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L-theanine – is one of the basic substances used to improve intellectual skills. It owes its great popularity to high effectiveness of action compared to other similar preparations, synergy in action with other nootropics, and above all the fact that L-theanine is very safe to use.

L-Theanine Origin

L-theanine is an amino acid of non-protein origin. It is obtained from tea leaves (Camellia sinensis) and was discovered in 1949.

About 1-2% of the weight of dried tea leaves is L-theanine and it constitutes about 50% of the amino acids of tea. In tea, it is only a free amino acid and is not associated with any proteins.

It is synthesized in the root of the plant and concentrated in its leaves, where it is converted into polyphenols under the influence of sunlight. It is also what gives green tea, which is its most abundant source of occurrence, a characteristic and at the same time exotic taste of ‘umami’.

Mechanism Of Action

It is a water-soluble compound and enters the blood from the digestive tract on the small intestine.

In studies conducted in rats, L-theanine delivered via the oral route reached its peak concentration as soon as 30 minutes after its consumption.

It crosses the blood-brain barrier through the LNAA (large neural amino acid) transport mechanism, which is a mechanism by which such neurotransmitters as dopamine and serotonin are also formed in the brain.

L-theanine in the rat study showed elevated levels of serotonin and dopamine in the brain. Though the research may be contradictory, as in one study the rats that received the amino acid reported decreased levels of serotonin. Regardless, L-theanine bound is with the induction of so-called alpha waves in the brain, which are identified with the state of relaxation.

It has an inhibitory effect on another neurotransmitter, which may have a toxic effect, which is glutamate. In the context of cancers, this is a desirable phenomenon as glutamate reduces the cellular level of glutathione (endogenous antioxidant). It also protects non-cancer cells from being damaged by chemotherapeutic drugs through antioxidant activity, especially by maintaining the cellular levels of glutathione.

The antioxidant effect itself, however, seems to be smaller than the one exerted by the green tea from which the L-theanine supplements is usually derived. This dependence of polyphenol content in green tea is attributed.

Influence On Cognity Functions And Stress

L-theanine is known for its properties that promote relaxation without the unwanted dementia effect. An interesting fact is that depending on the dose it can produce completely different effects. In a rat study that added L-theanine to caffeine (at a similar dose), a high dose of L-theanine achieved a caffeine-inducing effect. However, when reducing the dose of L-theanine by 60-80% of the original value, an effect enhancing the caffeine-stimulating effect was achieved.

As previously mentioned, studies show that L-theanine increases the activity of the so-called alpha waves in the brain, which are identified with the state of relaxation. This effect can cause a dose of 50-200 mg after about 40 minutes of consumption, while not causing a decrease in vigilance.

The effectiveness of low doses, in the order of 50 mg, is confirmed by another study, where a group of 16 people taking L-theanine was compared to a control group of 19 people. Electroencephalograph measurements were taken in both groups every 15 minutes for 45-105 minutes after administration of L-theanine/placebo. The group that consumed L-theanine had higher alpha activity in these measurements compared to the placebo group. Thus, a dose of 50 mg can be considered sufficient to promote a state of relaxation.

Electroencephalograph measurements were taken in both groups every 15 minutes for 45-105 minutes after administration of L-theanine/placebo.

The group of rats that received L- Theanine had a higher frequency of pressing the appropriate lever on rats from the control group.

An interesting study of the impact of L-theanine on cognition – here specifically on the memory and ability to learn – is a study in rats, where they were tested how they will manage in the test, where pressing a particular lever resulted in the provision of food for them.

In the context of cognition, it is worth mentioning the mechanism eliminating the effects of excess glutamate, where L-theanine counteracts the degradation of brain neurons, as shown in study. In this study, performed in rats, attempts were made to cause neuronal damage to high levels of glutamate. It turned out that after the administration of L-theanine, the degree of neuronal damage drastically decreased.This is attributed to the antioxidant properties of L-theanine. Thus, L-theanine may inhibit the neurotoxic effect of glutamate and prevent conditions with which high levels of glutamate are correlated, such as Alzheimer’s after L-theanine, the degree of neuronal damage drastically decreased

Due to its silencing and facilitating properties, L-theanine often finds its application in practice with caffeine (usually from coffee), where caffeine leads to arousal, but is often accompanied by a decrease in the ability to focus thoughts.

In the context of the above combination, an interesting study was conducted in the form of a double randomized controlled group. In another study, the effect of a combination of caffeine at a dose of 250 mg and L-theanine at a dose of 150 mg – both together and separately. In the group supplementing L-theanine alone, there was a greater calmness and relaxation of the subjects, while in the group that received a dose of caffeine and in the group of caffeine + L-theanine the situation was reversed.

Nevertheless, only in the group of caffeine and l-theanine there was a positive effect on the time-delayed recognition of words, which translates into a smaller reaction time. These observations support the previous experience of people who combined caffeine and L-theanine, that such a combination leads to improvement of cognitive parameters and vigilance – thus L-theanine in combination with caffeine acts synergistically with it, quite differently than when L-theanine is used it is separate, where it then promotes greater relaxation.

Moving the relaxing effect of L-theanine, it is worth mentioning the study in which it was noted that a single dose affects the psychological and physiological state at stress intensity 18. In the study, the stress was a mathematical test. Her influence on stress in different dosages on the same people was checked (4x people approached the test) – before and during the tasks, placebo was given or nothing at all.

L-theanine showed an effect on lowering the heart rate during stress, the level of immunoglobulin A from saliva (a stress marker), and also reduced the subjective feeling of stress. Based on the measured heart rate, it was concluded that L-theanine reduces the activation of the sympathetic nervous system responsible for the perceived stress.


L-theanine is an excellent addition to all stimulants, such as coffee, improving cognitive properties during stimulation. It can be said that it allows focusing thoughts and actions in a state of arousal, which translates into productivity and efficiency.

At the same time, the use of L-theanine completely allows you to relax as well as facilitates psychological coping with stress stimuli. Thus, it will find its application in the reduction of perceptible psychological stress, as well as facilitate falling asleep through the relaxation effect.

Long-term use of L-theanine seems safe, and its supply may also help to prevent neurodegenerative diseases and help protect the brain from the destructive effects of stress.