L-theanine, an amino acid derivative also known as Y-glutamylcthylamide, is used in alternative medicine as a treatment for a wide variety of conditions including stress, anxiety, hypertension, sleep disturbance, insomnia, depression and some symptoms of schizophrenia. Research has only just begun on the therapeutic potential of L-theanine with regard to stress. As yet, no definitive evidence for its efficacy in the treatment of any condition exists. Talk with your doctor before taking products containing L-theanine.
Pharmacodynamics
Found naturally only in tea leaves and a few mushroom species, L-theanine can cross the blood-brain barrier, affecting a number of different neurochemical pathways. The majority of L-theanine's purported stress-reducing activity is believed to result from its stimulation of GABA, the brain's own inhibitory chemical. This is the same neurochemical pathway that Valium modifies to exert its anti-stress effects. L-theanine also may increase dopamine levels and moderate serotonin levels in other parts of the brain, although no research has been done on how this may affect L-theanine's supposed therapeutic activity.
Research
While most research on L-theanine suggests that it may have therapeutic potential for treating stress, there have been some conflicting results. While a 2007 study published by Dr. Kiriyama Kimura in "Biological Psychology" indicated that supplementing the diet with L-theanine may reduce the heart rate and stress hormones, a study by the same author later in the year questioned that finding. In 2010, a large-population study by Dr. Michael Ritsner in the "Journal of Clinical Psychiatry" did find that L-theanine used alongside existing medications produced a statistically significant reduction in stress and anxiety.
Side Effects and Interactions
No interactions are known to occur between over-the-counter or prescription drugs and supplements containing L-theanine. Although L-theanine may increase the action of sedative, anxiolytic or tranquilizing drugs, this must be considered speculative until more research is done. The incidence of side effects is rare. These can include headache, dizziness and digestive discomfort.
Safety Considerations
Although the suggested dose of L-theanine in many nutritional supplements is much larger than that generally available in foods, the U.S. Food and Drug Administration has reaffirmed its listing of L-theanine supplements as "Generally Recognized as Safe." A 2006 animal study in "Food Chemistry and Toxicology" lends credence to this, with the authors finding no adverse effects on food consumption, body weight, behavior, hematology, urinalysis, hematology, clinical chemistry, morbidity or mortality in rats given large doses of L-theanine for 13 weeks. According to Drugs.com, ingesting a dose of L-theanine large enough to be acutely toxic would be impractical. The safety of long-term therapy with L-theanine, however, cannot be determined until researchers conduct long-term studies in human populations.
References
- "Journal of Herbal Pharmacotherapy"; The Neuropharmacology of L-Theanine (N-ethyl-L-glutamine): A Possible Neuroprotective and Cognitive Enhancing Agent; P.J. Nathan, et al; 2006
- "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
- "Journal of Functional Foods"; Human Disposition of L-Theanine in Tea or Aqueous Solution; P.C. van der Pijla; October 2010
- "Biological Psychology"; L-Theanine Reduces Psychological and Physiological Stress Responses; K. Kimura, et al; January 2007
- "Biological Psychology"; The Effects of L-Theanine, Caffeine and Their Combination on Cognition and Mood; C.F. Haskell, et al; February 2008
- "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
