Recent research indicates that tea contains compounds that may prevent certain cancers, reduce blood pressure, lower blood cholesterol, regulate intestinal function and help ward off heart disease. Drinking tea may also reduce tooth decay and gum disease. Studies conclude that tea "polyphenols" may be responsible. These polyphenols are present in black, green and oolong teas, in particular.

Polyphenols are thought to counteract destructive oxygen molecules known as free radicals. Free radicals play a role in the degenerative diseases such as cancer and heart disease. Polyphenols may prevent damage to DNA and may block the formation of carcinogens (or aid in their detoxification) and halt the out-of-control cell proliferation seen in cancer.

Catechins, a class of polyphenols found in tea, are seen as the most beneficial to health. Epigallocatechin (EgCg), the main constituent of green tea, may be the most interesting of all tea compounds. Green tea contains the highest level of catechins, but black and oolong teas also contain significant amounts of distinctive catechins with similar base attributes. Preliminary reports show that black and oolong teas are as beneficial as green tea. 

It also appears that tea drinking reduces plaque formation and bacterial infections in the mouth, since tea polyphenols are selectively bactericidal. For many of the world's people, tea plays a major role in maintaining fluid balance.The contribution tea makes to good health is one more compelling reason to drink tea.

Here's some tea-related term definitions you may find useful:

antioxidants:
Compounds which neutralize reactive oxygen molecules by donating or accepting hydrogen atoms, i.e., they suppress free radicals.

flavonoids:
Compounds that naturally occur in fruits, vegetables, and tea. They may modulate free radicals.

oxidants/free radicals:
Humans cannot survive without oxygen, yet the body is constantly impacted by toxic side effects of normal cell oxidation, resulting in oxidants/free radicals. These molecules are veritable "loose cannons" which circulate through the body and are capable of damaging cellular lipids, proteins, membranes and DNA.

phytochemicals:
Chemicals from a plant. Greek in origin, "phyto" means "to bring forth" and is used as a prefix to designate "from a plant".

polyphenols (also referred to as tannins):
Compounds abundant in tea, measuring up to 36% of dry weight. These compounds possess a series of phenolic rings which readily accept or donate hydrogen atoms, enabling them to function as anti-oxidants. They may act as "garbage collectors", disposing of mutagens and cancer causing agents and blocking tumor development.