Energy drinks are beverages that boost energy. Energy drinks generally contain methylxanthines (including caffeine), B vitamins, and herbs. Other commonly used ingredients are carbonated water, guarana, yerba mate, acai, and taurine, plus various forms of ginseng, maltodextrin, inositol, carnitine, creatine, glucuronolactone, and ginkgo biloba. Some contain high levels of sugar, and many brands offer artificially sweetened 'diet' versions. A common ingredient in most energy drinks is caffeine (often in the form of guarana or yerba mate). Caffeine is the stimulant that is found in coffee and tea. Energy drinks contain about three times the amount of caffeine as cola

Energy Drinks

A variety of physiological and psychological effects have been attributed to energy drinks and their ingredients. Two studies reported significant improvements in mental and cognitive performances as well as increased subjective alertness. Excess consumption of energy drinks may induce mild to moderate euphoria primarily caused by stimulant properties of caffeine and may also induce agitation, anxiety, irritability and insomnia. During repeated cycling tests in young healthy adults an energy drink significantly increased upper body muscle endurance.
It has been suggested that reversal of caffeine withdrawal is a major component of the effects of caffeine on mood and performance.