L-Theanine

 

-Relaxes without drowsiness
-Increases mental clarity and focus
-Reduces nervous tension
-Promotes mental calmness

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Biol Psychol. 2007 Jan;74(1):39-45. Epub 2006 Aug 22.
L-Theanine reduces psychological and physiological stress responses.
Kimura K, Ozeki M, Juneja LR, Ohira H.
Source
Nagoya University Department of Psychology, Chikusa-ku, Nagoya, 464-8601, Japan. s050308d@mbox.nagoya-u.ac.jp

Abstract
L-Theanine is an amino acid contained in green tea leaves which is known to block the binding of L-glutamic acid to glutamate receptors in the brain. Because the characteristics of L-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took L-Theanine at the start of an experimental procedure, one in which they took L-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.
PMID: 16930802