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'''Green tea''' is [[tea]] made solely with the leaves of ''[[Camellia sinensis]]'' that have undergone minimal [[Tea processing|oxidation during processing]]. Green tea originates from [[China]] and has become associated with many cultures in [[Asia]] from [[Japan]] and [[South Korea]] to the [[Middle East]]. Recently, it has become more widespread in the [[Western World|West]], where [[black tea]] is traditionally consumed. Many varieties of green tea have been created in countries where it is grown. These varieties can differ substantially due to variable growing conditions, processing, and harvesting time.
'''Green tea''' is [[tea]] made solely with the leaves of ''[[Camellia sinensis]]'' that have undergone minimal [[Tea processing|oxidation during processing]]. Green tea originates from [[China]] and has become associated with many cultures in [[Asia]] from [[Japan]] and [[South Korea]] to the [[Middle East]]. Recently, it has become more widespread in the [[Western World|West]], where [[black tea]] is traditionally consumed. Many varieties of green tea have been created in countries where it is grown. These varieties can differ substantially due to variable growing conditions, processing, and harvesting time.

Over the last few decades green tea has been subjected to many scientific and medical studies to determine the extent of its long-purported health benefits, with some evidence suggesting that regular green tea drinkers have lower chances of [[heart disease]] and developing certain types of cancer.<ref>{{cite web|url=http://www.sciencedaily.com/releases/2003/08/030805072109.htm|title=Green Tea’s Cancer-fighting Allure Becomes More Potent}}</ref> Although there is no scientific evidence that plain green tea can produce [[weight loss]], a green tea extract rich in [[polyphenols]] and [[caffeine]] has been shown to be useful for "obesity management", since it induces [[thermogenesis]] and stimulates fat oxidation.<ref>{{cite web|url=http://www.ajcn.org/cgi/content/full/70/6/1040|title=Dulloo et al Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.}}</ref>

==Chinese tea==
==== Hunan Province ====
Junshan Yinzhen (Silver Needle tea), known as one of the ten most famous Chinese Teas, is one variety of Yellow Tea, like the Huo Mountain Yellow Buds and the Mengding Yellow Buds. It is cultivated on Junshan Island, Yueyang City, Hunan Province.

==== Zhejiang Province ====
[[Zhejiang]] is home to the most famous of all teas, Xi Hu Longjing, as well as many other high-quality green teas.
* '''龙井 [[Longjing tea|Longjing]]'''
: The most well-known of [[China Famous Tea|famous Chinese teas]] from [[Hangzhou]], whose name in Chinese means ''dragon well''. It is pan-fired 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|date=August 2007}} and hence not authentic Longjing.
* '''[[Hui Ming Tea|Hui Ming]]'''
: Named after a temple in [[Zhejiang]].
* '''[[Long Ding tea|Long Ding]]'''
: A tea from [[Kaihua County]] known as ''Dragon Mountain''.
* '''[[Hua Ding tea|Hua Ding]]'''
: A tea from [[Tiantai County]] and named after a peak in the Tiantai mountain range.
* '''[[Qing Ding tea|Qing Ding]]'''
: A tea from Tian Mu, also known as ''Green Top''.
* '''珠 [[Gunpowder tea|Gunpowder]]'''
: A popular tea also known as ''zhuchá''. It originated in [[Zhejiang]] but is now grown elsewhere in [[China]].

==== Jiangsu Province ====
[[Image:Biluochun (medium grade, spring 2007).jpg|thumb|A plate of [[Bi Luo Chun tea]], from Jiangsu Province in China.]]
* '''碧螺春 [[Bi Luo Chun tea|Bi Luo Chun]]'''
: A [[China Famous Tea|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 tea|Rain Flower]]'''
: A tea from [[Nanjing]].
* '''[[Shui Xi Cui Bo]]'''
:

==== Fujian Province ====
[[Image:Organic mountain grown tea leaf.jpg|thumb|Camellia Sinensis, the tea plant]]

: The Fujian Province is known for mountain-grown organic green tea as well as white and oolong teas. The coastal mountains provide a perfect growing environment for tea growing. Green tea is picked in spring and summer seasons.

: Famous tea varieties from this south-eastern region of mainland China include Mao Feng ("fur tip"), Cui Jian ("jade sword") and Mo Li Hua Cha ("dragon pearl") green teas as well as Bai Mu Dan (white peony) white tea and Ti Kwan Yin ("iron goddess") oolong tea. Green tea is heat-cured using ovens or dings; white tea is fast-dried; oolong tea is oxidized through carefully-controlled fermentation.

==== Hubei Province ====
* '''[[Yu Lu tea|Yu Lu]]'''
: A steamed tea known as ''Gyokuro (Jade Dew)'' made in the [[Japanese cuisine|Japanese]] style.

==== Henan Province ====
[[Image:Maojian.jpg|thumbdXi Hu Longjing.png|thumb|An example of a slightly higher grade of Chinese green tea, called [[Mao Jian tea|Mao Jian]].]]
* '''信阳毛尖 [[Mao Jian tea|Xin Yang Mao Jian]]'''
: A [[China Famous Tea|Chinese famous tea]] also known as ''Green Tip,'' or ''Tippy Green.''

