The tea bush has been cultivated in East Asia for more than 2000 years. Green tea is prepared from the unfermented young leaves and buds of Camellia sinensis (L.) O. KUNTZE. Tea, along with coffee and mineral water, is one of the most popular beverages worldwide.
In the Western World green tea is known as a refreshing drink, while in East Asia its medicinal properties have been valued since ancient times.
Epidemiological observations record a significantly reduced incidence of cardiovascular diseases and cancer in populations which frequently consume green tea. In the last 15 years this has led to increased scientific interest in the various active components of green tea.
Active components of green tea
The traditional preparation is an infusion and contains a broad spectrum of active ingredients: polyphenols, methylxanthines, flavonols, amino acids and other components - which are characteristic of a multi-component method.
The monomeric polyphenol epigallocatechingallate (EGCG) is specific to green tea and has strong antioxidant properties. Its concentration is naturally high and unlike black tea, no fermentation has taken place. As a result the monomeric polyphenols almost completely preserve their native form. The ORAC value is 5000-6000 micromol TE/g (in comparison Vitamin C is: 3000 micromol TE/g). This confirms the strong antioxidant properties of green tea.
The dominant xanthine, caffeine, has a dosedependent stimulating effect on the central nervous system and enhances lipolysis and increases diuresis. Despite its caffeine content, green tea is better tolerated than coffee, since the caffeine content is considerably lower. The second xanthine is theobromine, its effects are similar to caffeine but without the stimulatory effect on the central nervous system.
Theanine (glutamic acid ethylamide) is an amino acid which is only found in the tea shrub and has mood-balancing properties. Researchers in Japan have discovered that theanine influences the glutamic acid receptors in the cerebral cortex and therefore brings about a feeling of relaxation.