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Green tea



 


Green tea (simplified Chinese: 绿茶; traditional Chinese: 綠茶; pinyin: lǜchá; Japanese: 緑茶; ryokucha) is a "true" tea, meaning it is made solely with the leaves of Camellia sinensis, that has undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures in Asia from Japan to the Middle East. Recently, it has become more widespread in the West, where black tea is traditionally consumed. Many varieties of green tea have been created in countries where it is grown that can differ substantially due to variable growing conditions, processing and harvesting time. Over the last few decades green tea has begun to be subjected to many scientific and medical studies to determine the extent of its long purported health benefits, with some evidence suggesting regular green tea drinkers may have lower chances of heart disease and contracting certain types of cancer.[citation needed]

Additional recommended knowledge

Contents

Chinese green teas

   

Zhejiang Province

Zhejiang is home to the most famous of all teas, Xi Hu Longjing, as well as many other high-quality green teas.

Longjing
The most well-known of famous Chinese teas from Hangzhou, its name in Chinese means dragon well. It is pan-fried and has a distinctive flat appearance. Falsification of Longjing is very common, and most of the tea on the market is in fact produced in Sichuan Province[citation needed] and hence not authentic Longjing.
Hui Ming
Named after a temple in Zhejiang.
Long Ding
A tea from Kaihua County known as Dragon Mountain.
Hua Ding
A tea from Tiantai County and named after a peak in the Tiantai mountain range.
Qing Ding
A tea from Tian Mu, also known as Green Top.
Gunpowder
A popular tea also known as zhuchá. It originated in Zhejiang but is now grown elsewhere in China.

Jiangsu Province

 

Bi Luo Chun
A Chinese famous tea also known as Green Snail Spring, from Dong Ting. As with Longjing, falsification is common and most of the tea marketed under this name may, in fact, be grown in Sichuan.
Rain Flower
A tea from Nanjing.
Shui Xi Cui Bo

Hubei Province

Yu Lu
A steamed tea known as Gyokuro (Jade Dew) made in the Japanese style.

Henan Province

Xin Yang Mao Jian
A Chinese famous tea also known as Green Tip, or Tippy Green.

Jiangxi Province

Chun Mee
Name means "precious eyebrows"; from Jiangxi, it is now grown elsewhere.
Gou Gu Nao
A well-known tea within China and recipient of numerous national awards.
Yun Wu
A tea also known as Cloud and Mist.

Anhui Province

Anhui Province is home to three Chinese famous teas.

Da Fang
A tea from Mount Huangshan also known as Big Square.
Huangshan Mao Feng
A Chinese famous tea from Mount Huangshan.
Lu An Guapian
A Chinese famous tea also known as Melon Seed.
Hou Kui
A Chinese famous tea also known as Monkey tea.
Tun Lu
A tea from Tunxi District.
Huo Qing
A tea from Jing County, also known as Fire Green.
Hyson
A medium-quality tea from many provinces, an early-harvested tea.

Japanese green teas

    Green tea (緑茶; ryokucha) is so ubiquitous in Japan that it is more commonly known simply as "tea" (お茶; ocha) and even as "Japanese tea" (日本茶; nihoncha),although it was invented in China during the Song Dynasty, and brought to Japan by Myōan Eisai, a Japanese Buddhist priest who also introduced the Rinzai school of Zen Buddhism. Types of tea are commonly graded depending on the quality and the parts of the plant used as well as how they are processed. There are large variations in both price and quality within these broad categories, and there are many specialty green teas that fall outside this spectrum. The best Japanese green tea is said to be that from the Yame region of Fukuoka Prefecture and the Uji region of Kyoto. Shizuoka Prefecture(静岡県) crops 40% of raw tea leaf.

玉露 Gyokuro (Jade Dew)
The highest grade Japanese green tea cultivated in special way. Gyokuro's name refers to the pale green color of the infusion. The leaves are grown in the shade before harvest, which alters their flavor. Gyokuro has a high caffeine content (Generally 0.16% in infusion[1]), but the significant L-Theanine content of Gyokuro slows down and counteracts the caffeine assimilation, and also the amount of drinking is very small such as 10ml - 60ml.
抹茶 Matcha (rubbed tea)
A fine ground Ten-cha (碾茶: has very similar cultivation process as Gyokuro) used primarily in the tea ceremony. Matcha is also a popular flavor of ice cream and other sweets in Japan.
煎茶 Sencha (broiled tea)
The first and second flush of green tea, which is the commonest green tea in Japan made from leaves that are exposed directly to sunlight. The first flush is also called Shin-cha (新茶: a new tea)
玄米茶 Genmaicha (Brown-Rice tea)
Bancha (sometimes Sencha) and roasted genmai (brown rice) blend. It is often mixed with small amount of Matcha to make the colour better.
冠茶 Kabusecha (covered tea)
kabusecha is sencha tea, the leaves of which have grown in the shade prior to harvest, although not for as long as Gyokuro. It has a more delicate flavor than Sencha.
番茶 Bancha (common tea)
Sencha harvested as a third or fourth flush tea between summer and autumn. The leaves are larger than Sencha and the flavor is less full.
焙じ茶 Hōjicha (pan fried tea)
A strong roasted green tea.
茎茶 Kukicha (stalk tea)
A tea made from stalks produced by harvesting one bud and three leaves.
玉緑茶 Tamaryokucha
A tea that has a tangy, berry-like taste, with a long almondy aftertaste and a deep aroma with tones of citrus, grass, and berries.
Okinawan Tea

