L Theanine -- gamma-glutamylethylamide -- is one of the major amino acid components in green tea and black tea. L-theanine is considered the main substance responsible for the taste of green tea. There's been little research regarding L-theanine supplementation in humans, therefore I don't have a clear idea of benefits or side effects of this supplement, but it appears that it has a role to play in reducing stress and anxiety. l-Theanine blocks the binding of l-glutamic acid to glutamate receptors in the brain. Individuals who take a l-theanine supplement are noted to have more alpha-brain wave activity in the brain which is sign of enhanced relaxation.

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L-Theanine is an amino acid that helps promote a mild, restful, relaxed state with minimal daytime sedation.
Suntheanine, a patented form of L Theanine, is a trademark of Taiyo International, Inc.

The relaxation effects begin about an hour or two after intake.

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Promotes relaxation and stress reduction, so does 5-HTP supplement

Supplement Facts: L Theanine 200 mg each pill

Dosage, how much to take
Use 100 mg to 300 mg a few hours before bed or during the day if you feel very tense and have a lot of stress. Make sure to take it on an empty stomach. If you are driving or operating heavy machinery, do not take more than 200 mg.

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How it may work
L-Theanine (γ-glutamylethylamide) is a unique non-protein amino acid that is naturally found in tea plants. It contributes to the umami taste and unique flavor to green tea infusion, and thus its content in tea leaves highly impacts the tea quality and price. In addition to the graceful taste, it has been proved to have many beneficial physiological effects, especially promoting relaxation and improving concentration and learning ability.

Orally administered l theanine is absorbed through the intestinal tract and hydrolyzed in the liver to glutamic acid and ethylamine. Ethylamine, a molecule that primes the response of an immune system element called the gamma-delta T cell, which may protect against infection.

L Theanine and stress reduction
Nutrients. 2016. Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial. This study explored the effects of an L-theanine-based nutrient drink on mood responses to a cognitive stressor. Oure findings further support the anti-stress effects of L-theanine.

l-Theanine reduces psychological and physiological stress responses.
Biol Psychol. 2006.
Twelve participants underwent four separate trials: one in which they took l-Theanine at the start of an experimental procedure, one in which they took l-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that l-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of l-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.

Pharmacol Biochem Behav. 2013 . Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress. Theanine, an amino acid in tea, has significant anti-stress effect on experimental animals under psychosocial stress. Anti-stress effect of theanine on humans was evaluated in 5th-year university students during pharmacy practice. Theanine or placebo (lactose) tablets (200 mg, twice a day, after breakfast and lunch) were taken from 1 week prior to the pharmacy practice and continued for 10 days in the practice period. Results suggest that theanine intake suppressed initial stress response of students assigned for a long-term commitment of pharmacy practice.

Research and benefits
L-Theanine is one of the predominant amino acids ordinarily found in green tea, and historically has been used as a relaxing agent.

Anxiety help, reduction of stress and tension - Another herb to consider for stress and anxiety reduction is kava which is effective for relaxation.
Sleep benefit
May be useful for preventing ischemic neuronal damage.
This amino acid increases the idarubicin-induced antitumor activity and ameliorates its toxicities.

Blood pressure
Q. So I really want to start trying l-theanine for my life-long anxiety problems, as it is one of the only suppliments or drugs I have found that is touted for being helpful for anxiety, and yet not making the user feel dopey and tired. My concern is that I have low blood pressure. Does l-theanine lower blood pressure, or regulate it? Should a person with low blood pressure avoid this suppliment, or does it only lower blood pressure when it needs lowering? Is the lowering of blood pressure that comes along with it significant enough to worry about, even if it will take down the blood pressure of an already low person?
   A. Not enough human studies have been done to determine its role of in influencing blood pressure in those who have normal or low blood pressure. We could only find one human that showed theanine prevents the rise in blood pressure from caffeine intake. Very, very large theanine dosages given to rats lowers their blood pressure. Since the effects of herbs and amino acids are dose dependent, one option is to take half of a 100 mg capsule and monitor one's blood pressure over the next few hours to see how it affects you and then base future dosages on the initial response. Have approval by your doctor.

Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together.
Psychopharmacology 2007.
Although both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. To study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers. In a randomised, double-blind, placebo-controlled study, healthy adult participants received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task. Caffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.

Liver health
Asia Pac J Clin Nutr. 2017. Theanine: the unique amino acid in the tea plant as an oral hepatoprotective agent. For thousands of years, humans have consumed tea made from leaves of Camellia sinensis, first as a medicinal herb and then as a widely popular beverage. Theanine, a tea-derived, unique, nonproteinic amino acid, has been extensively studied for its health benefits. Recently, multiple lines of evidence have proven its beneficial effects on hepatic and immune functions. One possible mechanism for its biological activity involves the downregulation of the inflammatory response through the induction of nitric oxide production and glutathione synthesis. In this review, we summarize published results describing the potential mechanisms for these beneficial health effects and provide new insight into how theanine can be therapeutic for liver injury and chronic liver disease.

Schizophrenia patients for better sleep
Acta Neuropsychiatr. 2015. Effect of L-theanine on glutamatergic function in patients with schizophrenia. Glutamatergic dysfunction in the brain has been implicated in the pathophysiology of schizophrenia. Previous studies suggested that L-theanine affects the glutamatergic neurotransmission and ameliorates symptoms in patients with schizophrenia.  The subjects were 17 patients with schizophrenia and 22 age- and sex-matched healthy subjects. L-theanine (250 mg/day) was added to the patients' ongoing antipsychotic treatment for 8 weeks. There were significant improvements in sleep quality after the L-theanine treatment.

Stress and tension
Holist Nurs Pract. February 2014. L-theanine (suntheanin): effects, an amino acid derived from Camellia sinensis (green tea), on stress response parameters.

Pharmacol Biochem Behav. 2013. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress.

Weight loss
Anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, in mice.
In Vivo. 2004.
To elucidate the anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, female mice were fed on diets containing 2% green tea powder and diets containing 0.3% catechins, 0.05% caffeine and 0.03% theanine, which correspond, respectively, to their concentrations in a 2% green tea powder diet, singly and in combination for 16 weeks. Our results indicated that at least caffeine and theanine were responsible for the suppressive effect of green tea powder on body weight increase and fat accumulation. Moreover, it was shown that catechins and caffeine were synergistic in anti-obesity activities.

Review and summary
Human research with this nutrient is limited, and hence the clinical usefulness of theanine is not clear to me at this time. However, some users report that l-theanine helps them relax and helps with sleep.

L Theanine side effects, safety, danger, risk
I have not come across any research regarding l theanine side effects. In my experience, dosages greater than 300 mg of l-theanine cause an adverse reaction of transient lightheadedness. It is possible that adverse reactions regarding drowsiness could be elicited when combined with kava, 5-HTP, passion flower, valerian, or other herbs and nutrients that have a sedative effect. Rat studies have not found any l-theanine side effects of concern.

A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats.
Food Chem Toxicol. 2006. Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA
This study was conducted to evaluate the safety of l-theanine ( Suntheanine ) when administered as a dietary admixture to male and female rats at concentrations providing doses of 0, 1500, 3000 or 4000 mg/kg body weight per day for 13 weeks. There were no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, hematology, or urinalysis. There were no consistent treatment-related L theanine side effects in gross pathology, organ weights or ratios or histopathology. The increased incidence of renal tubular cell adenomas in high-dose females only were not consistent with the characteristics of a renal carcinogen (due to early onset and low number of animals affected) but were more consistent with a genetic predisposition than with direct organ toxicity. The no-observed-adverse-effect-level was 4000 mg/kg bw/day, the highest Suntheanine dose tested.

