Today, tea is grown throughout Asia and parts of the Middle East and Africa. Black tea is more common in the United States. But black tea is fermented and not as healthy as green tea. Green tea is unfermented. The leaf buds and young leaves make the best green tea.
Tea contains the purine alkaloids caffeine, theophylline, and theobromine.
But the most important active ingredients are polyphenols, which are responsible for many of the therapeutic and preventive actions of green tea. Most green tea products are sold as dried leaf tea. There are also extracts made from the leaves and leaf buds. Green tea has 300 to 400 polyphenols and 50 to 100 mg caffeine per cup. How to Take It One of the active compounds in green tea is as effective as aspirin in keeping blood platelets from clumping together, which improves circulation.