How strong is a cup of tea? Some
people drink a cup of tea to go to sleep, others to keep awake. Some drink
tea to calm their nerves, others for a lift. How can the same beverage
possess such opposing qualities? Precisely because tea -- unlike coffee
-- can produce both these effects upon the body, it is viewed as a wonder
drink.
Tea and coffee both contain the stimulating substance caffeine, but only
tea contains both caffeine and tannin. The presence of these chemical
compounds together in tea leaves allows tea to act as a calming or exciting
agent.
Here is how it works. Once boiling water is poured onto tea leaves, in
the first two minutes all the caffeine in the leaves is drawn out. At
this point tea is at its most stimulating. Only during the next minute
win tannin gradually be drawn out of the tea leaves. This will not only
cancel out the effects of the caffeine but after five minutes will actually
make a relaxing, calming tea. Graphically it can be shown thus:
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