In humans, caffeine is a quick acting stimulant drug and is the most consumed stimulant drug in the world. In many countries caffeine is legal and most religions tolerate its use.
The main effects of caffeine are that it can change the body's metabolism, stimulating the central nervous system, respiratory system and heart.
As caffeine acts upon the central nervous system (CNS), altering and simulating brain function, it is considered to be a psychoactive stimulant drug.
Most often taken from drinks such as coffee, tea and soft drinks including Coca-Cola, caffeine can help lift fatigue and increase alertness in those who consume it.
In nature, caffeine is used for different purposes. Caffeine is found in many species of plant where it can act as a natural pesticide, protecting the plant . Insects can be paralyzed or killed by the caffeine. Concentrations of caffeine are found to be higher in many seedlings and surrounding soil, giving the seedlings an increased chance of survival.
Whilst records of caffeine consumption date as far back to the Stone Age , caffeine as a compound was first discovered and isolated in 1819 by Friedrich Runge a German chemist.
However, the caffeine consumed by most people is not synthesized in a laboratory and is derived from natural sources.
Natural sources of caffeine include:
- beans (aka cherries) of the coffee plant
- tea bush
- kola nut
- guarana berries
- yerba mate