Green tea has been consumed for more than three thousand years for both its refreshing and health promoting benefits. In fact, a historical perspective1 on green and black tea reported that they are among the most widely consumed beverages in the world, second only to water. Dogma has it that, for 4,000 years people knew tea might have health-promoting properties since it was frequently used as fluid supply for patients suffering from infectious diseases. This article will review a number of green tea's many benefits to human health, including its antioxidant and anti-inflammatory properties, its anti-cancer activity, and its ability to promote both cardiovascular health and weight loss. Before jumping into its benefits, however, let's first take a look at the difference between green, black and oolong tea.

Green, black and oolong tea
Green, black and oolong tea all come from the same species, Camellia sinensis. Green tea, however, is different than black and oolong teas because it is not fermented. Black tea is fully fermented and oolong tea is partially fermented, whereas green tea is produced by steaming fresh leaves. The steaming doesn't decrease polyphenols in green tea, such as flavanols, flavandiols, flavonoids, and phenolic acids, which are abundant. One group of flavanols are known as catechins. These include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC), which are responsible for many of green tea's benefits. Growing conditions, leaf age, and storage during and after transport affect the amount of polyphenols and catechins in green tea. For example, green tea catechins can range from 69 to 103 mg/gram of tea,2,3 although green tea extracts may provide significantly higher amounts.

Antioxidant properties
Green tea has significant antioxidant properties.4 Laboratory research5 found that green tea slowed down the oxidation of LDL cholesterol ('bad cholesterol'), which is associated with atherosclerosis, or the build-up of plaque on arterial walls. A cup of green tea contains 50 to 100 mg of polyphenols (approximately 6,300 to 12,600 times higher than the dose used in the laboratory study). Therefore, one cup of green tea a day may provide a therapeutic dose of antioxidant polyphenols, and green tea extracts with higher polyphenol content likely provide even greater antioxidant activity. In fact, in human research,6 the consumption of green tea extract (high in polyphenols) led to a greater increase in plasma antioxidant activity than when given as a standard tea. This makes sense when considering that the antioxidant score (aka, ORAC score) for a cup of brewed green tea is 1253 ORAC units,7 while one gram of green tea extract has 3,996 ORAC units.8 Depending upon the actual extract, some green tea products may even have a higher ORAC value.

Anti-inflammatory activity
Catechins in green tea have anti-inflammatory activity. This includes a reduction in the following inflammatory markers: leukotriene-B4, 5-lipoxygenase,9 COX-2 and nitric oxide synthase.10 In addition, EGCG and other catechins in green tea might reduce inflammation and protect cartilage by inhibiting proteoglycan and collagen breakdown,11 which may have positive implications for joints as seen in laboratory models of rheumatoid arthritis.12 Other examples of green tea's anti-inflammatory effect include a reduction gum (gingival) inflammation,13 protection against sunburn inflammation,14 and a reduction in a marker of chronic inflammation as a cardiovascular risk factor.15

Anti-cancer activity
Research suggests that green tea may protect against some kinds of cancer. Tea polyphenols have antimutagenic effects and protect DNA,16 reduce oxidative DNA damage, lipid peroxidation, and free radical generation.17 In animal or laboratory research green tea catechins prevented new blood vessel growth (angiogenesis) in tumors and inhibited tumor cell proliferation resulting cell death (apoptosis).18,19,20,21,22,23 In human research, green tea was shown to reduce mutagenic activity in smokers.24

Cardiovascular health
A population based study25 of 40,530 healthy adults aged 40 to 79 years found that the consumption of three or more cups of green tea daily for 11 years significantly decreases the risk of cardiovascular and all-cause mortality compared to drinking less than one cup daily, and this association was primarily related to a decrease in risk for stroke (cerebral infarction). In another population study of 1371 men, aged 40 years or older, increased daily consumption of green tea resulted in significantly decreased serum levels of total cholesterol, LDL cholesterol (‘bad cholesterol'), and triglycerides, while increasing HDL cholesterol (‘good cholesterol'). Moreover, there was a decrease in other serum markers of liver disease, especially when more than 10 cups of green tea daily was consumed.

Weight loss properties
A population study26 of 1,210 adults examined the relationship between habitual tea consumption (mostly green and oolong tea) and changes in total body fat and fat distribution in humans. Results were that habitual tea drinkers for more than 10 years showed a 19.6 percent reduction in body fat percentage and a 2.1 percent reduction in waist-to-hip ratio compared with nonhabitual tea drinkers. Other research27 has shown that higher intakes of polyphenols (favonols/flavones, catechins) from tea and other sources were associated with a significantly lower increase in BMI (body mass index), a measure of healthy body weight. Furthermore, other research has shown that green tea extract stimulates thermogenesis (i.e. fat burning)28 and helped obese individuals lose weight.29

Conclusion
Green tea has many health benefits to offer, and it is a worthwhile endeavor to include it as part of your daily routine. Drinking a few cups of green tea each day or, better yet, using a green tea extract high in polyphenols will provide you with antioxidant protection while providing a plethora of other benefits.

References

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