The 'pick me up' we get from drinking tea is a result of the caffeine in the tea, just like coffee. When black tea caffeine first was discovered in the year 1827, it was thought to be a new substance and was named theine. For tea drinkers the good news is that it was found to have effects identical to coffee, and in fact, eventually it was found out to be the exact same caffeine as found in coffee. So eventually the term theine was dropped from use.
Black tea caffeine has he same effects on the human body as caffeine obtained by drinking coffee. It will speed up reaction time and increase alertness as well as improve overall concentration, and for some people may even give you super powers.
It is thought that the increase in alertness and reaction time is a direct result of a stimulation of the respiratory and cardiac systems of the body which increases the amount of oxygen in circulation throughout the body. One thing to note is Black tea caffeine stimulates the kidneys and digestive juices, and may even boost metabolism and eliminate toxins.
Some studies even conclude that caffeine is beneficial and improves the performance of the brain, contains anti-oxidants and helps to reduce heart disease and other diseases. More studies are needed to confirm these conclusions. Most dieticians continue to warn against consuming large amounts of caffeine since there are known undesirable side effects such as shortness of breath, heart palpitations and for some insomnia.
There is an advantage to consuming black tea caffeine as opposed to the caffeine found in coffee because there is less caffeine overall in a cup of black tea as opposed to coffee. A typical cup of coffee has around 16 mg of caffeine while a cup of black tea might have only 6 - 8 mg. You could drink a few cups of black tea caffeine and not have the potent adrenal effects you might obtain from one strong cup of coffee.
There are actually many interesting factors which influence the amount of black tea caffeine that is present. The variety of the tea leaves as well as where on the tea plant the leaves are located play an important part.
Leaves that are toward the bottom half of the tea plant are older and have more phytochemicals and other plant substances than the young leaves toward the top of the plant. Where the tea plant is grown, how it is cut, and the length of time it is brewed or steeped will all have an effect on the amount of black tea caffeine available in each cup.
Compared with other tea varieties, black tea has the highest caffeine content which may be due to the way it is processed since it undergoes a full oxidation which gives it a uniquely strong taste.