EFSA explains risk assessment: Caffeine
Caffeine is a naturally occurring chemical compound found in plant constituents such as coffee and cocoa beans, tea leaves, guarana berries and the kola nut, and has a long history of human consumption. It is added to a variety of foods, such as baked pastries, ice creams, sweets, and cola drinks. Caffeine is also found in so-called energy drinks, alongside other ingredients such as taurine, and D-glucurono-γ-lactone. It is also present in combination with p-synephrine in a number of food supplements that are marketed for weight loss and sports performance. Some medicines and cosmetics contain caffeine.
When consumed by humans, caffeine stimulates the central nervous system, and in moderate doses increases alertness and reduces sleepiness.