The Efficacy of Camellia Sinesis on Thermogenic Activity

The Efficacy of Camellia sinesis on Thermogenic Activity

Camellia sinensis, commonly known as green tea, has been used in medicine and social culture for thousands of years. Only recently it has gained scientific validity in its active principles in the treatment of a variety of ailments such as a cancer chemopreventive, a protective of cardiovascular disease, and its antioxidant, anticarcinogenic, anti-inflammatory, thermogenic and antimicrobial activities.1 All teas (green, black, and oolong) are derived from the same plant, Camellia sinensis. The difference is in how the plucked leaves are prepared. Green tea, unlike black and oolong tea, is not fermented, so the active constituents remain unaltered in the herb.2

The Chinese emperor Shen Nung first discovered tea around 2750 BC, when he found that steeping the leaves of certain plants in hot water not only tasted good, but also had health benefits. Tea was popular in China first as a medicine, and second as a satisfying drink. While its popularity soared in China and the eastern countries in that region, it took almost 4,000 years for it to reach western culture. The Dutch were the first European country to adopt tea drinking in 1610, and the rest of the area was soon to follow with Britain gaining interest in 1650. Tea came to the Americas with colonists who, in Britain, had largely incorporated tea into their culture since its introduction, and thus brought that with them to the Americas. 3

Only recently scientists have expressed interest in the health benefits of green tea, largely due to the surge of popularity in tea since the beginning of the decade. With growing obesity in America, the thermogenic activity of green tea is of particular interest with scientists as well as consumers. A clinical study found that in 10 healthy men put in a respiratory chamber and given a placebo, 50 mg caffeine and 90 mg epigallocatechin gallate (EGCG--thought to be the most potent antioxidant in green tea), or just 50 mg of caffeine, the 24-hour energy expenditure of those who took EGCG was about 4% higher than those who took the placebo or caffeine. It is thought by some that weight loss and thermogenesis can be attributed to the caffeine found naturally in green tea. It is shown in this study, however, that treatment with only caffeine in a similar dose to that of green tea had no effect on 24-hour energy expenditure, which validates the hypothesis that EGCG found in green tea increases energy expenditure.4 The catechin EGCG has been shown to inhibit the enzyme catechol-O-methyl-transferase, which inactivates norepinephrine, thus leading to more norepinephrine and the release of energy from fat.5

Green tea has also been shown to be effective in the prevention of some cancers. Green tea catechins have demonstrated efficacy in protection against chemically induced cancers in vitro. Convincing evidence in support of cancer prevention is shown by the low frequency of cancer