Also known as Camellia sinensis.
There are only three categories of teas; green, oolong, and black. Each of these is the leaf of Camellia sinensis and differs only in duration of fermentation. ‘Black’ is fully fermented, ‘oolong’ is partially fermented, and ‘green’ is not fermented at all, only steamed (types of tea such as Ceylon and Darjeeling refer to the region in which they are grown).
Green tea has greater health benefits because, as the leaves are steamed, the polyphenol Epigallocatechin gallate (EGCG) is prevented from being oxidised. By contrast, black and oolong tea leaves are made from fermented leaves, which results in the EGCG being converted into other compounds that are not nearly as effective in preventing and fighting various diseases.
EGCG is a powerful antioxidant - at least 100 more times more effective than vitamin C, and 25 times more effective than vitamin E, at protecting cells and DNA from damage believed to be linked to heart disease, and other serious illnesses. This antioxidant also has twice the benefits of resveratrol, found in high amounts in red wine.
There are four primary polyphenols in green tea and they are often collectively referred to as catechins. Powerful antioxidants, catechins have been shown in recent studies to fight viruses, slow aging and destroy free radicals that damage cells, leaving the body susceptible to degenerative diseases.
Benefits of green tea:
Reduces high blood pressure - drinking green tea represses angiotensin II, which leads to high blood pressure
Lowers blood sugar - green tea polyphenols and polysaccharides are effective in lowering blood sugar
Lowers cholesterol levels - Preliminary studies suggest that theaflavins and other flavonoids found in green tea block the production of cholesterol in the body, and increase cholesterol excretion Prevents tooth decay - the bacteria-destroying abilities of green tea can help prevent food poisoning and it can also kill the bacteria that causes dental plaque.
Helps lose weight - new evidence is emerging that green tea can help dieters. It has been shown to metabolise fat and one recent study found that men who were given a combination of caffeine and green tea extract burned significantly more calories than those given only caffeine, or a placebo.