Does black or green tea prevent you from sleeping?
Black and green teas contain theine, which is the same molecule as caffeine, a stimulating substance that can potentially delay falling asleep, reduce the total duration of sleep, and alter its structure, leading to more frequent awakenings.
However, the caffeine in tea (or theine) is not absorbed in the same way as caffeine from coffee. Other molecules (such as tannins and L-theanine) mitigate and delay its absorption in the intestinal tract. Released gradually, it acts in a more gradual and extended manner over time, without causing an overly stimulating effect. Furthermore, L-Theanine counterbalances these effects with its recognized relaxing properties.
Moreover, in general, teas, especially black teas, contain less caffeine than coffee. For 150 ml (1 small cup), a coffee provides about 60 mg (arabica) to 115 mg (robusta) of caffeine, while for the same volume of beverage, tea contains only 26 to 70 mg depending on the variety, with an average content close to 30-40 mg.
Finally, the rate of caffeine elimination varies among individuals. The enzymes responsible for metabolizing caffeine in the liver have a genetic component, leading to distinctions between slow and fast metabolizers. There is also a genetic sensitivity difference, related to individual variances in brain receptors to which caffeine binds.