title: L-Theanine reduces psychological and physiological stress responses.
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.
authors.affiliation: Nagoya University Department of Psychology, Chikusa-ku, Nagoya, 464-8601, Japan. s050308d@mbox.nagoya-u.ac.jp
authors.forename: Kenta
authors.initials: K
authors.lastname: Kimura
authors.forename: Makoto
authors.initials: M
authors.lastname: Ozeki
authors.forename: Lekh Raj
authors.initials: LR
authors.lastname: Juneja
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohira
mesh_terms: D000208:Acute Disease; D000328:Adult; D001921:Brain / Q000378:metabolism; D003071:Cognition / Q000187:drug effects; D004311:Double-Blind Method; D004562:Electrocardiography; D005260:Female; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D011598:Psychoneuroimmunology / Q000379:methods*; D017470:Receptors, Glutamate / Q000378:metabolism; D012463:Saliva / Q000737:chemistry; D013315:Stress, Psychological / Q000188:drug therapy* / Q000276:immunology*; D013564:Sympathetic Nervous System / Q000187:drug effects
chemical_list: D005971:Glutamates; D007070:Immunoglobulin A; D017470:Receptors, Glutamate; D018698:Glutamic Acid; C026166:theanine