To Your Health:
How ‘Bout A Cup Of Tea?
By Nancy DiMarco,
Ph.D.
As I sit here drinking
my cup of green tea, I decided you all also might like to know about the benefits
of tea drinking.
Tea is the second most-consumed beverage in the world, right behind water.
And green tea is the most commonly consumed beverage in China and Japan.
The antioxidant compounds
in tea — polyphenols — are associated with health benefits, such
as the prevention of heart disease and cancer. In fact, one of the reasons
American researchers began looking at potential health benefits of tea drinking
is because the Japanese smoke twice as much as Americans do but their rate
of lung cancer is about half that in the United States.
Many research studies
have shown that white, green and yellow teas (also called non-oxidized teas)
have the highest amounts of antioxidants, with green tea capturing most of
the attention. Red and black teas (also known as oxidized teas) have similar
levels, but a different composition, of the antioxidants compared to non-oxidized
teas.
The primary polyphenols
found in teas are catechins, including epigallocatechin. Steeping tea for
approximately 5 minutes releases more than 80 percent of the catechins in
either green or black teas. Instant tea, however, contains negligible amounts
of the catechins and herbal teas have none.
All teas (green, black, red, etc.) are derived from the evergreen plant, camellia
sinensis. What makes them different is the amount of processing they undergo.
White teas are the
least processed. White tea refers to the buds and leaves that are steamed
and dried. Green tea leaves are steamed and then rapidly packaged. Black and
red teas are partially dried, crushed and/or fermented. Fermentation causes
the leaves to blacken, and the length of fermentation determines whether the
tea is red or black.
Decaffeination also
changes the content of the catechins in tea. In the U.S., there are two decaffeinate
methods. The first involves extraction of the caffeine using the solvent ethyl
acetate. The second, called effervescence, uses carbon dioxide and water to
remove caffeine. Green teas that are decaffeinated by ethyl acetate retain
only 30 percent of the catechins, but when decaffeinated by effervescence,
retain about 95 percent of the compounds.
Research has shown
that the protective function of tea is connected its antioxidant components.
Our bodies are constantly
producing unstable molecules called free radicals, which damage cells and
set the stage for possible invasion of bacteria, viruses or even cancer. A
diet rich in antioxidants, such as vitamins E, C, selenium and now possibly
the catechins, helps our bodies prevent free-radical damage.
The catechins, in
addition to their antioxidant properties, also play a role in cell growth
inhibition and apoptosis (programmed cell death). Both of these properties
have been shown to be important in the prevention and spread of cancer.
Studies in laboratory
animals have shown that catechins decrease the occurrence and the size of
tumors that were chemically induced. Studies in humans, however, have been
contradictory.
At least one study
completed in China, involving 18,000 male tea drinkers, showed that those
men who drank tea were 50 percent less vulnerable to developing stomach or
esophageal cancer compared to those who did not drink tea. A Dutch study,
however, found no benefit from tea drinking and the American Botanical Council
says that the overall evidence for a cancer-protective effect, especially
of green tea, is weak to moderate.
As far as heart disease
goes, another Dutch study showed that drinking one to two cups of tea daily
decreased the occurrence of aortic atherosclerosis, the narrowing of the major
artery from the heart, by 46 percent. Those who drank four cups a day decreased
their risk by 69 percent.
We certainly don’t
have all the answers, but the following lifestyle changes can go a long way
in reducing both cardiovascular disease and cancer: