Last updated on

My experience with L-theanine: dose, benefits, side effects

Article at a Glance
  • L-theanine is an amino acid found in green and black tea.
  • Studies show that, even with 50mg doses mimicing normal dietary behavior, theanine increases production of alpha brain waves, which are the brain waves that increase creativity and decrease depression.
  • Theanine is a glutamate antagonist, meaning it blocks glutamate receptors in the brain, which is part of the reason some people report a calming effect after taking theanine.
  • Theanine has also shown promise as a sleep aid and in stopping the release of histamine from mast cells.
  • Despite efficacy at 50mg doses, many theanine supplements up this dose to 100mg and beyond, so keeping an eye on dose is important.
  • Also, be aware that some supplements that claim to have proven efficacy in studies, such as Alpha Brain, are really just piggy backing on previous theanine research showing theanine effective at increasing alpha brain waves at 50mg doses.
Genes Mentioned
l-theanine dosage

If you’re researching L-theanine, also known as theanine, you may already know that it’s an amino acid, found in green and black tea, that boosts mood, and promotes a sense of calm without drowsiness. I will let Aaron get into the science of how L-theanine works to create these benefits later in this post, but before I do, I want to describe how I felt when I took L-theanine for the first time.

As you’ll see, it made me really nice to the people at Hertz rent-a-car.

Why I supplement with L-theanine

Please do not take this as an endorsement of her work on autism, of which I do not have an informed opinion, but I have found the the top level nutrigenomic theories outlined in Dr. Amy Yasko’s book Feel Good Nutrigenomics very useful. It was Dr. Yasko’s discussion of the glutamate/GABA ratio that first motivated me to use L-theanine as stand alone supplement.

Dr. Yasko believes the first step in crafting an effective health regimen is tackling imbalances in the glutamate/GABA ratio. Glutamate and GABA are both essential neurotransmitters, with important roles to play in cognitive function, however, when glutamate levels get too high, as they can during times of prolonged stress, when GAD1 mutations are present, or on a high glutamate diet, the usually beneficial glutamate can become an excitotoxin. (R)

In fact, elevated glutamate has been linked to a number of neurological diseases. (R)

See also: The MSG in your supplements

L-theanine can help balance glutamate levels

Science Score: 

One of the supplements Yasko recommends to get glutamate levels under control is, you guessed it, theanine.

Here is what Dr. Yasko has to say on the issue:

Addressing imbalances in the glutamate / GABA ratio as well as the calcium to magnesium ratio is what I consider the starting point of this program.

Look to support with nutrients that help calm the nervous system including GABA, THEANINE, valerian root, pycnogenol, grape seed extract, resveratrol, and CoQ10.

Theanine is an important supplement for glutamate/GABA balance because it blocks glutamate receptors in the brain. (R) One of the primary reasons people experience an anti-anxiety effect when taking theanine is due to this glutamate blocking activity.

How L-theanine makes me feel

In a word, great. L-theanine gives me a calm, creative focus. I feel unrestrained by mental clutter and notice a marked improvement in mood.

For example, I was recently in San Diego, where I visit often, and was returning a Hertz rental car. When I returned the car, the people at Hertz ignored me for a very long time, taking their sweet time processing my car. This would have irritated me under normal circumstances (many years in NYC gives you this ridiculous sense of time when it comes to the performance of services, you want it now!). However, rather than indulge in a moment of self imposed stress, I waited patiently. When the Hertz man finally came over, I asked how his day was going.

I went into duck mode, water rolled off my back.

Overall happier, calmer, and less stressed. I felt a noticeable increase in creative energy. I normally have lots of ideas, but the increased focus allowed me to digest and organize, rather than feeling overwhelmed by all the things I wanted to create/ things I had to do.

As I used theanine over the course of a week, I found that it was also a meditation aide.

L-theanine and alcohol

Science Score: 

I have found that theanine can also be a fun supplement to take socially. I will normally take 100mg prior to a night of drinking as it can reduce the effect of a hangover, and adds to the relaxing effects of alcohol. (R) How does theanine reduce hangovers? It appears theanine speeds the metabolism of alcohol by helping the body produce glutathione, although the study we cite to here is in mice and not yet established. However, I can attest anecdotally to theanine being helpful at reducing the impact after a night of drinks.

Not an everyday supplement for some people

Science Score: 

Theanine produced solid benefits for me, both in work and socially, and I will definitely continue using it, however, it is contraindicated for those on high blood pressure medication because it lowers blood pressure. (R) When I’ve taken high doses for a number of days in a row, I have noticed a few episodes of light headedness after standing.

I wouldn’t recommend taking high doses of lumbrokinase, nattokinase or N-acetyl-cysteine alongside theanine, especially for lengthy periods of time.

Theanine will be a 1-2 times a week supplement for me, and potentially more frequently when I am looking to balance glutamate/GABA ratios.

L-theanine benefits – proven by studies

Ok, now we dig into some of the more noteworthy studies evaluating theanine.

There have been a number of studies looking at the benefits of L-theanine. The FDA considers theanine as a GRAS (“Generally recognized as safe”) supplement.

In a randomized, double blind study, theanine was shown to significantly improve sleep quality in boys with ADHD. (R)

This study found that L-theanine prevented the cold and flu and had an immune boosting effect “enhancing gamma-delta T cell function.” The New York Times, reporting on the study, had this to say in summary:

Tea increases the body’s defenses against infection and contains a substance (L-theanine) that may be turned into a drug to protect against disease, a study has found. Coffee does not have the same effect, the researchers say in an article today in Proceedings of the National Academy of Sciences. A component in tea primes the immune system to attack invading bacteria, viruses and fungi, the study concluded. An experiment showed that immune system blood cells of tea drinkers responded five times faster to germs than did the blood cells of coffee drinkers.

This study found that L-theanine reduces physiological and psychological stress by blocking glutamate receptors in the brain. (R)

There are a few studies that show L-theanine improves alpha brain wave function, even at low 50 mg doses meant to mimic “normal dietary levels.” (R)

I am now passing the mic to Aaron for a deeper dive into how L-theanine works in the body.

L-theanine and allergy

Science Score: 

Thanks, John. L-theanine’s “mechanism of action” is quite interesting.

L-theanine has shown some promise as a modulator of allergic reactions. (R) A major event in allergic reactions is the secretion of histamine from immune cells known as mast cells. Mast cells can be thought of as the first responders of the immune system, they are constantly sensing the environment and when they detect something potentially harmful they secrete a wide range of factors to kick start the immune response. When mast cells detect something as harmful (even if it’s harmless) this causes an allergic reaction. (R) Theanine inhibits histamine release from mast cells.

Interestingly, this inhibition of histamine also ties in with L-theanine’s glutamate inhibitory activities as well. Histamine can induce glutamate release (R), which as we’ve established above, is an excitatory neurotransmitter our bodies need. Excess histamine may cause an unhealthy build-up of glutamate, although there is some evidence that there is an upper maximum of glutamate build-up associated with histamine (R).

L-theanine mechanism of action

Science Score: 

So the interesting questions then becomes how does L-theanine link all these together, and is there a single gene or SNP which is of particular interest?

Lets look at histamine first, a major gene involved in histamine metabolism is AOC1, which encodes for the enzyme Di-amine Oxidase (DAO – pay attention to that abbreviation as it’s the cause of much confusion). In health DAO functions to break down histamine following its release from mast cells, curtailing the immune response. There are several SNPs within AOC1 which are associated with reduced DAO activity, resulting in histamine intolerance, which is characterized by symptoms often associated with allergy such as headaches, flushing of the skin and irritation (R).

The benefit of L-theanine here is clear. By suppressing histamine release from mast cells (R), it is prevented from building up to harmful levels, even in those with reduced DAO activity.

We’ve already described how L-theanine can inhibit stress by blocking glutamate receptors (R). As excess histamine can lead to the buildup of glutamate there’s a clear mechanism for impaired DAO activity leading to increased histamine, leading to increased glutamate. L-theanine works by both preventing histamine release, and also blocking glutamate activity as well.


There’s a nice indirect mechanism linking DAO, histamine and glutamate.

However, if you read around on the internet, you may find articles discussing a direct action for DAO interacting with glutamate. While there may be evidence linking them directly I’ve not come across it; rather I think it’s a case of confusing DAO the enzyme with DAO the gene. DAO is encoded for by the AOC1 gene and functions to breakdown histamine (R). There is however a DAO gene which confusingly encodes for an enzyme called  d-amino acid oxidase (DAAO), which is involved in glutamate metabolism (R).

