Written by Vitaminstuff :
Theanine (gamma-glutamylethylamide, or 5-N-ethyl-glutamine) is a glutamic acid analog or amino acid derivative commonly found in tea (infusions of Camellia sinensis), and also in the basidiomycete mushroom Boletus badius. In 1950 the Tea laboratory of Kyoto successfully separated theanine from Gyokuro leaf, which has the highest theanine content among all teas. Theanine is an analog to glutamine and glutamate, and can cross the blood-brain barrier.
Able to cross the blood-brain barrier, theanine has psychoactive properties. Theanine has been shown to reduce mental and physical stress, and improves cognition and mood in a synergistic manner with caffeine.
While structurally related to the excitatory neurotransmitter glutamate, theanine only has weak affinity for the glutamate receptor on post-synaptic cells. Rather, its primary effect seems to increase the overall level of the brain inhibitory transmitter GABA. Theanine also increases brain dopamine levels and has micromolar affinities for AMPA, kainate and NMDA receptors. Its effect on serotonin is still a matter of debate in the scientific community, with studies showing increases and decreases in brain serotonin levels using similar experimental protocols. It has also been found that injecting spontaneously hypertensive mice with theanine significantly lowered levels of 5-hydroxyindoles in the brain. Researchers also speculate that it may inhibit glutamic acid excitotoxicity. Theanine also promotes alpha wave production in the brain.
Studies on test rats have shown that even repeated, extremely high doses of theanine cause little to no harmful psychological or physical effects. Theanine showed neuroprotective effects in one rat study. Several beverage manufacturers are selling drinks containing theanine and are marketing them as drinks that help people focus and concentrate, while other manufacturers claim relaxing and tranquillizing properties.
L-Theanine may help the body’s immune response to 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.
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