L-Theanine is an amino acid that helps promote a mild, restful, relaxed state with minimal daytime sedation. L-Theanine has much fewer side effects than other commonly used relaxing agents. For better sleep at night, consider Good Night Rx.

• Suntheanine, a patented form of L Theanine, is a trademark of Taiyo International, Inc.
• Promotes relaxation and stress reduction

L-Theanine Supplement Facts
L Theanine - 100 mg
   (Suntheanine brand)

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Subscribe to a FREE Supplement Research Update newsletter. Twice a month we email you a brief abstract of several new studies on various supplements and natural medicine topics, including l theanine research, and their practical interpretation  by Ray Sahelian, M.D.

Good Night Rx, Developed by Ray Sahelian, M.D.

Herbal natural sleep helper for occasional sleepless nights.

Mind Power Rx - Formulated by Ray Sahelian, M.D.

Mind Power Rx is a sophisticated cognitive formula. It combines a delicate balance of brain circulation agents and neurotransmitter precursors with powerful natural brain chemicals that support:

• Memory and Mood
• Mental clarity
• Concentration 
• Alertness & Focus

Why buy all the individual herbs and nutrients separately -- at great expense -- when you can buy this excellent combination?

The herbs in Mind Power Rx include: Ashwagandha, Bacopa, Fo-Ti, Ginkgo biloba, Ginseng, Mucuna pruriens, and Reishi.  The nutrients and vitamins in Mind Power Rx include Acetyl-l-carnitine, Carnitine, Carnosine, Choline, DMAE, Inositol, Methylcobalamin, Pantothenic acid, Trimethylglycine, Tyrosine, and Vinpocetine.
Click L Theanine above in blue for more information

How L Theanine may work
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
l-Theanine reduces psychological and physiological stress responses.
Biol Psychol. 2006 Aug 21; Nagoya University Department of Psychology, Chikusa-ku, Nagoya, 464-8601, Japan.
Because the characteristics of l-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. 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.

L Theanine research shows
L-Theanine (delta-glutamylethylamide) is one of the predominant amino acids ordinarily found in green tea, and historically has been used as a relaxing agent.

L-Theanine might be useful for preventing ischemic neuronal damage.
L-Theanine increases the idarubicin-induced antitumor activity and ameliorates its toxicities.

L-Theanine summary
Human research with l-theanine 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
I have not come across any research regarding the side effect profile of l theanine side effects. In my experience, dosages greater than 300 mg of l-theanine cause a side effect of transient lightheadedness. It is possible that L-theanine side effects 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.

Theanine and 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 (so much so that the nurses who check me always think they've done it wrong), and I have read that l-theanine lowers blood pressure. So my question is this: 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 this suppliment 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 the role of l-theanine 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 (Berl). 2007 Sep 23; Rogers PJ, Smith JE, Heatherley SV, Pleydell-Pearce CW. Department of Experimental Psychology, University of Bristol, 12a Woodland Road, Bristol, BS8 1TU, UK,
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. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats. 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 (n = 48) 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.

Toxicity and Safety of L Theanine
A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats.
Food Chem Toxicol. 2006 Jul;44(7):1158-66. Borzelleca JF, Peters D, Hall W. 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.

Theanine Research Update
Anti-obesity effects of three major components of green tea, catechins, caffeine and theanine, in mice.
In Vivo. 2004 Jan-Feb;18(1):55-62.
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. Body weight and food intake were determined monthly during this period, kidneys, adrenals, liver, spleen, brain, pituitary and intraperitoneal adipose tissues (IPAT) were weighed and lipid levels in the serum and liver were measured at the end of this period. The body weight increase and weight of IPAT were significantly reduced by the diets containing green tea, caffeine, theanine, caffeine + catechins, caffeine + theanine and caffeine + catechins + theanine. Noticeably, the IPAT weight decreased by 76.8% in the caffeine + catechins compared to the control group. Serum concentrations of triglycerides and non-esterified fatty acids (NEFA) were decreased by green tea, catechins and theanine. Moreover, caffeine + catechins, caffeine + theanine and caffeine + catechins + theanine also decreased NEFA in the serum. The triglyceride level in the liver was significantly reduced by catechins and catechins + theanine in comparison with the control. These 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.  I theanine side effects

Neuroprotective effect of gamma-glutamylethylamide ( theanine ) on cerebral infarction in mice.
Neurosci Lett. 2004 Jun 3;363(1):58-61.
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.

Theanine Emails
Q. Dear Dr. Sahelian, 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 i think 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.

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Q. I've been taking L-theanine for insomnia for about a month and it seems to really help. My question is this: If there are immune stimulating effects from L-theanine, 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 L theanine and the immune system have not been done.

Q. Question about Theanine: Thanks so much for the work that you do! History: 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 Apr;62(4):816-7. 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, physicanformulas.com sells good products, too
   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 l theanine product. See our page on hypertension for suggestions on blood pressure control.

Q. Absolutely love your site. I send it to everybody I know! What do you know about L-Theanine? A doctor recommends l theanine for anxiety. Just wondering what your thoughts were.
   A. There are herbs and other nutrients more potent than l theanine for anxiety.

Q. Could you tell me please if taking L Theanine supplement, which is supposedly better absorbed than GABA, if L Theanine is more helpful for sleep than GABA.
   A. In my opinion, L theanine is more potent than GABA. Good Night Rx is more potent than L theanine for sleep.

Q. 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.
   A. 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.