The types of Green Tea differ also in levels of caffeine. Some have a higher content and others have it very low. One of Green Teas with lower amount of caffeine is the Bancha tea, which can be safely drunk in the evening. On the other hand there are some rare exceptions, such as premium green tea Gyokuro, which contains larger amount of caffeine than some of black teas. It is also known that usual tea bags, with their broken leaves of smaller sizes, contain more caffeine than tea made from the whole tea leaves.
In the tea, the caffeine (named tein) is in a complex with tannins. For this reason the absorption of caffeine from the intestines is slower, since this complex has to dissolve first.
Because the caffeine in tea binds to tannins, operates quite differently than the one in coffee. Caffeine in tea does not work on the hearth and bloodstream such as in coffee. Through better blood circulation in brains and increased brain fluid exchange it directly affects the brain and central nervous system instead. Thus we can explain the increase in concentration and reaction ability after drinking Green Tea.
There exists also a technique to reduce the caffeine in tea – the washing. You put in a cup the quantity of Green Tea required to prepare the infusion and then pour the hot water needed to cover all the leaves. After this mix for 20 seconds the water, so that all the leaves get wet and then throw away the water, catching the leaves with a strainer. In this way great part (approx. 80%) of the caffeine is removed immediately. Finally you can repeat with pouring the hot water, performing the normal preparation of your Green Tea.