Green Tea - Teas That Promote Weight Loss

Green tea is made from the leaves from Camellia sinensis that have undergone minimal oxidation during processing. 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. 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

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.

A book written by Lu Yu in 600-900 AD (Tang Dynasty), "Tea Classic" (simplified Chinese: ??; traditional Chinese: ??; pinyin: cháj?ng), is considered important in green tea history. The Kissa Yojoki (????? 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 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

Chinese green tea

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 (????), as well as many other high-quality green teas.

• ????? Huiming

• ???? Kaihua Longding

• ???? Hua Ding

• ???? Qing Ding

• ???? Gunpowder

• Jiangsu Province

• ????? Rain Flower

• ???? Que She (Tongue of golden altar sparrow)

• ???? White Cloud

• 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.

• ?? Mao Feng tea

• ?? Cui Jian

• Hubei Province

• Henan Province

• Jiangxi Province

• ?? Gou Gu Nao

• ?? Yun Wu

• Anhui Province is home to several varieties of tea, including three Chinese famous teas. These are:

• ???? Huangshan Maofeng

• ???? Liuan Leaf

• ?? Hou Kui

• ?? Tun Lu

• ?? Huo Qing

• ??? Wuliqing

• Hyson

• Sichuan Province

• ???? Meng Ding Gan Lu

• ???? Baimei Green Tea

• Shaanxi Province

Japanese green tea

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

Japanese green tea is made from the Yabukita (???) 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 h?jicha, a Japanese roasted tea. Japanese green teas are categorized by the age of the leaves: young leaves are called sench 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. 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 (??, yame) region of Fukuoka Prefecture and from the Uji region of Kyoto. Uji has been producing Ujicha (Uji tea) for four hundred years, predating the prefectural 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.

• Sencha (??, decocted tea)

• Gyokuro (??, Jade Dew)

• Kabusecha (??, covered tea)

• Tamaryokucha (???, lit. ball green tea)

• Bancha (??, coarse tea)

• Kamairicha (???, pan-fired tea)

• By-product of Sencha or Gyokuro

• Other

Other green teas

• Green tea from Ceylon
• Kahwah

Research and health effects

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. 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. 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. 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.

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. 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. 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.

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. 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 this medication.

Cardiovascular disease

Green tea consumption may be associated with a reduced risk of stroke. 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). Additional analyses examining the effects of long-term green tea consumption on blood pressure have reached similar conclusions.

Glycemic control

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.

Hyperlipidemia

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. 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.

Weight loss

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

Toxicity

Moderate, regular, and habitual consumption of green tea is safe; however, there are reports of liver toxicity in humans after consuming high doses (10-29 mg/kg/day) of green tea extract dietary supplements. 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.

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 - 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. 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-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.

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, 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 Renh? 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."

See also

References

Array

Further reading

• "Green tea (Chinese tea)". Cancer Research UK. 7 January 2013. Retrieved December 2014. 
• "Green tea: the elixir of life or just hype?". NHS Choices. 12 June 2013. Retrieved December 2014. 
• Evans, John C. Tea in China: The History of China's National Drink. Greenwood Press, 1992. ISBN 978-0-313-28049-8
• Lam, K.C./Lam, K.S. The Way of Tea: The Sublime Art of Oriental Tea Drinking. Barron's Educational Series, 2002. ISBN 978-0-7641-1968-2

External links

• Green Tea (an overview from the University of Maryland Medical Center)
• NCCIH - Green Tea Side Effects and Cautions (From the National Center for Complementary and Integrative Health)
• WebMD review about the health benefits of green tea

Interesting Informations

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