Green Tea - What Is Green Tea Good For

Green tea is a type of tea that is made from Camellia sinensis leaves that have not undergone the same withering and oxidation process used to make oolong and black tea. Green tea originated in China, but its production has spread to many countries in Asia.

Several varieties of green tea exist, which differ substantially because of the variety of C. sinensis used, growing conditions, horticultural methods, production processing, and time of harvest.

History

Tea consumption has its legendary origins in China during the reign of Emperor Shennong.

A book written by Lu Yu in 600-900 AD (Tang Dynasty), "Tea Classic" (simplified Chinese: 茶经; traditional Chinese: 茶ç¶"; pinyin: chájÄ«ng), is considered important in green tea history. The Kissa Yojoki (喫茶養ç"Ÿè¨˜ 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

Steeping, or brewing, is the process of making tea, generally using two grams of tea per 100 ml of water or about 1 teaspoon of green tea per 150 ml cup. Higher-quality teas, like gyokuro, use more tea leaves and are steeped multiple times for short durations.

Steeping temperatures range from 61°C (142°F) to 87°C (189°F) and 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 for multiple times (2-3 typically). Steeping too hot or for 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 leaf in the pot and gradually add more hot water as you drink the tea.

Extracts

Green tea extracts have been used in traditional Chinese and Indian medicine for a variety of uses.

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. Extracts may be sold in liquid, powder, capsule, or tablet form. Decaffeinated versions are also available.

Green tea extract supplements are accessible over the counter in various forms. Standardized green tea extract is 90 percent total polyphenols, and 1 capsule equals 5 cups of tea.

Health effects

Regular green tea is 99.9% water, provides 1 Calorie per 100 mL serving, is devoid of significant nutrient content (table) and contains phytochemicals, such as polyphenols and caffeine. Polyphenols found in green tea include epigallocatechin gallate (EGCG), epicatechin gallate, epicatechins and flavanols, which have antioxidant, anticarcinogen, anti-inflammatory, and anti-radiation biochemical effects in vitro. Other components include three kinds of flavonoids, known as kaempferol, quercetin, and myricetin. A remarkably higher content of myricetin is detected in tea and its extracts than in many other plants, and this high concentration of myricetin may have some implications for the experimentally-observed bioactivity of tea and its extracts in vitro.

Although numerous claims have been made for the health benefits of green tea, human clinical research has not provided conclusive evidence of any effects. 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. 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, flavonoids and catechins have no proven biological effect in humans.

Cancer

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

Daily consumption of black tea (but not green tea) has been associated with a significant reduction in death from all cancers. There is limited evidence to suggest 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. A 2015 meta-analysis of nine prospective cohort studies concluded that a high amount of green tea consumption may be associated with a lower risk of liver cancer in Asian women. This association was not seen in Asian men or when one cup of green tea was consumed daily. Similarly, 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. A 2011 meta-analysis of epidemiological studies found limited evidence that green tea consumption may b e associated with a moderately reduced risk of liver cancer in Chinese and Japanese people. Limited evidence suggests that green tea consumption is not associated with the risk of developing pancreatic cancer or prostate cancer. The link between green tea consumption and stomach cancer risk is unclear due to inconsistent evidence.

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.

Cardiovascular disease

Observational studies have shown a correlation between daily consumption of green tea and a lower risk of death from cardiovascular disease. In a 2015 meta-analysis of such observational studies, an increase in one cup of green tea per day was correlated with a 5% lower risk of death from cardiovascular causes. Green tea consumption may be correlated with a reduced risk of stroke. Meta-analyses of randomized controlled trials have found that green tea consumption for 3â€"6 months appears to lower systolic and diastolic blood pressures a small amount (about 3 mm Hg each).

Glycemic control

Green tea consumption lowers fasting blood sugar but in clinical studies the beverage's effect on hemoglobin A1c and fasting insulin levels was inconsistent.

Hyperlipidemia

Drinking green tea or taking green tea supplements decreases the blood concentration of total cholesterol (about 7 mg/dL), LDL cholesterol (about 2 mg/dL), and does not affect the concentration of HDL cholesterol. 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.

Inflammation

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).

Mortality risk

Daily consumption of green tea is significantly correlated with a lower risk of death from any cause; an increase of one cup of green tea per day is linked with a 4% lower risk of death from any cause. A separate analysis found an increase of three cups of green tea per day was associated with a lower risk of death from any cause.

Weight loss

There is no conclusive evidence that green tea aids in weight loss.

Toxicity

Moderate, regular, and habitual consumption of green tea is safe; however, there are reports of liver toxicity in humans after consuming high doses (10â€"29 mg/kg/day) of green tea extract dietary supplements, and high doses may act as a pro-oxidant to damage DNA.

