Green tea (Camellia sinensis)

Scientific names

According to the fermentation degree and plants sources, there are classifications as green tea, white tea, yellow tea, black tea and dark tea. With increasing fermentation, the number of bioactive elements decrease. Green tea is derived from Camellia sinensis, an evergreen shrub of the Theaceae family. It comes from the same plant as black tea but it is produced in a non-fermenting process thus is believed to be the strongest tea with the least loss of herbal elements.

Ingredients

The main active ingredients identified in green tea include polyphenolic compounds such as epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), which are thought to be responsible for their anti-carcinogenic and anti-mutagenic activity. Other polyphenols in green tea include flavanols and their glycosides and depsides such as cholorogenic acid, quinic acids, carotenoids, trigalloylglucose, lignin, protein, chlorophyll, minerals (depending on the soil content, aluminum and manganese), caffeine, and very small amount of methylxanthines.

Mechanism of action

Human studies on the pharmacokinetics of green tea polyphenols have been conducted. Polyphenols from green tea have been shown to be powerful antioxidants with anticarcinogenic properties. Studies have shown that ingested polyphenols and their metabolites play a role against gastrointestinal cancers. Catechins in green tea are rapidly absorbed and the addition of milk does not impair catechin bioavailability.

Prevalence

The medicinal use of green tea dates back to 4,700 years ago in China. Tea is the most popular beverage next to water around the world, and green tea accounts for 20% of tea consumption. It is particularly popular in China, Japan, and other South-East Asian countries.

Application/dosage/providers/cost

Green tea can be consumed in the form of a brewed beverage or as capsules containing green tea extract. Commercial products, or green tea for medicinal use, are provided by tea manufacturers or different pharmaceutical herbal medicine companies. Tea can also be used as dietary supplements in some countries. Currently, there is no established recommended dose for green tea extract. For cancer prevention, studies have examined the effects of habitually drinking between one to ten cups per day, although these findings require confirmation. The cost of tea is low.