If brewed differently than recommended, the flavor may be underdeveloped or too strong. A strong tannic quality can emerge if over-steeped, which ruins a good cup of tea. To obtain a stronger brew, add more tea, but use the same water temperature and brewing time as you otherwise would. Caffeine is an element of tea, and other plants, which acts as a central nervous system stimulant and promotes digestion. All types of tea contain caffeine, however the amount of caffeine varies according to the way in which the tea leaves are processed.
Green tea contains the least caffeine, Black tea the most, and Oolong falls in the middle range.
A cup of Oolong tea contains 12.50 mg of caffeine. A cup of Black tea ranges from 25 - 110, depending on the variety. Coffee generally contains 60 - 120 mg of caffeine. Caffeine in tea metabolizes differently in our bodies than caffeine in coffee. Caffeine from coffee is quickly absorbed, thus producing an immediate cardiovascular response, whereas caffeine from tea is more slowly metabolized, probably due to other compounds in the beverage which are thought to slow down the absorption rate.