====Jiangxi Province====
* '''珍眉 [[Chun Mee tea|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 tea|Yun Wu]]'''
: A tea also known as ''Cloud and Mist''.

====Anhui Province====
[[Anhui]] Province is home to several varieties of tea, including three [[China Famous Tea|Chinese famous teas]]. These are:
* '''大方 [[Da Fang tea|Da Fang]]'''
: A tea from [[Mount Huangshan]] also known as ''Big Square suneet''.
* '''黄山毛峰 [[Huang Shan Mao Feng tea|Huangshan Maofeng]]'''
: A [[China Famous Tea|Chinese famous tea]] from [[Mount Huang]].
* '''六安瓜片 [[Liu An Guapian tea|Lu'An Guapian]]'''
: A [[China Famous Tea|Chinese famous tea]] also known as ''Melon Seed''.
* '''猴魁 [[Hou Kui tea|Hou Kui]]'''
: A [[China Famous Tea|Chinese famous tea]] also known as ''Monkey tea''.
* '''屯绿 [[Tun Lu tea|Tun Lu]]'''
: A tea from [[Tunxi District]].
* '''火青 [[Huo Qing tea|Huo Qing]]'''
: A tea from [[Jing County, Anhui|Jing County]], also known as ''Fire Green''.
* '''雾里青 [[Wuliqing]]'''
: Wuliqing was known since the Song dynasty. Since 2002 Wuliqing is produced again according to the original processing methods by a company called Tianfang (天方). Zhan Luojiu a tea expert and professor at the Anhui Agricultural University who relived its production procedure.
* '''[[Hyson]]'''
: A medium-quality tea from many [[Province (China)|provinces]], an early-harvested tea.

====Sichuan Province====
* '''[[Zhu Ye Qing tea|Zhu Ye Qing]]'''
: Also known as ''Meng Ding Cui Zhu'' or ''Green Bamboo''.
* '''[[Meng Ding Gan Lu tea|Meng Ding Gan Lu]]'''
: A yellowish-green tea with sweet aftertaste.

==Japanese green teas==
[[Image:Sencha.jpg|thumb|Japanese green tea]]
[[Image:Genmaicha.jpg|thumb|''Genmaicha'']]
{{nihongo|Green tea|緑茶|Ryokucha}} is ubiquitous in [[Japan]] and therefore is more commonly known simply as {{nihongo|"tea"|お茶|ocha}}. It is even referred to as {{nihongo|"Japanese tea"|日本茶|nihoncha}} though it was first used 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.<ref>{{cite book|title=The story of tea: a cultural history and drinking guide|first1=Mary Lou |last1=Heiss|first2=Robert J.|last2=Heiss|url=http://books.google.com/?id=3NBtM5aAAGgC&pg=PA179#v=onepage&q=|pages=179–185|year=2007|publisher=Ten Speed Press|isbn=1-58008-745-0}}</ref> 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 {{nihongo|[[Yame]]|八女|yame}} region of [[Fukuoka Prefecture]] and the [[Uji]] region of [[Kyoto]]. [[Shizuoka Prefecture]] produces 40% of raw tea leaf.

*{{nihongo||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.

*{{nihongo||冠茶|'''[[Kabusecha tea|Kabusecha]]'''|covered tea}}
: ''Kabusecha'' is made from the leaves grown in the shade prior to harvest, although not for as long as ''Gyokuro''. It has a more delicate flavor than ''Sencha''. It is sometimes marketed as Gyokuro.

*{{nihongo||煎茶|'''[[Sencha]]'''| decocted tea}}
: The first and second flush of green tea made from leaves that are exposed directly to sunlight. This is the most common green tea in Japan. The name describes the method for preparing the beverage.

:* {{nihongo||深蒸し茶| '''Fukamushicha'''|long-steamed green tea}}
:: Sencha which, in the processing of the leaves, has been steamed two times longer than usual Sencha, giving it a deeper color and producing a fuller flavor in the beverage.

*{{nihongo||玉緑茶| '''[[Tamaryokucha]]'''|lit. ball green tea}}
: ''Tamaryokucha'' has a tangy, berry-like taste, with a long almondy aftertaste and a deep aroma with tones of citrus, grass, and berries. It is also called ''Guricha''.

*{{nihongo||番茶|'''[[Bancha]]'''|coarse tea}}
: Lower grade of ''[[Sencha]]'' harvested as a third or fourth flush tea between summer and autumn. ''Aki-Bancha'' (autumn Bancha) is not made from entire leaves, but from the trimmed unnecessary twigs of the tea plant.

*{{nihongo||窯煎茶| '''[[Kamairicha tea|Kamairicha]]'''|pan-fried tea}}
: ''Kamairicha'' is a pan-fried green tea that does not undergo the usual steam treatments of Japanese tea and does not have the characteristic bitter taste of most Japanese tea.

* By-product of Sencha or Gyokuro

:*{{nihongo||茎茶| '''[[Kukicha tea|Kukicha]]'''|stalk tea}}
:: A tea made from stems, stalks, and twigs. ''Kukicha'' has a mildly nutty, and slightly creamy sweet flavor.

