Theanine: Does it Work? (Supplements: Reviewing the Evidence)

This is a standard procedure and ensures unbiased comparison across conditions. However, in the case of the present data, the variance in behavioral measures arising from the day of testing order effect far superseded that arising from treatment. Thus, a normalization of these measures was necessary to remove the variance caused by practice, and this was carried out by transforming each data point to a z -score with respect to the mean and SD of all scores measured on that day d 1, d 2, d 3, d 4.

Because the distribution of scores for each day contains an equal number of data points from each treatment, it cannot result in any bias for treatment but, rather, optimizes statistical power to test for treatment effects.

Summary of Theanine

Mean alpha amplitude was calculated using the temporal spectral evolution TSE technique TSE is carried out simply by filtering each epoch with a passband of 8—14 Hz, rectifying, then averaging across trials. The averaged TSE waveforms were then smoothed by averaging data points within a sliding ms window.

The first analysis concerned tonic background alpha amplitude, which was found to decrease on L-theanine in our previous 2 studies 18 , M. The dependent measure was computed as the baseline alpha amplitude averaged across 6 electrodes, chosen on the basis of the grand-average scalp distribution of alpha amplitude, collapsed across the 4 d.

In a second analysis, we tested lateralized, anticipatory alpha amplitude for effects of attention and possible interactions with treatment. This narrows down the analysis to attention-related differential activity, independent of tonic effects. The anticipatory alpha dependent measure was computed as the integrated TSE amplitude over the postcue interval to ms, ending just before the S2.

Amplitude was averaged across 6 electrodes over each hemisphere, determined based on grand-average difference topographies cue-left minus cue-right collapsed across the 4 d. A 4-d balanced repeated-measures design was employed, with subjects receiving 1 of the 4 treatments including placebo on each day in counterbalanced order.

SPSS for Windows version In the analysis of behavioral data, we tested specifically for improvements in performance as a result of any of the 3 treatments. Further post hoc paired comparisons among the 4 treatment conditions were conducted as appropriate through additional t -tests.

L-Theanine: Scientific review on benefits, anxiet, dosage, side effects | www.newyorkethnicfood.com

Thus reduced, testing of treatment effects on the alpha cueing effect, as found in the analogous intersensory study of Gomez-Ramirez et al. There were no significant effects of L-theanine, and no effects of any of the 3 treatments on RT Fig. Asterisks indicate difference from P: P did not differ from either T or C see Fig. TSE waveforms at midline electrodes from which the baseline tonic alpha measure was derived upper panel.

Cue-left and cue-right trials are collapsed. Integrated amplitude over the baseline period for each treatment, with significant difference from placebo marked with an asterisk lower panel. The electrodes from which tonic alpha measures were derived are marked on the channel montage. The typical alpha cueing effect was readily apparent in both the nonnormalized alpha amplitude waveforms and normalized pretarget measures Fig. Upper panel TSE waveforms over left and right hemispheres, with cue-left solid and cue-right dashed superimposed, collapsed across treatment. The overall alpha-mediated spatial cueing effect is highlighted.

Electrode sites for cueing effect measurement are marked on the montage.

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This study was aimed at extending our knowledge of the effects of compounds contained in tea on the cognitive function of attention. Testing relatively low-dosage treatments of L-theanine alone mg , caffeine alone 50 mg , and their combination, we observed an interesting pattern of effects for both behavioral and electrophysiological measures. Tonic alpha amplitude was not found to decrease significantly on the lower dosage of L-theanine.

This indicates that the effect is dose dependent because a drop was seen in both of our previous studies using a mg dosage 18 , M. There was, however, a significant decrease in tonic alpha for the combined treatment. That this decrease marks a synergy between the 2 compounds is suggested by the numerical difference in the alpha decrease caused by L-theanine with and without caffeine Fig.

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That is, it seems unlikely that the greater decrease on the combined treatment is simply a linear sum of the decreases from each compound alone. Because only single dosages of each compound were tested, however, a fair degree of caution is appropriate in the interpretation of synergy at this juncture.

This study marks the third finding of decreased alpha as a result of L-theanine ingestion albeit a partial cause here to date, demonstrating the reliability of the effect. At this point, the question of whether it translates to an improved functional brain state requires serious consideration. In the 80 y since the discovery of alpha waves 24 , alpha has been measured in almost any experimental situation and human population, with significant effects abounding, but with a complicated picture and quite disparate theoretical frameworks arising 25 — The tonic depression of alpha during task performance over the day of testing, as observed here, is neither an individual trait nor a phasic event-related response but a lasting, tonic treatment effect, making it difficult to draw comparisons with such previous studies.

