Theanine

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Theanine is an amino acid commonly found in tea (infusions of Camellia sinensis). Theanine is related to glutamine, and can cross the blood-brain barrier.^[1] Because it can enter the brain, theanine has psychoactive properties.^[2] Theanine has been shown to reduce mental and physical stress^[3] and may produce feelings of relaxation.^[4]

Theanine is speculated to produce these effects by increasing the level of gamma-aminobutyric acid (GABA) production. Theanine increases brain serotonin, dopamine, GABA levels and has micromolar affinities for AMPA, Kainate and NMDA receptors.^[5] It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of 5-hydroxyindole in the brain.^[6] Researchers also speculate that it may inhibit glutamic acid excitotoxicity.^[5] Theanine also promotes alpha wave production in the brain.^[2]

Studies on test rats have shown that even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects.^[7]

L-theanine may help the body's immune system response when fighting infection by boosting the disease-fighting capacity of gamma delta T cells. The study, published in 2003 by the Brigham and Women's Hospital, included a four-week trial with 11 coffee drinkers and 10 tea drinkers, who consumed 600 milliliters of coffee or black tea daily. Blood sample analysis found that the production of anti-bacterial proteins was up to five times higher in the tea-drinkers, an indicator of a stronger immune response.^[8]

Recently, marketing campaigns from tea companies have been emphasizing the natural presence of L-theanine in their tea and that L-theanine boosts the production of alpha brainwaves. ^[9]

See also

• gamma-Glutamylmethylamide

References