Green tea has been shown to mildly lower total cholesterol levels and improve the cholesterol profile (decreasing LDL “bad” cholesterol and increasing HDL “good” cholesterol) in most,2 3 4 5 but not all,6 studies. Green tea may also promote cardiovascular health by making platelets in the blood less sticky.
Green tea has also been shown to protect against damage to LDL (“bad”) cholesterol caused by oxygen.7 Consumption of green tea increases antioxidant activity in the blood.8 Oxidative damage to LDL can promote atherosclerosis. While population studies have suggested that consumption of green tea is associated with protection against atherosclerosis,9 the evidence is still preliminary
Green tea polyphenols have been shown to stimulate the production of several immune system cells, and have topical antibacterial properties—even against the bacteria that cause dental plaque.22 23 24
One study found that intake of 10 cups or more of green tea per day improved blood test results, indicating protection against liver damage.25 Further studies are needed to determine if taking green tea helps those with liver diseases.
Tea flavonoids given by capsule reduced fecal odor and favorably altered the gut bacteria in elderly Japanese with feeding tubes living in nursing homes.26 The study was repeated in bedridden elderly not on feeding tubes, and green tea was again shown to improve their gut bacteria.27 These studies raise the possibility of using green tea in other settings where gut bacteria are disturbed, such as after taking antibiotics. Further studies are needed to clarify the role of green tea in this respect, however.
High-tannin tea has been shown to reduce the need for blood removal from people with iron overload, or hemochromatosis, in an open study.28 The tea had to be taken with meals and without lemon or milk to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption.
How much is usually taken? Much of the research documenting the health benefits of green tea is based on the amount of green tea typically consumed in Asian countries—about 3 cups (750 ml) per day (providing 240–320 mg of polyphenols).29 However, other research suggests as much as 10 cups (2,500 ml) per day is necessary to obtain noticeable benefits from green tea ingestion.30 31 To brew green tea, 1 teaspoon (5 grams) of green tea leaves are combined with 1 cup (250 ml) of boiling water and steeped for three minutes. Decaffeinated tea is recommended to reduce the side effects associated with caffeine, including anxiety and insomnia. Tablets and capsules containing standardized extracts of polyphenols, particularly EGCG, are available. Some provide up to 97% polyphenol content—which is equivalent to drinking 4 cups (1,000 ml) of tea. Many of these standardized products are decaffeinated.
i found these studies at
http://www.mycustompak.com/healthNotes/Herb/Green_Tea.htm