:*{{nihongo||芽茶| '''[[Mecha tea|Mecha]]'''|buds and tips tea}}
:: ''Mecha'' is green tea derived from a collection of leaf buds and tips of the early crops. ''Mecha'' is harvested in spring and made as rolled leaf teas that are graded somewhere between ''Gyokuro'' and ''Sencha'' in quality.

:*{{nihongo||粉茶| '''[[Konacha tea|Konacha]]'''|(coarse) powdered tea}}
:: ''Konacha'' is the dust and smallest parts after processing ''Gyokuro'' or ''Sencha''. It is cheaper than ''Sencha'' and usually served at [[Sushi]] restaurants. It is also marketed as {{nihongo||玉露粉| ''[[Gyokuroko]]'' }} or ''[[Gyokurokocha]]''.

* Other

:*{{nihongo||抹茶| '''[[Matcha]]'''|powdered tea}}
:: A fine ground tea made from ''Tencha''. It has a very similar cultivation process as ''Gyokuro''. It is used primarily in the [[tea ceremony]]. ''Matcha'' is also a popular [[green tea ice cream|flavor of ice cream]] and other sweets in Japan.

:*{{nihongo||玄米茶|'''[[Genmaicha]]'''|brown rice tea}}
:: ''Bancha'' (sometimes ''Sencha'') and roasted ''genmai'' ([[brown rice]]) blend. It is often mixed with a small amount of ''Matcha'' to make the color better.

:*{{nihongo||焙じ茶| '''[[Hojicha|Hōjicha]]'''|roasted tea}}
:: A green tea roasted over [[charcoal]] (usually ''Bancha'').

:*{{nihongo|| 碾茶|'''Tencha'''|milling tea}}
:: Half-finished products used for ''Matcha'' production. The name indicates its intended eventual milling into matcha. Because, like [[gyokuro]], it is cultivated in shade, it has a sweet aroma. In its processing, it is not rolled during drying, and tencha therefore remains spread out like the original fresh leaf.

:*{{nihongo||荒茶| '''[[Aracha]]'''|raw green tea}}
:: Half-finished products used for ''Sencha'' and ''Gyokuro'' production. It contains all parts of the tea plant.

:*{{nihongo||新茶|'''[[Shincha]]'''|a new tea}}
:: First flush tea. The name is used for either ''Sencha'' or ''Gyokuro''.

:*{{nihongo||粉末茶| '''funmatsucha'''|instant powdered tea}}
:: Milled green tea, used just like instant coffee.　Another name for this recent style of tea is ''"tokeru ocha,"'' or "tea that melts."

==Other green teas==
* [[Ceylon tea (green)|Green tea from Ceylon]]
* [[Kahwah]]
==Production==
{|
|-
|2006 Green tea production and export. (thousand metric ton)<ref>{{cite web|url=ftp://ftp.fao.org/docrep/fao/Meeting/013/K2054e.pdf|page=9|title=CURRENT SITUATION AND MEDIUM-TERM OUTLOOK|publisher=INTERGOVERNMENTAL GROUP ON TEA, UN Food and Agriculture Organization|date=May 2008}}</ref>
{| class="wikitable" style="margin-left:auto;margin-right:auto"
! style="width:2em;" | Country!! Production!! Export
|-
|{{flag|China}}||782.4 (80.8%)||218.7 (83.0%)
|-
|{{flag|Japan}}||91.8 (9.5%)||1.6 (0.6%)
|-
|{{flag|Vietnam}}||66.0 (6.8%)||26.0 (9.9%)
|-
|{{flag|Indonesia}}||20.0 (2.1%)||9.1 (3.5%)
|-
|'''World'''||'''968.1''' (100%)||'''263.5''' (100%)
|}
|}

==Steeping==
While commonly called brewing, the process of making a cup of tea is actually steeping. Generally, 2 grams of tea per 100ml of water, or about one teaspoon of green tea per 5 ounce cup (150ml), 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 steeping time and temperature varies with individual teas. The hottest steeping temperatures are 180°F to 190°F (81°C to 87°C) water and the longest steeping times 2 to 3 minutes. The coolest brewing temperatures are 140°F to 160°F (61°C to 69°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, regardless of the initial quality. It is thought that excessively hot water results in [[tannin]] chemical release, which is especially problematic in green teas as they have higher contents of these. High quality green teas can be and usually are steeped multiple times; 2 or 3 steepings is typical. The steeping technique also plays a very important role to avoid the tea developing an overcooked taste. Preferably, the container in which the tea is steeped or teapot should also be warmed beforehand so that the tea does not immediately cool down. It is common practice for tea leaf to be left in the cup or pot and for hot water to be added as the tea is drunk until the flavor degrades.

== Health effects ==
{{Cleanup-rewrite|'''Undue weight to this section compared to other sections'''|2=section|date=April 2010}}
{{Main|Health effects of tea}}

Green tea contains salubrious [[polyphenol]]s, particularly [[catechin]]s, the most abundant of which is [[epigallocatechin gallate]]. Green tea also contains carotenoids, tocopherols, ascorbic acid (vitamin C), minerals such as chromium, manganese, selenium or zinc, and certain phytochemical compounds. It is a more potent antioxidant than [[black tea]],<ref name=BeneficialEffects2006/> although black tea has substances which green tea does not such as [[theaflavin]].

