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Green Tea: the Marvelous Drink

Currently, tea in the form of green or black tea, next to water, is the most widely consumed beverage in the world. According to Chinese legends, tea was discovered by the Emperor Shen Nong in about 2700 BC, when a gust of wind blew tea leaves into a kettle of boiling water.

Teas contain polyphenols which act as antioxidants and exhibit numerous biochemical activities. Tea polyphenols consist mostly of catechins, the most powerful of which is epigallocatechin gallate (EGCG) which is found only in green tea. Since ancient times green tea has been considered a health-promoting beverage and currently researchers find more convincing proof of its healing qualities.

Based on the growing range of studies that research health properties of green tea, I made this article about clear benefits you can get with regular drinking.

1 Longevity

Green tea may protect against death from all causes, especially cardiovascular disease. Japanese scientists[1] analyzed data from a National Cohort Study that began in 1994 and had over 40,000 participants, age 40 to 79, who initially were free of stroke, heart disease and cancer. People were followed for up to 11 years.

Compared with participants who consumed less than 1 cup of green tea per day, those drinking 5 or more cups a day had a significantly lower risk of death from all causes, especially lower risk of dying from cardiovascular disease and stroke. The findings might explain in part the reason why the Japanese live longer than people in any other country. However, there was no cancer prevention benefit of green tea.

2 Memory and learning

One of the important health benefits of regular green tea drinking is improved memory and learning ability. In Japan there was revealed[2] that high green tea drinking maintains cognitive function. Also, green tea consumption may enhance learning and memory ability[3].

The main components of green tea that are thought to work on improving brain function are polyphenols, epigalochatechin-3-gallate (EGCG), a very strong antioxidant. The high use of oxygen during the metabolic processes leads to the generation of a large number of free radicals (highly reactive molecules). EGCG can penetrate the brain's blood barrier and is able to enact its antioxidative affects on the free radicals that cause damage in the brain.

3 Weight control

There is strong evidence that green tea has fat-burning properties and promotes weight loss, especially when combined with increased physical activity and a healthy diet. Green tea polyphenols are known to increase the metabolism of fats by the liver (thermogenic effect), inhibit lipase (fat absorption enzyme) in the digestive tract, and provide a feeling of satiety and fullness[4]. Green tea can reduce body weight in obese persons by increasing energy expenditure and fat oxidation[5].

Continuous ingestion of a green tea extract high in catechins promotes reduction in body fat, systolic blood pressure, and LDL cholesterol, that in its turn contributes to a decrease in obesity and cardiovascular disease risks.

4 Skin protection from Ultraviolet

Green tea polyphenols protect the skin from the damage caused by ultraviolet radiation such as UV-induced sunburn, UV-induced immunosuppression and photoaging of the skin. They exert photoprotection by various cellular, molecular and biochemical mechanisms[6]. Also, green tea polyphenols protect the skin by improving the elastic tissues[7].

5 Lowering cholesterol

Green tea lowers total cholesterol and LDL cholesterol levels and improves the ratio of HDL to LDL cholesterol. People who drink green tea daily have lower cholesterol levels than those who do not drink it [8].

It is believed that one of the underlying mechanisms by which green tea lowers blood cholesterol levels is by reducing lipids absorption in the digestive tract and promoting their excretion from the body[9].

6 Diabetes and blood glucose levels

Green tea has been traditionally used to control blood sugar. Recent evidence also suggests it may help regulate the blood sugar and reduce the risk for type 2 diabetes. People who drink more than 6 cups per day are less likely to develop diabetes than those who drink less than 1 cup per week[10]. Green tea antidiabetic properties may be partly explained by its caffeine content.

Japanese researchers[11] demonstrated that daily intake of green tea extract lowered the hemoglobin A1c level in people with borderline diabetes, that indicates the increased body's ability to utilize blood sugar. Hemoglobin A1c is a test that measures the amount of glycosylated hemoglobin molecules in red blood cells. These molecules attach to glucose and so people have more of them if they have more glucose in the blood.

7 Heart protection: Asian paradox

Green tea may protect against heart disease. Green tea might explain the "Asian paradox" - when people living in Asian countries smoke cigarettes heavily, but have relatively low incidence of heart disease. The Japanese confirm[12] that the more green tea people drink, the less likely they are to have coronary artery disease. Underlying mechanisms for this include vasculoprotective, antioxidative, antithrombogenic, anti-inflammatory, and cholesterol-lowering properties of tea flavonoids.

