Discussions of food normally focus on nutritional content and flavor. However, a great deal of attention is recently being paid to the role of food in bioregulation. Foods that possess such functions are called “functional foods.” Green tea, with its sweet aroma and eternally fresh taste, has been loved and consumed since its introduction to Japan centuries ago. But recent studies have scientifically proven the health-promoting effects of green tea. The healing properties of green tea are
the properties of leaf constituents, especially tea catechins. Nowadays, various functional foods and/or products containing tea catechins are produced and marketed commercially in Japan as well as overseas. To become informed about the functionality of such commercial products, it is necessary to trace the scientific history of green tea. In this chapter, we briefly review the history, health benefits, and industrial applications of green tea, with particular emphasis on the functional foods and products containing tea catechins.