To understand the truth behind the medical claims for green tea and the antioxidant properties of EGCG, it is first necessary to have a close look at what green tea is, and why these claims are being made.
Green tea is a form of tea made from the leaves of the Carmellia Sinensis, a shrub that is native to China and has spread to other areas of Asia including Japan and the Middle East. Drinking it is believed to impart many health benefits, including the prevention of obesity, heart disease and some forms of cancer and it has been used in traditional Chinese medicine for over 400 years.
Tea is known to have been consumed in China for around 5,000 years, and used, not only in Chinese medicine, but also in that of Japan, Thailand and India for a number of ailments including regulating blood sugar, treating wounds and digestive problems. The drinking of green tea to benefit the heart and other vital organs is described in the Kissa Yojoki (Book of Tea), written in 1191 by Eisai, a Japanese Zen priest.
This two-part book talks about the various medicinal benefits of green tea, such as preventing fatigue, curing beriberi, quenching thirst, clearing the thoughts, maintaining health of the urinary tract and improving digestive problems. It also explains how to grow tea and how to prepare and use the leaves. The methods of treatment of various ailments and medical conditions are described in the second part of the book.