For many of us freshly brewed coffee is as much a part of our morning routine as brushing our teeth. Some even claim to be incapable of anything before the first coffee. In addition to its desired effect, the active ingredient in coffee, caffeine, however, also has other effects that can influence sleep.


What is caffeine?

Caffeine is a pharmacologically active substance. This means that when caffeine is ingested, there are verifiable effects in the body. Caffeine is one of the oldest, most effective, best tolerated and most commonly consumed active ingredients. It occurs naturally in coffee beans, tea leaves and cocoa beans. It is a component of many stimulants in our diet.


Caffeine content of selected stimulants:

  •     A cup of filter coffee (200 ml) - 90 mg
  •     A can of energy drink (250 ml) - 80 mg
  •     A cup of espresso (60 ml) - 80 mg
  •     A cup of black tea (200 ml) - 45 mg
  •     A cup of green tea (200 ml) - 30 mg
  •     A can of a cola drink (330 ml) - 35 mg
  •     A cup of cocoa drink (200 ml) - 8 to 35 mg
  •     Half a bar of dark chocolate (50 g) - 25 mg

letsleep tips

  • Those who have problems with falling asleep or sleeping through should not drink caffeinated drinks after 5 p.m..
  • Pregnant women should only take small doses of caffeine, a maximum of 200 mg throughout the day.
  • Children should not drink cola, energy drinks or similar products - on the one hand because of the caffeine, on the other hand because of the high sugar content. If they do, then the drinks should be strongly diluted.

How does caffeine work?

The probably best-known effect is the reduction of fatigue and daytime sleepiness. It also has an activating effect on the central nervous system and thus increases heart rate and blood pressure.

It has a slight diuretic effect and promotes digestion. It also increases concentration and has a positive effect on drive and mood. At higher doses, it even expands the bronchial tubes. Caffeine ingested during the day also has an effect on night sleep, it suppresses deep sleep. It is possible to develop tolerance. This tolerance develops after about 6-15 days of heavy caffeine consumption.

Side effects include deposit symptoms such as headaches and nausea. In addition, the intake of large quantities can lead to stomach problems. The lethal dose for humans is about 10 grams of caffeine.

Hornyak, M. (2007). Koffein. In H. Peter, T. Penzel & J. H. Peter (Hrsg.), Enzyklopädie der Schlafmedizin (S. 629-632), Heidelberg: Springer;
Bundesinstitut für Risikobewertung (2015). Fragen und Antworten zu Koffein und koffeinhaltigen Lebensmitteln, einschließlich Energy Drinks.