The Science Behind Caffeine's Duration of Effectiveness.
Caffeine is a naturally occurring substance found in coffee, tea leaves, and cacao nuts. It is a stimulant drug that can make people feel alert and energized, but can also cause jitteriness and anxiety. The half-life of caffeine is between 4-6 hours, meaning even if the effects start to wane, there is still some caffeine in the system. The exact way caffeine works in the body is still unclear, but it is thought to affect neurotransmitter receptors. Three cups of black, caffeinated coffee can help liver function.