A Benefits-Laden Beverage
The tea plant (Camellia sinensis L.) is a small shrub with dark green, narrow, serrated leaves primarily grown in India, Sri Lanka, China, Indonesia and Japan. Both black and green teas are produced from the leaves of the same plant - the difference between the two is a result of different processing.
Green tea accounts for approximately one fifth of the world's tea production. It is a non-fermented tea in which the fresh young leaves are lightly stemmed or pan-heated and then dried. Black tea, in contrast, undergoes a controlled "fermentation" before drying, where an enzyme in the leaves - polyphenoloxidase - polymerizes (or links together) chains called tannins. As a result of such processing, the characteristics and the health benefits of black tea differ somewhat from those found with green tea.
The former produces more powerful effects in the area of vasodilation and cardiovascular health; whereas the latter is noted in traditional Asian medical systems as being an excellent blood purifier as well as a cardio tonic.
The other traditional uses for green tea are as an intestinal astringent, diuretic, and central nervous system stimulant. Although the green tea beverage does contain caffeine, even sensitive individuals usually find that drinking tea does not produce excessive stimulation that the same amount of caffeine from coffee can induce. This may be because green tea also contains the amino acid theanine, which is known to facilitate relaxation.
Toxin Reduction and Cellular Health
Most epidemiological and clinical studies have examined the qualities of green tea that inhibit the production and the activation of compounds which damage cells, including their DNA. Strong epidemiological evidence suggests that the low rate of certain health problems in Japan is linked to the consumption of green tea.
Green tea polyphenols may inhibit the formation of cell-damaging nitrosamines. Nitrosamines are compounds which are formed when nitrites bind to amino acids. Modern farming practices often increase the nitrite and nitrate load found in foods due to the use of chemical fertilizers. Modern food processing often adds nitrites to meat products as preservatives to maintain freshness and color. Both animal and human trials have demonstrated that green tea strongly inhibits the formation of nitrosamines. Diets which are high in protein will tend to increase the formation of nitrosamines as a result of digestive actions upon protein, and therefore green tea is an important addition to such diets.
Green tea catechins are powerful antioxidants which also may increase the activity of indigenous antioxidant enzyme systems, such as the glutathione detoxification system. The glutathione detoxification system is an important component in the process that transforms fat-soluble toxins to water-soluble compounds which then can be removed from the body.
Activating the production of enzymes such as glutathione perioxidase, glutathione reductase, glutathione-S-transferase, catalase, quinone, reductase, etc. helps to eliminate the toxins from the body and bring into play natural defenses against cellular damage, including to DNA. Women in particular might note that tea may be beneficial in helping the body to eliminate spent estrogens.
Increasing 24-Hour Energy Expenditure
Clinical trials have found increased 24-hour energy expenditure with three doses per day of caffeine (50 mg) and 90 mg epigallocatechins from green tea. This level of intake of caffeine plus epigallocatechins leads to a "significant increase" (+4%) in energy expenditure. Supplementing with 150 mg caffeine alone, however, does not lead to a significant increase in energy expenditure.
In European trials, the individuals taking green tea extract used more fat calories than those taking the placebo. A serving of 500 mg of green tea extract supplies approximately 140 mg epigallocatechins (as EGC and EGCG). Two servings per day would therefore match the epigallocatechin intake found to be useful in these studies when consumed with a moderate amount of caffeine. Source: Jarrow Formulas
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Scientific References
Dulloo A, et al. Efficacy of a green tea extract rich in catechin polypherols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. American Journal of Clinical Nutrition 1999; 70: 1040-1045.
Graham, H. N. Green Tea composition, consumption, and polypherol chemistry. Preventive Medicine 1992; 21(3): 334-350.
Kada, T. et al. Detection and chemical identification of natural bioantimutangens: A case of the green tea factor. Mutation Research 1985; 150: 127-132.
Mukhtar, H. et al. Tea components: Antimutagenic and Anticarcinogenic Effects. Preservative Medicine 1992, 21(3): 351-360.
Osawa, T. et al. Tea polyphenols as antioxidants. Abstracts of papers presented at the First International Symposium on the physiological and pharmacological effects of Camellia sinensis (Tea). Preservative Medicine 1992, 21(3): 331-333.
Sagesaka-Mitane, Y. et al. Platelet aggregation inhibitors in hot water extract of green tea. Chemical and Pharmaceutical Bulletin 1990. 38(3): 790-793.
Shim, J. S. et al. Chemo preventative effect of green tea (Camellia sinensis) among cigarette smokers. Cancer Epidemiology Biomarkers and Prevention 1995. 4(4): 387-391.
Tanizawa, H. et al. Natural antioxidants. I. Antioxidative components of tea leaf (Thea sinensis L). Chemical and Pharmaceutical Bulletin 1964, 32(5): 2011-2014.
Zhao, B. et al. Scavenging effects of extracts of green tea and natural antioxidants on active oxygen radicals. Cell Biophysics 1989, 14: 175-185.
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