Type | Tea |
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Country of origin | China |
Region of origin | East Asia |
Colour | Green |
Ingredients | Tea leaves |
Related products | Tea |
Green tea | |||||||||||||||||||||||||
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Chinese name | |||||||||||||||||||||||||
Traditional Chinese | 綠茶 | ||||||||||||||||||||||||
Simplified Chinese | 绿茶 | ||||||||||||||||||||||||
Literal meaning | Green tea | ||||||||||||||||||||||||
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Japanese name | |||||||||||||||||||||||||
Kanji | 緑茶 | ||||||||||||||||||||||||
Hiragana | りょくちゃ | ||||||||||||||||||||||||
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Green tea is a type of tea made from the leaves and buds of the Camellia sinensis that have not undergone the withering and oxidation process that creates oolong teas and black teas. [1] Green tea originated in China in the late 1st millennium BC,and since then its production and manufacture has spread to other countries in East Asia.
Several varieties of green tea exist,which differ substantially based on the variety of C. sinensis used,growing conditions,horticultural methods,production processing,and time of harvest.
Tea consumption has its legendary origins in China during the reign of mythological Emperor Shennong. [2]
A book written by Lu Yu in 618–907 AD, The Classic of Tea (Chinese : 茶 經 ; pinyin :chájīng),is considered important in green tea history[ citation needed ]. The Book of Tea (Kissa Yōjōki,lit. Record [of] Drinking Tea [for] Nourishing Life ),written by Zen priest Eisai in 1211,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[ citation needed ].
Steeping,or brewing,is the process of making tea from leaves and hot water,generally using 2 grams (0.071 oz) of tea per 100 millilitres (3.5 imp fl oz;3.4 US fl oz) of water or about 1 teaspoon of green tea per 150 millilitres (5.3 imp fl oz;5.1 US fl oz) cup. Steeping temperatures range from 61 °C (142 °F) to 87 °C (189 °F) and steeping times from 30 seconds to three minutes.
Generally,lower-quality green teas are steeped hotter and longer while higher-quality teas are steeped cooler and shorter,but usually multiple times (2–3 typically). Higher-quality teas like gyokuro use more tea leaves and are steeped multiple times for short durations. Steeping too hot or too long results in the release of excessive amounts of tannins,leading to a bitter,astringent brew,regardless of initial quality. The brew's taste is also affected by the steeping technique;two important techniques are to warm the steeping container beforehand to prevent the tea from immediately cooling down,and to leave the tea leaves in the pot and gradually add more hot water during consumption.[ citation needed ]
Polyphenols found in green tea include epigallocatechin gallate (EGCG),epicatechin gallate,epicatechins and flavanols, [1] which are under laboratory research for their potential effects in vivo. [3] Other components include three kinds of flavonoids,known as kaempferol,quercetin,and myricetin. [4] 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, [5] flavonoids and catechins have no proven biological effect in humans. [6] [7]
Green tea leaves are initially processed by soaking in an alcohol solution,which may be further concentrated to various levels;byproducts of the process are also packaged and used.[ citation needed ] Extracts are sold over the counter in liquid,powder,capsule,and tablet forms, [3] [8] and may contain up to 17.4% of their total weight in caffeine, [9] though decaffeinated versions are also available. [10]
Green tea extract is usable as a clean label food preservative,protecting fats from rancidity. The oil-soluble form used is palmitoylated green tea catechins,ruled generally recognized as safe in 2020. [11]
Nutritional value per 100 g (3.5 oz) | |||||||||||||||||||||||||||||||||||
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Energy | 4 kJ (0.96 kcal) | ||||||||||||||||||||||||||||||||||
0 g | |||||||||||||||||||||||||||||||||||
0 g | |||||||||||||||||||||||||||||||||||
0.2 g | |||||||||||||||||||||||||||||||||||
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Other constituents | Quantity | ||||||||||||||||||||||||||||||||||
Water | 99.9 g | ||||||||||||||||||||||||||||||||||
Caffeine | 12 mg | ||||||||||||||||||||||||||||||||||
†Percentages estimated using US recommendations for adults, [12] except for potassium,which is estimated based on expert recommendation from the National Academies. [13] |
Regular green tea is 99.9% water,provides 1 kcal per 100 mL serving,is devoid of significant nutrient content (table),and contains phytochemicals such as polyphenols and caffeine.