See also: You say DAO, I say DAAO

Quite why it seemed a good idea for DAO to be encoded for by AOC1 and DAAO to be encoded for by DAO I’ll never know, but I think this is the basis for much confusion. So be careful when you’re trying to interpret your genetic results!

L-theanine dosage and complementary supplements

Ok, taking the mic back from Aaron for some closing thoughts.

I have found L-theanine to be an effective nootropic that produces a calm focus. For me, it’s an effective tool for writing, meditating, creative bursts, and even to unwind and get to sleep at the end of the day. I also like it socially.

If you’re using theanine as an anti-anxiety supplement, the calming effects for me were greatest when paired with GABA and valerian. Keep in mind that both GABA and valerian can upset the stomach, so start slow. I also don’t recommend this stack for daily use over extended periods of time, best to cycle on and off.

As we discussed, theanine lowers blood pressure. Because there can be side effects, I would encourage everyone to experiment with different doses to see what amount of theanine suits them best. Some will tolerate 200mg quite well, while others may want to dose more in line with the studies that used 50mg.

Choosing a theanine supplement

If you’ve read thus far and want to add theanine to your supplement stack, I’ve included a short section below that gives a tour around some of the best theanine products on the market, standalone supplements, as well as a couple blends that have positive reviews and are made with good manufacturing practices from brands I trust.

Theanine supplement comparison

Jarrow Formulas Theanine 100100mg L-theanine60/ct
Onnit Alpha Brain650mg Onnit Flow Blend (L-tyrosine, L-theanine, oat extract, phosphatidylserine), 350mg Cat's Claw bark extract, 240mg Onnit Focus Blend (L-alpha GPC, Bacopa extract, Huperzia serrata extract), 65mg Onnit Fuel Blend (L-leucine, vinpocetine, pterostilbene), 10mg Vitamin B690/ct
Jarrow Formulas GABA Soothe225mg Ashwagandha extract, 100mg GABA, 100mg Suntheanine30/ct

Jarrow Formulas Theanine

This is the theanine I take, although I take the 100mg capsules. Jarrow also makes a 200mg capsule if you find you do well with larger doses of theanine. In both cases, the capsules are easily broken apart so you can experiment with smaller doses. Remember, it’s the 50mg dose that triggered the increase in alpha brain waves in the studies, and the 50mg dose is also closer to what you’ll find in tea, but in today’s culture we assume that more is always better, which isn’t necessarily true. I will often take apart a 100mg capsule and empty out approximately 40-50mg so I have a conservative dose. Another advantage of the Jarrow products is they use a high quality theanine, called Suntheanine.

Alpha Brain by Onnit

Note: I don’t take Alpha Brain.

As a resident of Austin, Texas, I am perhaps more familiar than most with Onnit, the supplement brand started by Aubrey Marcus. You also may have heard of Onnit if you listen to the Joe Rogan podcast, as Joe has a stake in the company. Alpha Brain is one of Onnit’s top selling nootropic supplements, and it features a 200mg dose of theanine, along with a host of other ingredients, including tyrosine.

Reviews, both on the Onnit website, as well as on Amazon, are mixed, with some swearing by the product and others finding no benefit. Since Onnit adds tyrosine to the formula, efficacy may have something to do with the user’s dopamine receptor genes. We wrote a blog post on how genetics impact tyrosine metabolism, which I’d encourage you to read if tyrosine becomes a part of your supplement regimen.

I would also note that amino acids like tyrosine compete for uptake in the brain with tryptophan, which is the precursor to serotonin, so watch closely how this product makes you feel. For more on the impact of food and supplements on serotonin, see how to boost serotonin naturally and safely. As with standalone theanine blends, it’s best to cycle on and off of Alpha Brain, and be conservative with dosage.

I mention Alpha Brain in this post because I know they use quality ingredients, and because Onnit did a clinical trial that showed Alpha Brain improved alpha brain state, verbal recall and focus. Of course, this isn’t a big surprise because, as we know from theanine studies, theanine alone would likely have yielded all of these results, but nonetheless, conducting the trial is a sign of good faith and professionalism.

GABA Soothe by Jarrow

Note: I don’t take GABA Soothe.

But it is an interesting product because it blends theanine, GABA and ashwagandha, and adaptogenic herb used to promote relaxation. Now, you’ll remember, that for stress relief, I found theanine most effective when paired with GABA and valerian. This product adds GABA to the formula, as well as an herb that is popular with many people for reducing anxiety. The issue I see here is that the dose of GABA is very small.

