Hello Yogiman45, I'd like to point out perhaps your L-theanine dose many be too low I personally take 3,600mg a day in a 2:1:1 ratio so I maintain a ~1,600mg dose. Now I am not suggesting anyone go this high. However, it just makes it more plausible that higher doses may be still safe.
"Researchers in Korea conducted a randomized, double-blind, placebo-controlled study to look at the effect of L-theanine on memory and attention in 91 people with mild cognitive impairment. 6 Half of the participants were given
1,680 mg of L-theanine (LGNC-07) and the other half was given placebo for 16 weeks. Memory and word tests were conducted, as well as EEG tests. The researchers found that L-theanine improved memory and selective attention, as well as cognitive alertness." (Park SK, Jung IC, Lee WK, et al.)
"There have not been any side effects reported from taking L-theanine." (http://www.med.nyu.edu/content?ChunkIID=653856)
(At 200mg) "Some other studies that measure state anxiety fail to find a difference between theanine and placebo at this dose." (Effects of l-theanine on attention and reaction time response)
"L-theanine has failed to produce toxicity in rats at either 6,500mg/kg for 2 weeks or 2,000mg/kg over 28 days." (Suntheanine: A pure and safe L-theanine dietary supplement for relaxation and stress relief)
"L-Theanine at an oral dose of 2,000-8,000mg/kg in rats (human estimated dose of 320-1280mg/kg) cause a dose dependent increase in brain tryptophan and reduction of serotonin, reaching 20.5% and 15.5% at the highest dose" (Yokogoshi H, Mochizuki M, Saitoh K. Theanine-induced reduction of brain serotonin concentration in rats. Biosci Biotechnol Biochem. (1998))
My conclusions, based on this body of evidence, is that one may consider increasing the dose of l-theanine beyond what typical "vitamin store" (Aka GNC, Vitamin Shoppe) formulations carry. While far from snakeoil, all too common inadequate dosing simply won't work.
