Have you ever taken time to consider Green Tea?
Green tea is an oriental evergreen tree that can reach a height of 30 feet in the wild, the tea plant is kept as a shrub on tea plantations, where it is pruned to a height of about 3 feet to encourage new growth. Being a relative of the camellia with the botanical name of Camellia sinesis, the tea plant produces abundant foliage, a camellia-like flower and berries containing one to two seeds. Only the smallest, youngest parts of the plant—the two leaves and bud at the tip of each new shoot—are picked for tea.
A bag of green tea contains zero calories, approximately 0.06 mg of caffeine, and 80-100 mg of polyphenols, 25-30 mg of which are epigallocatechin-3-gallate (EGCG).
Tea History
The tea plant, source of the most popular beverage in the world, is believed to have originated in the landmass encompassing Tibet, western China, and northern India. According to ancient Chinese legend, tea was discovered by the Chinese emperor Shen-Nung in 2737 B.C., when leaves from a wild tea bush accidentally fell into a pot of water he was boiling. The first recorded mention of tea appears in a contract for slaves known as "Tan Yuch," written by Wang Pao, poet laureate to Emperor Husan, in 59 B.C. By 780 A.D., when Lu Yu's The Classic of Tea was published in China, the cultivation and consumption of tea, whose name derives from the Chinese Amoy dialect word "t'e," pronounced "tay," had developed into a fine art. Today, "cha" means tea in Chinese. As this word moved westward into Middle Eastern languages, it sometimes became altered to "chai."
India attributes the discovery of tea to the Buddhist monk Siddhartha in the 6th century. Legend has it that the prince-turned-monk traveled north from India to China to preach Buddhism, vowing he would meditate without sleeping for nine years. Reaching Canton in 519 A.D., he stationed himself before a wall of meditation where, after a mere five years, he was overcome by drowsiness. Inspired by divine intervention, he picked and chewed the leaves of a nearby tree, discovering, to his delight, a great sense of alertness and well-being. The tree whose health-giving properties enabled him to keep his vow was, of course, Camellia sinesis, whose leaves and seeds he carried with him as he continued his journey into Japan. In Japan, Buddhist monks quickly embraced tea, using it to remain alert during their own meditations and creating a simple drinking ritual that several hundred years later, tea master Sen-no Rikyu (1521-1591) developed into the high art of chanoyu, the Japanese tea ceremony.
From Japan, where tea was widely cultivated and consumed by the 9th century A.D., tea culture spread to Java, the Dutch East Indies, and other tropical and subtropical areas. In the 16th century, traders from Europe sailing to and from the Far East introduced Europeans to the delicious Asian drink, and by the 18th century, tea had become the national beverage of England.
Thousands of Chinese bushes stealthily acquired by botanist Robert Fortune, a "spy" for Great Britain's East India Trading Company, were introduced into India in the 1840s, where they quickly became a popular and profitable crop for the Empire.
Tea crossed the Atlantic with the American colonists, among whom its popularity led to the British imposition in 1767 of a tea tax that so infuriated the colonists that they revolted, tossing tons of tea into the harbor in 1733 in what became known as the Boston Tea Party. Freedom from unfair British taxation, symbolized by the tax on tea, became a central contributing factor to the Revolutionary War. The type of tea tossed into Boston harbor? Probably green since it was likely "gunpowder tea," green tea rolled tightly into pellets that looked like gunpowder shot to preserve its freshness during long voyages.
Several new innovations in tea consumption originated in the United States. In 1904, when a New York City merchant, Thomas Sullivan, sent his customers samples of tea in small silk bags, they found the bags could be used to conveniently brew a single cup of tea, and the tea bag was born. Another American innovation in tea drinking, instant tea, was first marketed in 1948.
Today, not China but India ranks as the number one producer of tea, although Sri Lanka (formerly Ceylon) is the major tea supplier to the U.S. Worldwide, more than 2.5 million metric tons of tea are produced each year with India, China, Sri Lanka, Kenya, Indonesia, Turkey, U.S.S.R, Japan, Iran and Bangladesh being the leading tea growing countries.
