Both green and black teas have an estimated 10 times the antioxidant levels as most fruits and vegetables, including thearubigins, epicatechins, and catechins - all are considered polyphenols, a powerful type of antioxidant.
The difference between green and black teas, both from the same plant is mainly due to processing. Green tea leaves are dried and steam cured. Black tea leaves are crushed and fermented.
Numerous studies have shown that regular tea consumption improves LDL cholesterol levels and may protect against a variety of maladies. In laboratory test, green tea caused cancerous cells in rats to accelerate their lifecycle and then atrophy. Theorists believe that the antioxidant properties of tea prevent free radicals from attaching to healthy cellular tissues and beginning to homeostasize. Accumulation of free radicals is linked to blood vessel/valve damage, atherosclerosis, and cancers.
For example, in a study involving bladder cancer cells, green tea extract seemed to make the cancer cells behave oddly. They matured sooner, bound together tightly, and had a hard time multiplying. Another study found that men who drank oolong tea plus green tea extract lost more weight and total body fat, compared with men who drank plain oolong tea.
Other small studies have found that the antioxidants from drinking tea can help prevent skin cancer. There's also evidence that tea extracts applied to the skin can block sun damage that leads to skin cancer. Tea extracts have become an in-demand ingredient for various skin lotions and anti-aging treatments.
According to Dr. Jeffrey Blumberg at Tufts University, "Tea has no calories and lots of polyphenols. If you're drinking tea, you're not drinking soda, and that's a real benefit. Water doesn't give you those polyphenols."
What's the right amount?
Some benefit can be achieved with as little as two cups per day, while some tea cognoscenti (including medical researchers) drink eight to ten or more cups per day.