What is in Mountain Dew?

I realize how crazy my question is, but please let me explain. Please know that I only drink Mountain Dew and have been for as long as I can remember! The other day during lunch break I was drinking a bottle of Dew and someone said "if you knew what was in that stuff you wouldn't drink it". I had no idea what he was talking about and to be honest it wasn't the first time somebody asked me that same question. Does anyone know what this guy is talking about or what would give someone the idea that there was something in Dew that was so disgusting?? Ever since this guy said that I've been wondering what in the hell he could be talking about? So if there is anyone out there who does know, PLEASE let me know, as it's driving me crazy!!! Thanks