Health Benefits
1. It Protects the Liver from Alcohol and Other Harmful Chemicals
Alcohol metabolism results in the production of damaging free radicals that can overwhelm the liver's supply of antioxidants, resulting in liver injury. In a study published in the January 2004 issue of Alcohol in which rats were chronically intoxicated with alcohol for 4 weeks, green tea prevented damage to their livers.
Other animal research shows that epigallocatechin-3-gallate (EGCG) protects the liver against the free radicals generated when mice are exposed to carbon tetrachloride, a toxic chemical solvent. Without the protection afforded by EGCG, carbon tetrachloride exposure resulted in the production of numerous free radicals that destroyed a significant amount of the animals' liver cells. With EGCG, free radical production and liver injury was so greatly reduced that researchers suggested green tea should be used in the treatment of liver disease.
Unlike some herbs, green tea's protective effects do not appear to affect two of the liver enzymes most often responsible for detoxifying and eliminating drugs, cytochrome P-450 2D6 and 3A4. This suggests that green tea might be safely consumed when taking medications primarily dependent upon the CYP2D6 or CYP3A4 pathways of metabolism. Hopefully, future research studies will bear out this potential benefit.
On the other hand, one study found that Japanese green tea did increase the activity of the CYP1A1 enzyme. Researchers hypothesized that the increase in activity of this liver enzyme may be one of the ways in which green tea helps protect against cancers caused by various dietary carcinogens.
2. Promotes Fat Loss
Green tea not only promotes fat loss, but specifically, the loss of visceral fat—fat that accumulates in the tissues lining the abdominal cavity and surrounding the intestines (viscera) and internal organs. Unlike fat deposits on the hips and thighs (which result in the so-called "pear" body shape), visceral fat (which produces the "apple" body shape) is highly associated with increased risk for metabolic syndrome and type 2 diabetes.
Green tea contains three major components that promote fat loss: catechins, caffeine and theanine. Studies suggest that green tea compounds promote fat loss by inhibiting both gastric and pancreatic lipase, the enzymes that digest triglycerides, and fatty acid synthetase, the enzyme responsible for synthesizing fatty acids into the form in which they can be stored in the body's adipose (fat) cells.
In a study published in the January 2004 issue of In Vivo in which mice were fed diets containing 2% green tea powder for 16 weeks, visceral fat decreased by 76.8% in those receiving green tea compared to the control group. Green tea also decreased blood levels of triglycerides (the chemical form in which most fats exist in the body).
A human study, published in the January 2005 issue of the American Journal of Clinical Nutrition, confirms green tea's ability to not only reduce body fat, but damage to LDL cholesterol as well. After 12 weeks of drinking just one bottle of green tea each day, 38 normal-to-overweight men in Tokyo had a significantly lower body weight, BMI, waist circumference, body fat mass and amount of subcutaneous fat compared to men given a bottle of oolong tea each day.
After a 2 week diet run-in period, the men were divided into two groups, one of which drank a bottle of green tea containing 690 mg of catechins, while the other group drank a bottle of oolong tea containing 22 mg catechins. Not only did the men drinking green tea lose weight and fat, but the amount of their LDL cholesterol damaged by free radicals also dropped significantly. Since atherosclerotic plaques develop when cholesterol circulating in the bloodstream is damaged or oxidized, green tea's ability to prevent these oxidation reactions may explain some of its protective effects against cardiovascular diseases.
3. Increases Exercise Endurance
Green tea extract given to lab rats over a 10-week span increased the amount of time the animals could swim before becoming exhausted by as much as 24%.
Green tea's catechins appear to stimulate the use of fatty acids by liver and muscle cells. In muscle cells, the ability to burn more fat translates into a reduction in the rate at which glycogen, the form in which carbohydrates are stored for ready access in muscle, is used up, thus allowing for longer exercise times. Green tea's effect on muscle cells' ability to take in and burn fatty acids, speeding up fat breakdown, is also thought to be the reason why it helps weight loss.
The idea for the experiment came from the fact that skeletal muscles utilize carbohydrates, lipids (fats) and amino acids (protein) as energy sources, but the ratio in which they are used varies with the intensity and type of the exercise, and the level of the individual's fitness. During endurance exercise, the use of too much carbohydrate is undesirable because it triggers insulin secretion, which, in turn, both inhibits the burning of fatty acids and stimulates lactic acid production. (Lactic acid buildup is what causes that sore achy feeling in your muscles when you exercise.) Conversely, enhanced availability and utilization of free fatty acids reduces carbohydrate utilization, which in turn spares glycogen (the form in which carbohydrates are stored in muscle for quick use) and suppresses lactic acid production, resulting in an increase in endurance."
