A unique amino acid of green tea, L-Theanine, and its relaxation effect in humans

摘要

From old periods, it is said that drinking green tea brings relaxation. The essential substance, which causes a sense of relaxation, is theanine. Theanine is a unique amino acid as it is found almost solely in tea plants and the main component which is responsible for the exotic taste of green tea. It was found that L-theanine administered to rats intraperitoneally reached the brain within 30 min without any metabolic changes. Theanine also acts as a neutrotransmitter in the brain and decreased blood pressure in hypertension rats significantly. In general, animals always generate very weak electric pule on the surface of brain, called brain waves. Brain waves are classified into four types namely, #alpha#,#beta#,#delta# and #theta#-waves baed on the mental conditions. Generation of #alpha#-waves is considered as an index of relaxation. In human volunteers, #alpha#-waves were generated on the occipital and perietal regions of the brain surface within 40 min after the oral administration of theanine (50 approx 200 mg) by the mainfest relaxatoin without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine~TM (trade name of L-theanine) which offers tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress.