Theanine is a derivative of L-glutamic acid, which represents one of the 20 ordinary amino acids.

Unlike its precursor, contained in all dietary proteins, there are very few natural sources of theanine; significant quantities can only be found in tea leaves, in particular in green leaves, and in mushrooms of the species Boletus badius ( Xerocomus badius ).

Furthermore, unlike glutamic acid, theanine is not incorporated into polypeptide chains, but is present in free form.

Despite not intervening in the processes of protein synthesis, theanine has proved to be particularly valuable for humans, so much so as to encourage their use also in clinical settings.


Why is theanine used? What is it for?

The biological properties attributed to theanine are different.

Initially used for its relaxing and anxiolytic effects, over time theanine has provided numerous other biological and clinical indications.

Currently, theanine is attributed:

  • Sedative and anxiolytic properties;
  • Anti-tumor properties;
  • Adjuvant properties of chemotherapy;
  • Hypotensive properties, observed only on experimental models;
  • Neuroprotective properties;
  • Immunomodulating properties.

These activities justify the huge amount of work published in the literature, related to the clinical utility of theanine.

Property and Effectiveness

What benefit has Theanine shown during the studies?

Although most of the studies currently published on the clinical and biological efficacy of theanine are experimental in nature, the data obtained are certainly worthy of attention.

Theanine and stress

The most known and publicized property of theanine concerns the alleged anti-stress, anxiolytic and relaxing effect. Not surprisingly, its precursor (L-glutamic acid) has long been known to be an important amino acid for the good functioning of the central nervous system, as a precursor to GABA.

GABA, or gamma-aminobutyric acid, is a neurotransmitter with inhibitory action, which promotes the sensation of relaxation. Not surprisingly, many drugs with sedative, muscle relaxant, anticonvulsant and hypnotic action act by stimulating the GABA receptors (in technical terms it is said that they are their receptor agonists).

Rapidly absorbed in the intestine and distributed in the tissues, the theanine crosses the blood-brain barrier without obstacles, increasing the levels of GABA and consequently recreating the so-called "sense of well-being". Its inhibitory or stimulatory effect on the release of serotonin seems less clear, which would be modulated according to the situation; the ability of theanine to promote the release of dopamine appears more certain.

All the aforementioned actions would have resulted, in a recent clinical trial, in a clear anxiolytic action, also observed through the increase in the activity of the alpha-type brain waves, connected to the general state of rest and sedation.

Theanine and caffeine

The sedative effect of theanine is able to counteract the excitatory properties of caffeine present in tea or taken through other foods (guaranà, mate, cola, coffee, etc.).

In fact, caffeine acts as a competitive antagonist of adenosine receptors, increasing levels of adrenaline and noradrenaline; consequently it supports the body metabolism, heart rate, attention threshold, arterial pressure and the number of breaths.

Theanine, glutamic acid and nervous system

Recent studies have investigated the ability of theanine to inhibit the "excitatory toxicity" of glutamic acid.

In addition to being a precursor of the "relaxing" inhibitory GABA neurotransmitter, glutamic acid would also present excitatory functions as it is.

Consequently, high concentrations of glutamic acid at the level of brain synapses could favor the onset of symptoms such as headaches, hyperexcitation, insomnia, dizziness, palpitations and hot flushes.

The accumulation of glutamic acid in the brain would also seem to be responsible for the neuronal damage typical of progressive sclerosis (such as amyotrophic lateral sclerosis) and Alzheimer's disease.

Finally, the ability of glutamate to lower the excitability threshold of neurons, would increase the metabolic activity of nerve cells, which would therefore need a greater flow of blood and nutrients.

The efficacy of theanine in regulating the levels of glutamic acid in the brain, demonstrated in vitro and on experimental animals, seems linked to its modulatory effect at the level of the receptors of this neurotransmitter; in practice, given the structural analogy, theanine could bind to the receptors of glutamic acid stimulating them in a much lower way than the endogenous agonist, or even inhibiting them.

Theanine and hypertension

The modulatory activity against glutamate receptors would partly justify the central antihypertensive action of theanine.

This activity could therefore reduce the damage, both cerebral and cardiac, related to hypertension.

Theanine and chemotherapy

According to recent evidence, mostly conducted in vitro, theanine could enhance the antitumor effect of doxorubicin and other chemotherapeutic drugs.

This synergy would determine:

  • A more effective antitumor action;
  • Greater success in drug therapy, in tumors such as ovarian sarcoma and liver metastases;
  • A reduction in the potential side effects of chemotherapy;
  • An improvement in the patient's quality of life.

Doses and method of use

How to use theanine

The dosages of theanine commonly recommended range from 50 to 100 mg a day; higher doses, in the order of 100-200 mg, are suggested in the adjuvant treatment of situations of anxiety and heightened agitation.

Given the abundant presence of theanine in the dry extract of green tea, the daily consumption of 2-3 cups could provide as much as 30 mg of theanine.

Side effects

At present, no clinically relevant side effects related to theanine intake are known.


When should theanine not be used?

The use of theanine is contraindicated in subjects hypersensitive to the active principle or to structurally related molecules.

Pharmacological Interactions

Which drugs or foods can change the effect of theanine?

Theanine could increase the antitumor effect of chemotherapy drugs such as doxorubicin and idarubicin.

Theanine could also enhance the sedative effect of alcohol and other hypnotic drugs.

Precautions for use

What do you need to know before taking theanine?

The use of theanine is contraindicated during pregnancy and in the subsequent period of breastfeeding.

Theanine use, together with chemotherapy therapy, should be closely supervised by medical personnel.


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