L-THEANINE er en aminosyre som finnes utelukkende i Camellia Sinensis – en plante som blant annnet brukes til å produsere grønn te. Aminosyren har en stressreduserende effekt, uten at den virker utmattende på kroppen.
L-THEANINE passer utmerket som en supplement til f.eks kaffe ved å balansere den irritable og urolige effekten koffein har på kroppen.
- Absorberes raskere og varer lengre enn koffein.
- Fobedrer humør, gir mental klarhet og økt konsentrasjonsevne.
L-Theanine is an amino acid that is not common in the diet (not one of the essential amino acids or even one of the common nonessential amino acids), and is deemed a nondietary amino acid similar to L-Ornithine or L-Citrulline. L-Theanine has structural similarity to glutamine and both neurotransmitters that are produced from it (GABA and glutamate) and is known to reach the brain and act in the brain following oral ingestion.
The properties of L-theanine can be summed up as being a relaxing agent without sedation (relative to something like lemon balm which relaxes but may also sedate), and is also implicated in reducing the perception of stress and slightly improving attention. While L-theanine does not appear to induce sleep, it may (quite weakly) help with sleep although its potency suggests it may not be a good first line treatment for this.
Interestingly, the relaxing and attention promoting properties of L-theanine coupled with the lack of sedation may L-Theanine have its most significant supplemental role in attenuating the ‘edge’ of many stimulants. A combination of L-Theanine with caffeine (200mg each) is noted to be synergistic in promoting cognition and attention.
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.
One study using a supplement called LGNC-07 (360mg 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).
A comparative study between L-theanine (200mg 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. Some other studies that measure state anxiety fail to find a difference between theanine and placebo at this dose.
In studies assessing relaxation or attention/reaction time, it appears that only persons with high baseline anxiety note benefits associated with relaxation whereas those who are not anxious fail to outperform placebo.
4.12. Attention and ADHD
In persons with mild cognitive impairment, a combination supplement of green tea extract (360mg) 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.
Rats fed 0.3% of their drinking water as L-theanine appear to have less circulating corticosterone at rest and after stress testing to approximately half of control, and in hippocampal CA1 cells theanine appears to cause a shift away from NMDA-dependent long term potentiation (LTP) towards NMDA-indepedent potentiation while protecting from stress-induced memory impairment at this oral dose.
It is known that increases in corticosterone and stress itself 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.
Oral intake of L-theanine in rats at feasible dosages is able to reduce circulating biomarkers of stress with or without an actual stressor being present, and can reduce the adverse effects of stress such as memory impairment
Supplementation of 200mg 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.
Reductions of percieved stress have been reported in human subjects given oral theanine at the standard dosages
5.1. Blood Flow
Theanine appears to promote nitric oxide formation via phosphoryating the endothelial variant of the nitric oxide enzyme (eNOS) on Ser 1177 with concentration dependent effects between 0.01-1µM (10µM being as effective as 0.01µM). This phosphorylation and subsequent endothelial relaxation is PI3K/ERK dependent (not dependent on Akt).
Theanine appears to promote nitric oxide formation at relatively low concentrations, and is likely practically relevant following oral ingestion
In comparison to 50mg caffeine in isolation, the addition of 100mg 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 which has been replicated elsewhere with similar doses in improving sustained attention and ratings of fatigue. A study using these two doses (in isolation or in combination) did not note any differences in reducing the number of errors in a sustained attention task when comparing combination therapy against either in isolation.
The usage of caffeine in isolation (150mg) is able to improve perceptions of fatigue, rapid visual information processing (RVIP), and reaction time while adding 250mg 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). Reaction time (as well as the ability to switch between tasks) has been improved with combination therapy at lower doses (50mg caffeine and 100mg L-Theanine) with this study also noting an improvement in attention via less interference with distracting stimuli.
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.
6.2. Green Tea
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. Theanine is absorbed via passive diffusion and is generally well absorbed with concentrations above 4mM being effluxed back out of intestinal cells, but under this dose had two-fold absorption into intestinal cells (apical to basolateral) relative to secretion and incubation with green tea noted that while absorption rate was only hindered 35% the efflux rate was increased dramatically. Although no causation was shown, it was thought that small mounts of D-Theanine in green tea (2.2-4.7% of total content) may have competed with absorption due to their lower absorption rates; the authors cast doubt on this possibility though.
Glutamine appears to share the same intestinal transporter as L-Theanine (a sodium-coupled brush border transporter) except with much higher affinity. The kinetics of both glutamine and L-Theanine across the intestinal membrane is via passive diffusion, suggesting similar absorption kinetics. 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, Tannic acid has not been investigated on the intestinal glutamine transporter (different than mitochondrial glutamate).
Safety and Toxicology
It has been reported that (via a publication from Taiyo co; producers of Suntheanine®) that oral ingestion of 99% L-theanine has failed to produce toxicity in rats at either 6,500mg/kg for 2 weeks or 2,000mg/kg over 28 days. 5% of the diet as L-theanine for 78 weeks has also failed to produce toxic effects. A 13 week toxicity test in rats has established a No Observable Adverse Effect Limit (NOAEL) of 4,000mg/kg bodyweight, which was the highest dose tested.