L-theanine is an amino acid derivative or analog of glutamic acid found naturally only in tea leaves and a few species of fungus. Biologists have discovered that L-theanine is able to cross the blood-brain barrier and affect the brain's neurochemistry. Subsequent research has suggested that L-theanine may be helpful in the treatment of conditions as varied as cancer, hypertension and depression. More research must be done before the efficacy of this compound can be determined, but early studies for some conditions are promising. You should talk with your doctor first before incorporating L-theanine into your treatment program.
Neurobiology of Depression
The neurotransmitter long believed to be responsible for regulating mood is serotonin. Found throughout the body, serotonin plays a role in other bodily functions as varied as digestion, body temperature and blood pressure. Since most antidepressant medications increase synaptic serotonin levels, it has been assumed that increasing serotonin levels in neural synapses will treat depression. Since the approval of antidepressants like tianepeptine, which elevate mood by lowering extra-cellular serotonin levels, this theory has been called into question. Nonetheless, despite the conflicted findings on whether L-theanine increases or decreases serotonin levels in the brain, L-theanine's established impact on serotonin levels has led some to believe that it may be helpful for depression.
Research
In 2005, Johns Hopkins issued a press release that offered an alternative model for the efficacy of antidepressant medications. This new model accounts for the discrepancy between the immediate effect of drugs like Paxil on brain serotonin levels and the four- to six-week period before the medication becomes effective. According to neuropathologist Dr. Vassilis Koliatsos, these drugs may promote the rewiring of parts of the limbic system in the frontal and partietal lobes responsible for mood by stimulating the growth of new serotonergic neurons. Research on the psychoactive activity of L-theanine has been the subject of several studies published in the journal "Biological Psychology." In the 2007 findings of the Nagoya University Department of Psychology, the authors found that biochemical stress indicators were lower in patients administered 200 mg of L-theanine than in those receiving a placebo. A later eight-week study by Dr. Michael Ritsner in the 2010 "Journal of Clinical Psychiatry" employed 400 mg of L-theanine in patients, finding that it significantly reduced anxiety, but the study made no mention of depression.
Analysis
L-Theanine is believed to produce the majority of its psychotherapeutic activity by increasing levels of extra-cellular GABA, the brain's sedative neurotransmitter and the pathway used by most anti-anxiety drugs. L-Theanine is also believed to affect serotonin levels in the brain, although there is as yet no consensus as to whether or not it promotes or inhibits serotonin synthesis. Regardless, treating L-theanine's net effect on serotonin levels as an indicator of its efficacy in the treatment of depression is unnecessarily reductionist. Clinical studies may provide a better indication of L-theanine's utility in treating depression and other conditions. There are no strong indications that L-theanine is useful in depression unless it is exacerbated by generalized anxiety disorder. The standard dose for the treatment of anxiety according to its monograph in the 2005 "Alternative Medicine Review" is 200 mg two to three times daily.
Safety
Since L-theanine is a relatively new therapeutic agent, you should talk to your doctor to assess the risks and benefits before taking this supplement. L-theanine does have an excellent safety record. According to Drugs.com, there are no known drug interactions or contraindications for the use of L-theanine, and the toxic dose is high enough that overdose is all but impossible. L-theanine is also classified as "Generally Recognized as Safe" by the United States Food and Drug Administration, although the administration makes no claims as to its efficacy.
References
- "Psychopharmacology"; Time for Tea: Mood, Blood Pressure and Cognitive Performance Effects of Caffeine and Theanine Administered Alone and Together; P.J. Rogers, et al; June 2008
- "Trends in Food Science and Technology"; Review: L-Theanine---A Unique Amino Acid of Green Tea and its Relaxation Effect in Humans; L.R. Juneja, et al; June 1999
- "Bioscience, Biotechnology, and Biochemistry"; Theanine-Induced Reduction of Brain Serotonin Concentration in Rats; H. Yokogoshi, et al; April 1998
- "Biological Psychology"; L-Theanine Reduces Psychological and Physiological Stress Responses; K. Kimura, et al; January 2007
- "Johns Hopkins Medicine";Popular Antidepressants Boost Brain Growth, Hopkins Scientists Report; Vassilis E. Koliatsos, M.D.; December 2005
- "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; M.S. Ritsner, et al; 2010
Member Comments