L-Theanine is a “unique non-protein amino acid found in green tea” which according to the study below, has shown benefits when used short-term or acutely as a supplement for it’s anti-stress effects, reducing anxiety, improving sleep quality, improving cognition and even easing depression.
This 2019 study, Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial, aimed to examine the effects of four weeks use of l-theanine:
on stress-related symptoms and cognitive functions in healthy adults. Participants were 30 individuals (nine men and 21 women; aged 20-69) who had no major psychiatric illness.
The trial was randomized, placebo-controlled, crossover, and double-blind.
L-theanine (200 mg/day of Suntheanine), was used by study participants before going to bed each night and was used for four-weeks.
Study participants who used the theanine for two weeks observed the following:
- For sleep: Reductions in sleep latency (the amount of time it takes to fall asleep), sleep disturbance and less use of sleep medication
- For cognitive function: Improvements in verbal fluency (especially letter fluency) and improvements in executive function (planning, multi-tasking etc)
The Japanese versions of The Self-rating Depression Scale, State-Trait Anxiety Inventory-trait, and Pittsburgh Sleep Quality Index (PSQI) scores decreased and the study concludes as follows:
Our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.
The authors also note that “there were no significant adverse events, demonstrating the safety of four weeks of L-theanine administration.”
As expected, the participants saw increases in serum theanine concentrations.
Some of the reported possible mechanisms of action
Here are some of the reported possible mechanisms of action of theanine from some studies referenced in his paper:
- via glutamate receptors (improving cognitive dysfunction)
- as a neuroprotective agent and “increases in brain serotonin, dopamine, GABA levels” (improving mood and focus and reducing anxiety)
- enhances hippocampal activity (the hippocampus has a major role in learning and memory)
- via a proposed increase in the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus (BDNF is a protein implicated in the stress response, long-term memory, Alzheimer’s disease, and psychiatric disorders)
Impacts on cortisol levels?
What is unusual and inconsistent with previous studies, is the fact that there was “no significant effect on cortisol or immunoglobulin A levels in the saliva or serum.” The authors report that “the reduction of salivary cortisol and immunoglobulin A levels may be a short term, recoverable effect of L-theanine administration.”
Update Sept 2025:
In this 2021 paper, A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave®l-Theanine on Stress in a Healthy Adult Population “there was a significant reduction in salivary cortisol with a single dose of AlphaWave® l-Theanine relative to the placebo, immediately following the stress-inducing task 1 h post-dose.”
In other words, within an hour of taking AlphaWave l-theanine, cortisol levels were lower. This paper also mentions that in a previous study, cortisol levels were only lower 3 hours after taking theanine.
Suntheanine and AlphaWave are different theanine products, each produced by their own proprietary manufacturing process. There are a number of other l-theanine products/manufacturing processes and this may explain why some individuals do well on some theanine products and not others, and why impacts on cortisol levels may vary.
Theanine or GABA – which one to use when?
I typically start my clients with a trial of GABA Calm for low GABA symptoms like physical tension, stress and overwhelm, panic attacks and insomnia. If we are not getting all the expected benefits with GABA and there is a need for added cognitive benefits then we’ll consider adding theanine too. Some folks find one works better than the other and some like a combination (at the same time or theanine in the day/GABA at night or GABA in the day/theanine at night).
I recently reached out on facebook asking:
“Theanine or GABA? Which do you prefer for anxiety and why? How much helps? And any other benefits (like reduced body pain, better thinking/cognition, easing IBS (irritable bowel syndrome) and gut pain, reduced cravings, less negative self-talk etc)? Or do you like a combination of both?”
As you can see from these varied responses it’s a matter or trialing both to find what works for each person’s unique needs:
- Lorraine shared this: “They are both good, but I reach for GABA Calm first.. 2 or 3 lozenges. If anxiety doesn’t leave quickly with GABA ( which works well for a panic attack), and I continue to have anxiety humming along in the background, then I’ll reach for theanine.”