Other green teas

  • Green Tea from Ceylon

Brewing

Generally, 2.25 grams of tea per 6 ounces of water, or about one teaspoon of green tea per cup, should be used. With very high quality teas like gyokuro, more than this amount of leaf is used, and the leaf is steeped multiple times for short durations.

Green tea brewing time and temperature varies with individual teas. The hottest brewing temperatures are 180°F to 190°F (82°C to 88°C) water and the longest steeping times 2 to 3 minutes. The coolest brewing temperatures are 140°F to 150°F (60°C to 66°C) and the shortest times about 30 seconds. In general, lower quality green teas are steeped hotter and longer, while higher quality teas are steeped cooler and shorter. Steeping green tea too hot or too long will result in a bitter, astringent brew. High quality green teas can and usually are steeped multiple times - 2 or 3 steepings is typical.

Caffeine

Green teas have about a quarter the caffeine content, by liquid volume, of coffee.[citation needed] Green teas contain two caffeine metabolites (caffeine like substances) theophylline which is stronger than caffeine and theobromine which is slightly weaker than caffeine.

Potential effects of green tea on health

Main article: Potential effects of tea on health

History

There is archaeological evidence that suggests that tea has been consumed for almost 5000 years, with China and India being two of the first countries to cultivate it. Green tea has been used as traditional medicine in areas such as India, China, Japan and Thailand to help everything from controlling bleeding and helping heal wounds to regulating body temperature, blood sugar and promoting digestion.

The Kissa Yojoki (Book of Tea), written by Zen priest Eisai in 1191, describes how drinking green tea can have a positive effect on the five vital organs, especially the heart. The book discusses tea's medicinal qualities, which include easing the effects of alcohol, acting as a stimulant, curing blotchiness, quenching thirst, eliminating indigestion, curing beriberi disease, preventing fatigue, and improving urinary and brain function. Part One also explains the shapes of tea plants, tea flowers, and tea leaves, and covers how to grow tea plants and process tea leaves. In Part Two, the book discusses the specific dosage and method required for individual physical ailments.

Unproven claims

Green tea has been credited with providing a wide variety of health benefits, many of which have not been validated by scientific evidence. These claims and any for which academic citations are currently missing are listed here:

  • Stopping certain neurodegenerative diseases such as Alzheimer's and Parkinson's.[1]
  • The prevention and treatment of cancer [2]
  • Treating multiple sclerosis [3]
  • Preventing the degradation of cell membranes by neutralizing the spread of free radicals which occur during oxidation process. [4]
  • Reducing the negative effects of LDL cholesterol (bad cholesterol) by lowering levels of triglycerides and increasing the production of HDL cholesterol (good cholesterol).
  • Increasing fat oxidation (helps the body use fat as an energy source) and raising metabolism. [5]
  • Joy Bauer, a New York City nutritionist, says [the catechins in green tea] increase levels of the metabolism speeding brain chemical norepinephrine.
  • Japanese researchers claim that drinking five cups of green tea a day can burn 70 to 80 extra calories. Dr. Nicholas Perricone, an anti-aging specialist, appeared on the Oprah Winfrey show and told Oprah's viewers they can lose 10 lbs (4.5 kg) in 6 weeks drinking green tea instead of coffee.
  • Some green tea lovers restrict their intake because of the caffeine it contains — about a quarter the amount as is found in coffee. Too much caffeine can cause nausea, insomnia or frequent urination. [6]

United States Food and Drug Administration (FDA)

The article Tea: A Story of Serendipity[7] appeared in the March 1996 issue of FDA Consumer Magazine and looked at the potential benefits of green tea. At that time they had not done any reviews of the potential benefits of green tea and were waiting to do it until health claims were filed. They have since denied two petitions to make qualified health claims as to the health benefits of green tea. [8]

On June 30, 2005, in response to "Green Tea and Reduced Risk of Cancer Health Claim", they stated: "FDA concludes that there is no credible evidence to support qualified health claims for green tea consumption and a reduced risk of gastric, lung, colon/rectal, esophageal, pancreatic, ovarian, and combined cancers. Thus, FDA is denying these claims. However, FDA concludes that there is very limited credible evidence for qualified health claims specifically for green tea and breast cancer and for green tea and prostate cancer, provided that the qualified claims are appropriately worded so as to not mislead consumers." [9]

On May 9, 2006, in response to "Green Tea and Reduced Risk of Cardiovascular Disease", they concluded "there is no credible evidence to support qualified health claims for green tea or green tea extract and a reduction of a number of risk factors associated with CVD." [10]

However in October 2006, the FDA approved an ointment based on green tea. New Drug Application (NDA) number N021902, for kunecatechins ointment 15% (proprietary name Veregen) was approved on October 31, 2006 [11], and added to the "Prescription Drug Product List" in October 2006. [12] Kunecatechins ointment is indicated for the topical treatment of external genital and perianal warts. [13]

Scientific studies

According to research reported at the Sixth International Conference on Frontiers in Cancer Prevention, sponsored by the American Association for Cancer Research, a standardized green tea polyphenol preparation (Polyphenon E) limits the growth of colorectal tumors in rats treated with a substance that causes the cancer. "Our findings show that rats fed a diet containing Polyphenon E are less than half as likely to develop colon cancer," Dr. Hang Xiao, from the Ernest Mario School of Pharmacy at Rutgers University, Piscataway, New Jersey, noted in a statement.

A 2006 study published in the September 13 issue of the Journal of the American Medical Association concluded "Green tea consumption is associated with reduced mortality due to all causes and due to cardiovascular disease but not with reduced mortality due to cancer." The study, conducted by the Tohoku University School of Public Policy in Japan, followed 40,530 Japanese adults, ages 40-79, with no history of stroke, coronary heart disease, or cancer at baseline beginning in 1994. The study followed all participants for up to 11 years for death from all causes and for up to 7 years for death from a specific cause. Participants who consumed 5 or more cups of tea per day had a 16 percent lower risk of all-cause mortality and a 26 percent lower risk of cardiovascular disease than participants who consumed less than one cup of tea per day. The study also states, "If green tea does protect humans against CVD or cancer, it is expected that consumption of this beverage would substantially contribute to the prolonging of life expectancy, given that CVD and cancer are the two leading causes of death worldwide."[14] [15]

A study in the February 2006 edition of the American Journal of Clinical Nutrition concluded "A higher consumption of green tea is associated with a lower prevalence of cognitive impairment in humans."[16] [17]

In May 2006, researchers at Yale University School of Medicine weighed in on the issue with a review article that looked at more than 100 studies on the health benefits of green tea. They pointed to what they called an "Asian paradox," which refers to lower rates of heart disease and cancer in Asia despite high rates of cigarette smoking. They theorized that the 1.2 liters of green tea that is consumed by many Asians each day provides high levels of polyphenols and other antioxidants. These compounds may work in several ways to improve cardiovascular health, including preventing blood platelets from sticking together (This anticoagulant effect is the reason doctors warn surgical patients to avoid green tea prior to procedures that rely on a patient's clotting ability) and improving cholesterol levels, said the researchers, whose study appeared in the May issue of the Journal of the American College of Surgeons. Specifically, green tea may prevent the oxidation of LDL cholesterol (the "bad" type), which, in turn, can reduce the buildup of plaque in arteries, the researchers wrote.[18]

A study published in the August 22, 2006 edition of Biological Psychology looked at the modification of the stress response via L-Theanine, a chemical found in green tea. It "suggested that the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation."[19]

In a double-blind, randomized, placebo-controlled trial done by Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, 240 adults were given either theaflavin-enriched green tea extract in form of 375mg capsule daily or a placebo. After 12 weeks, patients in the tea extract group had significantly less low-density lipoprotein cholesterol (LDL-C) and total cholesterol (16.4% and 11.3% lower than baseline, p<0.01) than the placebo group. The author concluded that theaflavin-enriched green tea extract can be used together with other dietary approaches to reduce LDL-C.

A study published in the January, 2005 edition of the American Journal of Clinical Nutrition concluded "Daily consumption of tea containing 690 mg catechins for 12 wk reduced body fat, which suggests that the ingestion of catechins might be useful in the prevention and improvement of lifestyle-related diseases, mainly obesity." [20]

According to a Case Western Reserve University School of Medicine study published in the April 13 2005 issue of the Proceedings of the National Academy of Sciences, antioxidants in green tea may prevent and reduce the severity of rheumatoid arthritis. The study examined the effects of green tea polyphenols on collagen-induced arthritis in mice, which is similar to rheumatoid arthritis in humans. In each of three different study groups, the mice given the green tea polyphenols were significantly less likely to develop arthritis. Of the 18 mice that received the green tea, only eight (44 percent) developed arthritis. Among the 18 mice that did not receive the green tea, all but one (94 percent) developed arthritis. In addition, researchers noted that the eight arthritic mice that received the green tea polyphenols developed less severe forms of arthritis.

A German study found that an extract of green tea and hot water (filtered), applied externally to the skin for 10 minutes, three times a day could help people with skin damaged from radiation therapy (after 16-22 days). [21]

A study published in the December 1999 American Journal of Clinical Nutrition found that "Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both."[22]

In lab tests, EGCG, found in green tea, was found to prevent HIV from attacking T-Cells. However, it is not yet known if this has any effect on humans. [23]

A study in the August, 2003 issue of a new potential application of Cellular and Molecular Life Sciences found that "a new potential application of (–)-epigallocatechin-3-gallate [a component of green tea] in prevention or treatment of inflammatory processes is suggested" [24]

Tea
v  d  e
Black tea | Green tea | Red tea | White tea | Yellow tea | Oolong tea | Blended and flavored teas
Ceremonies and methods Related to tea
China | India | Japan | Korea | Mongolia | Morocco | Turkey Tea house | Teapot | Tearoom | Tea and health

See also

  • Chinese tea culture
  • Japanese tea ceremony
  • Potential effects of tea on health
  • Reactive oxygen species
  • Yellow tea

References

  1. ^ http://greentealovers.com/greenteahealthotherconditions.htm#brain
  2. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16785249
  3. ^ http://www.annalsnyas.org/cgi/content/abstract/928/1/274
  4. ^ http://www.nadraszky.com/fitness/archives/green-tea-health-benefits.html
  5. ^ http://www.actabit.com/diet-nutrition/how-effective-is-green-tea-for-weight-loss
  6. ^ http://www.cancer.org/docroot/ETO/content/ETO_5_3X_Green_Tea.asp?sitearea=ETO
  7. ^ http://www.fda.gov/FDAC/features/296_tea.html
  8. ^ http://www.medterms.com/script/main/art.asp?articlekey=38989
  9. ^ http://www.cfsan.fda.gov/~dms/qhc-gtea.html
  10. ^ http://www.cfsan.fda.gov/~dms/qhcgtea2.html
  11. ^ http://www.fda.gov/cder/rdmt/InternetNME06.htm
  12. ^ http://www.fda.gov/cder/rxotcdpl/pdpl_200610.htm
  13. ^ http://www.fda.gov/cder/foi/label/2006/021902lbl.pdf
  14. ^ http://jama.ama-assn.org/cgi/content/abstract/296/10/1255
  15. ^ http://www.denverpost.com/nationworld/ci_4326770 Article in the Denver Post
  16. ^ http://www.ajcn.org/cgi/content/abstract/83/2/355
  17. ^ http://www.foodnavigator.com/news/ng.asp?id=66142
  18. ^ http://www.yale.edu/opa/newsr/06-06-01-01.all.html
  19. ^ http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16930802&query_hl=3&itool=pubmed_docsum
  20. ^ http://www.ajcn.org/cgi/content/abstract/81/1/122
  21. ^ http://www.cbsnews.com/stories/2006/12/04/earlyshow/contributors/emilysenay/main2224186.shtml
  22. ^ http://www.ajcn.org/cgi/content/abstract/70/6/1040
  23. ^ http://www.webmd.com/content/article/122/114877.htm
  24. ^ http://www.springerlink.com/content/xqa0w01wd87q1nca/
  • Master Lam Kam Cheun et al (2002). The way of tea. Gaia Books. 

Press coverage

  • Tea and Cancer Prevention from The National Cancer Institute
  • An interview with Thomas Gasiewicz on green tea and cancer
  • Scientists on Trail of Dioxin Pinpoint How Green Tea Protects Against Cancer
  • Green Tea May Aid Liver Disease Patients
  • Tea: the New Anti-Aging Beverage?
  • Tea may help prevent diabetes and cataracts
  • Green tea 'can block cancer'
  • Green Tea's Medical Resurgence
  • Green Tea Catechins
  • Green Tea (an overview from the University of Maryland Medical Center)
  • Green Tea a Performance-enhancing Drug
  • Green Tea for HIV? from AIDSmeds.com
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Green_tea". A list of authors is available in Wikipedia.
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