Green tea

From Wikipedia, the free encyclopedia
  (Redirected from Green Tea)
Jump to: navigation, search
This article is about the type of tea. For other uses, see Green Tea (disambiguation).
The appearance of green tea in three different stages (from left to right): the infused leaves, the dry leaves, and the liquid. Notice that the infused leaves look greener than the dry leaves.
The tea fields in the foothills of Gorreana, Azores Islands, Portugal: the only European region other than Georgia to support green tea production.

Green tea is made from the leaves from Camellia sinensis that have undergone minimal oxidation during processing.[1] Green tea originated in China, but it has become associated with many cultures throughout Asia. Green tea has recently become relatively widespread in the Western World where black tea has been traditionally consumed.

Green tea has become the raw material for extracts used in various beverages, dietary supplements, and cosmetic items.[2] Many varieties of green tea have been created in the countries where it is grown. These varieties can differ substantially due to variable growing conditions, horticulture, production processing, and harvesting time.

Many claims have been made for the beneficial health effects of green tea consumption, but they have generally not been borne out by scientific investigation; excessive consumption is associated with some harmful health effects but moderate, regular consumption is safe.

History[edit]

Main article: History of tea

Tea consumption has its legendary origins in China dating back to more than 4,000 years ago, making it the oldest herbal tea known. Green tea was first brewed in 2737 BC during the reign of Emperor Shennong.[3]

A book written by Lu Yu in 600-900 AD (Tang Dynasty), "Tea Classic" (simplified Chinese: ; traditional Chinese: ; pinyin: chájīng), is considered important in green tea history. The Kissa Yojoki (喫茶養生記 Book of Tea), written by Zen priest Eisai in 1191, describes how drinking green tea may affect five vital organs, the shapes of tea plants, flowers and leaves, and how to grow and process tea leaves.

Brewing and serving[edit]

Green tea leaves steeping in a gaiwan

Steeping is the process of making a cup of tea; it is also referred to as brewing. In general, two grams of tea per 100 ml of water, or about one teaspoon of green tea per five-ounce (150 ml) 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 steeping time and temperature varies with different tea. The hottest steeping temperatures are 81 to 87 °C (178 to 189 °F) water and the longest steeping times two to three minutes. The coolest brewing temperatures are 61 to 69 °C (142 to 156 °F) and the shortest times about 30 seconds. In general, lower-quality green teas are steeped hotter and longer, whereas 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, because it will result in the release of an excessive amount of tannins. High-quality green teas can be and usually are steeped multiple times; two or three steepings is typical. The steeping technique also plays a very important role in avoiding the tea developing an overcooked taste. 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.

Varieties of green tea[edit]

Chinese green tea[edit]

Green tea is the most popular form of tea in China. Chinese green teas are made from over 600 different cultivars of the Camellia sinensis plant, giving plenty of variety and regional teas. Chinese green teas are traditionally pan-fired, unlike the Japanese steaming process. Other processes in China include oven-dried and sun-dried. Due to the different production process, Chinese teas are said to have a more "earthy" taste than Japanese teas.

  • Zhejiang Province is home to the most famous of all teas, Xi Hu Longjing (西湖龙井), as well as many other high-quality green teas.
Maybe the most well-known green tea in China; originates from Hangzhou (杭州), the capital of Zhejiang Province. Longjing in Chinese literally means dragon well. It is pan-fired and has a distinctive flat appearance. The tasteless frying oil is obtained from tea seeds and other plants. There are many fake Longjings on the market[4] and in less-scrupulous tea houses around the country.
Named after a temple in Zhejiang.
A tea from Kaihua County known as Dragon Mountain.
A tea from Tiantai County, named after a peak in the Tiantai mountain range.
A tea from Tian Mu, also known as Green Top.
A popular tea also known as zhuchá, originates in Zhejiang but is now grown elsewhere in China. This tea is also the quintessential ingredient in brewing Maghrebi mint tea, which is brewed green tea with fresh mint.
A plate of Bi Luo Chun tea, from Jiangsu Province in China
A Chinese famous tea also known as Green Snail Spring, from Dong Ting. As with Longjing, inauthentic Bi Luo Chun is common and most of the tea marketed under this name may, in fact, be grown in Sichuan.
A tea from Nanjing.
originate in Jin Tan city of Jiangsu Province.
Camellia sinensis, the tea plant
  • Fujian Province is known for mountain-grown organic green tea as well as white tea and oolong tea. The coastal mountains provide a perfect growing environment for tea growing. Green tea is picked in spring and summer seasons.
A tea with added jasmine flowers.
Meaning "furry peak".
  • 翠剑 Cui Jian
Meaning "jade sword".
A steamed tea also known as Gyokuro (Jade Dew) in Japanese, made in the Japanese style.
An example of a Chinese green tea, called Mao Jian.
A Chinese famous tea also known as Green Tip, or Tippy Green.
Meaning "precious eyebrows"; from Jiangxi, it is now grown elsewhere.
A well-known tea within China and recipient of numerous national awards.
A tea also known as Cloud and Mist.
A tea from Huangshan also known as Big Square suneet.
A Chinese famous tea from Huangshan
A Chinese famous tea also known as Melon Seed
A Chinese famous tea also known as Monkey tea
A tea from Tunxi District.
A tea from Jing County, also known as Fire Green
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.
A medium-quality tea from many provinces, an early-harvested tea.
Also known as Meng Ding Cui Zhu or Green Bamboo
A yellowish-green tea with sweet after taste.
  • 百美绿茶 Baimei Green Tea
A green tea from the Han Zhong.