Q. I have read studies online that says it can increase kidney tumors in rats? I understand that it is metabolized in the kidneys. Does this mean it causes kidney tumors in humans? Or am I at increased risk for getting kidney tumors from taking l theanine?
   A. I doubt that the dosages used by humans for anxiety relief or sleep cause kidney tumors or cancer in humans although I have not seen any studies that have looked at this connection.

Theanine Research studies
Neuroprotective effect of gamma-glutamylethylamide on cerebral infarction in mice.
Neurosci Lett. 2004.
In the present study, we examined the neuroprotective effect of gamma-glutamylethylamide (theanine) on the ischemic brain damage in a middle cerebral artery occlusion model in mice. L-Theanine was injected i.p. 3 h after the occlusion or immediately before and 3 h after the occlusion. Theanine (1 mg/kg) significantly decreased the size of the cerebral infarcts 1 day after the occlusion. In contrast, theanine did not affect the cerebral blood flow, brain temperature and physiological variables (pH, pCO(2), pO(2) and hematocrit) in this model. These results suggest that theanine directly provides neuroprotection against focal cerebral ischemia and may be clinically useful for preventing cerebral infarction.

The L theanine content of commercial tea samples varies from 2 to 5 mg per gram of leaf.

Emails
Q. I have extreme anxiety, depression and insomnia. I am taking Cortisol Manager to try to get some sleep. I take two every night. I have just added L-Theanine. How effective and how long can you take this supplement, as my anxiety is still very high. I have been reading different things about this supplement. I really need something to calm my nervous system down and try to get sleep every night. Is L-Theanine safe to take? How much is necessary to take to get results?
   A. Each person is different, some feel the benefit on 100 mg, others need 200 mg or much more. As to safety, I am not aware of long term studies to determine how safe it is. So far it appears to be non toxic.

Q. I've been reading your site for awhile and I must thank you for such an informative, and most importantly, honest resource on supplements. You provide research with every review and list side-effects many others don't care to. I have had anxiety problems since early childhood. SSRI and MAOIs that I've taken couldn't even scratch it. I believe it to be OCD, altough I have been diagnosed with things from poor hand-eye coordination to general anxiety disorder, severe depression, and cyclothymia. It seems I can't "pass" the Yale-Brown OCD test for me to be considered for that, however. I've known people to gain a great benefit from the calming effects of L-theanine. 5HTP was reccommended on your site as well as others for helping lessen anxiety. I wish to try these together, but I have seen that L-theanine suppresses serotonin production while helping raise dopamine levels? As 5HTP is used to increase serotonin levels, wouldn't the use of L-theanine counteract its effects?
     A. Each person is unique in their response to 5-HTP and L Theanine, and it is difficult to say how you would respond to each one separately and together. The timing and dosage could make a significant difference. It is best to try 5HTP and L-theanine by themselves first and then consider combining at different times of day. Of course, we have to say that medical supervision is recommended.

Q. I'm using L-theaning and it just saved my life, it helped me with social anxiety, concentration, sleep or just feeling good. i had several panic attacks and now when i discovered this i just take it when i feel like it's starting and it causing it to completely disappear. BUT, but question is, I know all the benzodiazepines (Valium, Xanax) are causing an increase in the GABA, but they are extramly addictive and dangerous. Is L-theanine addictive too? Sometime if i take like 300mg of L-theanine a day I start to feel depressed after like 6-8 hours, could it have something to do with it? I've been asking this a couple of psychiatrists and they just say they don't know anything about alternative medicine and they don't think any amino acids could cause any addiction
     A. We don't know enough about long term theanine use, hence it is difficult to say whether long term l theanine use causes low mood. However, as with most supplements, taking breaks is useful and other anti-anxiety agents can be substituted, such as 5-htp, kava, ashwagandha, passionflower, etc. I am not aware of any serious cases of addiction to amino acids. A lower dose of l-theanine, such as 200 mg, may not cause the low mood after several hours. Or, using l-theanine only in the evening could make a difference.

