Research has shown that energy drinks are the most popular supplement besides multivitamins in the American young adult population, with more than 30% using it on a regular basis. The primary uses for caffeine in energy drinks, coffee, and tablets is to reduce or control body fat, improve performance, and improve focus.
Caffeine alone has been demonstrated to have a significant effect on fat oxidation, reducing glycogen breakdown, and increasing metabolic rate. Many energy drinks with caffeine supplemented with herbal or synephrine significantly increase caloric expenditure and have a positive effect on metabolism. The role of the ingredients is not well understood. Studies have also shown that caffeine supplements combined with omega-3 fatty acids and several vitamins lead to significant decreases in body mass and body fat. Again, the mechanism for this is not well understood, so the possible exacerbation on conditions like anorexia are not known.
Another effect of caffeine is a delay in fatigue for endurance or resistance training. It won’t help improve your strength or your speed (its effect is mixed in scientific studies), but it does allow athletes to be active for longer periods of time. The idea is that caffeine stimulates exercise metabolism by enhancing fat oxidation, which preserves muscle glycogen. Energy drinks and caffeine also have a limited effect on improving focus, alertness, and reaction time; Red Bull has been demonstrated to have some enhanced effect on cognitive performance.
The dangers of caffeine are the same with any stimulant. The documentation doesn’t show a correlation between energy drinks and cardiovascular damage, but it can potentially exacerbate an underlying condition, particularly in energy drinks where caffeine is mixed with ephedra or other beta-agonists (which were banned by the FDA in 2004). Caffeine is also a diuretic, so it is linked to dehydration – a potential concern if used to improve athletic performance or as a weight-loss supplement, or if combined with alcohol. Caffeine can also have side effects such as headache or irritability, and overuse can be associated with withdrawal symptoms. From a biological perspective, it should also be noted that caffeine speeds the aging process and reduces the cell’s ability to repair DNA damage. It is commonly used by geneticists to stem the repair process in cells to study the effects of damaged DNA. So don’t abuse it.