History of Tea

Tea is one of the most widely consumed beverages in the world, besides water. It is generally consumed in the form of black, oolong or green tea which originates from Camellia sinensis grown mainly in China and Southeast Asia. Black tea is consumed mainly in Western and some Asian countries and green tea is consumed predominantly in China, Japan and India. Tea was first used as a medicine in Southwest China 5000 years ago. Between 1100BC and 200BC, drinking tea was recommended to maintain health. By the Tang Dynasty (AD618-907), tea became an object of veneration and the tea trade inside China flourished. Since then, drinking tea has become an important part of Chinese culture and is still regarded as an important part of health maintenance. Green tea is produced in most areas of China and is the most popular category of tea. Representative varieties include Dragon Well (Long Jing) and Biluochun from Zhejiang and Jiangsu Provinces respectively Green tea is made from freshly picked tea leaves which go through heating and drying processes, but not fermentation like black tea varieties. This enables the leaves to keep their original green color and retain most of its natural substances like polyphenols and chlorophyll contained within the leaves.

Health Benefits of Tea

According to Traditional Chinese Medicine (TCM) understanding, tea has both sweet and bitter flavors and possesses cooling properties. It helps to refresh the mind, enhance alertness and boost concentration. Tea can also promote body fluid production, quench the thirst, clear heat  and phlegm and promote digestion and urination. Traditionally, it is used as:

• A beverage to relieve indigestion and smooth bowel movements. It can also be used to relieve headaches, dizziness, heat stroke and sleepiness.
• An antidote to clear toxic heat evils by promoting bowel movements and urination.

Many beneficial effects of tea have been attributed the strong antioxidative activities of its polyphenolic compounds. Modern studies have found that green tea contains a unique set of catechins, namely tea polyphenols, including (-)-epicatechin (EC), (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin-3-gallate (EGCG). EGCG is considered the major component responsible for tea's antioxidant activity, anti-aging properties and cardiac health maintenance. 1

Scientific Research on Green Tea or Green Tea Extract-based Supplements

A recent literature search revealed no fewer than 8,000 citations relating to green tea's chemistry, bioactivity, production and potential health benefits.

Effects of Green Tea in oxidative stress and cardiac health

Tea, especially green tea, is an important source of polyphenols, which act as strong antioxidants by scavenging reactive oxygen and nitrogen species and by chelating redox-active transition metal ions. 2 Green tea's beneficial effects are attributed to its ability to reduce oxidative stress, lipid peroxidation, free radical generation and unhealthy LDL cholesterol-oxidation. 3,4,5,6,7 There is also suggestive evidence that green tea catechins have a role in the protection against degenerative disorders. 8 Several oxidative stress conditions such as highly competitive physical exercise or pregnancy result in an increase of membrane-bound haemoglobin (MBH) due to the degradation of red blood cell metabolism and of the antioxidant defenses in aged and damaged red blood cells. A clinical study found that drinking green tea corresponds to a significant decease in MBH, suggesting a reduced oxidative stress within red blood cells. 9 Experimentally, some catechins have also been shown to inhibit a key enzyme (squalene epoxidase) in the pathway of cholesterol biosynthesis. 10 The potent antioxidant properties of tea polyphenols reduce free radical damage to cells and prevent the oxidation of LDL cholesterol. 11

Green Tea for Immune Health

There is evidence to suggest green tea may be beneficial in supporting immune health. Several in vitro studies found tea polyphenols inhibit a vast array of clinically relevant molecular targets and cellular processes such as antiapoptotic Bcl-2 proteins, 12 and vascular endothelial growth factor receptor (VEGFR) signaling. 13 There is further support by animal studies suggesting the consumption of green tea or green tea supplements with high levels of tea polyphenols may have a significant effect on the prevention of abnormal cell growth. 14

Conclusions

The health benefits of green tea are based on tradition or scientific theories. A number of pharmacological studies have demonstrated that the unique set of catechins in green tea possesses various biological activities in human body, such as antioxidant, immune system and cardiovascular system, which can potentially interfere with many disease-related biochemical processes. Green tea is a freely available phenomenal medicinal herb without a prescription and horrendous negative side effects. Hence, many people are turning to green tea to enhance their health and protect against chronic diseases.

References

1. Lambert JD, Yang CS. Cancer chemopreventive activity and bioavailability of tea and tea polyphenols. Mutation Res. 2003; 523-524: 201-208.
2. Frei B, Higdon JV. Antioxidant activity of tea polyphenols in vivo: evidence from animal studies. J Nutr 2003; 133:3275s-3284s.
3. Coimbra S, Santos-Silva A, et al. The effect of green tea in oxidative stress. Clin Nutr 2006; 25: 790-796.
4. Ishikawa T, Suzukawa M, et al. Effect of tea flavonoid supplementation on the susceptibility of low density lipoprotein to oxidative modification. Am J Clin Nutr 1997; 66: 261-266.
5. Klauning JE, Xu Y, et al. The effect of tea consumption on oxidative stress in smokers and nonsmokers. Proc Soc Exp Biol Med 1999; 220: 249-254.
6. Hashimoto R, Kojo S, et al. Inhibition of radical reaction of apolipoprotein B-100 and α-tocopherol in human plasma by green tea catechins. J Agric Food Chem 2000; 48: 6380-6383.
7. Pearson DA, German JB, et al. Inhibition of endothelial cell mediated low-density lipoprotein oxidation by green tea extracts. J Agric. Food Chem 1998; 46: 1445-1449.
8. Cooper R, Morre DM, et al. Medicinal benefits of green tea: part II . Review of anticancer properties. J. Altern. Complement. Med. 2005; 11: 639-652.
9. Low PS. Role of haemoglobin denaturation and band 3 clustering in initiating red cell removal. Red Blood Cell Ageing 1991; Plenum Press, New York: 173-183.
10. Abe I, Tanaka T, et al. Ellagitannins and hexahydroxydiphenoyl esters as inhibitor of vertebrate squalene epoxidase. J. Nat. Prod. 2001; 64: 1010-1014.
11. Cooper R, Morre DM, et al. Medicinal benefits of green tea: part I . Review of noncancer health benefits. J. Altern. Complement. Med. 2005; 11: 521 -528.
12. Leone M, Pellecchia M, et al. Cancer prevention by tea polyphenols is linked to their direct inhibition of antiapoptotic Bcl-2-family proteins. Cancer Res. 2003; 63: 8118-8121.
13. Lamy S, Beliveau R, et al. Green tea catechins inhibit vascular endothelial growth factor receptor phosphorylation. Cancer Res. 2002; 62: 381-385.
14. Khan N, Mukhtar H, et al. Targeting multiple signaling pathways by green tea polyphenol (-)-epigallocatechin-3-gallate. Cancer Research 2006; 66: 2500-2505.

Compiled and edited by:

Jennifer Eagleton, BA, MA (Asian Studies), Integrated Chinese Medicine Holdings Ltd. Stan Man, Integrated Chinese Medicine Holdings Ltd.