Q. I would like to know if one may take L Theanine pills with a history of thyroid problems?
   A. Thyroid problems is a non-specific term since there can be many form of thyroid issues including hyper and hypo. As a general rule, L theanine appears to be a safe supplement and if your doctor approves you can start with half a capsule daily and increase to a full capsule if no problems.

Q. I've been taking L-theanine for insomnia for about a month and it seems to really help. If there are immune stimulating effects from it, could this amino acid possibly be bad for auto-immune diseases?
   A. We have not seen any studies to indicate L theanine to have a major influence on the immune system. However, it often takes years of studies to determine the full impact of a supplement on the immune system, and thus far such studies regarding its effect on the immune system have not been done.

Q. My DO recently recommended that I try Theanine because I am struggling with anxiety / panic in my body. I recently got off Celexa, because it wasn't working any more, I'm not depressed, and I was having side effect. However, now I'm suffering terribly from insomnia (taking ambien every night). My neurotransmitter test (from NeuroScience labs) showed I am low in most areas, particularly seratonin, dopamine, and norepinephrine / epinephrine. I am taking 800mg of 5HTP and 1000of GABA, but it isn't touching the insomnia. Question: I read somewhere that Theanine reduces seratonin in the brain. Is this true? If so, would it be counter-productive for me to take thenanine of I am already low on seratonin and dopamine?
   A. There's been a study in rats where theanine reduced brain serotonin, however many times when studies are done in rodents, massive amounts are used and it is difficult to interpret these results in humans where a much lesser dose is taken. I am not certain that blood level testing of neurotransmitters has much use clinically and sometimes people are steered in the wrong direction focusing on a few neurotransmitters and not recognizing that the body and mind are extremely complex and are influenced by countless substances. We suggest reading the information on the anxiety page. Too high a dose of 5-HTP can sometimes in some people have a stimulatory effect.

Theanine -induced reduction of brain serotonin concentration in rats.
Biosci Biotechnol Biochem. 1998. Laboratory of Nutritional Biochemistry, School of Food and Nutritional Sciences, University of Shizuoka, Japan.
Following the administration of theanine, the brain tryptophan content significantly increased or tended to increase, but the contents of serotonin and 5-hydroxyindole acetic acid (5HIAA) decreased. The use of inhibitors of serotonin metabolism enable us to speculate that theanine reduced serotonin synthesis and also increased serotonin degradation in the brain.

Q. i just finished reading your page about yohimbe and there is one thing not mentioned there which i am concerned about. i am planning to take l-theanine or theanine for anxiety, maybe i will take 200mg or so in the morning, can i take yohimbe at noon time or in the afternoon? is it ok? Thanks and i would like like u to know that u have a wonderful website, physician formulas com sells good products.
   A. We have not seen any research with the combination of yohimbe and theanine, but if your doctor approves you can start with low dosages of each to see how your body reacts. Each person reacts differently to herbs and supplements, and to combinations of supplements.

Q. I have been taking L-theanine occasionally and I've noticed that the two times I've taken it fairly close to going to bed I've had insomnia! I'm taking it in an attempt to lower my creeping-up blood pressure with the hope that I'll feel calmer and less stressed and that this will help my labile hypertension to stabalize. I would appreciate any information you might have about whether l theanine could be causing the insomnia and how it might be used for lowering blood pressure.
   A. In some people l theanine may cause a slight alertness, and this may also depend if there are other supplements added to the product. See our page on hypertension for suggestions on blood pressure control.

How nice to find a website that has solid information on more natural alternatives to pharmaceuticals! Hope you will be around a long time. I have been reading about L-Theanine and wondered if you have any information on whether it has been used to treat ADHD. My 7 year old son has been diagnosed with ADHD and we do not want to put him on stimulant medication.
   I searched Medline for the keywords theanine ADHD and could not find any studies regarding the treatment of ADHD with a l theanine supplement. Sometimes the only way to tell if a supplement will work is by trial and error. Theanine appears to be a safe amino acid, at least in the short term. I am not aware of long term human studies using l theanine supplements.

