L-Theanine: Benefits, Dosage, Contraindications
Other name(s)
Gamma-glutamylethylamide, Gamma-N-ethylglutamine
Scientific name(s)
Theanine
Family or group:
Amino acids
Indications
Rating methodology
EFSA approval.
Cognitive performance ✪✪✪✪✪
Theanine may improve attention and verbal response during cognitive tests, but does not seem to enhance other cognitive functions like memory and motor speed. There are contradictory data regarding the effects of theanine on cognitive performance when taken in combination with caffeine. A meta-analysis of 10 clinical trials suggests that taking theanine with caffeine improves accuracy and alertness. A single dose of 100 mg of theanine before cognitive tests has been used. Theanine has also been used at a dosage of 200 mg per day for 4 weeks.
Posologie
Oral
100 - 200 mg
4 - weeks
L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness
Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness
The combined effects of L-theanine and caffeine on cognitive performance and mood
Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task
A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood
Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task
Chemotherapy ✪✪✪✪✪
Preliminary clinical research shows that oral administration of 700 mg of cystine and 280 mg of theanine mitigates the adverse effects of adjuvant chemotherapy in colon cancer patients. The combination of cystine and theanine reduced the incidence of diarrhea by 37% and appetite loss by 33% compared to chemotherapy alone in colon cancer patients. Furthermore, it increased the completion rate of the first treatment cycle by 49%.
Posologie
Oral
280 mg
Theanine, a specific glutamate derivative in green tea, reduces the adverse reactions of doxorubicin by changing the glutathione level.
Theanine and glutamate transporter inhibitors enhance the antitumor efficacy of chemotherapeutic agents.
Enhancement of the activity of doxorubicin by inhibition of glutamate transporter.
Inhibition of glutamate transporter by theanine enhances the therapeutic efficacy of doxorubicin.
Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients.
Stress ✪✪✪✪✪
There are contradictory findings regarding the effect of theanine on experimentally induced stress. A clinical study shows that taking 200 mg of L-theanine before a psychological examination reduces anxiety and prevents increased blood pressure due to psychological stress. Other preliminary clinical research shows that taking 200 mg of theanine twice a day for a week before and during the first 10 days of a pharmacy practice period in pharmacy students decreases subjective stress scores compared to placebo.
Posologie
Oral
200 - 400 mg
Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary -amylase activity, trait anxiety and subjective stress
Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses
Emotional balance ✪✪✪✪✪
Once it crosses the blood-brain barrier, L-theanine affects amino acid levels that impact serotonin, dopamine, and GABA, which may have a mood-modulating effect.
Posologie
Oral
200 mg
Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary -amylase activity, trait anxiety and subjective stress
The effects of L-theanine, caffeine and their combination on cognition and mood
Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses
Depression ✪✪✪✪✪
A clinical study shows that taking 250 mg of theanine orally for 8 weeks reduces depressive symptoms and improves sleep quality in people with mild major depressive disorder.
Posologie
Oral
250 mg
8 - weeks
Properties
Neurological
Theanine has a neuroprotective effect. It can protect against cerebral ischemia and glutamate toxicity by decreasing glutamate reuptake and inhibiting the glutamate transporter. Theanine can also stimulate the release of nerve growth factor. Animal research suggests that the neuroprotective effects of theanine are due to its ability to block N-methyl-D-aspartate (NMDA) receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (glutamate receptors), and gamma-aminobutyric acid (GABA) type A receptors. Theanine is structurally similar to glutamate and can act as a GABA agonist and increase its levels in the brain, leading to relaxation. GABA may then influence dopamine and serotonin levels. Additionally, theanine stimulates the production of alpha waves in the brain (a brain rhythm that occurs when a person is awake, closes their eyes, and relaxes), also leading to relaxation and mental alertness.
Usages associés
Antioxidant
After absorption, theanine breaks down into glutamic acid and ethylamine. Inside the cell, cysteine and glutamic acid combine with glycine to form glutathione, which, in its reduced form, is the major antioxidant in cells and protects them from free radicals.
Anxiolytic
Theanine is used for its relaxing and anxiolytic effects. It is believed that theanine could act on anxiety by increasing GABA (an inhibitory neurotransmitter) and serotonin levels, while reducing the release of glutamate, which is an excitatory neurotransmitter. Theanine also seems to reduce cortisol production, a stress hormone, by promoting relaxation and stress reduction.
Usages associés
Cognitive function
Theanine stimulates the production of alpha waves in the brain (a brain rhythm that occurs when a person is awake, closes their eyes, and relaxes), leading to mental alertness. In animals, theanine supplementation increases synaptic plasticity in the brain, which may explain the effect of theanine on cognition, as glutamatergic signaling regulates synaptic plasticity.
Usages associés
Antidepressant
Theanine is similar to L-glutamate in structure and competes with it at the glutamate receptors. The antidepressant effects of theanine are likely linked to its effects on the glutamatergic pathway, regulating the amounts of glutamate and glutamine in the brain. In animals, theanine supplementation increases synaptic plasticity in the brain, which may relate to the antidepressant effect of theanine, as glutamatergic signaling regulates synaptic plasticity.
Usages associés
Anticancer
In studies involving doxorubicin (an anticancer drug used in chemotherapy), theanine increases the concentration of doxorubicin in tumors by blocking drug efflux from tumor cells. It appears to also increase the concentration of doxorubicin in tumor cells by inhibiting glutamate transporters. Moreover, animal research shows that theanine decreases doxorubicin-induced toxicity related to oxidative damage by increasing glutamate concentrations.
Usages associés
Cardiovascular
Theanine appears to prevent the development of atherosclerosis by inhibiting the lipid peroxidation of low-density lipoproteins (LDL).
Safety dosage
Adult from 18 years: 200 mg - 400 mg
Orally, theanine has been used safely at doses up to 400 mg per day for 8 weeks. However, there is not enough reliable information on the safety of supplement use for long-term application.
Interactions
Médicaments
Antihypertensive: moderate interaction
Theoretically, concurrent use of theanine and antihypertensive drugs could enhance the activity of antihypertensives.
Precautions
Pregnant women: avoid
Avoid use due to lack of reliable information.
Breastfeeding women: avoid
Avoid use due to lack of reliable information.