Japanese green tea[edit]

Japanese green tea
Genmaicha
Aracha

Green tea (緑茶 Ryokucha?) is ubiquitous in Japan and is commonly known simply as "tea" (お茶 ocha?). Tea was first used in China, and was brought to Japan by Myōan Eisai, a Japanese Buddhist priest who also introduced the Rinzai school of Zen Buddhism. Teas from Japan may be referred to as "Japanese tea" (日本茶 nihoncha?).

Japanese green tea is made from the Yabukita (薮北?) cultivar of the camellia sinensis plant. Unlike Chinese green teas which are pan-fired, Japanese green teas are steamed giving them a more "vegetative" or "leafy" taste. The exception is hōjicha, a Japanese roasted tea. Japanese green teas are categorized by the age of the leaves: young leaves are called sench[citation needed] and the more mature, larger leaves are called bancha. Types of tea are commonly graded depending on the quality and the parts of the plant used as well as how they are processed.[5] There are large variations in both price and quality within these broad categories, and there are many green teas that fall outside this spectrum. The best Japanese green tea is said to be from the Yame (八女 yame?) region of Fukuoka Prefecture and from the Uji region of Kyoto. Uji has been producing Ujicha (Uji tea) for four hundred years, pre-dating the prefecture system. It is now a combination of the border regions of Shiga, Nara, Kyoto, and Mie prefectures. Shizuoka Prefecture produces 40 percent of raw tea leaf.

The first and second flushes 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.
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.
Gyokuro is a fine and expensive type that differs from Sencha (煎茶) in that it is grown under the shade rather than the full sun for approximately 20 days.[6] The name "Gyokuro" translates as "jade dew" and refers to the pale green color of the infusion. The shading causes the amino acids (Theanine) and caffeine in the tea leaves to increase, while catechins (the source of bitterness in tea, along with caffeine) decreases, giving rise to a sweet taste.[7] The tea also has a distinct aroma.
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.
Tamaryokucha has a tangy, berry-like taste, with a long almondy after-taste and a deep aroma with tones of citrus, grass, and berries. It is also called Guricha.
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.
Kamairicha is a pan-fired 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
A tea made from stems, stalks, and twigs. Kukicha has a mildly nutty, and slightly creamy sweet flavor.
  • Mecha (芽茶?, 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.
  • Konacha (粉茶?, (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 Gyokuroko (玉露粉?) or Gyokurokocha.
  • Other
A fine ground tea made from Tencha. It has a very similar cultivation process as Gyokuro. It is expensive and is used primarily in the Japanese tea ceremony. Matcha is also a popular flavor of ice cream and other sweets in Japan.
  • Tencha ( 碾茶?, 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.
Bancha (sometimes Sencha) and roasted genmai (brown rice) blend. It is often mixed with a small amount of Matcha to make the color better.
A green tea roasted over charcoal (usually Bancha).
Half-finished products used for Sencha and Gyokuro production. It contains all parts of the tea plant.
First flush tea. The name is used for either Sencha or Gyokuro.
  • funmatsucha (粉末茶?, 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[edit]

Research and health effects[edit]

