The tea plant is a large shrub with evergreen leaves. It originally came from China, where it has been used for more than 5,000 years. 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.