''[[In vitro]]'', animal, preliminary observational, and clinical human studies suggest that green tea can reduce the risk of cardiovascular disease, dental cavities, kidney stones, and cancer, while improving bone density and cognitive function. However, the human studies are inconsistent.<ref name=BeneficialEffects2006>{{cite journal |author=Cabrera C, Artacho R, Giménez R |title=Beneficial effects of green tea--a review |journal=J Am Coll Nutr |volume=25 |issue=2 |pages=79–99 |year=2006 |month=April |pmid=16582024 |doi= |url=http://www.jacn.org/cgi/pmidlookup?view=long&pmid=16582024}}</ref>

Green tea consumption is associated with reduced heart disease in epidemiological studies. Animal studies have found that it can reduce cholesterol. However, several small, brief human trials found that tea consumption did not reduce cholesterol in humans. In 2003 a randomized clinical trial found that a green tea extract with added theaflavin from black tea reduced cholesterol.<ref name=2003RCT>{{cite journal |author=Maron DJ, Lu GP, Cai NS, ''et al.'' |title=Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial |journal=Arch. Intern. Med. |volume=163 |issue=12 |pages=1448–53 |year=2003 |month=June |pmid=12824094 |doi=10.1001/archinte.163.12.1448 |url=http://archinte.ama-assn.org/cgi/content/full/163/12/1448}}</ref>

A study performed at Birmingham (UK) University, showed that average fat oxidation rates were 17% higher after ingestion of green tea extract than after ingestion of a placebo.<ref>{{cite web|url=http://www.ajcn.org/cgi/content/abstract/87/3/778 |title=Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans |publisher=American Journal of Clinical Nutrition |year=2008 |month=March |coauthors=Venables, Michelle C; Hulston, Carl J; Cox, Hannah R ; Jeukendrup, Asker E |work=Vol. 87, No. 3|pages=778–784 |accessdate=2008-10-25}}</ref> Similarly the contribution of fat oxidation to total energy expenditure was also significantly higher by a similar percentage following ingestion of green tea extract. This implies that ingestion of green tea extract can not only increase fat oxidation during moderately intensive exercise but also improve insulin sensitivity and glucose tolerance in healthy young men.

A recent study looked at the effects of short term green tea consumption on a group of students between the ages of 19–37. Participants were asked not to alter their diet and to drink 4 cups of green tea per day for 14 days. The results showed that short term consumption of commercial green tea reduces systolic and diastolic [[Blood Pressure]], fasting total cholesterol, body fat and body weight. These results suggest a role for green tea in decreasing established potential cardiovascular risk factors. This study also suggests that reductions may be more pronounced in the overweight population where a significant proportion are obese and have a high risk of cardiovascular disease.<ref>{{cite journal |author=Emad Al-Dujaili, Jon-Paul Bradley, Suzana Almoosawi & Lorna Fyfe |title=Effects of green tea consumption on blood pressure, total cholesterol, body weight and fat in healthy volunteers |journal=Endocrine Abstracts |volume=20 |pages=P470 |year=2009 |url=http://www.endocrine-abstracts.org/ea/0020/ea0020P470.htm}}</ref>

In a study performed at the Israel Institute of Technology, it was shown that the main antioxidant polyphenol of green tea extract, [[epigallocatechin gallate|EGCG]], when fed to mice induced with Parkinson's and Alzheimer's disease, helped to protect brain cells from dying, as well as 'rescuing' already damaged neurons in the brain, a phenomenon called neurorescue or neurorestoration. The findings of the study, led by Dr. Silvia Mandell, were presented at the Fourth International Scientific Symposium on Tea and Human Health in Washington D.C., in 2007. Resulting tests underway in China, under the auspices of the [[The Michael J. Fox Foundation|Michael J. Fox Foundation]], are being held on early Parkinson's patients.<ref>[http://www.israel21c.org/bin/en.jsp?enDispWho=Articles^l1805&enPage=BlankPage&enDisplay=view&enDispWhat=object&enVersion=0&enZone=Health]</ref>

A study <ref>Gradišar et al., (2007) Green Tea Catechins Inhibit Bacterial DNA Gyrase by Interaction with Its ATP Binding Site http://pubs.acs.org/doi/abs/10.1021/jm060817o</ref> performed at the National institute of Chemistry in [[Ljubljana]], [[Slovenia]], demonstrated that [[epigallocatechin gallate|EGCG]] from green tea inhibits an essential bacterial enzyme [[gyrase]] by binding to the [[adenosine triphosphate|ATP]] binding site of the B subunit. This activity probably contributes to the antimicrobial activity of green tea extract and may be responsible for the effectiveness of green tea in oral hygiene.

