Theanine

Theanine (<img alt="play" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Loudspeaker.svg/11px-Loudspeaker.svg.png" width="11" height="11" /> <a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English#Key" title="Wikipedia:IPA for English" >ˈθiːəniːn</a><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English" >/</a>), also gamma-glutamylethylamide or 5-N-ethyl-glutamine, is an <a href="http://en.wikipedia.org/wiki/Amino_acid" title="Amino acid" >amino acid</a> and a <a href="http://en.wikipedia.org/wiki/Glutamic_acid" title="Glutamic acid" >glutamic acid</a> analog commonly found in <a href="http://en.wikipedia.org/wiki/Tea" title="Tea" >tea</a> (infusions of <a href="http://en.wikipedia.org/wiki/Camellia_sinensis" title="Camellia sinensis" >Camellia sinensis</a>), primarily in <a href="http://en.wikipedia.org/wiki/Green_tea" title="Green tea" >green tea</a>,<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-0" >[1]</a> and also in the basidiomycete mushroom <a href="http://en.wikipedia.org/wiki/Boletus_badius" title="Boletus badius" >Boletus badius</a> and in <a href="http://en.wikipedia.org/wiki/Ilex_guayusa" title="Ilex guayusa" >guayusa</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-casimir-1" >[2]</a> More specifically, this compound is called L-theanine, being the L- amino acid (note: this is different than being the <a href="http://en.wikipedia.org/wiki/Levorotatory" title="Levorotatory" class="mw-redirect" >levorotatory</a> <a href="http://en.wikipedia.org/wiki/Enantiomer" title="Enantiomer" >enantiomer</a>). In 1950, the tea laboratory of Kyoto successfully separated theanine from <a href="http://en.wikipedia.org/wiki/Gyokuro" title="Gyokuro" >gyokuro</a> leaf, which has high theanine content. Theanine is an <a href="http://en.wikipedia.org/wiki/Structural_analog" title="Structural analog" >analog</a> to <a href="http://en.wikipedia.org/wiki/Glutamine" title="Glutamine" >glutamine</a> and <a href="http://en.wikipedia.org/wiki/Glutamate" title="Glutamate" class="mw-redirect" >glutamate</a>, and can cross the <a href="http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier" title="Blood–brain barrier" >blood–brain barrier</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-yokogoshi-2" >[3]</a> It is sold in the US as a dietary supplement, and is FDA confirmed as <a href="http://en.wikipedia.org/wiki/Generally_recognized_as_safe" title="Generally recognized as safe" >generally recognized as safe</a> (GRAS).<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-3" >[4]</a> The Japanese Ministry of Health and Welfare approved the use of theanine for universal consumption in 1964.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-4" >[5]</a>

<h2 >Effects on the brain</h2>

Able to cross the <a href="http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier" title="Blood–brain barrier" >blood–brain barrier</a>, theanine has <a href="http://en.wikipedia.org/wiki/Psychoactive_drug" title="Psychoactive drug" >psychoactive</a> properties.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-gomez-5" >[6]</a> Theanine has been shown to reduce mental and physical<a href="http://en.wikipedia.org/wiki/Stress_(medicine)" title="Stress (medicine)" class="mw-redirect" >stress</a>,<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-kimura-6" >[7]</a> and improves cognition<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-7" >[8]</a> and mood in a synergistic manner with <a href="http://en.wikipedia.org/wiki/Caffeine" title="Caffeine" >caffeine</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-pmid18006208-8" >[9]</a><a href="http://en.wikipedia.org/wiki/Theanine#cite_note-9" >[10]</a>