Green tea can promote cardioprotection and reduce heart muscle cells death after a heart attack (myocardial infarction)[13]. The primary catechin in tea, EGCG, prevents heart muscle damage by blocking the activation of inflammation-related compounds that promote the oxidative damage that kills heart cells in heart attack. EGCG also appears to speed up the recovery of heart cells.

8 Anti-hypertensive

Green tea lowers blood pressure and helps prevent hypertension. Tea increases body's production of nitric oxide, which dilates arteries and thereby reduces blood pressure[14]. Among persons consuming tea regularly for at least one year, the risk of developing high blood pressure was 46% lower among those who drank 1/2 cup to 2 1/2 cups per day, and 65% less among those consuming more than 2 1/2 cups per day[15].

9 Stroke

Green tea shows promise in the prevention of stroke[1, 16]. Furthermore, the green tea polyphenols, particularly EGCG, have been shown to protect brain cells from destructive processes following stroke[17].

10 Alzheimer's and Parkinson's Diseases

Green tea may reduce the risk of degenerative disorders of the central nervous system, such as cognitive decline, Alzheimer's and Parkinson's diseases. Green tea catechin polyphenols produce several neuroprotective (i.e. lessening the damage to brain cells) activities like iron chelation, scavenging of radicals, activation of survival genes and cell signaling pathways, and inhibitory action on Abeta fibrils/oligomers formation[18, 20].

Japan scientists have discovered that people who consumed more than 2 cups of green tea a day had a 50% lower chance of having cognitive impairment, than those who drank fewer than 2 cups a day, or who consumed other tested beverages[19].

11 Atherosclerosis

Regular green tea drinking may be beneficial for the prevention of atherosclerosis, when the plaque builds up on the insides of the arteries [21]. Green tea has been shown to effectively lower the risk of atherosclerosis by lowering LDL cholesterol, triglycerides, lipid peroxides (free radicals that damage LDL cholesterol and other lipids) and fibrinogen (a protein in the blood involved in the formation of blood clots). Green tea is a powerful antioxidant and protects LDL cholesterol from oxidation[22]. Oxidized cholesterol gets sticky and tends to cling to the walls of he arteries, leading to the development of atherosclerosis.

12 Anticlotting effect

Green tea also appears to prevent the formation of blood clots (thrombosis). Green tea catechins produce potent antithrombotic effect by inhibition of platelet aggregation (blood clot formation)[23].

13 Increased exercise endurance

Animal studies indicate that green tea increases exercise endurance. Green tea catechins increase metabolic capacity and utilization of fatty acid as a source of energy in muscles during exercise[24].

14 Smoking

Regular green tea drinking may protect smokers from oxidative damages and reduce cancer risk or other diseases caused by free radicals associated with smoking[25]. Green tea may prevent future cardiovascular disorders in chronic smokers[26].

15 Bones

Green tea may prevent osteoporosis and bone loss. Researchers at the University of Tokyo[27] have shown that green tea may increase bone mineral density. Australian researchers[28] report that bone mineral density is 2.8% greater in tea drinkers than non-drinkers. Over the 4 years period, tea drinkers lost an average of two times less of their total hip bone mineral density, than non-tea drinkers.

16 Tooth decay (dental caries)

Green tea prevents tooth decay. It kills the bacteria that cause dental plaques and halitosis (bad breath) and increases the acid resistance of tooth enamel [29].

17 Arthritis

Green tea may help people with arthritis by reducing inflammation and slowing cartilage breakdown[30].

18 Antimicrobial activity

Green tea catechins have anti-bacterial, anti-viral and anti-fungal activities[31]. These include some types of salmonella, influenza and herpes simplex. Its bacteria-destroying abilities can help prevent food poisoning. A component of green tea may be useful in treating severe sepsis, an abnormal immune system response to bacteria[32].

19 Liver protection

Green tea appears to support healthy liver and protect it from the damage by toxic substances such as alcohol. Men who drink more than 10 cups of green tea per day are less likely to develop disorders of the liver[33].

20 Gastrointestinal tract

In the gastrointestinal tract, green tea was found to activate intracellular antioxidants and reduce inflammation. Drinking more than 10 cups per day may prevent chronic atrophic gastritis[34]. Also, it may help reduce inflammation associated with Crohn's disease and ulcerative colitis.

References
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Published: 2009
Last updated: March 01, 2014

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