All teas are made from the Camellia Sinensis tea plant, whose leaves produce the antioxidant chemical, polyphenol. Antioxidants seem to promote health by protecting normal cells from reactive, free radicals. Free radicals have been implicated in the damage that leads to cancers and other diseases.

The amount of polyphenol in a tea is related to the tea’s level of processing. Green tea, for instance, is the least processed tea – its leaves are simply steamed and dried before packaging. Oolong teas are partially fermented, whereas black teas are completely fermented before drying. This causes their leaves to be darker, and also cuts out some of the beneficial polyphenol. However, even Oolong and black teas have polyphenols. Ironically, herbal teas are not derived from this leaf and so do not have the same antioxidant benefits.