Stimulant Effects of Caffeine
Caffeine is a mild stimulant which acts on the central nervous system and some other organs of the body, for example the kidneys.
It is readily absorbed into the bloodstream and does not accumulate in the body, being rapidly metabolised and excreted. The stimulant effects of a small amount (say one cup of coffee) take effect after 15 – 45 minutes and last normally for about four hours. However, caffeine is absorbed from soft drinks at a slightly slower rate than that from coffee and tea, thought to be because of their acid pH.
The effects of caffeine do not last so long in smokers – nicotine doubles the speed at which caffeine is broken down in the body. Alcohol has a similar effect.
Caffeine metabolises more slowly in pregnant women and those taking the contraceptive pill. Its effects last longer in small children than in adults.
A moderate amount of caffeine is considered safe from a general health point of view, and people who consume higher amounts will not necessarily experience health problems.
The effects of caffeine vary from one individual to another. The effects also vary depending on the amount drunk relative to age, bodyweight, time of day, over what period of time, a person’s sensitivity to it, and other factors such as smoking and pregnancy.
Caffeine does not reduce the symptoms of intoxication after drinking alcohol and is not an antidote to it. Caffeine can, however, help to reduce the after-effects of heavy alcohol consumption (hangover) by increasing alertness and wakefulness.