Like anything else, it's the dose and not the substance. In moderation it's unlikely to be a problem, it's when the stuff is consumed in large quantity that there's a problem. BTW most if not all "energy drinks" get their "energy" from caffeine. Before spending a bundle on energy drinks, you might look in the pharmacy for "NoDoz" or "Vivarin"---caffeine tablets. Or get the generic variety nearby. One dollar for a dozen tablets, heckuva lot cheaper than a single energy drink. If you find that it does the same for you as energy drinks... But remember: in MODERATION.