There is a lot of controversy over whether GABA can cross the blood brain barrier as we know theanine does. Many say it cannot, however, in light of the fact that GABA moves out of cells much faster than it moves in, it may just be difficult to measure. For those who don’t need a large dose of GABA, this could be a product worth trying. However, as a point of reference, when I take GABA, I take a 750mg dose, which is 7 times higher than the GABA content of GABA Soothe.

The very latest on genetics, nutrition and supplements delivered to your inbox!


Leave Comment

  1. Gurps says:

    Great article! I’ve more confidence to take Theanine.
    What type of diet would be looking at to complement this? Its almost impossible to avoid glutamate as its in everything. However, there are supplements such as B6 and Taurine which convert glutamate tonGABA so maybe we don’t need to be as restrive?

  2. Tyler says:

    I’ve tried many different known supplements over the years that don’t seem to positively help anything in the end. However, that is not the case with Theanine. It’s absolutely amazing. I’ve been using it daily for a couple of years and have never had any side effects at all whatsoever. It really calms my nerves and anxiety. Not massively like you’re drugged. Just a gradual soft calm starts to ease through me where I’m suddenly not bothered by much when I would be easily aggravated or explosive before taking this. So this definitely is compatible with me. I stumbled upon this article as I was curious if others had the same experience because no one talks much about theanine. They talk about antidepressants, but this is just as good without the side effects. Of course as should be understood everyone’s physical and brain chemistry is different. Just because this is fantastic for me doesn’t mean it will be for you. You’ll have to find out for yourself and what dosage is right. Too little might not do anything, but the too much can bring up side effects.

    • Travis says:

      ” Just a gradual soft calm starts to ease through me where I’m suddenly not bothered by much when I would be easily aggravated or explosive before taking this. ”

      I just started taking L-theanine today, it arrived in the mail.

      About a week ago I started taking tongkat ali 200:1 extract which I noticed increased testosterone, confidence, reduced anxiety.

      I was making some food today and I dropped the spoon on the floor, which normally would have pissed me off but something different happened in my mind. I grabbed another spoon and was totally fine.

      Normally little things like that I find really annoying. Weird to explain but I think the combo of tongkat ali and l-theanine is pretty good.

  3. Joanna says:

    Is there any research on mixing theanine with Klonopin? I am currently using klonopin to help take the edge off my intense anxiety/agoraphobia.

  4. JoAnne says:

    GREAT and informative article and I sure hope L-thenanine helps me sleep a full night. In addition to numerous physical injuries that required titanium implants, I also suffered Traumatic Brain Injury (TBI) all from a bicycle accident 2 1/2 years ago. One of the ongoing issues from the TBI is that often my brain only shuts off for 2 to 3 hours of sleep each night which then renders my brain deficient in allowing me to properly walk, talk, or process thoughts the following day. I do not and will not take sleep medication and have tried a number of natural, plant based supplements, none of which have helped.

    My problem and question is as follows; I have very low blood pressure (92/58 and occasionally lower), are there any studies that claim L-theamine causes low blood pressure to go even lower? I am on a vegan diet and foods that are considered to help lower blood pressure have never affected my blood pressure and I’m hoping L-theamine is the same.

    Thank you for any information you can provide. I NEED a full night sleep to get this damaged brain healed,

    • Dale Hoover says:

      Hello JoAnne, – I am a 72 year old female who has had low b.p. all my life (usually around 96/54); I just recently discovered L-theanine for sleep, as I too only can sleep 2-3 hours, then can’t get back to sleep (adult-long scenario) without taking a whole lot of vit. C (it acts as an anti-histamine), or taking an anti-histamine pill. Last night I took 200 mg. L-theanine at bedtime & after waking I got back to sleep(!), – plus even had dream recall! Tonight I will do the same. I believe the warning about low b.p. and theanine is for ppl who are taking b.p.-lowering meds.

  5. David says:

    Maybe I’m looking at it wrong. Isn’t a proper histamine response something that is beneficial, though? If the mast cells are supposed to be responding to allergens or invaders, Isn’t blocking the histamine response effectively suppressing the immune system?