Numerous claims have been made for the health benefits of green tea,but human clinical research has not found good evidence of benefit. [14] [6] [15] In 2011,a panel of scientists published a report on the claims for health effects at the request of the European Commission:in general they found that the claims made for green tea were not supported by sufficient scientific evidence. [6] Although green tea may enhance mental alertness due to its caffeine content,there is only weak,inconclusive evidence that regular consumption of green tea affects the risk of cancer or cardiovascular diseases,and there is no evidence that it benefits weight loss. [14]
In some cases of excessive consumption,green tea extract is hepatotoxic with evidence of liver damage. [16] [17] A 2020 review by the Cochrane Collaboration listed some potential adverse effects of green tea extract including gastrointestinal disorders,higher levels of liver enzymes,and,more rarely,insomnia,raised blood pressure,and skin reactions. [18]
Cancer Council Australia and Cancer Research UK have stated that there is not enough reliable evidence that green tea can prevent cancer. [19] [20] The National Cancer Institute have noted that "the evidence regarding the potential benefits of tea consumption in relation to cancer is inconclusive at present". [21]
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. [22]
A meta-analysis of observational studies reported an increase in one cup of green tea per day was correlated with slightly lower risk of death from cardiovascular causes. [23] Green tea consumption may be correlated with a reduced risk of stroke. [24] [25] Meta-analyses of randomized controlled trials found that green tea consumption for 3–6 months may produce small reductions (about 2–3 mm Hg each) in systolic and diastolic blood pressures. [25] [26] [27] [28] A separate systematic review and meta-analysis of randomized controlled trials found that consumption of 5–6 cups of green tea per day was associated with a small reduction in systolic blood pressure (2 mmHg),but did not lead to a significant difference in diastolic blood pressure. [29]
Green tea consumption lowers fasting blood sugar but in clinical studies the beverage's effect on haemoglobin A1c and fasting insulin levels was inconsistent. [30] [31] [32]
Drinking green tea or taking green tea supplements decreases the blood concentration of total cholesterol (about 3–7 mg/dL),LDL cholesterol (about 2 mg/dL),and does not affect the concentration of HDL cholesterol or triglycerides. [29] [30] [33] A 2013 Cochrane meta-analysis of longer-term randomized controlled trials (>3 months duration) concluded that green tea consumption lowers total and LDL cholesterol concentrations in the blood. [30]
A 2015 systematic review and meta-analysis of 11 randomized controlled trials found that green tea consumption was not significantly associated with lower plasma levels of C-reactive protein levels (a marker of inflammation). [34]
There is no good evidence that green tea aids in weight loss or weight maintenance. [14] [35]
Excessive consumption of green tea extract has been associated with hepatotoxicity and liver failure. [36] [37] [38] In 2018,a scientific panel for the European Food Safety Authority reviewed the safety of green tea consumption over a low-moderate range of daily EGCG intake from 90 to 300 mg per day,and with exposure from high green tea consumption estimated to supply up to 866 mg EGCG per day. [17] Dietary supplements containing EGCG may supply up to 1000 mg EGCG and other catechins per day. [17] The panel concluded that EGCG and other catechins from green tea in low-moderate daily amounts are generally regarded as safe,but in some cases of excessive consumption of green tea or use of high-EGCG supplements,liver toxicity may occur. [17]
In 2013,global production of green tea was approximately 1.7 million tonnes,with a forecast to double in volume by 2023. [39] As of 2015,China provided 80% of the world's green tea market,leading to its green tea exports rising by 9% annually,while exporting 325,000 tonnes in 2015. [40] In 2015,the US was the largest importer of Chinese green tea (6,800 tonnes),an increase of 10% over 2014,and Britain imported 1,900 tonnes,15% more than in 2014. [40]
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. The first flush in the spring brings the best-quality leaves,with higher prices to match.
