Generally energy drinks include methylxanthines (including caffeine), B vitamins, and herbs. Other common ingredients are guarana, which has a high caffeine content, taurine, plus various forms of ginseng, maltodextrin, Carbonated water, inositol, carnitine, creatine, glucuronolactone and ginkgo biloba. Some contain high levels of sugar, and many brands also offer artificially-sweetened 'diet' versions. The central ingredient in most energy drinks is caffeine, the same stimulant found in coffee or tea, often in the form of guarana or yerba mate. The average 237 milliliter (8 fluid ounce) energy drink has about 80 mg of caffeine, with 480 ml (16 fl. oz.) drinks containing around 150 mg, although more recently, drinks containing as much as 400 mg of caffeine have been marketed.