark-colored regular cola) can increase your risk of kidney disease.

Based on a report published in the journal Epidemiology, drinking two or more dark-colored sodas -- such as Coke, Pepsi, Dr. Pepper, and similar generic brands -- per day doubles your chances of kidney disease.

The phosphoric acid found in dark colas, but not in clear sodas such as Sprite and 7-Up, is what gives it its unique taste, but also what may lead to the development of kidney stones. This, in turn, can potentially lead to complications and disease.

I suppose this is yet another reason to just stick to plain ol' water.

Source