Green tea is the unoxidized leaf of the tea plant, Camellia sinensis (black tea comes from the same plant but undergoes oxidation that darkens the leaves and changes their aroma, flavor, and polyphenol content). Tea polyphenols may help protect the body from cancer by destroying free radicals, and may protect the heart by lowering cholesterol and improving lipid metabolism. They also have significant anti-bacterial effects.
Black tea also has health benefits but delivers less antioxidant activity than green tea. The least processed tea, white tea (from China), is even higher in antioxidant activity than green tea but is more delicate to handle, doesn t have as much flavor and is often quite expensive.