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After water, tea is the most commonly consumed beverage in the world. This is good news, because tea offers important health benefits.
Green tea was the first tea studied for its cancer-fighting
benefits. Recent research shows that any tea derived from the
leaf of a warm-weather evergreen known as Camellia sinensis has
similar cancer-fighting properties. This includes all green,
black and red (oolong) teas. The leaves of this tree contain
chemicals called polyphenols, which give tea its antioxidant
properties. Herbal teas are not derived from this leaf and so do
not have this particular health-promoting chemical.
The degree of processing determines whether a tea will be
green, black or red. Green teas are the least processed. They are
simply steamed quickly before packaging. Black and red teas are
partially dried, crushed and fermented. The length of
fermentation, which causes the leaves to blacken, determines
whether the tea will be red or black. Regardless of the
processing method, all teas contain polyphenols.
Polyphenols, like other antioxidants, help protect cells
from the normal, but damaging, physiological process known as
"oxidative stress." Although oxygen is vital to life, it's also
incorporated into reactive substances called free radicals. These
can damage the cells in our body and have been implicated in the
slow chain reaction of damage leading to heart disease and
cancer.
Many studies have demonstrated the anti-cancer properties
of polyphenols. They can stop the damage that free radicals do to
cells, neutralize enzymes essential for tumor growth, and
deactivate cancer promoters. Their effect on heart disease is
less well understood. Some laboratory studies have found that
polyphenols help prevent blood clotting and lower cholesterol
levels. The leap to preventing heart attacks, however, has not
yet been made. The majority of evidence comes from studies done
on lab animals. The effect on people is unclear.
Although much remains to be learned about the health
benefits of tea, it is considered a good choice for at least some
of the 6 to 8 cups or glasses of fluids recommended daily.
The best teas are those brewed from loose leaves or tea bags of
black, green or red tea, as they have the most antioxidant power.
Allow your tea to steep for three to five minutes to allow the
maximum amount of antioxidants to be released. Iced teas can
provide as much antioxidant power as hot teas. Keep them covered
and refrigerated. Bottled teas often have a lower antioxidant
level because they contain mostly water and sugar.
Some people think that milk lowers tea's anti-oxidant power
because it binds to polyphenols and inactivates them. This has
not been proven, however, so go ahead and add some milk if you
like. You'll also increase your calcium intake.
Tea also has fluoride for strong teeth, virtually no
calories, and half the amount of caffeine found in an
equally-sized cup of coffee. Whether decaffeinated teas have the
same polyphenols, and thus the same health benefits, as regular
teas has not yet been studied. Caffeine is a natural component of
tea leaves. It is not yet known if removing caffeine also removes
polyphenols.
For more information, contact your local
Colorado State University Extension office.
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