Main article: Health effects of tea

Green tea contains a variety of enzymes, amino acids, carbohydrates, lipids, sterols, related compounds, dietary minerals, and phytochemicals such as polyphenols, flavanols, and caffeine. Polyphenols found in green tea include but are not limited to epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin; flavanols such as kaempferol, quercetin, and myricitin are also found in green tea.[1] Numerous claims have been made for the health benefits of green tea based on its chemical composition, in vitro studies, animal studies, and human epidemiological studies. Preliminary research on many of these claims is promising, but many also require further study to evaluate.[1][8] In 2011 a panel of scientists published a report on green tea's claimed health effects at the request of the European commission: in general they found that the claims made for green tea were not supported by good scientific evidence.[9] Although the mean content of flavonoids and catechins in a cup of green tea is higher than that in the same volume of other food and drink items that are traditionally considered to promote health,[10] flavonoids and catechins have no proven biological effect in humans.[9][11]

Cancer[edit]

There is no conclusive evidence that green tea helps to prevent or treat cancer in people.[8][12] A review of existing studies concluded that while suggestive evidence existed, it did not amount to a clear indication of benefit.[12]

Meta-analyses in 2014 found limited evidence that green tea consumption may be associated with a slightly lower risk of esophageal cancer in the Chinese population, a lower risk of lung cancer in women, and a lower risk of oral cancer in Asian people.[13][14][15] Another analysis of observational data conducted in 2012 suggested that green tea consumption may have a favorable effect on lung cancer risk. The observed effect was strongest in those who consumed more than seven cups of green tea daily.[16] In 2011, a meta-analysis of epidemiological studies found limited evidence that green tea consumption may be associated with a moderately reduced risk of liver cancer in Chinese and Japanese people.[17]

In contrast, separate 2014 meta-analyses found limited evidence that green tea consumption is not associated with the risk of developing pancreatic cancer or prostate cancer.[18][19] The link between green tea consumption and stomach cancer risk is unclear due to inconsistent evidence.[20]

Green tea interferes with the chemotherapy drug bortezomib (Velcade) and other boronic acid-based proteasome inhibitors, and should be avoided by people taking these medications.[21]

Cardiovascular disease[edit]

Green tea consumption may be associated with a reduced risk of stroke.[22][23][24] A 2013 Cochrane review of randomized controlled trials concluded that green tea consumption for 3–6 months appears to lower systolic and diastolic blood pressures a small amount (about 3 mmHg each).[24][25] Additional analyses examining the effects of long-term green tea consumption on blood pressure have reached similar conclusions.[26][27][28]

Glycemic control[edit]

Two meta-analyses concluded that drinking green tea lowers fasting blood sugar, but the effect of green tea consumption on hemoglobin A1c and fasting insulin levels was inconsistent.[24][29][30]

Hyperlipidemia[edit]

A 2011 meta-analysis of 14 short-term randomized controlled trials concluded that consumption of green tea or green tea supplements decreases the blood concentration of total cholesterol (about 7 mg/dL), LDL cholesterol (about 2 mg/dL), and had no effect on the concentration of HDL cholesterol.[24][31] A 2013 Cochrane review performed a meta-analysis of longer-term randomized controlled trials (>3 months duration) and concluded that green tea consumption lowers total and LDL cholesterol concentrations in the blood.[24][25]

Weight loss[edit]

There is no conclusive evidence that green tea aids in weight loss for obese people.[32]

Toxicity[edit]

Moderate, regular, and habitual consumption of green tea is safe;[8] however, there are reports of liver toxicity in humans after consuming high doses (10–29 mg/kg/day) of green tea extract dietary supplements.[33] High doses of epigallocatechin gallate (EGCG), an abundant catechin found in green tea, have also been found to cause oxidative stress in mice and in vitro.[33]

Production[edit]

Growing, harvesting and processing[edit]

Hand rolling green tea after steaming

Green tea is processed and grown in a variety of ways, depending on the type of green tea desired. As a result of these methods, maximum amounts of polyphenols and volatile organic compounds are retained, affecting aroma and taste. The growing conditions can be broken down into two basic types − those grown in the sun and those grown under the shade. The green tea plants are grown in rows that are pruned to produce shoots in a regular manner, and in general are harvested three times per year. The first flush takes place in late April to early May. The second harvest usually takes place from June through July, and the third picking takes place in late July to early August. Sometimes, there will also be a fourth harvest. It is the first flush in the spring that brings the best-quality leaves, with higher prices to match.

