Green tea antioxidants are the beneficial substances known as polyphenols that are being researched for their protective effects against cancer and heart disease. The polyphenols in green tea are a type of flavenoid called catechins. There are four types of catechins in green tea: epicatechin, epicatechin gallate, epigallocatechin, and apigallocatechin gallate, also known as EGCG. EGCG is the most powerful and most researched green tea antioxidant.
The three main types of teas are black, green, and oolong. These differ in how they are processed, which affects the levels of catechins in each type. Black contains around 4 percent catechins, oolong contains 24 percent, and green tea contains 27 percent catechins. Polyphenols make up as much as 30 percent of the weight of green tea leaves.
One cup of green tea has 10 to 200 milligrams (mg) of polyphenols. A variety of research has been conducted on green tea antioxidants, specifically ECGC. Green tea antioxidants are said to be 25 to 100 times more active than vitamin C and are available in much higher levels than other fruit and vegetable sources of polyphenols. Matcha green tea, a traditional green tea used in Japanese tea ceremonies, is believed to have the highest concentration of ECGC of all the types of green tea available.
Green tea antioxidants attack substances in the body known as free radicals, which cause aging, heart disease, and cancer. Although free radicals can occur naturally in the body, they are produced more rapidly in response to environmental substances like smoking and exposure to toxins in the environment.
Antioxidants are found in whole foods like fruits, vegetables, and grains. These substances neutralize free radicals while repairing tissue damage done by free radicals. The antioxidants in green tea are unique in that they appear to attack cancer in all its stages, from preventing cancer cells from forming to killing active cancer cells.
Some studies have shown ECGC to suppress growth of cancerous tumors, while others have had mixed results. Green tea antioxidants may have an effect at slowing cancer of the bladder, breast, and ovaries, as well as pancreas and prostate. Results are still inconclusive about effects on lung, esophageal, and colon cancer.
Green tea antioxidants have other benefits besides cancer prevention. Some research has shown increases in cognitive skills and learning ability in animal and human subjects. Green tea may also regulate glucose levels, lower total cholesterol, and raise HDL, or good, cholesterol levels. The flavenoids in green tea may also have antimicrobial properties.