Green tea is processed after picking using either artisanal or modern methods. Sun-drying,basket or charcoal firing,or pan-firing are common artisanal methods. Oven-drying,tumbling,or steaming are common modern methods. [41] 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 take 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 flavour. 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 blending order by the tasters and packed for sale. [42]
On 17 June 2011,at Charles de Gaulle airport in Paris,France,radioactive caesium of 1,038 becquerels per kilogram was measured in tea leaves imported from Shizuoka Prefecture,Japan as a result of the Fukushima Daiichi nuclear disaster on 11 March,which was more than twice the restricted amount in the European Union of 500 becquerels per kilogram. The government of France announced that they rejected the leaves,which totalled 162 kilograms (357 lb). [43]
In response,the governor of Shizuoka Prefecture,Heita Kawakatsu,stated:"there is absolutely no problem when they [people] drink them because it will be diluted to about 10 becquerels per kilogram when they steep them even if the leaves have 1,000 becquerels per kilogram;" a statement backed by tests done in Shizuoka. [44] Japanese Minister for Consumer Affairs and Food Safety Renhō stated on 3 June 2011 that "there are cases in which aracha [whole leaves of Japanese green tea] 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." [45]
In 2018,the US Food and Drug Administration updated its import status on Japanese products deemed to be contaminated by radionuclides,indicating that tea from the Ibaraki prefecture had been removed from the list by the Government of Japan in 2015. [46]
Chinese name | |||||||||||||||||||
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Traditional Chinese | 綠茶 | ||||||||||||||||||
Simplified Chinese | 绿茶 | ||||||||||||||||||
Hanyu Pinyin | lǜchá | ||||||||||||||||||
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Loose leaf green tea has been the most popular form of tea in China since at least the Southern Song dynasty. [47] [48] While Chinese green tea was originally steamed,as it still is in Japan,after the early Ming dynasty it has typically been processed by being pan-fired in a dry wok. [49] Other processes employed in China today include oven-firing,basket-firing,tumble-drying and sun-drying. [50] Green tea is the most widely produced form of tea in China,with 1.42 million tons grown in 2014. [51]
Popular green teas produced in China today include:
Tea seeds were first brought to Japan in the early 9th century by the Buddhist monks Saicho and Kūkai. During the Heian period (794–1185),Emperor Saga introduced the practice of drinking tea to the imperial family. The Zen Buddhist priest Eisai (1141–1215),founder of the Rinzai school of Buddhism,brought tea seeds from China to plant in various places in Japan. Eisai advocated that all people,not just Buddhist monks and the elite,drink tea for its health benefits. [59]
The oldest tea-producing region in Japan is Uji,located near the former capital of Kyoto. [59] It is thought that seeds sent by Eisai were planted in Uji,becoming the basis of the tea industry there. [60] Today,Japan's most expensive premium teas are still grown in Uji. [61] The largest tea-producing area today is Shizuoka Prefecture,which accounts for 40% of total Japanese sencha production. [62] [61] Other major tea-producing regions include the island of Kyushu and the prefectures of Shiga,Gifu,and Saitama in central Honshu. [61]
All commercial tea produced in Japan today is green tea, [63] though for a brief period black tea was also produced in the late 19th and early 20th centuries. Japanese tea production is heavily mechanized,and is characterized by the use of modern technology and processes to improve yields and reduce labour. Because of the high cost of labour in Japan,only the highest quality teas are plucked and processed by hand in the traditional fashion. [64]