While structurally related to the excitatory neurotransmitter glutamate, theanine only has weak affinity for the glutamate receptor on postsynaptic cells.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-10" >[11]</a> Rather, its primary effect seems to increase the overall level of the brain inhibitory transmitter <a href="http://en.wikipedia.org/wiki/GABA" title="GABA" class="mw-redirect" >GABA</a>. Theanine also increases brain <a href="http://en.wikipedia.org/wiki/Dopamine" title="Dopamine" >dopamine</a> levels and has a low affinity for <a href="http://en.wikipedia.org/wiki/AMPA_receptor" title="AMPA receptor" >AMPA</a>, <a href="http://en.wikipedia.org/wiki/Kainate_receptor" title="Kainate receptor" >kainate</a> and <a href="http://en.wikipedia.org/wiki/NMDA_receptor" title="NMDA receptor" >NMDA receptors</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-nathan-11" >[12]</a> Its effect on <a href="http://en.wikipedia.org/wiki/Serotonin" title="Serotonin" >serotonin</a> is still a matter of debate in the scientific community, with studies showing increases and decreases in brain serotonin levels using similar experimental protocols.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-12" >[13]</a><a href="http://en.wikipedia.org/wiki/Theanine#cite_note-13" >[14]</a> It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of <a href="http://en.wikipedia.org/w/index.php?title=5-hydroxyindole&action=edit&redlink=1" class="new" title="5-hydroxyindole (page does not exist)" >5-hydroxyindoles</a> in the brain.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-yokogoshi-5hydroxyindoles-14" >[15]</a> Researchers also speculate it may inhibit <a href="http://en.wikipedia.org/wiki/Glutamic_acid" title="Glutamic acid" >glutamic acid</a> <a href="http://en.wikipedia.org/wiki/Excitotoxicity" title="Excitotoxicity" >excitotoxicity</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-nathan-11" >[12]</a> Theanine also promotes <a href="http://en.wikipedia.org/wiki/Alpha_wave" title="Alpha wave" >alpha wave</a> production in the brain.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-gomez-5" >[6]</a>

Studies on test rats have shown even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-borzelleca-15" >[16]</a> Theanine showed neuroprotective effects in one rat study.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-pmid17705146-16" >[17]</a>

A placebo-controlled trial has shown adding theanine to ongoing <a href="http://en.wikipedia.org/wiki/Antipsychotic" title="Antipsychotic" >antipsychotic</a> medication is helpful in reducing some symptoms of<a href="http://en.wikipedia.org/wiki/Schizophrenia" title="Schizophrenia" >schizophrenia</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-BfR-17" >[18]</a>

Several beverage manufacturers are selling drinks containing theanine and are marketing them as drinks to help people focus and concentrate,<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-18" >[19]</a> while other manufacturers claim relaxing and tranquillizing properties.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-BfR-17" >[18]</a>

<h2 >Immune system benefits</h2>

L-Theanine may help the body's immune response to infection by boosting the disease-fighting capacity of gamma delta <a href="http://en.wikipedia.org/wiki/T_cells" title="T cells" class="mw-redirect" >T cells</a>. The study, published in 2003 by the <a href="http://en.wikipedia.org/wiki/Brigham_and_Women%27s_Hospital" title="Brigham and Women's Hospital" >Brigham and Women's Hospital</a>, 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 the production of antibacterial proteins was up to five times higher in the tea drinkers, an indicator of a stronger immune response.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-19" >[20]</a>

<h2 >[<a href="http://en.wikipedia.org/w/index.php?title=Theanine&action=edit&section=3" title="Edit section: As a supplement" >edit</a>]As a supplement</h2>

In 2003, the German Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung, BfR) objected to the addition of isolated theanine to beverages. The institute stated the amount of theanine consumed by regular drinkers of tea or coffee is virtually impossible to determine. While it was estimated the quantity of <a href="http://en.wikipedia.org/wiki/Green_tea" title="Green tea" >green tea</a> consumed by the average Japanese tea drinker per day contains about 20 mg of the substance, there are no studies measuring the amount of theanine being extracted by typical preparation methods, or the percentage lost by discarding the first infusion. Therefore, with the Japanese being exposed to possibly much less than 20 mg per day, and Europeans presumably even less,<a href="http://en.wikipedia.org/wiki/Pharmacological" title="Pharmacological" class="mw-redirect" >pharmacological</a> reactions to drinks typically containing 50 mg of theanine per 500 millilitres cannot be excluded, in the opinion of the BfR. Such reactions could include impairment of <a href="http://en.wikipedia.org/wiki/Psychomotor" title="Psychomotor" >psychomotor</a> skills and amplification of the <a href="http://en.wikipedia.org/wiki/Sedating" title="Sedating" class="mw-redirect" >sedating</a> effects of alcohol and <a href="http://en.wikipedia.org/wiki/Hypnotics" title="Hypnotics" class="mw-redirect" >hypnotics</a>.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-BfR-17" >[18]</a>

In 2006, a study found no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, <a href="http://en.wikipedia.org/wiki/Hematology" title="Hematology" >hematology</a>, or <a href="http://en.wikipedia.org/wiki/Urinalysis" title="Urinalysis" >urinalysis</a> in rats fed high doses of theanine for 13 weeks.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-borzelleca-15" >[16]</a> Large studies in humans have not been undertaken.

Theanine has also been found to be potentially useful for treating allergies and asthma in an animal model.<a href="http://en.wikipedia.org/wiki/Theanine#cite_note-20" >[21]</a>