Green tea is processed using either artisanal or modern methods.[34] Sun-drying, basket or charcoal firing, or pan-firing are common artisanal methods.[34] Oven-drying, tumbling, or steaming are common modern methods.[34] Processed green teas, known as aracha are stored under low humidity refrigeration in 30- or 60-kilogram paper bags at 0–5 °C (32–41 °F). This aracha has yet to be refined at this stage, with a final firing taking place before blending, selection, and packaging takes place. The leaves in this state will be re-fired throughout the year as they are needed, giving the green teas a longer shelf-life and better flavor. The first flush tea of May will readily store in this fashion until the next year's harvest. After this re-drying process, each crude tea will be sifted and graded according to size. Finally, each lot will be blended according to the blend order by the tasters and packed for sale.[35]

Production by country[edit]

2006 Green tea production and export (in thousands of metric tons)[36]
Country Production Export
 China 782.4 (80.8%) 218.7 (83.0%)
 Japan 91.8 (9.5%) 1.6 (0.6%)
 Vietnam 66.0 (6.8%) 26.0 (9.9%)
 Indonesia 20.0 (2.1%) 9.1 (3.5%)
World 968.1 (100%) 263.5 (100%)

Import of Japanese tea[edit]

On 17 June 2011, radioactive cesium of 1,038 becquerels per kilogram was detected at Charles de Gaulle airport in France in tea leaves imported from Shizuoka Prefecture, Japan, which was more than twice as much as the restricted amount of 500 becquerels per kilogram designated by the European Union, and the government of France announced that they rejected the tea leaves, which amounted to 162 kilograms (357 lb).[37] The governor of Shizuoka Prefecture Heita Kawakatsu stated that "there is absolutely no problem when they [people] drink them because it will be diluted to about ten becquerels per kilogram when they steep them even if the leaves have 1,000 becquerels per kilogram," which was a consequence of own examinations of the prefecture.[38] Minister for Consumer Affairs and Food Safety Renhō stated on 3 June 2011, that "there are cases in which aracha are sold as furikake [condiments sprinkled on rice] and so on and they are eaten as they are, therefore we think that it is important to inspect tea leaves including aracha from the viewpoint of consumers' safety."[39]

See also[edit]

References[edit]

