Green Tea


 

Green Tea Clinical Report Summary

 

Research shows that green tea and its supplemental extracts can help burn fat and calories. It also may prevent the development of coronary heart disease and cancer, according to numerous clinical studies (1, 2, 3 4, 5, 6,). Research shows that many active ingredients in green tea are at work in these results. The caffeine and other chemicals in tea can help burn calories, while antioxidant chemicals like epigallocatechin-3-gallate (EGCG) kill off cancer cells and reduce blockage in arteries (1, 2, 3, 5, 6). Green tea is a popular beverage throughout Asia with traditional health benefits (1, 2).     

 

Green Tea Overview

 

Green tea is one of the most popular beverages in the world and a dietary staple in many Asian cultures (1, 2). It has also been used for thousands of years in traditional Indian and Chinese medicine as a stimulant, diuretic and treatment to improve heart health (2). Green tea, like the beverage black tea, is brewed from the leaves of the Camellia Sinensis plant. It is in the production of the leaves where these beverages differ; black tea leaves are aged and fermented versus green tea where the leaves are harvested and steamed to prevent oxidation (1). This process creates a beverage that is rich in phytonutrients, which are chemicals rich in cell protective anti-oxidants (2). The most abundant phytonutrients in green tea are flavanols and polyphenols, the most significant being a catechin called epigallocatechin-3-gallate or EGCG (1). Researchers believe EGCG is the most important compound in green tea for human health as studies shown it can kill off cancer cells and stop tumor progression (1, 2). Green tea has also become a popular ingredient in dietary supplements. Capsules or tablets should show that the tea extracts contain EGCG and other polyphenols. 

 

Safe Use of Green Tea

 

Dosages vary according to treatment plan but supplements should include a significant extract of polyphenols and EGCG. Studies and years of dietary consumption show that green tea is generally safe with few side effects (1, 2). People who are sensitive to caffeine or have heart, kidney and anxiety disorders may not be able to take green tea supplements (2). Pregnant and breast-feeding women should consult a doctor before taking green tea (2).

 

Clinical Reports for Green Tea

 

Hundreds of research studies have examined the health benefits of green tea and its active compounds. Promising results have been found in many categories but the strongest evidence supports the use of green tea for artherosclerosis, energy expenditure and cancer prevention (1, 2, 3, 4, 5, 6). Numerous population studies, research that asks people to record what they eat, support the consumption of green tea to prevent cancer (1, 2). In a study of nearly 500 women diagnosed with cancer, those who say they consumed green tea had the most minor cases and were least likely to have recurrence (1, 2). Animal and human in vitro studies show that green tea extracts prevent cancer or kill tumors directly, one study found that EGCG stopped the growth of prostate cancer cells isolated in the laboratory (1). Green tea has also been associated with weight loss from fat and calorie expenditure. Two notable randomized placebo-controlled double-blind studies investigated if the fat and calorie burning effects of green tea come from compounds like caffeine and EGCG. The tests were inconclusive for EGCG but found that the caffeine in green tea increases thermogenesis, fat burning and weight loss (2, 3, 4). Other studies speculate that polyphenols like EGCG also contribute to fat burning effects (2). Green tea studies also show benefit for the heart. Population studies of more than 200 men in Japan found that those who consumed higher amounts of green tea were less likely to have coronary artery disease or CAD (5). Coronary artery disease is also known as artherosclerosis or hardening of the arteries (1, 5). Animal studies of coronary artery disease show that the EGCG in green tea can reduce plaque, or blockage, levels during a 42-day treatment period (6).

 

Green Tea References

 

  1. Brown MD. Green tea (Camellia Sinensis) extract and its possible role in the prevention of cancer. Alt Med Rev. 1999; 4(5):360-370.
  2. Paturel A et al. Complementary medicine review: Green Tea. University of Maryland Medical Center website. 2006; http://www.umm.edu/altmed/articles/green-tea-000255.htm.
  3. Westerterp-Plantenga MS et al. Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation. Obes Res. 2005; 13(7):1195-1204.
  4. Berube-Parent S et al. Effects pf encapsulated green tea and Guarana exracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Br J Nutr. 2005; 94(3):432-436.
  5. Sano J et al. Effect of green tea intake on the development of coronary artery disease. Circ J. 2004; 68(7):665-670.
  6. Kuang-Yuh C et al. Differential effects of green tea-derived catechin on developing versus established atherosclerosis in apolipoprotein e-null mice. Circulation. 2004; 109: 2448-2453.
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