Japanese green teas have a thin,needle-like shape and a rich,dark green colour. Unlike Chinese teas,most Japanese teas are produced by steaming rather than pan-firing. This produces their characteristic colour,and creates a sweeter,more grassy flavour. A mechanical rolling/drying process then dries the tea leaves into their final shape. [63] The liquor of steamed Japanese tea tends to be cloudy due to the higher quantity of dissolved solids. [65]
Most Japanese teas are blended from leaves grown in different regions,with less emphasis on terroir than in the Chinese market. Because of the limited quantity of tea that can be produced in Japan,the majority of production is dedicated to the premium tea market. Cheaper bottled teas and tea-flavoured food products usually use lower-grade Japanese-style tea produced in China. [66]
Although a variety of commercial tea cultivars exist in Japan,the vast majority of Japanese tea is produced using the Yabukita cultivar developed in the 1950s. [67]
Popular Japanese green teas include:
Korean name | |
Korean name | |
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Hangul | 녹차 |
Hanja | 綠茶 |
Revised Romanization | nokcha |
McCune–Reischauer | nokch'a |
IPA | [nok̚.tɕʰa] |
According to Record of Gaya cited in Memorabilia of the Three Kingdoms ,the legendary queen Heo Hwang-ok,a princess of the Ayodhya married to King Suro of Gaya,brought the tea plant from India and planted it in Baegwolsan,a mountain in current Changwon. [76] : 3 However,it is a widely held view that systematic planting of tea bushes began with the introduction of Chinese tea culture by the Buddhist monks around the 4th century. [77] Amongst some of the earliest Buddhist temples in Korea,Bulgapsa (founded in 384,in Yeonggwang),Bulhoesa (founded in 384,in Naju) and Hwaeomsa (founded in Gurye,in 544) claim to be the birthplace of Korean tea culture. [77] Green tea was commonly offered to Buddha,as well as to the spirits of deceased ancestors. [77] Tea culture continued to prosper during the Goryeo period,with the tea offering being a part of the biggest national ceremonies and tea towns were formed around temples. [78] Seon-Buddhist manners of ceremony prevailed. [78] During the Joseon period,however,Korean tea culture underwent secularization,along with the Korean culture itself. [78] Korean ancestral rite jesa ,also referred to as charye (차례;茶禮,"tea rite"),has its origin in darye (다례;茶禮,"tea rite"),the practice of offering tea as simple ancestral rites by the royal family and the aristocracy in Joseon. [78]
Tea culture of Korea was actively suppressed by the Japanese during the Japanese forced occupation period (1910‒1945),and the subsequent Korean War (1950‒1953) made it even harder for the Korean tea tradition to survive. [79] The restoration of the Korean way of tea began in the 1970s,around Dasolsa. [79] Commercial production of green tea in South Korea only began in the 1970s,. [80] By 2012 the industry was producing 20% as much tea as Taiwan and 3.5% as much as Japan. [81] [82] Green tea is not as popular as coffee or other types of Korean teas in modern South Korea. The annual consumption per capita of green tea in South Korea in 2016 was 0.16 kg (5+1⁄2 oz), compared to 3.9 kg (8 lb 10 oz) coffee. [83] Recently however, as the coffee market reached saturation point, South Korean tea production doubled during 2010‒2014, [84] as did tea imports during 2009–2015, [85] despite very high tariff rate (513.6% for green tea, compared to 40% for black tea, 8% for processed/roasted coffee, and 2% for raw coffee beans).
Korean green tea can be classified into various types based on several different factors. The most common is the flush, or the time of the year when the leaves are plucked (and thus also by leaf size).
The mode of preparation also differs:
Leaf teas are processed either by roasting or steaming.
Southern, warmer regions such as Boseong in South Jeolla Province, Hadong in South Gyeongsang Province, and Jeju Island are famous for producing high-quality tea leaves. [97]
Green tea can be blended with other ingredients.
Green tea is the most popular tea among the Vietnamese people. In 2011, it accounted for over 63% of overall retail volume sales. [101] Vietnamese tea culture is ancient, but large scale cultivation was introduced in the late 19th century by French colonists who ran the first plantations in the Phú Thọ area.