  1. ^ a b c Khan N, Mukhtar H (2013). "Tea and health: studies in humans". Current pharmaceutical design (Literature Review) 19 (34): 6141–7. PMC 4055352. PMID 23448443. 
  2. ^ Reich, Eike; Anne Schibil, Valeria Widmer, Ruth Jorns, Evelyn Wolfram, Alison DeBatt (August 2006), "HPTLC methods for identification of green tea and green tea extract", Journal of Liquid Chromatography & Related Technologies 29 (14): 2141–2151, doi:10.1080/15512160600760293 
  3. ^ Dattner, Christine; Boussabba, Sophie (2003). Emmanuelle Javelle, ed. The Book of Green Tea. Universe Books. p. 13. ISBN 978-0-7893-0853-5. Retrieved 24 March 2013. 
  4. ^ http://www.chinadaily.com.cn/business/2010-02/23/content_9489252.htm
  5. ^ Heiss, Mary Lou; Heiss, Robert J. (2007), The Story of Tea: A Cultural History and Drinking Guide, Ten Speed Press, pp. 179–185, ISBN 1-58008-745-0 
  6. ^ Illustrated explanation of the process for producing gyokuro tea, Ippodo-tea.co.jp, retrieved 2013-01-13 
  7. ^ About the effects of the shading process, and the components of this tea compared to others, Ippodo-tea.co.jp, retrieved 2013-01-13 
  8. ^ a b c Boehm K, Borrelli F, Ernst E et al. (2009). "Green tea (Camellia sinensis) for the prevention of cancer". Cochrane Database Syst Rev (Systematic review) (3): CD005004. doi:10.1002/14651858.CD005004.pub2. PMID 19588362. 
  9. ^ a b "Scientific Opinion on the substantiation of health claims related to Camellia sinensis (L.) Kuntze (tea), including catechins in green tea, and improvement of endothelium-dependent vasodilation (ID 1106, 1310), maintenance of normal blood pressure (ID 1310, 2657), maintenance of normal blood glucose concentrations (ID 1108), maintenance of normal blood LDL cholesterol concentrations (ID 2640), protection of the skin from UV-induced (including photo-oxidative) damage (ID 1110, 1119), protection of DNA from oxidative damage (ID 1120, 1121), protection of lipids from oxidative damage (ID 1275), contribution to normal cognitive function (ID 1117, 2812), "cardiovascular system" (ID 2814), "invigoration of the body" (ID 1274, 3280), decreasing potentially pathogenic gastro-intestinal microorganisms (ID 1118), "immune health" (ID 1273) and "mouth" (ID 2813) pursuant to Article 13(1) of Regulation (EC) No 1924/2006". European Food Safety Authority. 8 April 2011. Retrieved 9 November 2014. 
  10. ^ USDA Database for the Flavonoid Content of Selected Foods, Release 2.1 (2007)
  11. ^ EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3 European Food Safety Authority (EFSA), Parma, Italy (2010). "Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061" (PDF). EFSA Journal 8 (2): 1489. doi:10.2903/j.efsa.2010.1489. 
  12. ^ a b Johnson R, Bryant S, Huntley AL (December 2012). "Green tea and green tea catechin extracts: an overview of the clinical evidence". Maturitas (Review) 73 (4): 280–7. doi:10.1016/j.maturitas.2012.08.008. PMID 22986087. In conclusion, whilst there is a considerable body of evidence for green tea with some of it suggesting a positive effect, it is difficult to be definitive as to its health benefits. 
  13. ^ Zheng JS, Yang J, Fu YQ, Huang T, Huang YJ, Li D (January 2013). "Effects of green tea, black tea, and coffee consumption on the risk of esophageal cancer: a systematic review and meta-analysis of observational studies". Nutr Cancer (Systematic Review and Meta-Analysis) 65 (1): 1–16. doi:10.1080/01635581.2013.741762. PMID 23368908. 
  14. ^ Wang L, Zhang X, Liu J, Shen L, Li Z (October 2014). "Tea consumption and lung cancer risk: a meta-analysis of case-control and cohort studies". Nutrition (Meta-Analysis) 30 (10): 1122–7. doi:10.1016/j.nut.2014.02.023. PMID 25194612. 
  15. ^ Wang W, Yang Y, Zhang W, Wu W (April 2014). "Association of tea consumption and the risk of oral cancer: a meta-analysis". Oral Oncol (Meta-Analysis) 50 (4): 276–81. doi:10.1016/j.oraloncology.2013.12.014. PMID 24389399. 
  16. ^ Wang Y, Yu X, Wu Y, Zhang D (November 2012). "Coffee and tea consumption and risk of lung cancer: a dose-response analysis of observational studies". Lung Cancer (Meta-Analysis) 78 (2): 169–70. doi:10.1016/j.lungcan.2012.08.009. PMID 22964413. 
  17. ^ Fon Sing M, Yang WS, Gao S, Gao J, Xiang YB (May 2011). "Epidemiological studies of the association between tea drinking and primary liver cancer: a meta-analysis". European journal of cancer prevention: the official journal of the European Cancer Prevention Organisation (ECP) (Meta-Analysis) 20 (3): 157–65. doi:10.1097/CEJ.0b013e3283447497. PMID 21403523. 
