I'm not sure, as I know a lot of people who drink several cups of coffee and tea a day and have done for years. I drink around 7 myself. Which surely is more than a can of Relentless or Redbull a day?
I used to drink 3 Red Bulls a day but it started giving me headaches so I cut down to 0/1... I usually drink one before the gym and that helps me keep the stamina up.
My theory is that lots of caffeine in it so it is going to keep you awake when you should be sleeping. Distrurbing your sleeping patterns. Leading to lack of energy then if you reach for more caffeine drinks you will have sudden burst of energy. Than gets in to a cycle. Not good for your health either! I would suggest to excercise and eatting healthly. If your drinking those energy drinks make sure you have breaks from them from time to time.
I used to drink 3 Red Bulls a day but it started giving me headaches so I cut down to 0/1... I usually drink one before the gym and that helps me keep the stamina up.
...Did you mean what you said there? Red bull in no way helps stamina, it helps most with sprinting and even then it's very counter-productive. It gives you a short burst of energy, and then enduces what is effectively a sugar crash. Drinking it before the gym is a bad idea, take that from someone who does a lot of sport (swimming and land training).
Caffeine is a pretty harmless drug unless you overdose on it, which isn't going to happen if you drink energy drinks at a normal rate. There's nothing particularly bad about them, especially the sugar free ones, and some of the ingredients are somewhat unnatural, yet none of them are harmful (taurine, for instance, actually aids sleep!). However, I really do suggest you take it easy on the caffeine, as after a while it really does mess with you a bit; none of the side effects are serious, but quite unpleasant nonetheless.