L-Theanine: benefits, dosage, contraindications
Other name(s)
Gamma-glutamylethylamide, Gamma-N-ethylglutamine
Scientific name(s)
Theanine
Family or group:
Amino acids
Indications
Scoring methodology
EFSA approval.
Cognitive performance ✪✪✪✪✪
Theanine may improve attention and verbal response during cognitive tests, but does not appear to improve other measures of cognitive function such as memory and motor speed. There are conflicting data regarding the effects of theanine on cognitive performance when it is 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 testing has been used. Theanine has also been used at a dose of 200 mg per day for 4 weeks.
Posologie
Oral administration
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 attenuates the adverse effects of adjuvant chemotherapy in patients with colon cancer. Indeed, the combination of cystine and theanine reduced the incidence of diarrhea by 37% and loss of appetite by 33% compared with chemotherapy alone in patients with colon cancer. Moreover, it increased the completion rate of the first treatment cycle by 49%.
Posologie
Oral administration
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 is conflicting evidence 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 the increase in blood pressure secondary to psychological stress. Other preliminary clinical research shows that taking theanine at a dose of 200 mg twice daily for one week before and during the first 10 days of a period of practical training in pharmacies among pharmacy students decreases subjective stress scores compared with placebo.
Posologie
Oral administration
200 - 400 mg
Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-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 alters amino acid levels affecting serotonin, dopamine and GABA, which may have a mood-modulating effect.
Posologie
Oral administration
200 mg
Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-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 administration
250 mg
8 weeks
Properties
Neurological
Theanine has a neuroprotective effect. It may 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), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) (glutamate receptors) and gamma-aminobutyric acid (GABA) type A receptors. Theanine is structurally similar to glutamate and may act as a GABA agonist and increase GABA levels in the brain, leading to relaxation. GABA can then influence dopamine and serotonin levels. In addition, theanine stimulates the production of alpha waves in the brain (this is a brain rhythm that appears when an awake person closes their eyes and relaxes), also leading to relaxation and mental alertness.
Usages associés
Antioxidant
After absorption, theanine is broken down into glutamic acid and ethylamine. Inside the cell, cysteine and glutamic acid are combined with glycine to form glutathione, which in its reduced form is the major cellular antioxidant and protects cells from free radicals.
Anxiolytic
Theanine is used for its relaxing and anxiolytic effects. It is thought that theanine may act on anxiety by increasing levels of GABA (an inhibitory neurotransmitter) and serotonin, and by reducing the release of glutamate, which is an excitatory neurotransmitter. Theanine also appears to reduce the production of cortisol, a stress hormone, through relaxation and stress reduction.
Usages associés
Cognitive function
Theanine mimics the production of alpha waves in the brain (this is a brain rhythm that manifests when an awake subject closes their eyes and relaxes), leading to mental alertness. nnIn animals, theanine supplementation increases synaptic plasticity in the brain, which may explain theanine's effect on cognition. Indeed, glutamatergic signaling regulates synaptic plasticity. nn
Usages associés
Antidepressant
Theanine resembles L-glutamate in structure and competes with it at glutamate receptors. It is likely that the antidepressant effects of theanine are related to its effects on the glutamatergic pathway, by regulating the amounts of glutamate and glutamine in the brain. nnIn animals, theanine supplementation increases synaptic plasticity in the brain, which may be related to theanine's antidepressant effect. Indeed, glutamatergic signaling regulates synaptic plasticity. nn
Usages associés
Anticancer
In studies on doxorubicin (an anticancer drug used in chemotherapy), theanine increases the concentration of doxorubicin in tumors by blocking the efflux of the drug from tumor cells. It also appears to increase the concentration of doxorubicin in tumor cells by inhibiting glutamate transporters. nnFurthermore, animal research shows that theanine reduces doxorubicin-induced toxicity related to oxidative damage by increasing glutamate concentrations. nn
Usages associés
Cardiovascular
Theanine appears to prevent the development of atherosclerosis by inhibiting lipid peroxidation of low-density lipoproteins (LDL). nn
Safe dosage
Adults aged 18 and over: 200 mg - 400 mg
Orally, theanine has been used safely at doses of up to 400 mg per day for 8 weeks. However, there is not enough reliable information on the safety of long-term supplementation.
Interactions
Médicaments
Antihypertensive: moderate interaction
Theoretically, concomitant use of theanine and antihypertensive drugs could potentiate 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.