  18. ^ Zeng JL, Li ZH, Wang ZC, Zhang HL (October 2014). "Green tea consumption and risk of pancreatic cancer: a meta-analysis". Nutrients (Meta-Analysis) 6 (11): 4640–50. doi:10.3390/nu6114640. PMC 4245553. PMID 25353660. 
  19. ^ Lin YW, Hu ZH, Wang X, Mao QQ, Qin J, Zheng XY, Xie LP (February 2014). "Tea consumption and prostate cancer: an updated meta-analysis". World J Surg Oncol (Meta-Analysis) 12: 38. doi:10.1186/1477-7819-12-38. PMC 3925323. PMID 24528523. 
  20. ^ Hou IC, Amarnani S, Chong MT, Bishayee A (June 2013). "Green tea and the risk of gastric cancer: epidemiological evidence". World J Gastroenterol (Review) 19 (24): 3713–22. doi:10.3748/wjg.v19.i24.3713. PMC 3699047. PMID 23840110. 
  21. ^ Jia L, Liu FT (December 2013). "Why bortezomib cannot go with 'green'?". Cancer Biol Med (Review) 10 (4): 206–13. doi:10.7497/j.issn.2095-3941.2013.04.004. PMC 3860349. PMID 24349830. 
  22. ^ Shen L, Song LG, Ma H, Jin CN, Wang JA, Xiang MX (August 2012). "Tea consumption and risk of stroke: a dose-response meta-analysis of prospective studies". J Zhejiang Univ Sci B (Review) 13 (8): 652–62. doi:10.1631/jzus.B1201001. PMC 3411099. PMID 22843186. 
  23. ^ Arab L, Khan F, Lam H (December 2013). "Tea consumption and cardiovascular disease risk". Am J Clin Nutr (Review) 98 (6 Suppl): 1651S–1659S. doi:10.3945/ajcn.113.059345. PMID 24172310. 
  24. ^ a b c d e Larsson SC (January 2014). "Coffee, tea, and cocoa and risk of stroke". Stroke (Review) 45 (1): 309–14. doi:10.1161/STROKEAHA.113.003131. PMID 24326448. 
  25. ^ a b Hartley L, Flowers N, Holmes J, Clarke A, Stranges S, Hooper L, Rees K (June 2013). "Green and black tea for the primary prevention of cardiovascular disease" (PDF). Cochrane Database Syst Rev (Systematic Review and Meta-Analysis) 6: CD009934. doi:10.1002/14651858.CD009934.pub2. PMID 23780706. 
  26. ^ Liu G, Mi XN, Zheng XX, Xu YL, Lu J, Huang XH (October 2014). "Effects of tea intake on blood pressure: a meta-analysis of randomised controlled trials". Br J Nutr (Meta-Analysis) 112 (7): 1043–54. doi:10.1017/S0007114514001731. PMID 25137341. 
  27. ^ Khalesi S, Sun J, Buys N, Jamshidi A, Nikbakht-Nasrabadi E, Khosravi-Boroujeni H (September 2014). "Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trials". Eur J Nutr (Systematic Review and Meta-Analysis) 53 (6): 1299–1311. doi:10.1007/s00394-014-0720-1. PMID 24861099. 
  28. ^ Peng X, Zhou R, Wang B, Yu X, Yang X, Liu K, Mi M (September 2014). "Effect of green tea consumption on blood pressure: a meta-analysis of 13 randomized controlled trials". Sci Rep (Meta-Analysis) 4: 6251. doi:10.1038/srep06251. PMC 4150247. PMID 25176280. 
  29. ^ Liu K, Zhou R, Wang B, Chen K, Shi LY, Zhu JD, Mi MT (August 2013). "Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials". Am J Clin Nutr (Meta-Analysis) 98 (2): 340–8. doi:10.3945/ajcn.112.052746. PMID 23803878. 
  30. ^ Zheng XX, Xu YL, Li SH, Hui R, Wu YJ, Huang XH (April 2013). "Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials". Am J Clin Nutr (Meta-Analysis) 97 (4): 750–62. doi:10.3945/ajcn.111.032573. PMID 23426037. 
  31. ^ Zheng XX, Xu YL, Li SH, Liu XX, Hui R, Huang XH (August 2011). "Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials". Am J Clin Nutr (Meta-Analysis) 94 (2): 601–10. doi:10.3945/ajcn.110.010926. PMID 21715508. 
  32. ^ Jurgens TM, Whelan AM, Killian L, Doucette S, Kirk S, Foy E (2012). "Green tea for weight loss and weight maintenance in overweight or obese adults". Cochrane Database Syst Rev (Systematic review) 12: CD008650. doi:10.1002/14651858.CD008650.pub2. PMID 23235664. 
  33. ^ a b Lambert JD, Sang S, Yang CS (April 2007), "Possible controversy over dietary polyphenols: benefits vs risks", Chem Res Toxicol 20 (4): 583–5, doi:10.1021/tx7000515, PMID 17362033 
  34. ^ a b c Heiss, Mary Lou; Heiss, Robert J. (2007), Hardcover, ed., The Story of Tea: A Cultural History and Drinking Guide, Ten Speed Press, pp. 56–69, ISBN 978-1-60774-172-5 
  35. ^ Green Tea Processing, O-cha.com, retrieved 2013-01-13 
  36. ^ Current situation and medium-term outlook (PDF), Intergovernmental Group on Tea, UN Food and Agriculture Organization, May 2008, p. 9 
  37. ^ "日本からの緑茶に基準超えるセシウム パリの空港で検出." (Japanese) Asahi Shimbun. 2011-06-18. Retrieved 2011-06-19.
  38. ^ "静岡知事「飲用茶にすれば問題ない」 仏での検出受け." (Japanese) Asahi Shimbun. 2011-06-18. Retrieved 2011-06-19.
  39. ^ "蓮舫内閣府特命担当大臣記者会見要旨(平成23年6月3日(金))." (Japanese) Consumer Affairs Agency. 2011-06-03. Retrieved 2011-06-19.

Further reading[edit]

External links[edit]