Theanine /ˈθiːəniːn/, also known as L-γ-glutamylethylamide and N5-ethyl-L-glutamine (see box for more synonyms), is an amino acid analogue of the proteinogenic amino acids L-glutamate and L-glutamine and is found primarily in particular plant and fungal species. It was discovered as a constituent of a green tea in 1949; in 1950 it was isolated from gyokuro leaves, which have high theanine content. Appearance of the name "theanine" without a prefix can be understood to imply the L-enantiomer; this is the form found in fresh teas and in some, but not all human dietary supplements; the opposite D-enantiomer has far less studied pharmacologic properties, but is present in racemic chemical preparations, and substantially in some studied theanine supplements.
Wiki is paranoid about allowing unproven medical advice being published but do say this:
Theanine increases serotonin, dopamine, GABA, and glycine levels in various areas of the brain, as well as BDNF and NGF levels in certain brain areas. However, 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 glutamate excitotoxicity.
This is from a site advertising a product containing it:
XXXXX® (L-Theanine 99% Pure)
L-theanine, an amino acid found in green tea, produces a pronounced feeling of tranquility in as little as fifteen (15) minutes. L-theanine increases the activity of GABA, a neurotransmitter (i.e. natural messenger in the brain) that promotes relaxation and reduces anxiety. L-theanine also stimulates the release of dopamine, a neurotransmitter responsible for confidence and a sense of well-being.
Could this be of interest and if so has anyone studied it further?