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.