NEW YORK, Dec 30 (Reuters Health) -- Already lauded as a powerful
antioxidant, green tea extract may also help dieters shed fat, say researchers
reporting in the December issue of the American Journal of Clinical Nutrition.
The extract may also be a safe improvement on traditional diet drugs
because its benefits are "not accompanied by an increase in heart rate," write
Dr. Abdul Dulloo, of the University of Geneva in Switzerland, and colleagues.
As part of their study, the investigators measured the 24-hour energy
expenditure of 10 healthy men receiving three doses of caffeine (50 mg), green
tea extract (containing 50 mg caffeine and 90 mg epigallocatechin), or a 'dummy'
placebo per day.
The study authors report that, compared with placebo, treatment with green
tea was associated with a "significant increase" (+4%) in daily energy
expenditure. This effect was not linked to the relatively small amounts of
caffeine found in tea, since subjects receiving amounts of caffeine similar to
those found in green tea displayed no change in daily energy output.
Dulloo's team points out that "there are only two ways to treat obesity:
reduce energy intake (i.e., dieting), or increase energy expenditure." According
to their analysis, green tea extract seems to perform the latter function,
although the mechanisms behind its action remain unclear.
The investigators note, however, that green tea extract contains a high
amount of catechin polyphenols. These compounds may work with other chemicals to
increase levels of fat oxidation and thermogenesis, where the body burns fuel
such as fat to create heat.
"Stimulation of thermogenesis and fat oxidation by the green tea extract"
did not raise subjects' heart rates, the researchers note. This may render green
tea superior to stimulant diet drugs, which can have adverse cardiac effects,
especially in "obese individuals with hypertension and other cardiovascular
complications."