- Jackie shared this: “I take 200mg theanine in morning, then 100mg GABA around 4pm, when the kids get home from school. I had a panic attack in the middle of the night last week, took GABA 100 mg, then seemed to calm down.” I asked if theanine gives her a feeling of calm focus and she said: “yes, I think so. I noticed if I take 200mg of GABA, it makes me drowsy.”
- Evelyn shared this: “I use both at night for sleep. If I could only use one it would be l-theanine.” Theanine is more consistently helpful for stress reduction and sleep for me. I use 200mg. When I use GABA it’s 500mg of chewables.”
- Sara shared this: “GABA during the day, theanine at night.”
- Karine shared this: “GABA!! The Source Naturals Theanine Serene with Holy Basil is really good. But GABA Calm (also Source Naturals which is a sublingual lozenge) is the only thing for a severe issue/episode and helps me concentrate right before an important presentation at work etc. Pure GABA from any supplier is good for long periods where you need a boost or to tone down general anxiety. I also bought a probiotic that also includes GABA (Jarrodophilus Mood) and notice it improves digestion too.”
Some of my top GABA/theanine products
You can find my favorite GABA/theanine combination product, a theanine-only product and my most popular GABA products on the supplements blog here (and with details for how to set up an account for my online store)
Nutritional Fundamentals for Health GABA-T SAP: 300mg GABA, 150mg theanine. This is pleasant-tasting when opened on to the tongue and works very well when GABA Calm can’t be used.
Pure Encapsulations L-Theanine: 200mg theanine. This is also pleasant-tasting when opened on to the tongue. Unlike like GABA, it can also be swallowed.
Source Naturals GABA Calm. This is a pleasant-tasting sublingual product that is my most popular and most effective form of GABA I use with my clients. It can be used in conjunction with theanine.
Enzymatic Therapy GABA: 250 mg GABA. This is also pleasant-tasting when opened on to the tongue and works very well when GABA Calm can’t be used. It can also be used in conjunction with theanine.
BeSerene IR (instant relief): a topical GABA/theanine cream which can be used in conjunction with other GABA and theanine products or instead of them.
Additional resources when you are new to using GABA or theanine and other amino acids as supplements
We use the symptoms questionnaire to figure out if low serotonin or low GABA or low dopamine or other neurotransmitter imbalances may be an issue for you.
If you suspect low levels of any of the neurotransmitters and do not yet have my book, The Antianxiety Food Solution – How the Foods You Eat Can Help You Calm Your Anxious Mind, Improve Your Mood, and End Cravings. I highly recommend getting it and reading it before jumping in and using amino acids on your own so you are knowledgeable. And be sure to share it with the practitioner/health team you or your loved one is working with.
There is an entire chapter on the amino acids and they are discussed throughout the book in the sections on gut health, gluten, blood sugar control (this is covered in an entire chapter too), sugar cravings, anxiety and mood issues. The importance of quality animal protein and healthy fats is also covered.
The book doesn’t include product names (per the publisher’s request) so this blog, The Antianxiety Food Solution Amino Acid and Pyroluria Supplements, lists the amino acids that I use with my individual clients and those in my group programs.
If, after reading this blog and my book, you don’t feel comfortable figuring things out on your own (i.e. doing the symptoms questionnaire and respective amino acids trials), a good place to get help is the GABA QuickStart Program (if you have low GABA symptoms too). This is a paid online/virtual group program where you get my guidance and community support.
If you need serotonin support, the Serotonin QuickStart Program is a good place to get help. This is also a paid online/virtual group program where you get my guidance on using tryptophan and 5-HTP safely, and community support during 5 LIVE Q&A calls. You can sign up to be notified when the next live launch of this program is happening.
If you are a practitioner, join us in The Balancing Neurotransmitters: the Fundamentals program. This is also a paid online/virtual program with an opportunity to interact with me and other practitioners who are also using the amino acids.
Now I’d love to hear from you
Please let us know … theanine or GABA: which do you prefer for anxiety and why? How much helps? And any other benefits (like reduced body pain, better thinking/cognition, easing IBS gut pain, reduced cravings, less negative self-talk etc)? Or do you like a combination of both?”
Feel free to share and ask your questions below.