Tein is the name for a stimulant substance (like caffeine) that has been found in tea. Modern research has also confirmed that tein and caffeine have the same chemical formula. Thus, they are indeed the same substance.
Caffeine is a bitter alkaloid that is known and used primarily for its stimulant effect. It can eliminate fatigue, increase concentration and enhance performance.
The beneficial effect is also described by people with low blood pressure.
It is therefore considered the most widely used drug worldwide. Its effect is based on its ability to block the action of adenosine.
Specific to tea caffeine is that it has a bound form. This predisposes it to a different mode of absorption and action compared to coffee caffeine. The effect of tea is gentler on the human body and the stimulating effect lasts longer.
More tein is contained in black tea.
The slightly lower theine content in green tea is due to the lower temperature as well as the shorter steeping time.
It is possible to overdose on caffeine, but in practice it is not practically realistic to do so from tea. Available sources put the dangerous dose at around 30 cups of tea.
A single cup contains an average of 40 mg of tein.