    With that said I took L-Theanine (SunTheanine) last night for the first time, the day after my ativan prescription ran out. I was going through some anxiety effecting sleep, and couldn’t sleep without at least a small piece of ativan.
    The Theanine really did seem to make me relaxed, and I fell asleep surprisingly easily and slept through the night.

  6. Laura says:

    Hi, I’ve just started looking into Theanine to help manage my anxiety symptoms. The only kind I could find at my local health store though was 400mg doses. Is this too high? They’re capsules, could I break them open at take half at a time or would that screw with how it’s absorbed?

    Also, would taking Theanine clash with my regular antihistamine (loratadine)? I have grass, animal and dust allergies so I usually take 2 a day in summer and 2-3 times a week in winter.

  7. Marie says:

    I have aaib and am on medication for it. I have had 2 tia”s and normally cant drink caffeine so I am wondering if theane will cause palpitations

  8. Ron says:

    l-theanine while blocks AMPA and the other glutamate receptor it is an agonist of the NMDA receptor. and it increases glutamate neurotransmission via blocking the glutamate transporter.

  9. Benette says:

    Can i give this to my child that has ADHD to lessen his hyperactivity and poor sleep? If yes,
    what will be the recommened dosage. Thank you in advance.

  10. Danielle says:

    I wish I would’ve found this years ago. Funny, the doctors don’t recommend this and push all the other drugs with terrible side effects.

    I ordered Natures Trove brand from Amazon based on the reviews but didn’t notice the benefits until I started taking Finest Nutrition brand from Walgreens.

    I find myself taking a few doses during the day as I can feel agitation arising. Im sure it can’t be good, but have yet to read anything about too-high of doses.

  11. Anna says:

    I was recommended to give this to my son who was recently diagnosed with ADHD and has been taking 27mg of Ritalin with only negative side effects and no benefit. He noticed an improved feeling of his overall mood (and I noticed as well) in taking L-Theanine for 1 day – 200mg which was recommended by his psychiatrist – along with magnesium, B-6, 12, zinc & Inositol but I haven’t added those in yet. What I’m confused about is all the discussion around the different brands of L-Theanine. Jarrow, Nature’s Trove, Nutricost, etc. How can the brand impact it’s effect if that is the main ingredient and same dosage is given?

    • Danielle says:

      I too, wondered the same thing. I work in a pharmacy and never questioned different manufactures, or brands vs. generics. However, I came across it in an Amazon review where someone had wondered why one brand was substantially greater in cost versus every other brand. Someone had commented that specific brand actually made the ingredient, opposed to the other ones which contained the ingredient derived from the plant? It was a while ago and I don’t remember the specifics and tried to find it again with no luck.

      How old is your son that you give this to? I wanted mine to try it but I don’t know if he is too young. However, I feel that everyone could benefit from this.

    • Danielle says:

      I really hope this helps him and he can get off of the ADD prescriptions. I hate that they prescribe them for children, they are a serious controlled substance. Unfortunately, so many drugs are pushed by doctors and approved by the FDA with worse side effects and detrimental results, and we have no choice but to trust our health care professionals and believe they and the FDA have our best interest in mind.

      • Lisa says:

        Has anyone taken the supplement Zen 200mg? A single dosage contains 550mg of GABA and 200MG L-Theanine. My integrative/functional doctor wants me to start taking 1 per day and then work up to 2 a day. I’m currently taking 5MG of Valium to help with the dizziness/spinning from a vestibular disorder and autonomic nervous system disorder. I don’t know if Zen will interact with the Valium and I have to be careful bc my blood pressure can go low or high. I would greatly appreciate any comments/suggestions.

  12. Irene Kittrell says:

    If green tea “primes the immune system against bacteria, etc.” does it also prime the immune system of people with an autoimmune disease, thereby making it worse?

    • Jason says:

      Not sure yet. I supposedly have vitiligo, and AA. Only on second day of dosing. I have had anxiety and worries that the vitiligo maybe caused by something else other than the so called autoimmune disorder. So far it has helped me with my anxiety. I am curious to see what it does for my white patches, if anything. As a side note I have my suspiscions of bacteria, fungus, or parasite as with any problem. I am curious myself. See in a month or so. Still dosing various mg. 200 and higher.

Leave a Reply

Facebook icon Twitter icon Instagram icon Pinterest icon Google+ icon YouTube icon LinkedIn icon Contact icon Info icon