Caffeine

Caffeine is a bitter, white crystalline methylxanthine alkaloid that stimulates the central nervous system. It is used for wakefulness, physical performance, cognitive effects, and recreation. It occurs naturally in several plants, with tea leaves and coffee beans among the most common human sources. Caffeine blocks adenosine binding at receptors and may improve reaction time, but it can also cause sleep disruption, anxiety, dependence, and withdrawal symptoms in some people.

Chemical class

Methylxanthine alkaloid

Primary action

Blocks adenosine binding at receptors

Common sources

Tea leaves and coffee beans