The finding of increased alpha on ingestion of theanine has previously been taken to indicate increased relaxation without increased drowsiness But this qualification appears tenuous in light of other observations of treatment-related increased alpha, e. Previous studies have reported a drop in absolute alpha power during resting with eyes open on ingestion of caffeine at higher dosages, e. From this, it is clear that alpha effects of both L-theanine and caffeine are dose dependent, demonstrating that full characterization of dose-response functions in future studies is called for.

Evidence of a synergistic relationship between L-theanine and caffeine has been presented in recent behavioral studies. These authors found improvements in simple and numeric working memory RT, sentence verification accuracy, and alertness ratings for the combined treatment but not for either treatment alone.

Using a similar crossover design but with a greater dosage of caffeine mg than L-theanine mg , Rogers et al. Although the measures examined in these investigations and our study are quite distinct in nature, an emerging possibility is that the presence of synergistic effects closely hinges on dosages.

That is, it may be that theanine was not effective in augmenting the caffeine-induced effects in Rogers et al. In the present study, lower dosages were used, and a significant drop in tonic alpha was observed for L-theanine and caffeine ingested together but not for either L-theanine or caffeine when ingested alone. However, the absence of a significant difference between the caffeine-alone and combined treatments calls for caution in making strong claims of synergy at this point.

Similar to our previous visuospatial attention study M. Foxe, unpublished results , we did not find any change in the alpha differential cueing effect for the L-theanine-alone treatment. However, it is interesting that the cueing effect was found to be smaller on caffeine alone but not for the combined treatment.

This result was unexpected and thus will bear replication and further investigation. For now, it appears that within visual space, attentional biasing as indexed by alpha amplitude is not affected by L-theanine. In contrast, the cued biasing of attention between sensory modalities does appear to be affected A tentative interpretation of the current pattern of results is that L-theanine works to enhance the tonic apportionment of attentional resources to the visual modality and does so to a significant degree when a large dosage is ingested by itself or in combination with caffeine when a smaller dosage is ingested.

Other articles in this supplement include references 35 — Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account.

Evidence Update: Anxitane (L-theanine) for Anxiety in Dogs (and Cats)

Close mobile search navigation Article navigation. Abstract Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. View large Download slide. The acute physiological and mood effects of tea and coffee: A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality.

Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Effects of hot tea, coffee and water ingestion on physiological responses and mood: The role of caffeine, water and beverage type. The effects of tea on psychophysiological stress responsivity and post-stress recovery: Neuroprotective effects of the green tea components L-theanine and catechins.

The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. L-Theanine—a unique amino acid of green tea and its relaxation effect in humans. Increases in alpha oscillatory power reflect an active retinotopic mechanism for distracter suppression during sustained visuospatial attention. Attention-dependent suppression of distracter visual input can be cross-modally cued as indexed by anticipatory parieto-occipital alpha-band oscillations. The deployment of intersensory selective attention: Anticipatory biasing of visuospatial attention indexed by retinotopically specific alpha-band EEG increases over occipital cortex.

L-Theanine is an non-dietary amino acid not required in the diet to support life that is also a nonprotein amino acid, not being able to be used to make enzymes; it is known technically as r-glutamylethylamide [1] and is commonly known as a sedative amino acid. The leaves of camellia sinensis source of green tea catechins and the plant used to produce green, black, and white teas at 0.

Introduction

Structurally, L-theanine is quite similar to the neurotransmitters glutamate and GABA ; modifying one of the carboxylic ends of glutamic acid further from the amine group with another amine group followed by an ethyl group will produce L-theanine. It has been noted that theanine may be able to alter the taste perception by reducing bitter nodes chocolate, zinc , caffeine , grapefruit [8] due to being a substrate of the umami perception on the tongue; [9] it is actually synergistic with the umami research drug inosine 5'-monophosphate [10] and it is reported to be the sole agent in green tea that promotes the sensation of umami.

It has been noted that theanine is metabolized in the kidneys via the phosphate independent variant of the enzyme glutaminase , and is not affected by the phosphate dependent version; [18] a similar metabolism as glutamine. Elegans exposed to L-theanine at concentrations of ,nM, it appears that supplementation can extend lifespan by an average value of 3.

Theanine has been found to cross the blood brain barier, as systemic injections [20] and oral intake [21] can increase brain concentrations of the compound which appears to be mediated via the leucine-preferring transport system [22] the neutral amino acid transport [23]. Specific brain organs that have been shown to have increases in theanine concentration following oral intake include the hippocampus. This may only occur in persons with somewhat higher baseline anxiety [25] [26] or under periods of stress positive [14] and negative [27] results , but has been noted to occur during closed eye rest [5] as well as during visuospatial tasks [16] around minutes after ingestion.

