The leaf and bud of the camellia plant are the basis of both green and black tea. Unlike black tea, which is fermented, green tea is steamed dry immediately after harvesting, which leaves it with larger amounts of polyphenols. It's most effective polyphenol is epigallocatechin gallate (EGCG). Most of the benefits of green tea consumption appear to be preventive in nature. It is not known exactly how much you need to reap the potential benefits, but four cups a day or more may be required for benefit. Oolong tea has been "fermented" (or more accurately, "oxidized") more than green tea but less than black tea. Oolong tea is sometimes referred to as "semi-fermented". Decaffeinated green tea does have the same amount of EGCG as regular green tea. Check your local health food store for decaffeinated green tea capsules. Depending on the brand, one capsule can supply as much EGCG as four cups of tea.

Bottled tea and instant tea have few antioxidants, research shows. Herbal teas do not have the same health properties as real tea (Camellia sinensis). Tea with caffeine has slightly more antioxidant activity. Steep tea leaves or bags in hot water 3 to 5 minutes to thoroughly release antioxidants. Adding milk to tea does not block absorption of antioxidants, new Dutch research finds.