In a recent case-control study of the eating habits of 2,018 women, consumption of [[Mushrooms#Edible_mushrooms|mushrooms]] and green tea was linked to a 90% lower occurrence of [[breast cancer]].<ref name="International Journal of Cancer 2009">
{{cite journal
| last1 = Zhang
| first1 = M
| title = Dietary intakes of mushrooms and green tea combine to reduce the risk of breast cancer in Chinese women.
| journal = International Journal of Cancer
| volume = 124
| issue = 6
| pages = 1404–8
| date = 2009
| pmid=19048616
| doi = 10.1002/ijc.24047
| last2 = Huang
| first2 = J
| last3 = Xie
| first3 = X
| last4 = Holman
| first4 = CD
}}</ref>

A recent study on rats at the [[University of Hong Kong]], published in the February issue of [[Journal of Agricultural and Food Chemistry]], found that the [[catechins]] in green tea were absorbed by the [[Lens (anatomy)|lens]], [[retina]] and other parts of the [[eye]]<ref>{{cite web|url=http://www.ncbi.nlm.nih.gov/pubmed/20085274 |title=Green Tea Catechins and Their Oxidative Protection in the Rat Eye. |publisher=Journal of Agricultural and Food Chemistry |year=2010 |month=February |coauthors=Kai On Chu; Kwok Ping Chan; Chi Chiu Wang; Ching Yan Chu; Wai Ying Li; Kwong Wai Choy; Michael Scott Rogers; Chi Pui Pan|work=Vol. 58, No. 3|pages=1523–1534 |accessdate=2010-02-19}}</ref>. The absorbed catechins reduced oxidative stress in the eye for up to 20 hours, suggesting that green tea may be effective in preventing [[glaucoma]] and other diseases of the eye.

===History===
Tea consumption had its origin in China more than 4000 years ago.<ref>[http://inventors.about.com/od/tstartinventions/ss/tea.htm About.com. ''The History of Tea - Tea Bags and Makers]</ref> Green tea has been used as both a beverage and a method of traditional medicine in most of Asia, including China, Japan, Taiwan, Vietnam, Korea, India 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|beriberi disease]], preventing [[fatigue (physical)|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. However, many of these claims have not been validated by scientific evidence. Any claims for which academic citations are currently missing are listed here:
* Stopping certain [[neurodegenerative disease]]s such as [[Alzheimer's disease|Alzheimer's]] and [[Parkinson's syndrome|Parkinson's]].
* The prevention and treatment of cancer.<ref>{{cite journal |author=Sartippour MR, Pietras R, Marquez-Garban DC, ''et al.'' |title=The combination of green tea and tamoxifen is effective against breast cancer |journal=Carcinogenesis |volume=27 |issue=12 |pages=2424–33 |year=2006 |month=December |pmid=16785249 |doi=10.1093/carcin/bgl066 |url=http://carcin.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=16785249}}</ref><ref>[http://news.bbc.co.uk/1/hi/health/7947620.stm BBC news - 17 March 2009 - green tea may have the power to ward off breast cancer]</ref> See also [[Flavonoid#Cancer|flavonoid and cancer]].
* Treating [[multiple sclerosis]].<ref>{{cite journal |author=Sueoka N, Suganuma M, Sueoka E, ''et al.'' |title=A new function of green tea: prevention of lifestyle-related diseases |journal=Ann. N. Y. Acad. Sci. |volume=928 |pages=274–80 |year=2001 |month=April |pmid=11795518 |url=http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0077-8923&date=2001&volume=928&spage=274}}</ref>
* Preventing the degradation of [[cell (biology)|cell]] [[cell membrane|membranes]] by neutralizing the spread of [[Radical (chemistry)|free radicals]] which occur during oxidation process.<ref>[http://www.nadraszky.com/fitness/archives/green-tea-health-benefits.html Green Tea Health Benefits<!-- Bot generated title -->]</ref>{{Dubious|date=October 2008}}
* Reducing the negative effects of [[LDL|LDL cholesterol]] (bad cholesterol) by lowering levels of triglycerides and increasing the production of [[High-density lipoprotein|HDL cholesterol]] (good cholesterol).
* Joy Bauer, a New York City nutritionist, says the catechins in green tea increase metabolic levels, by speeding the release of brain chemical norepinephrine (noradrenaline).
* Japanese researchers claim that drinking five cups of green tea a day can burn 70 to 80 extra calories. Dr. [[Nicholas Perricone]], a self-proclaimed anti-aging specialist, appeared on [[The Oprah Winfrey Show]] and told Oprah's viewers they can lose 10&nbsp;lbs (4.5&nbsp;kg) in 6 weeks drinking green tea instead of coffee.
* Some green tea lovers commonly restrict their intake because of the stimulants it contains &mdash; equivalent to about a third the amount of [[caffeine]] as is found in [[coffee]][http://www.celestialseasonings.com/products/caffeine.html/authentic-green-tea]{{Dubious|date=October 2008}}. Too much caffeine can cause [[nausea]], [[insomnia]], or [[frequent urination]].<ref>[http://www.cancer.org/docroot/ETO/content/ETO_5_3X_Green_Tea.asp?sitearea=ETO ACS :: Green Tea<!-- Bot generated title -->]</ref>

