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 can contain about three times the amount of caffeine as cola