No matter what we do to try to keep healthy there will always be something to hurt us in todays society. You can get cancer from breathing.
I think until my country bans Diet soda I will still partake in it. We can't have sugared sodas cuz we will gain weight and the sugar will cause grief too. You get diabetis from partaking in too much sugar.
I think the key is moderation. I really dont think a drink or two a week of any diet soda will cause you to become sick. I've drank it for years and I am fine.
Like anything in life if you use it in moderation you will be ok