Though less well known than Japanese and Chinese green teas, there are various types of Vietnamese green tea and various cultivars. They have recently entered the international market, usually at lower prices. Vietnam is fifth in the world for tea production today. [102]
There is a long tradition of growing and processing green tea in the Thái Nguyên area, north of Hanoi, which has been called the "cradle" of Vietnamese tea. [103] This region is now known for its green tea, which is shipped internationally. [104]
There are also many scented varieties of Vietnamese green tea, most of which are scented with a certain flower petals. These include:
Oolong is a traditional semi-oxidized Chinese tea produced through a process that includes withering the leaves under strong sun and allowing some oxidation to occur before curling and twisting. Most oolong teas, especially those of fine quality, involve unique tea plant cultivars that are exclusively used for particular varieties. The degree of oxidation, which is controlled by the length of time between picking and final drying, can range from 8% to 85% depending on the variety and production style. Oolong is especially popular in southeastern China and among ethnic Chinese in Southeast Asia, as is the Fujian preparation process known as the gongfu tea ceremony.
Gyokuro is a type green tea from Japan that is grown in the shade. It differs from the standard sencha in being grown under the shade rather than the full sun. The name "gyokuro" translates as "jewel dew". According to the Japan Tea Central Association, gyokuro is defined as "a tea manufactured in the same manner as sencha from tea leaves picked from covered tea gardens that are almost completely shaded from sunlight for about 20 days using covering materials such as reed screens, straw, or shading nets, from the time when the new shoots of the first flush start to grow."
The history of tea spreads across many cultures throughout thousands of years. The tea plant Camellia sinensis is native probably originated in the borderlands of southwestern China and northern Myanmar. One of the earliest accounts of tea drinking is dated back to China's Shang dynasty, in which tea was consumed in a medicinal concoction. An early credible record of tea drinking dates to the 3rd century AD, in a medical text written by Chinese physician Hua Tuo. It first became known to the western world through Portuguese priests and merchants in China during the early 16th century. Drinking tea became popular in Britain during the 17th century. To compete with the Chinese monopoly on tea, the British East India Company introduced commercial tea production to British India.
Yellow tea is a particular lightly oxidized tea, either Chinese huángchá and Korean hwangcha.
Compressed tea, called tea bricks, tea cakes or tea lumps, and tea nuggets according to the shape and size, are blocks of whole or finely ground black tea, green tea, or post-fermented tea leaves that have been packed in molds and pressed into block form. This was the most commonly produced and used form of tea in ancient China prior to the Ming Dynasty. Although tea bricks are less commonly produced in modern times, many post-fermented teas, such as pu-erh, are still commonly found in bricks, discs, and other pressed forms. Tea bricks can be made into beverages like tea or eaten as food, and were also used in the past as a form of currency.
The tamaryokucha is a fine Japanese green tea, also commonly known as guricha. It has a tangy, berry-like taste, with a long almondy aftertaste and a deep aroma with tones of citrus, grass, and berries.
Kamairicha (釜炒り茶) is a Japanese green tea produced by pan-roasting or pan-firing tea leaves during the early stages of production. It is most commonly produced in the western region of Japan. Kamairicha has a mildly roasted flavour with more sweet and fresh notes than bitter ones.
The history of tea in Japan began as early as the 8th century, when the first known references were made in Japanese records. Tea became a drink of the religious classes in Japan when Japanese priests and envoys sent to China to learn about its culture brought tea to Japan. The Buddhist monks Kūkai and Saichō may have been the first to bring tea seeds to Japan. The first form of tea brought from China was probably brick tea. Tea became a drink of the royal classes when Emperor Saga encouraged the growth of tea plants. Seeds were imported from China, and cultivation in Japan began.
Korean tea is a beverage consisting of boiled water infused with leaves, roots, flowers, fruits, grains, edible mushrooms, or seaweed. It may or may not contain tea leaves.
Fermented tea is a class of tea that has undergone microbial fermentation, from several months to many years. The exposure of the tea leaves to humidity and oxygen during the process also causes endo-oxidation and exo-oxidation. The tea leaves and the liquor made from them become darker with oxidation. Thus, the various kinds of fermented teas produced across China are also referred to as dark tea, not be confused with black tea, which is actually referred to as "red tea" in Chinese. The most famous fermented tea is pu'er produced in Yunnan province.
