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Background
L-Theanine is an amino acid analogue of glutamate and glutamine found in green tea and in gyokuro leaves, thus demonstrating culinary use (1-2).
Scientific effects
L-Theanine is an amino acid analogue of glutamate and glutamine found in green tea and in gyokuro leaves, thus demonstrating culinary use (1-2).
L-theanine is well absorbed by the body (comparable to green tea) and increases in plasma based in a dose dependent manner. Below is the plasma levels of 100 mg of Theanine after administration in a human subject:
Studies using l-theanine have shown that l-theanine use in humans reduces psychological stress, physiological stress, promotes mental relaxation, decreases anxiety and improves reaction timing by increasing rates of attention. This is further supported by findings conducted on adults that found an increase in alpha waves following Theanine supplementation (3-6).
A study in pharmacy students who took 200 mg of Theanine twice a day (once after breakfast and once after lunch) found that taking Theanine for one week prior to a test decreased levels of salivary alpha-amylase activity (7). Another interesting finding is that they found that people with higher levels of salivary alpha-amylase activity slept less (to be discussed further in reference 13).
Further investigation of Theanine showed that doses of 200-400 mg significantly increases the sensory gating mechanism in humans (8). Sensory gating is essentially mental processes that filter out unnecessary information from someone’s information that is deemed irrelevant by the brain. If someone is interested in learning further, research Mike Posner and his work on visual search, or the theory known as “inhibition of return”; it's interesting when applied to the concept of foraging.
Interestingly enough, however, there are also studies showing that a combination of Theanine and caffeine improves these reaction timing effects, and that the combination of the two results in an improvement of mood, cognition, while attenuating blood pressure increase from caffeine use in adults (9-10). This remained true regardless to whether the task was visual or motor in nature (11).
The relationship between caffeine and Theanine was explored further (12) and it was shown that 50 mg of l-theanine was enough to eliminate the vasoconstrictive and behavioural effects of 75 mg of caffeine (see the table below). It’s important to note that this experiment did not find any significant benefit of Theanine supplementation, but it also used a very minor dose of Theanine (50 mg).
Research in young boys (ages 8-12) diagnosed with ADHD showed that 400 mg of Theanine had a significant effect on sleep efficiency (refer to the figure below); it effectively meant they spent more time asleep at night and woke up less (13).
This makes sense when one recalls that Theanine is anxiolytic in nature. Remember that reference 7 showed us that increased salivary alpha-amylase activity results in less sleep, and that Theanine lowers salivary alpha-amylase activity. Salivary alpha-amylase activity is considered a marker of stress (cortisol).
While there is some debate in the field on how ADHD and cortisol are linked, more recognized papers show that individuals with ADHD (particularly adults) tend to also suffer from higher than normal levels of cortisol (14). It is not surprising that to think that Theanine possibly helped the individuals with ADHD sleep better due to lowering salivary alpha-amylase activity rather than being sedative in nature.
Benefits
This makes Theanine an excellent addition to any product that is designed to:
Safety profile
Please consult with a physician before using Theanine. Theanine can be taken any time of day depending on the desired effects.
References
L-Tyrosine is an amino acid found that is involved in the production of neurotransmitters like dopamine, adrenaline, and noradrenaline. Through some studies on humans, Tyrosine has evidence showing it can improve the mood and performance of individuals under stressful conditions, improve working memory, and reduce the effects of stress and fatigue on cognitive exhausting tasks.
