Author:
Juneja LR, Chu DC, Okubo T, Nagato Y, Yokogoshi H

Source:
Trends in Food Science & Technology. 1999;10:199-204.

Abstract:
Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. 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 brain within 30 min without any metabolic change. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure significantly in hypertensive rats. In general, animals always generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely a, ß, delta and theta-waves, based on mental conditions. Generation of a-waves is considered to be an index of relaxation. In human volunteers, a-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50-200mg), signifying relaxation without causing drowsiness.