All teas appear to have health benefits but green tea (GT) may deliver more than common black or white teas because of GT’s unique contents. Although black, green, white and red tea are all made from the leaves of the same plant species, Camellia sinensis, it’s the way the leaves are processed after harvest that determine what type of tea it will become. Depending on harvest time, soil content and depth of processing, teas contain various ranges of polyphenols, notably flavonoids, which are considered to be the constituents of tea that yield its potential health benefits. One of the flavanoids contained in tea that’s thought to be responsible for most of its potential health benefits is the catechin epigallocatechin gallate (EGCG). Because of its unique catechin profile, green tea has received the most research. EGCG makes up anywhere from 10-50% of the total catechins contained in green tea. Among other positive biological activities, EGCG functions as a powerful antioxidant, with antioxidant activity up to 100 times greater than vitamins C & E. In fact, one cup of green tea may supply 10-40 mgs of polyphenols and has greater antioxidant activity than a serving of broccoli, spinach, carrots or strawberries. None of the other teas have exhibited this type of activity.
Below are noted potential benefits of specific amounts of GT catechins containing about 270 mg (equivalent to 4 cups of green tea depending on brewing time, harvest, etc.): ability to inhibit angiogenesis and to impair cell cycle progression (both actions may help ward off cancer growth); shown to induce glutathione S-transferase and to decrease the production of reactive oxygen species (or free radicals) thus demonstrating antioxidant qualities and possible reasons for its purported cardioprotective qualities, including lower LDL cholesterol in regular tea drinkers. Additionally, EGCG, at least in animal studies, has been shown to significantly decrease blood glucose, suggesting a potential role as an anti-diabetic agent.
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