Drinking a single cup of green tea before exercise, however, will not be effective. One single, higher "dose" of green tea did nothing to improve lab rats' performance. The animals had to receive green tea daily, and endurance increased gradually over the 10 weeks of the study.
To match the beneficial effect on test animals' endurance capacity seen in the experiments, the researchers estimate a 165-pound athlete would need to drink about 4 cups of green tea daily.
4. Protects against Cognitive Decline, Alzheimer's Disease and Parkinson's Disease
Damage to brain cells in Parkinson's, Alzheimer's and other neurodegenerative diseases seems to result from the combination of a number of damaging factors including excessive inflammation and increased levels of iron, both of which lead to increased free radical production, exhaust the brain's supply of protective antioxidants and trigger the production of certain proteins, such as amyloid-beta, which promote apoptosis (cell suicide).
Green tea catechins, until recently thought to work simply as antioxidants, are now known to invoke a wide spectrum of neuroprotective cellular mechanisms. These include iron chelation, scavenging of free radicals, activation of survival genes and cell signaling pathways, and regulation of mitochondrial function. (The mitochondria are the energy production factories inside our cells. When they are not working properly, they generate many free radicals and little energy.) The end result is a significant lessening of damage to brain cells.
Iron accumulation in specific brain areas and free radical damage to brain cells are considered the major damaging factors responsible for a wide range of neurodegenerative disorders including both Parkinson's and Alzheimer's disease.
In the brain, epigallocatechin-3-gallate (EGCG) has been shown to act as an iron chelator, binding to and removing iron, thus preventing it from contributing to the production of free radicals. In addition to removing iron, EGCG also increases the activity of two major antioxidant enzymes, superoxide dismutase (SOD) and catalase, further helping to decrease free radical damage.
Another active compound in green tea, epicatechin (EC), reduces the formation of a protein called amyloid-beta. Plaque-like deposits of amyloid-beta in the brain are a defining characteristic of Alzheimer's disease.
Animal studies conducted at the Douglas Hospital Research Centre, McGill University, Quebec, Canada, suggest that a daily cup or two of either black or green tea may reduce the risk of age-related degenerative brain disorders such as Alzheimer disease.
The researchers looked at the protective effects of two tea extracts and their main constituents, epigallocatechin gallate and epicatechin gallate, which are highly concentrated in green tea, on dying nerve cells. Both black and green tea extracts and catechins strongly blocked death of neurons (brain nerve cells)
When researchers exposed cultured neurons to amyloid alone, its effects were so toxic that the brain cells died, but when the cell cultures received amyloid immediately followed by tea extracts and catechins, the neurons were rescued and survived.
Green tea polyphenols have also demonstrated the ability to affect cell signaling pathways, in particular the MAPK pathways, which are triggered by oxidative stress (free radicals), and themselves set in motion a series of chemical reactions so damaging that they can result in brain cell death. MAPK signaling pathways inside brain cells are thought to play a critical role in neurodegenerative diseases.
Another important cell signaling pathway beneficially affected by EGCG, the PKC pathway, is also thought to play an essential role in the regulation of cell survival and programmed cell death.
Although no human studies on Alzheimer's disease have yet reported benefit from tea consumption, recent population studies have shown that simply consuming 2 or more cups of green tea daily reduces risk of cognitive decline and Parkinson's disease.
5. Keeps Elders Mentally Sharp
Green tea helps slow the age-related decline in brain function seen as declining memory, cognitive impairment, dementia and Alzheimer's, shows a human study published in the February 2006 issue of the American Journal of Clinical Nutrition.
Researchers at Japan's Tohoku University studied 1003 subjects over age 70, comparing their green tea intake and mental sharpness, using a Mini-Mental State Examination, a well-accepted standardized test for measuring cognitive function.
Drinking more than 2 cups a day of green tea slashed odds of cognitive impairment in elderly Japanese men and women by 64%! And a Japanese cup of green tea is much smaller than its American counterpart—only about 3.2 fluid ounces.
