The
three main components of the tea leaf are caffeine, polyphenols
(popularly but incorrectly know as tannins), and aromatic or
essential oils. Here in brief is what they do. Caffeine, in moderate
quantities, stimulates the central nervous system and promotes blood
circulation. It stimulates the process of elimination and acts as a
diuretic promoting better kidney function. There is some evidence
that regular tea drinkers have a lower incidence of kidney ailments
and gallstones. Some researchers have even claimed that it also
helps the body excrete radioactive strontium 90, the element which
entered the food chain from atmospheric fallout from nuclear bomb
testing.
Polyphenols isolated from tea may act as an anti-cancer agent in
that they have an antimutant factor which helps cell DNA to
reproduce itself accurately rather than in mutated forms which might
lead to cancer. Medicines made from tea polyphenols have become part
of the treatment for nephritis, chronic hepatitis, and leukemia in
China. The essential oils (sometimes called aromatic oils, sometimes
volatiles because they totally evaporate) are formed in the tea
leaves as they grow. They account for the aroma of the beverage.
These substances also aid digestion and help emulsify fat. Green tea
has more essential oils than the more highly processed black tea.
That is why black tea has less aroma. Jasmine tea is said to have
the greatest amount, ranging from .06% percent to .4%. Some of this
may come from the jasmine blossoms.
