Green tea extract (leaf)
Green tea extract is made from the leaves of the evergreen tree, Camellia sinensis. Green, black and oolong teas all come from the leaves of the same plant; their unique flavors and properties are the result of different processing methods. For green tea, the leaves are steamed, rolled and dried. This process inactivates the enzyme polyphenol oxidase, thus preserving the four principal polyphenol catechins in tea: epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and epigallocatechin gallate (EGCG). EGCG is the most abundant, accounting for 50-80% of catechins. When black tea is processed these polyphenols are oxidized, yielding other catechins, primarily theaflavins and thearubigins 1. A typical brewed cup (240 ml) of green tea can contain up to 300 mg catechins 2 and 30 mg caffeine 3 and also contains trace elements and vitamins.
Tea has been used by humans for thousands of years, first as a medicinal herb and then as a beverage. Today, it ranks second only to water as the world’s most popular beverage 4. In a recent review, subjects drinking tea consistently reported improvements attention, alertness and arousal following tea intake and there were also indications of improved work performance and creativity 5. Because populations in which tea is regularly consumed appear to enjoy longer and healthier lives, 6 scientists have been interested in better understanding how tea might exert such effects. The flavonoid compounds, particularly the catechins, are thought to be responsible for the majority of green tea’s health benefits7,8,9,10.
Intake of green tea, green tea extracts or EGCG have also shown promise for human subjects in increasing thermogenesis 11 and improving or maintaining a healthy body composition12. In overweight adults, intake of EGCG has increased fat oxidation 13,14,15, and a green tea extract increased whole body fat utilization during exercise in healthy normal BMI men 16. In addition, intake of green tea extracts or EGCG have supported healthy blood glucose/insulin levels in human subjects 17,18,19.
The antioxidant properties of tea components have been studied extensively. These molecules are free radical and oxy species interceptors, iron chelators, enzymatic radical generator inhibitors, electron donors, and superoxide radical scavengers 20. Most antioxidant compounds are active in either the lipid or aqueous portion of cells. EGCG is unique in that it is a potent antioxidant in both aqueous and lipid environments 21. The antioxidant potential of EGCG is far greater than that of vitamin E and/or vitamin C 22. Green tea constituents may also work synergistically with other antioxidants, including alpha-tocopherol and vitamin C 22,23.
Tea is considered to be safe when used orally in low or moderate amounts (up to approximately eight cups daily).
This ingredient can be found in the following products in United States:
- Ambrotose AO® Capsules
- Optimal Support Packets
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- Natural Standard Database. www.naturalstandard.com . 2014.
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- Islam MA. Cardiovascular effects of green tea catechins: progress and promise. Recent Pat Cardiovasc.Discov. 2012;7:88-99.
- Thavanesan N. The putative effects of green tea on body fat: an evaluation of the evidence and a review of the potential mechanisms. Br J Nutr 2011;106:1297-309.
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- Ota N, Soga S, Shimotoyodome A et al. Effects of combination of regular exercise and tea catechins intake on energy expenditure in humans. J Health Sci 2005;51:233-6.
- Ichinose T, Nomura S, Someya Y, Akimoto S, Tachiyashiki K, Imaizumi K. Effect of endurance training supplemented with green tea extract on substrate metabolism during exercise in humans. Scand J Med Sci Sports. 2011;21:598-605.
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- Ahmed S, Rahman A, Hasnain A, Lalonde M, Goldberg VM, Haqqi TM. Green tea polyphenol epigallocatechin-3-gallate inhibits the IL-1 beta-induced activity and expression of cyclooxygenase-2 and nitric oxide synthase-2 in human chondrocytes. Free Radic.Biol Med 2002;33:1097-105.
- Chen A, Zhang L, Xu J, Tang J. The antioxidant (-)-epigallocatechin-3-gallate inhibits activated hepatic stellate cell growth and suppresses acetaldehyde-induced gene expression. Biochem J 2002;368:695-704.
- Cai YJ, Ma LP, Hou LF, Zhou B, Yang L, Liu ZL. Antioxidant effects of green tea polyphenols on free radical initiated peroxidation of rat liver microsomes. Chem Phys.Lipids 2002;120:109-17.