Tea processing is the method in which the leaves from the tea plant Camellia sinensis are transformed into the dried leaves for brewing tea.
Matcha (抹茶) is a finely ground powder of green tea specially processed from shade-grown tea leaves. Shade growing gives matcha its characteristic bright green color and strong umami flavor. Matcha is typically consumed suspended in hot water.
Konacha is a type of green tea, composed of the dust, tea buds and small leaves that are left behind after processing Gyokuro or Sencha. Konacha is cheaper than Sencha and Matcha and is often served at sushi restaurants as palate-refresher that stands up to fish flavours under the name of agari. It is also marketed as Gyokurokonacha (玉露粉茶).
The phenolic content in tea refers to the phenols and polyphenols, natural plant compounds which are found in tea. These chemical compounds affect the flavor and mouthfeel of tea. Polyphenols in tea include catechins, theaflavins, tannins, and flavonoids.
Sencha is a type of Japanese ryokucha which is prepared by infusing the processed whole tea leaves in hot water. This is as opposed to matcha, powdered Japanese green tea, where the green tea powder is mixed with hot water and therefore the leaf itself is included in the beverage. Sencha is the most popular tea in Japan.
Uji tea is a common name for all Japanese green tea produced from Uji, Kyoto. The three main types of Uji tea are Matcha, Sencha and Gyokuro. Japanese tea is originated from the Tang dynasty of China, which is during the Heian period of Japan when Chinese influences were at its peak. When tea seeds were introduced to Japan, they were first planted at Toganoo. These seeds were later spread in Uji, which became the site to produce the highest quality of tea leaf in Japan.
Black tea is a type of tea that is more oxidized than oolong, yellow, white, and green teas. Black tea is generally stronger in flavour than other teas. All five types are made from leaves of the shrub Camellia sinensis, though Camellia taliensis is also rarely used.
Ujeon, also called cheonmul-cha, refers to nokcha made of young, tender leaves and buds hand-plucked before gogu. The delicate tea has sweet, soft, and subtle flavor profile, and is best steeped at a temperature of 50 °C (122 °F).
Kabuse tea, or kabusecha (かぶせ茶) is a class of Japanese tea leaf. Kabuseru (かぶせる) literally means to cover or place on top, as a hat on a head, therefore kabuse tea is a tea leaf harvested from a tea plant that, for some period of time ranging from 2–25 days, has had a porous material draped over the plant while the young leaves are being produced. Kabuse tea is almost exclusively a first flush tea. Though kabuse tea is usually processed into a green tea after picking, kabuse tea denotes a pre-picking process and the freshly picked leaf can be used to produce any kind of tea, from green tea to oolong tea to black tea, or other types.
Tea is an important part of Japanese culture. It first appeared in the Nara period (710–794), introduced to the archipelago by ambassadors returning from China, but its real development came later, from the end of the 12th century, when its consumption spread to Zen temples, also following China's example; it was then powdered tea that was drunk after being beaten. In the Middle Ages, tea became a common drink for the elite, and in the 16th century, the art of the "tea ceremony" was formalized. It is now one of the most emblematic elements of Japanese culture, whose influence extends beyond the simple context of tea drinking. Tea-growing developed in the pre-modern era, particularly during the Edo period (1603–1868), when tea became a popular beverage consumed by all strata of society. New ways of processing and consuming tea leaves were developed, starting with sencha, a steamed oxidation-stopped brew that became the most common.
Green tea extracts haven't been shown to produce a meaningful weight loss in overweight or obese adults. They also haven't been shown to help people maintain a weight loss.
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: CS1 maint: DOI inactive as of December 2024 (link)Green tea extract and, more rarely, ingestion of large amounts of green tea have been implicated in cases of clinically apparent acute liver injury, including instances of acute liver failure and either need for urgent liver transplantation or death.