L-theanine - a unique amino acid of green tea and its relaxation effect inhumans

Since ancient times, it has been said that drinking green tea brings relaxa tion. The substance that is responsible for a sense of relaxation, is thean ine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of 'green' tea. It was found that L-theanine administered intraperitoneally to rats reached the br ain within 30 min without any metabolic change. Theanine also acts as a neu rotransmitter in the brain and decreased blood pressure significantly in hy pertensive rats. In general, animals always generate very weak electric pul ses on the surface of the brain, called brain waves. Brain waves are classi fied into four types, namely alpha, beta, delta and theta-waves, based on m ental conditions. Generation of alpha-waves is considered to be an index of relaxation. In human volunteers, ar-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral admi nistration of theanine (50-200 mg), signifying relaxation without causing d rowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine(TM) (trade name of L-theanine) which offers a tremendous opportunity for designing foods and medical foods targeting re laxation and the reduction of stress. Taiyo Kagaku Co., Ltd, Japan won the 1998 'Food Ingredient Research Award' for development of Suntheanine(TM) at Food Ingredients in Europe (Frankfurt). The judges felt it was a particula rly well-documented and fascinating piece of research. (C) 1999 Published b y Elsevier Science Ltd. All rights reserved.