Green and black tea are both derived from the same plant, the tea plant.  This evergreen shrub or tree can grow to a height of 30 feet, but is usually pruned to a height of 2-3 feet.  The leaf bud and its two adjacent young leaves along with the stem are used medicinally.  An older leaf is considered to be of lower quality.

Green tea extract is produced by lightly steaming the fresh-cut leaf.  Black tea is made by allowing the leaves to oxidize, thereby converting the highly therapeutic polyphenols to less active compounds.  These polyphenols have potent antioxidant and anticancer properties.

Organic green tea has higher values of medicinal properties than other teas, because of the special way in which it is dried.

It was found that green tea extract resulted in a significant increase in energy expenditure (a measure of metabolism), plus also had a significant effect on fat oxidation. While some of the effects were originally theorized to be due to the caffeine content of green tea, the researchers discovered that the tea actually has properties that go beyond those that would be explained by the caffeine. The same amount of caffeine as was in the green tea, administered alone, failed to change energy expenditure in other studies. This led reseachers to believe that there is some interaction going on with the active ingredients of green tea that promotes increased metabolism and fat oxidation.

The researchers indicated that their findings have substantial implications for weight control. A 4% overall increase in 24-hour energy expenditure was attributed to the green tea extract, however, the research found that the extra expenditure took place during the daytime. This led them to conclude that, since thermogenesis (the body's own rate of burning calories) contributes 8-10% of daily energy expenditure in a typical cubject, that this 4% overall increase in energy expenditure due to the green tea actually translated to a 35-43% increase in daytime thermogenesis. Of critical importance to thyroid patients is the fact that none of the research subjects reported any side effects, and no significant differences in heart rates were noticed. In this respect, green tea extract is different from some of the prescription drugs for obesity, and herbal products like ephedra, which can raise heart rates and blood pressure, and are not recommended for many individuals, in particular, those with thyroid disease who may be particularly sensitive to stimulants.

Green tea nutrition may have health benefits which include preventing arthritis. Epidemiological studies show that people who drink green tea have significantly lower risks of many diseases, including cancer, heart disease and stroke. Laboratory studies show that green tea extract protects against, and may be an effective treatment for many common degenerative diseases.
The ability of green tea to prevent cancer is so well established that new studies are testing green tea as a potential cancer therapy. Green tea may be especially protective against lung cancer in former and current cigarette smokers. Its lung cancer protective effects are of significant importance based on new studies showing that former smokers are at greater risk for developing lung cancer than was previously thought.

However drinking green tea has been shown to provide the human body with numerous health enhancing components.