L-theanine, an amino acid found predominantly in tea, is able to cross the blood-brain barrier and influence brain function. By attaching to receptors in the brain, the inhibitory neurotransmitter GABA activates the receptors, causing a relaxation effect that can reduce stress and produce beneficial effects.
Anti-Psychotic
L-theanine has anti-psychotic properties, according to a study by M.S. Ritsner et al., at the Israel Institute of Technology, Haifa, Israel. In an eight-week trial, study participants with schizophrenia took 400 mg of L-theanine per day in addition to their ongoing antipsychotic treatment. The researchers reported reduced levels of anxiety in the participants, based on the Hamilton Anxiety Rating Scale, and modest to moderate improvements in scores on psychopathology evaluation tests. The study was published in the January 2011 "Journal of Clinical Psychiatry." Theanine was safe and well-tolerated in the study.
Synergistic With Drug
A study conducted at the U.S. Army Graduate Program in Anesthesia Nursing, Fort Hood, Texas, found L-theanine reduced anxiety in laboratory rats. In the study, rats that took L-theanine showed lower anxiety levels in maze tests than control rats that did not receive L-theanine. The researchers also noted that L-theanine had a synergistic effect when taken together with the sedative drug midazolam, but that L-theanine does not work by modulating the inhibitory brain neurotransmitter GABA. The study was published in the December 2009 "AANA Journal."
Acute Anxiety
Acute anxiety does not respond well to treatment with L-theanine, according to research by K. Lu et al., at the Brain Sciences Institute, Victoria, Australia. However, the anti-anxiety drug alprazolam did not fare well in the anxiety study either. Participants took either 200 mg of L-theanine or 1 mg of alprazolam and results were assessed under relaxed conditions as well as under conditions of induced anxiety. Although L-theanine produced anti-anxiety effects during the relaxed conditions, alprazolam was ineffective during both phases of the experiment. The study was published in the October 2004 "Human Psychopharmacology" journal.
Decrease Over-Stimulation
L-theanine may alleviate anxiety by inhibiting the barrage of brain excitation associated with anxiety states, according to a study published in the January 2007 "Biological Psychology" journal. The experiment was carried out by using an arithmetic test to induce anxiety in the study participants, who took L-theanine at the start of the testing procedure. Participants who received L-theanine showed reduced heart rate and immune stress response markers when compared with a control group that did not take L-theanine, say researchers K. Kimura et al., at Nagoya University Department of Psychology, Nagoya, Japan.
References
- "Journal of Clinical Psychiatry": L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study; Ritsner MS, Jan. 2011
- "AANA Journal": Anxiolytic effects of L-theanine--a component of green tea--when combined with midazolam, in the male Sprague-Dawley rat; Heese T, Dec. 2009
- "Human Psychopharmacology": The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans; Lu K; Oct. 2004
- "Biological Psychology": L-Theanine reduces psychological and physiological stress responses; Kimura K; Jan. 2007
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