===United States Food and Drug Administration===
The article ''Tea: A Story of Serendipity''<ref>[http://www.fda.gov/FDAC/features/296_tea.html Tea: A Story of Serendipity<!-- Bot generated title -->]</ref> appeared in the March 1996 issue of the United States [[Food and Drug Administration (United States)|Food and Drug Administration]] Consumer Magazine and looked at the potential benefits of green tea. At that time the FDA had not done any reviews of the potential benefits of green tea and were waiting to do so until health claims were filed. The FDA have since denied two petitions to make qualified health claims as to the health benefits of green tea.<ref>[http://www.medterms.com/script/main/art.asp?articlekey=38989 Qualified health claim definition - Medical Dictionary definitions of popular medical terms easily defined on MedTerms<!-- Bot generated title -->]</ref>

On June 30, 2005, in response to "Green Tea and Reduced Risk of Cancer Health Claim", the FDA 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."<ref>[http://www.cfsan.fda.gov/~dms/qhc-gtea.html US FDA/CFSAN — Letter Responding to Health Claim Petition dated January 27, 2004: Green Tea and Reduced Risk of Cancer Health Claim (Docket number 2004Q-0083)<!-- Bot generated title -->]</ref>

On May 9, 2006, in response to "Green Tea and Reduced Risk of Cardiovascular Disease", the FDA 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."<ref>[http://www.cfsan.fda.gov/~dms/qhcgtea2.html US FDA/CFSAN — Qualified Health Claims: Letter of Denial — Green Tea and Reduced Risk of Cardiovascular Disease (Docket No. 2005Q-0297)<!-- Bot generated title -->]</ref>

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,<ref>[http://www.fda.gov/cder/rdmt/InternetNME06.htm CDER New Molecular Entity (NME) Drug and New Biologic Approvals in Calendar Year 2006<!-- Bot generated title -->]</ref> and added to the "Prescription Drug Product List" in October 2006.<ref>[http://www.fda.gov/cder/rxotcdpl/pdpl_200610.htm Prescription and Over-the-Counter Drug Product List: 10/2006<!-- Bot generated title -->]</ref> Kunecatechins ointment is indicated for the topical treatment of external [[genital wart|genital]] and perianal warts.<ref>http://www.fda.gov/cder/foi/label/2006/021902lbl.pdf</ref>

===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 ("CVD") 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."<ref>{{cite journal |author=Kuriyama S, Shimazu T, Ohmori K, ''et al.'' |title=Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study |journal=JAMA |volume=296 |issue=10 |pages=1255–65 |year=2006 |month=September |pmid=16968850 |doi=10.1001/jama.296.10.1255 |url=http://jama.ama-assn.org/cgi/pmidlookup?view=long&pmid=16968850}}</ref>
<ref>http://www.denverpost.com/nationworld/ci_4326770 Article in the Denver Post</ref>

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."<ref>{{cite journal |author=Kuriyama S, Hozawa A, Ohmori K, ''et al.'' |title=Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1 |journal=Am. J. Clin. Nutr. |volume=83 |issue=2 |pages=355–61 |year=2006 |month=February |pmid=16469995 |url=http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=16469995}}</ref><ref>[http://www.foodnavigator.com/news/ng.asp?id=66142 Green tea could protect against Alzheimer's<!-- Bot generated title -->]</ref>{{Dubious|date=October 2008}}

In May 2006, researchers at [[Yale School of Medicine|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 [[polyphenol]]s and other [[antioxidant]]s. 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.<ref>[http://www.yale.edu/opa/newsr/06-06-01-01.all.html Green Tea and the “Asian Paradox”<!-- Bot generated title -->]</ref>

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."<ref>{{cite journal |author=Kimura K, Ozeki M, Juneja LR, Ohira H |title=L-Theanine reduces psychological and physiological stress responses |journal=Biol Psychol |volume=74 |issue=1 |pages=39–45 |year=2007 |month=January |pmid=16930802 |doi=10.1016/j.biopsycho.2006.06.006 |url=http://linkinghub.elsevier.com/retrieve/pii/S0301-0511(06)00145-1}}</ref>

In a [[double-blind]], randomized, placebo-controlled trial conducted by Division of Cardiovascular Medicine, [[Vanderbilt University Medical Center]], Nashville, Tennessee, 240 adults were given either theaflavin-enriched green tea extract in form of 375&nbsp;mg 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." <ref>{{cite journal |author=Nagao T, Komine Y, Soga S, ''et al.'' |title=Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men |journal=Am. J. Clin. Nutr. |volume=81 |issue=1 |pages=122–9 |year=2005 |month=January |pmid=15640470 |url=http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=15640470}}</ref>

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).<ref>[http://www.cbsnews.com/stories/2006/12/04/earlyshow/contributors/emilysenay/main2224186.shtml Studies: Green Tea May Help Prolong Life, Senay: Research Also Shows Benefits For Skin, Few Drawbacks - CBS News<!-- Bot generated title -->]</ref>

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."<ref>{{cite journal |author=Dulloo AG, Duret C, Rohrer D, ''et al.'' |title=Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans |journal=Am. J. Clin. Nutr. |volume=70 |issue=6 |pages=1040–5 |year=1999 |month=December |pmid=10584049 |url=http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=10584049}}</ref>

