Caffeine is a central nervous system stimulant found in coffee, tea, energy drinks, and some medications. It is the most widely consumed psychoactive drug in the world. Caffeine is a bitter, white powder that is soluble in water. It is absorbed into the bloodstream from the stomach and small intestine. Once in the bloodstream, caffeine travels to the brain where it binds to adenosine receptors. Adenosine is a neurotransmitter that promotes sleep. By blocking adenosine receptors, caffeine prevents drowsiness and promotes wakefulness.
Caffeine has a number of benefits, including: