Studies
CLINICAL STUDIES
In
a study reported on in the American Journal of Clinical Nutrition,
it was found that green tea extract resulted in a significant
increase in energy expenditure, plus also had a significant effect
on fat oxidation. While some of the effects were originally
theorized to be due to the caffeine content of green tea, the
researchers discovered that the tea actually has properties that go
beyond those that would be explained by the caffeine.
Today, scientific research in both Asia and the west is
providing hard evidence for the health benefits long associated
with drinking green tea. For example, in 1994 the Journal of the
National Cancer Institute published the results of an
epidemiological study indicating that drinking green tea reduced
the risk of esophageal cancer in Chinese men and women by nearly
sixty percent. University of Purdue researchers recently concluded
that a compound in green tea inhibits the growth of cancer cells.
There is also research indicating that drinking green tea lowers
total cholesterol levels, as well as improving the ratio of good
(HDL) cholesterol to bad (LDL) cholesterol.
In a study reported on in the American Journal of Clinical
Nutrition, it was found that green tea extract resulted in a
significant increase in energy expenditure (a measure of
metabolism), plus also had a significant effect on fat oxidation.
While some of the effects were originally theorized to be due to
the caffeine content of green tea, the researchers discovered that
the tea actually has properties that go beyond those that would be
explained by the caffeine.
The same amount of caffeine as was in the green tea,
administered alone, failed to change energy expenditure in other
studies. This led reseachers to believe that there is some
interaction going on with the active ingredients of green tea that
promotes increased metabolism and fat oxidation.
The researchers indicated that their findings have substantial
implications for weight control. A 4% overall increase in 24-hour
energy expenditure was attributed to the green tea extract,
however, the research found that the extra expenditure took place
during the daytime. This led them to conclude that, since
thermogenesis (the body's own rate of burning calories) contributes
8-10% of daily energy expenditure in a typical cubject, that this
4% overall increase in energy expenditure due to the green tea
actually translated to a 35-43% increase in daytime
thermogenesis.
Of
critical importance to thyroid patients is the fact that none of
the research subjects reported any side effects, and no significant
differences in heart rates were noticed. In this respect, green tea
extract is different from some of the prescription drugs for
obesity, and herbal products like ephedra, which can raise heart
rates and blood pressure, and are not recommended for many
individuals, in particular, those with thyroid disease who may be
particularly sensitive to stimulants.
SOURCE: Nagao, T. American Journal of Clinical Nutrition,
January 2005; vol 81: 122-129.
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