In lab tests, [[Epigallocatechin gallate|EGCG]], found in green tea, was found to prevent [[Human immunodeficiency virus|HIV]] from attacking T-Cells. However, it is not yet known if this has any effect on humans.<ref>[http://www.webmd.com/content/article/122/114877.htm Green Tea Blocks HIV in Test Tubes<!-- Bot generated title -->]</ref>

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" <ref>{{cite journal |author=Rodríguez-Caso C, Rodríguez-Agudo D, Sánchez-Jiménez F, Medina MA |title=Green tea epigallocatechin-3-gallate is an inhibitor of mammalian histidine decarboxylase |journal=Cell. Mol. Life Sci. |volume=60 |issue=8 |pages=1760–3 |year=2003 |month=August |pmid=14521154 |doi=10.1007/s00018-003-3135-310.1007/s00018-003-3135-3 |url=http://www.springerlink.com/content/xqa0w01wd87q1nca/}}</ref>

However, pharmacological and toxicological evidence does indicate that green tea polyphenols can in fact cause oxidative stress and liver toxicity in vivo at certain concentrations.<ref>{{cite journal |author=Lambert JD, Sang S, Yang CS |title=Possible controversy over dietary polyphenols: benefits vs risks |journal=Chem. Res. Toxicol. |volume=20 |issue=4 |pages=583–5 |year=2007 |month=April |pmid=17362033 |doi=10.1021/tx7000515 |url=http://pubs.acs.org/cgi-bin/sample.cgi/crtoec/2007/20/i04/html/tx7000515.html}}</ref> This would imply that consumers should exercise caution when consuming herbal products produced from concentrated green tea extract. Other evidence presented in the review cautions against the drinking of green tea by pregnant women.<ref>{{cite journal|url=http://www.pnas.org/content/97/9/4790.abstract |title=Dietary bioflavonoids induce cleavage in the MLL gene and may contribute to infant leukemia.|journal=Proc. Natl. Acad. Sci. USA |volume=97 |pages=4790–4795 |year=2000 |doi=10.1073/pnas.070061297|author=Strick ''et al.''|pmid=10758153|last2=Strissel|first2=PL|last3=Borgers|first3=S|last4=Smith|first4=SL|last5=Rowley|first5=JD|issue=9|pmc=18311}}</ref>

A more frequent consumption of green tea was associated with a lower prevalence of depressive symptoms in a Japanese study <ref>{{cite journal|url=http://www.ajcn.org/cgi/content/abstract/90/6/1615|title=Green tea consumption is associated with depressive symptoms in the elderly|journal=Am J Clin Nutr.|volume=90 |pages=1615–22 |year=2009 |doi=10.3945/ajcn.2009.28216
|author=Kaijun Niu et al|pmid=19828710|issue=6}}</ref>. Researchers conducted a cross-sectional study in 1,058 community-dwelling elderly Japanese individuals 70 years of age. The prevalence of mild and severe depressive symptoms was 34.1 percent and 20.2 percent, respectively. After adjustment for confounding factors, the odds ratios for mild and severe depressive symptoms when higher green tea consumption was compared with green tea consumption of 1 cup/d were: 2 to 3 cups green tea/d and 4 cups green tea/d. Similar relations were also observed in the case of severe depressive symptoms.

===Drug Interactions===
A 2009 study at the University of Southern California using mouse models showed that several of the polyphenolic ingredients of green tea, such as [[epigallocatechin gallate|EGCG]], can bind with the anticancer drug [[bortezomib]], significantly reducing its bioavailability and thereby rendering it therapeutically useless.<ref>{{cite journal|title=Green tea polyphenols block the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors.|journal=Blood |volume=113|pages=5927–5937|year=2009|doi= 10.1182/blood-2008-07-171389|author=Golden, E. |pmid=19190249|last2=Lam|first2=PY|last3=Kardosh|first3=A|last4=Gaffney|first4=KJ|last5=Cadenas|first5=E|last6=Louie|first6=SG|last7=Petasis|first7=NA|last8=Chen|first8=TC|last9=Schönthal|first9=AH|issue=23}}</ref> This chemical reaction between EGCG and bortezomib is highly specific and depends on the presence of a [[boronic acid]] functional group in the bortezomib molecule. Dr. Schönthal, who headed the study, suggests that consumption of green tea, concentrated green tea extract, and other green tea products (such as EGCG capsules) be strongly contraindicated for patients undergoing bortezomib treatment.<ref>{{cite web | last = Neith | first = Katie | title = Green tea blocks benefits of cancer drug, study finds | url=http://www.usc.edu/uscnews/stories/16226.html | accessdate = 2009-02-04 }}</ref>

===Caffeine===
Unless specifically decaffeinated, green tea contains [[caffeine]].<ref name="caf">http://www.medicinalfoodnews.com/vol10/2006/green_tea</ref> Normal green tea itself may contain more caffeine than coffee (by dry weight--for caffeine per serving size, see below), but the length of infusion with hot water and the number of times the leaves are reused can greatly alter caffeine intake.<ref name="caf" /> Using a given amount of green tea leaves steeped in 100 mL of water, experiments have shown that after the first 5 minutes of brewing, the tea contains 32&nbsp;mg caffeine.<ref name="caf" /> But if the same leaves are then used for a second and then a third five minute brew, the caffeine drops to 12&nbsp;mg and then 4&nbsp;mg, respectively.<ref name="caf" />

While coffee and tea are both sources of caffeine, the amounts of caffeine in any single serving of these beverages varies significantly. An average serving of coffee contains the most caffeine, the same serving size of tea provides 1/2 to 1/3 as much.<ref>[http://www.ific.org/publications/reviews/upload/CAF-Review-with-References_11-5-07.pdf Caffeine & Health: Clarifying the Controversies, IFIC Review, 2007]</ref> One of the more confusing aspects of caffeine content is the fact that coffee contains less caffeine than tea when measured in its dry form. The caffeine content of a prepared cup of coffee is significantly higher than the caffeine content of a prepared cup of tea.<ref>http://www.stashtea.com/caffeine.htm</ref>

Green teas contain two caffeine metabolites (caffeine-like substances): [[theophylline]], which is a stronger stimulant than [[caffeine]], and [[theobromine]], which is slightly weaker than caffeine.

=== Safety ===
{{Main|Epigallocatechin gallate#Drug Interactions}}

In 2008 the [[US Pharmacopeia]] reviewed the safety of green tea extract. It found 216 case reports, 34 on liver damage, of which 27 were categorized as possible and 7 were categorized as probable. Potential for adverse effects is increased when extracts are used, particularly on an empty stomach.<ref>{{cite journal |author=Sarma DN, Barrett ML, Chavez ML, ''et al.'' |title=Safety of green tea extracts : a systematic review by the US Pharmacopeia |journal=Drug Saf |volume=31 |issue=6 |pages=469–84 |year=2008 |pmid=18484782 |doi= 10.2165/00002018-200831060-00003|url=http://www.drugsafety.adisonline.com/pt/re/drs/fulltext.00002018-200831060-00003.htm;jsessionid=J81YxCnjct76DjB2STGgngMCsJn3FLqPxvmL6GJjjT7phpHTTyq2!928310026!181195629!8091!-1#P157}}</ref>

==See also==
{{Commons category|Green tea}}
* [[Green tea polyphenols]]
* [[Chinese tea culture]]
* [[Japanese tea ceremony]]
* [[Potential effects of tea on health]]
* [[Reactive oxygen species]]
* [[Yellow tea]]
* [[Korean tea]]
* [[White tea]]

==References==
{{Reflist|2}}

==Literature==
* {{cite book
| author=Master Lam Kam Cheun et al.
| year = 2002
| title = The way of tea
| publisher = Gaia Books
| isbn=1856751430
}}

* John C, Evans, ''Tea in China: The History of China's National Drink.'' Greenwood Press, 1992.
ISBN 0-313-28049-5

==External links==
* [http://www.umm.edu/altmed/ConsHerbs/GreenTeach.html Green Tea (an overview from the University of Maryland Medical Center)]
* [http://www.lipton.com/en_en/pdf/green_tea_catechins_and_body_shape.pdf Green Tea and Body Shape (overview from the Lipton Institute of Tea)]
* [http://www.scientistlive.com/European-Food-Scientist/Q&A/SLAM%3A_Green_Tea%27s_cancer_fighting_potential/22907/ Green Tea's cancer fighting potential (Audio interview)]

{{Teas}}

[[Category:Chinese tea]]
[[Category:Dietary antioxidants]]
[[Category:Green tea|*]]
[[Category:Japanese tea]]
[[Category:Monoamine oxidase inhibitors]]

[[ar:شاي أخضر]]
[[be:Зялёны чай]]
[[bo:ཇ་ལྗང་།]]
[[ca:Te verd]]
[[cs:Zelený čaj]]
[[da:Grøn te]]
[[de:Grüner Tee]]
[[el:Πράσινο τσάι]]
[[es:Té verde]]
[[eo:Verda teo]]
[[fr:Thé vert]]
[[gd:Tì uaine]]
[[gl:Té verde]]
[[ko:녹차]]
[[hi:हरी चाय]]
[[hr:Zeleni čaj]]
[[id:Teh hijau]]
[[it:Tè verde]]
[[he:תה ירוק]]
[[la:Thea viridis]]
[[hu:Zöld tea]]
[[nl:Groene thee]]
[[ja:緑茶]]
[[no:Grønn te]]
[[pl:Zielona herbata]]
[[pt:Chá verde]]
[[ro:Ceai verde]]
[[ru:Зелёный чай]]
[[simple:Green tea]]
[[sk:Zelený čaj]]
[[sl:Zeleni čaj]]
[[sh:Zeleni čaj]]
[[fi:Vihreä tee]]
[[sv:Grönt te]]
[[ta:பசும் தேநீர்]]
[[th:ชาเขียว]]
[[tr:Yeşil çay]]
[[uk:Зелений чай]]
[[zh:綠茶]]

Revision as of 20:06, 22 July 2010

This article is about the type of tea. For the 2003 Chinese film, see Green Tea (film).

Template:ChineseText

Green tea leaves steeping in an uncovered gaiwan

Green tea is tea made solely with the leaves of Camellia sinensis that have undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures in Asia from Japan and South Korea 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. These varieties can differ substantially due to variable growing conditions, processing, and harvesting time.

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