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Theanine is a natural psychoactive compound belonging to non-protein α-amino acids, which can cross the blood-brain barrier. As an enantiomer with the L configuration, it abundantly occurs in green tea leaves of the Camellia sinensis species. In the human body, it favors an increase of GABA (an important "inhibitory" neurotransmitter) and promotes alpha-type brain wave activity. Thus, it easily introduces a state of relaxation, leading to a decrease in tension and a reduction of stress and anxiety.

L-theanine continues to amaze scientists. Recent research results have revealed new and exciting properties for this substance. Until now, it has been known mainly for its anxiolytic and relaxing effects. However, it turns out that the activity of L-theanine goes much further. Researchers suggest that it may potentially reduce the risk of stroke, whereas, in the event of its occurrence, the substance seems to reverse or significantly reduce its negative effects. What is more, L-theanine may also contribute to the reduction of schizophrenia symptoms.

L-theanine in the prophylaxis of ischemic stroke
Ischemic stroke means focal damage to the central nervous system and is a consequence of a sudden blockage of blood supply to the brain. This causes extreme excitotoxicity, i.e. a pathological process leading to damage and death of neurons [1]. An unpleasant consequence of this occurrence are various neurological defects. Experts argue that L-theanine can help prevent strokes as well as eliminate damage caused by cerebrovascular events.


Studies show that L-theanine can significantly improve the production of nitric oxide in endothelial cells of blood vessels [2]. Nitric oxide has extremely high biological activity. It is, e.g. a regulator of blood pressure, and thus it conditions proper blood pressure. Note that hypertension is one of the major risk factors for stroke.

It has been scientifically proven that L-theanine inhibits the expression of tumor necrosis factor-alpha (TNF-α), resulting in the limitation of the adhesion of various molecules to endothelial walls. Consequently, this decreases the risk of forming a blood clot which may block an artery and subsequently cut off blood flow to the brain [3].

Interesting conclusions were reached by scientists who checked the effect of L-theanine on animals that suffered a stroke. It has been proved that the administration of L-theanine within 12 hours of the occurrence of a cerebrovascular event protects neuronal necrosis and significantly reduces the size of damaged areas in the brain. Moreover, L-theanine therapy taken up to 24 hours after induction of stroke significantly improved the neurological condition of the animals tested [4].


The potential of L-theanine in relieving symptoms of schizophrenia
Schizophrenia is one of the most severe mental disorders. People affected by this disease experience various psychotic episodes (delusions, hallucinations), but also some emotional impairment, apathy, anxiety, withdrawal. In the medical world, there has been known for long the so-called glutamatergic hypothesis of schizophrenia according to which abnormal glutamate neurotransmission in the brain is responsible for the symptoms of the disease [5]. Given the structural similarity of L-theanine to glutamate, attempts have been made to include it in the treatment plan for patients with schizophrenia.

Three clinical studies were carried out with the participation of a total of 100 people with schizophrenia. One of them (randomized, placebo-controlled, double-blind study) encompassed 40 patients who, in addition to the standard prescription drugs, for eight weeks regularly received 400 mg of L-theanine or placebo. People who received L-theanine significantly reduced anxiety and improved psychopathological symptoms [6]. It turns out that positive changes, including those associated with the improvement of the quality of sleep in sick people, could be observed even at a dose of 250 mg L-theanine per day [7]. Though the studies were carried out on a relatively small scale, they give solid evidence to believe that L-theanine may soon prove to be a "dark horse" in the fight against the symptoms of this terrible disease.


Undoubtedly, L-theanine has enormous health-promoting potential. Until now, it has become famous mainly as an effective anti-stress and nootropic agent. Nevertheless, it is worth taking a closer look at L-theanine and keep track of the newest reports from the scientific world, because it may turn out to be helpful also in many other more serious problems.




  1. Sumathi T, Shobana C, Thangarajeswari M, et al. Protective effect of L-Theanine against aluminium induced neurotoxicity in cerebral cortex, hippocampus and cerebellum of rat brain - histopathological, and biochemical approach. Drug Chem Toxicol. 2015;38(1):22-31.
  2. Siamwala JH, Dias PM, Majumder S, et al. L-theanine promotes nitric oxide production in endothelial cells through eNOS phosphorylation. J Nutr Biochem. 2013;24(3):595-605.
  3. Yamagata K, Xie Y, Suzuki S, et al. Epigallocatechin-3-gallate inhibits VCAM-1 expression and apoptosis induction associated with LC3 expressions in TNFalpha-stimulated human endothelial cells. Phytomedicine. 2015;22(4):431-7.
  4. Zukhurova M, Prosvirnina M, Daineko A, et al. L-theanine administration results in neuroprotection and prevents glutamate receptor agonist-mediated injury in the rat model of cerebral ischemia-reperfusion. Phytother Res. 2013;27(9):1282-7.
  5. Plitman E, Nakajima S, de la Fuente-Sandoval C, et al. Glutamate-mediated excitotoxicity in schizophrenia: a review. Eur Neuropsychopharmacol. 2014;24(10):1591-605.
  6. Ritsner MS, Miodownik C, Ratner Y, et al. 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. J Clin Psychiatry. 2011;72(1):34-42.
  7. Ota M, Wakabayashi C, Sato N, et al. Effect of L-theanine on glutamatergic function in patients with schizophrenia. Acta Neuropsychiatr. 2015;27(5):291-6.


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