Green Tea

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Green tea, the healthy sip

Aside from herbal teas, there are three classic types of teas: the Chinese-style green tea, the run-of-the-mill black tea, and the delicate oolong tea. But one thing links all these traditional teas: They all come from the leaves of the same Camellia senensis bush. The distinguishing factor is how they are processed. Green tea is unfermented, black tea is fully fermented, oolong is partially fermented. Each tea type possesses unique beneficial compounds.

Sipping one or two cups of green tea a day has been shown to have many favorable benefits on health, especially in relation to cancer incidence, specifically of the breast, prostate, skin and stomach, though human studies show mixed results.

Ever-curious researchers set out to explore the chemical constituents of green tea to try to discern what, exactly, was responsible for its healthful benefits. Their work has landed on two items of note. One is the green tea catechin epigallocatechin gallate, or EGCG for short. Research shows antioxidant and anti-cancer effects, as well as some research showing utility for weight loss.

In Petri dishes in research laboratories, EGCG has been shown to do a number on cancer cells, including prostate cancer cells, without affecting non-cancerous cells. In addition, animal models have consistently shown that standardized green tea polyphenols, when put in their drinking water, delay the development and progression of prostate cancer, especially in its early stages.¹

Altogether, three human clinical trials have been performed in prostate-cancer patients and suggest that green tea may have a distinct role as a chemopreventive agent. A review done by Chinese researchers at Beijing University of Chinese Medicine in 2008 assessed the whole of human studies. They identified 43 population studies, which try to pinpoint usage after the fact and associate that usage with cancer incidence, as well as four gold standard human clinical intervention trials. Their conclusion: “While some evidence suggests that green tea has beneficial effects on gastrointestinal cancers, the findings are not consistent.”²

The US Food and Drug Administration agreed with that sentiment, saying in 2005 that the evidence was not good enough to warrant an official health claim associating green tea with cancer prevention.

Whereas many laboratory studies have demonstrated the potential efficacy of green or black tea for preventing obesity, the underlying mechanisms remain unclear. The results of human intervention studies are mixed and the role of caffeine has not been clearly established.³

Thus armed, food formulators have inserted EGCG into non-tea drinks such as Coke’s Envigo brand soft drink. Coke claims that it is calorie-negative in that the EGCG burns more calories than is otherwise contained in the drink.

The other interesting item in green tea is the amino acid L-theanine. This unique compound threads the needle and can make you feel relaxed without feeling drowsy. No easy trick! These anti-stress effects have caught the eye of drinks makers who are putting the green tea amino acid into their products.⁴

Another recent study used the green-tea, polyphenol-rich extract called sunphenon (BG), and found that it was highly effective in scavenging free radicals,⁵ which many scientists believe are the main cause of aging.

And if these nouveau concoctions don’t float your boat, you can always emulate the age-old Chinese hermit on the mountaintop, with the world’s nascent knowledge percolating through his wise old soul, and drink one or two cups of green tea a day.

References:

1. Harper CE, et al. Epigallocatechin-3-Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: mechanisms of action. Prostate. 2007 Oct 1;67(14):1576-89. 

2. Liu J, et al. Green tea (Camellia sinensis) and cancer prevention: a systematic review of randomized trials and epidemiological studies. Chin Med 2008 Oct 22;3:12. 

3. Grove KA, Lambert JD. Laboratory, Epidemiological, and Human Intervention Studies Show That Tea (Camellia sinensis) May Be Useful in the Prevention of Obesity. J Nutr. 2010 Jan 20. 

4. Kimura K, et al. "L-Theanine reduces psychological and physiological stress responses". Biol Psychol 2007;74(1):39–45.

5. . Kaviarasan, A.S. Sivakumar, A. Barik, A. Kunwar, G.H. Naik and K.I. Priyadarsini.  “Potential radical scavenging ability of sunphenon: a green tea extract.”  Journal of Food Biochemistry, 26 April 2010; DOI: 10.1111/j.1745-4514.2010.00404.x.

Disclaimer: The information provided in this section is a public service of WellWise.org, and should not in any way substitute for the advice of a qualified healthcare professional and is not intended to constitute personal medical advice.