L theanine supplements work great for me at 100 mg for social anxiety, but has lead to depression and a certain feeling of joylessness and apathy in relation to others.

I have just started taking L-Theanine 100 mg in the evening two nights ago. My doctor recommended for severe anxiety. My salivatory neurotransmitter test shows very low levels of GABA and serotonin. Two nights ago when i first took it it kept me up all night. Last night i took it around 10pm. i got a moderately deeper sleep, yet woke up few times during the night. About half hour upon waking (around 8:30) i had about 5 gm L-Glutamine (i have been taking daily for several months). All during the morning until about 11:30 i felt very drowsy with a sense of low mood, apathy and joyless. I do have depression generally but it normally hits in the evenings and not in the mornings. Could this be a sdie effect from L Theanine? or maybe the combination with L Glutamine? I know that L-Glutamine alone didn't have any negative impact on my mood. How can i benefit from L Theanine and avoid the depressive effects of it?
   I have no reason to believe salivary neurotransmitter levels are an important tool in diagnosis or treatment. I have not heard of L theanine supplements causing side effects such as low mood but I have not had too much feedback regarding the use of this amino acid supplement. There are other supplements that can be used for anxiety.

Would you know if L Theanine interferes with Zoloft and Wellbutrin? I appreciate any help. My Doc's won't even call me back (military). I have had the gastric bypass about a year ago and right now I have a lot of stress in my life. 3 year old ADHD, husband is deployed and we just moved to another state and don't really have support. I am on 200 mg of Zoloft and 150 mg of Wellbutrin. I have been on those 2 for about a month. I just started yesterday opening the L Theanine capsules (100 mg) along with 2 teaspoons of D Ribose Powder. I put it in my smoothies with my protein powder twice a day. I am having insomnia really bad for a week now. I am exhausted and have tried melatonin, Tylenol PM, Benadryl, stress relieving teas. Nothing helps for my stress and anxiety.
    There are certain supplements that could be helpful for stress and anxiety including passion flower, kava, 5HTP, ashwagandha and valerian. It is difficult to predict which one will work best for you. Some people like to try different ones at different times rather than relying on just one supplement. It is difficult to predict the interactions between medications and supplements. Most medications are potent and may blunt the effects of the supplements.

Is the use of 5 HTP and/or L-Theanine recommended for children age 12?
    I have not seen studies with these nutrients in children or teenagers. If a child or young adult needs treatment for a condition, a doctor would need to balance the risk and benefits of supplements versus medications. As a general rule, supplements are safer than prescription meds. If 5-HTP or L theanine are used in children, it is best, as with adults, to use the lowest effective dosage and take breaks from use.

Testimonials
I have had anxiety issues off and on for over 7 years. Most of the time L-Theannine works great. A couple of weeks ago I felt this nervous ache in my spine, which is always associated with anxiety, came on during the night. Tried the L-Theannine, also added Hylands Calm, but it has not helped. Other night woke up with pounding heart rate. Took a Xanax and it calmed down. I do not like Kava or Valerian, they too sedate me. Even now with taking the Xanax, it is not completely calming me.

My very young daughter, 3 years ago, was diagnosed with Adductor Spasmodic Dysphonia. Today my child is 19 years old and receives botox injections into her vocal cords every 10 weeks in order for her to speak. We just started to use the amino acid, L-theanine, in between botox injections as it seems to calm the spasms and helps my child to speak.

I have been on theanine, for near 8 years. It has worked great, frankly I'm amazed. I have major PTSD from 3 causes. Finally, a long term counselor who I have know for near 30 years, suggested it 8 years ago. No side effects and I take between 400 to 600mg a day. Usually, 450mg when I awake at night for a bathroom visit.