One study has reported increased theta wave function, but with a combination supplement of both theanine 60mg and green tea extract mg taken thrice daily over 16 weeks. Direct injections of theanine into the striarum also cause dose-dependent increases in dopamine secretion for 40 minutes before returning to baseline.

Oral intake of theanine which increases plasma theanine to L-Theanine has been found to have affinity for all three glutamate receptor subsets with IC 50 and K i values respectively of Theanine has been found to accumulate in glutaminergic neurons via two mechanisms with K M values of In studies assessing sleep latency time taken to fall asleep and sleep duration time elapsed between going to bed and waking in the morning , these parameters appear unaffected. In persons with diagnosed schizophrenia or schizoaffective disorder given mg L-theanine in addition to standard antipsychotics, 8 weeks of supplementation was able to significantly reduce positive and general psychopathology symptoms and anxiety.

One study using a supplement called LGNC mg of green tea extract and 60mg theanine; thrice daily dosing for 16 weeks in persons with mild cognitive impairment based on MMSE scores, supplementation was associated with improved delayed recognition and immediate recall scores with no effect on verbal and visuospatial memory Rey-Kim test.

Theanine has been noted to have anticonvulsive properties at 2. A comparative study between L-theanine mg and alprazolam control; 1mg on anticipatory anxiety has noted that while theanine promoted relaxation, both theanine and alprazolam failed to significantly reduce anxiety symptoms in the model of anticipatory anxiety.

In persons with mild cognitive impairment, a combination supplement of green tea extract mg and theanine 60mg over 16 weeks was able to improve selective attention as assessed by a Stroop test. An improvement in attention has been noted in otherwise healthy persons with high baseline anxiety, with no apparent effect on those with lower anxiety scores at baseline.

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It is known that increases in corticosterone [46] [47] and stress itself [48] are able to suppress LTP and memory processing in the hippocampus and the reduction of corticosterone is thought to underlie the memory preserving effects of theanine. Supplementation of mg Theanine prior to an arithmatic stress test has been noted to reduce perceived stress following the task and to attenuate the risk in salivary IgA concentrations biomarker of stress by approximately half at the conclusion of the task.

Both green and black tea are known to be associated with enhanced vascular responsiveness [49] [50] and can stimulate nitric oxide production. Theanine appears to promote nitric oxide formation via phosphoryating the endothelial variant of the nitric oxide enzyme eNOS on Ser with concentration dependent effects between 0. In comparison to 50mg caffeine in isolation, the addition of mg of L-Theanine to the caffeine was able to beneficially influence parameters of accuracy and attention when it came to cognitive testing in otherwise healthy adults [53] which has been replicated elsewhere with similar doses in improving sustained attention and ratings of fatigue.

The usage of caffeine in isolation mg is able to improve perceptions of fatigue, rapid visual information processing RVIP , and reaction time while adding mg L-Theanine to this preserved those benefits while improving alertness and improving reaction time further and reducing ratings of headache which increased in caffeine control. At least one study noted that the increase in attention assessed via tasks requiring switching of attention with some distracting stimuli occurred independently of the subject's perception of alertness.

At least one study has noted that Theanine may have reduced bioavailability when consumed vicariously through Green Tea, as assessed by Caco-2 cell studies. Glutamine appears to share the same intestinal transporter as L-Theanine a sodium-coupled brush border transporter except with much higher affinity. A study noting less absorption of L-Theanine in the form of green tea relative to Theanine suggested that glutamine in green tea could be responsible for this effect, but did not demonstrate this beyond the hypothesis.

Tannic acid a major constituent of green tea may inhibit the mitochondrial glutamate transporter, [63] Tannic acid has not been investigated on the intestinal glutamine transporter different than mitochondrial glutamate. In an Ames test for carcinogenicity, theanine has reportedly failed to produce a response suggesting noncarcinogenic. Home Supplements Mood Theanine Theanine L-Theanine is one of the main active ingredients found in green tea, alongside caffeine and green tea catechins.

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This page is regularly updated, to include the most recently available clinical trial evidence. History Research analysis by Kamal Patel and verified by the Examine. Last updated on Oct 15, L-Theanine, for the most part, is a relaxing but not sedating amino acid that is synergistic with stimulants such as caffeine as it can 'take the edge off'. It is effective by itself in the standard supplemental dosages as well, and although it can be attained via a diet high in green tea ingestion that is the only dietary source of L-Theanine There are some health benefits associated with green and black tea ingestion that are thought to be more reflective of the Theanine content rather than the green tea catechins or the theaflavins , and this is thought to be related to cardiovascular health as L-Theanine positively regulates nitric oxide and some cognitive benefits.