And at every level of cognitive impairment—from minimal to severe—those drinking the most green tea experienced significantly less mental decline than those drinking the least:
Compared with elderly Japanese who drank less than 3 cups a week, those drinking more than 2 cups a day had a 54% lower risk of age-related declines in memory, orientation; ability to follow commands and attention.
Those drinking 4 to 6 cups of green tea a week (1 cup a day) had a 38 lower risk of declines in brain function.
Green tea's primary protective agent is thought to be its catechin phytonutrient epigallocatechingallate (EGCG).
6. Fights Flu
A cup of green tea may help prevent or lessen the duration of the flu. In a lab study, published in the November 2005 issue of Antiviral Research, EGCG dramatically inhibited influenza virus replication in cell culture in all the subtypes of influenza virus tested. EGCG appears to suppress viral RNA synthesis by altering the properties of the viral membrane.
7. Taking Green Tea with Black Pepper increases EGCG availability
An animal study suggests that consuming the spice, black pepper, when drinking green tea can significantly increase the amount of epigallocatechin-3-gallate (EGCG) absorbed. In this study, rats and mice given green tea along with piperine (a bioactive component in black pepper) absorbed 130% more EGCG than control animals receiving EGCG alone.
Also, piperine was found to inhibit the glucuronidation of EGCG in the intestines. Glucuronidation is a chemical pathway that serves as one of the major ways our bodies convert drugs, steroids, and many other substances into metabolites that can then be excreted into the urine or bile. By inhibiting EGCG's glucuronidation, piperine allowed more of this catechin to be absorbed and utilized. So, next time you have a cup of green tea along with a meal, be sure to spice up your soup, salad and/or entrée with a little freshly ground black pepper.
Health Concerns
1. Caffeine Content
Green tea contains caffeine, although half that found in coffee. The amount of caffeine that ends up in your cup of green tea will vary according to the amount of tea used, the length of time the leaves are infused, and if you drink the first or second infusion. Most of the caffeine in green tea is extracted into the water the first time the tea is infused.
2. Interaction with Drugs
The tannins in green tea may decrease the absorption and thus the activity of the following drugs: atropine, Cardec DM®, codeine, ephedrine and pseudoephedrine, Lomotil®, Lonox®, theoplylline, aminophylline, and warfarin.
The caffeine in green tea may interact with the following drugs heightening their effects to dangerous levels: ephedrine and pseudoephedrine, theophylline, aminophylline.
3. Interference with Iron Absorption
Due to their high tannin-content, teas, including green tea, have been shown to prevent iron absorption. While this effect is helpful in persons with too much iron, consuming several cups of green tea daily may not be a good idea for persons deficient in iron or susceptible to iron deficiency.
4. First Trimester of Pregnancy: Limit Green Tea Consumption
According to a study published in the March 2005 issue of Cancer Research, ECGC, a catechin present in green tea in amounts about 5 times higher than in black tea, inhibits the enzyme dihydrofolate reductase (DHFR), which cancer cells need to be able to grow, and which is a well recognized target of anti-cancer drugs.
Scientists decided to look at ECGC after they realized the green tea catechin looks a lot like the cancer drug methotrexate, which prevents cancer cells from making DNA by inhibiting the DHFR enzyme. They discovered that ECGC kills cancer cells in the same way as the drug.
Although ECGC binds strongly to DHFR, which is essential in both healthy and cancerous cells, it does not bind as tightly as methotrexate, so its side effects on healthy cells are less severe than those of the drug.
ECGC's binding to DHFR may also explain why women who drink large amounts of green tea around the time they conceive and early in their pregnancy may have an increased risk of having a child with spina bifida or other neural tube disorders.
Women are advised to take supplements of folic acid when trying to conceive and during the first trimester (the first 3 months) of pregnancy because it is during this time period that the baby's neural tube is developing. Folic acid helps ensure normal development and protects against spina bifida by enabling the production of the enzyme DHFR. While a cup or two of green tea is unlikely to pose a problem, drinking large amounts of green tea could decrease the activity of DHFR, increasing risk of neural tube defects.
So, what have you decided? Do green tea or not?
The Benefits out-weigh the Concerns, definitely!