Production

Growing, harvesting and processing

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 âˆ' 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 the 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. Sun-drying, basket or charcoal firing, or pan-firing are common artisanal methods. Oven-drying, tumbling, or steaming are common modern methods. Processed green teas, known as aracha are stored under low humidity refrigeration in 30- or 60-kg paper bags at 0â€"5 °C (32â€"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 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 blending order by the tasters and packed for sale.

Production by country

Import of Japanese tea

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 as a result of the Fukushima Daiichi nuclear disaster, 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). 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. 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."

Green tea by country

China

Loose leaf green tea has been the most popular form of tea in China since the Southern Song dynasty. 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. Other processes employed in China today include oven-firing, basket-firing, tumble-drying and sun-drying. Green tea is the most widely produced form of tea produced in China, with 1.42 million tons grown in 2014.

Popular or well-known Chinese green teas today include:

• Longjing tea
• Biluochun
• Gunpowder tea
• Huangshan Maofeng
• Maojian tea
• Chun Mee
• Lu'an Melon Seed tea
• Taiping houkui

Japan

Korea

Green tea, called nokcha (녹차; 綠茶) in Korean, 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).

• Ujeon (ìš°ì „; 雨前; lit. "pre-rain")
  Ujeon, or cheonmul-cha (첫물차; lit. "first flush tea"), is made of hand-picked leaves plucked before gogu (20â€"21 April). The ideal steeping temperature for ujeon tea is 50 °C (122 °F).
• Sejak (세ìž'; 細雀; lit. "thin sparrow")
  Sejak, or dumul-cha (ë'ë¬¼ì°¨; lit. "second flush tea"), is made of hand-picked leaves plucked after gogu (20â€"21 April) but before ipha (5â€"6 May). The tea is also called jakseol (ìž'설; 雀舌; lit. "sparrow tongue") as the tea leaves are plucked when they are about the size of a sparrow's tongue. The ideal steeping temperature for sejak tea is 60â€"70 °C (140â€"158 °F).
• Jungjak (ì¤'ìž'; 中雀; lit. "medium sparrow")
  Jungjak, or semul-cha (세물차; lit. "third flush tea"), is made of leaves plucked after ipha (5â€"6 May) until the mid May. The ideal steeping temperature for jungjak tea is 70â€"80 °C (158â€"176 °F).
• Daejak (대ìž'; 大雀; lit. "big sparrow")
  Daejak, or kkeunmul-cha (끝물차; lit. "final flush tea"), is made of tea leaves plucked in late May and after. It is usually made into tea bags or used in cooking. The ideal steeping temperature for daejak tea is 80â€"90 °C (176â€"194 °F).

The mode of preparation also differs:

• ipcha (잎차; lit. "leaf tea") or yeopcha (엽차; è'‰èŒ¶; lit. "leaf tea")
  The synonyms ipcha and yeopcha refer to loose leaf tea, often in contrast to tea in tea bags. As the words mean "leaf tea", they can also be used in contrast to powdered tea.
• garucha (가루차; lit. "powder tea") or malcha (말차; 末茶; lit. "powder tea")
  The synonyms garucha and malcha refer to powdered tea.

Leaf teas are processed either by roasting or steaming.

• deokkeum-cha (덖음차; lit. "roasted tea") or bucho-cha (부초차; 麩ç‚'茶; lit. "roasted tea")
  Roasting is the most common and traditional way of tea processing in Korea. Also translated into "pan-fried tea", the roasted tea varieties are richer in flavour.
• jeungje-cha (증제차; è'¸è£½èŒ¶; lit. "steamed tea")
  Steaming is less popular in Korean tea processing, but the method is used in temple cuisine. Tea prepared with steamed tea leaves are more vivid in colour.

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.

• Banya-cha (반야차; 般若茶; lit. "prajñā tea")
  It is one of the most renowned Korean green tea. The steamed tea is developed by Buddhist monks in Boseong. The tea is grown on sandy loam near mountains and sea. The word banya is a Korean transliteration of the Buddhist concept prajñā.
• Jungno-cha (죽로차; 竹露茶; lit. "bamboo dew tea")
  It is one of the most renowned Korean green tea. The roasted variety of tea is made of tea leaves grown among the bamboo in Gimhae, Hadong, and Jinju in South Gyeongsang Province.

Green tea can be blended with other ingredients.

• hyeonmi-nokcha (현미녹차; 玄米綠茶; lit. "brown rice green tea")
  nokcha (green tea) blended with hyeonmi-cha (brown rice tea)
• remon-nokcha (레몬 녹차; lit. "lemon green tea")
  nokcha (green tea) blended with lemon

Other countries