More people consume caffeine more often than any other drug. Worldwide the predominant sources of caffeine are tea and coffee, although colas, ‘energy’ drinks, mate, guarana, and cocoa (chocolate) also contribute significantly to consumption.
After consumption of a caffeine-containing drink, caffeine is distributed rapidly throughout the body, reaching its highest concentration in the bloodstream and in the brain within 30-40 minutes. Caffeine and its metabolites are then gradually eliminated from the body, mainly in the urine. For adults, the elimination half-life of caffeine – the time it takes for half of the caffeine consumed to be eliminated from the body – is around 3 to 6 hours.