GABA vs L-Theanine: Differences for Sleep, Stress and Taking Both

GABA is the brain's main calming messenger, while L-theanine is an amino acid from tea leaves that research shows can reach the brain. In human trials, L-theanine eased the body's response to a stressful mental task and improved several sleep quality scores, while reviews of oral GABA describe a smaller research base and an open question about whether it gets past the blood brain barrier. Here is how the two compare for stress and sleep, and what is known about taking them together.

Key Takeaways

• GABA is the main inhibitory, or calming, messenger in the brain, and it is also sold as a supplement to take by mouth (Boonstra et al., 2015).
• Whether oral GABA crosses the blood brain barrier in people is still debated; a 2020 review of 14 placebo-controlled trials found no human data showing that it does (Hepsomali et al., 2020).
• L-theanine is able to pass the blood brain barrier, according to a 2022 review of animal and human research (Wang et al., 2022).
• In 30 healthy adults, 200 mg of L-theanine at bedtime for 4 weeks improved three sleep quality subscores more than placebo, with no adverse events seen (Hidese et al., 2019).
• A GABA and L-theanine mix shortened the time to fall asleep in mice and rats more than either alone; this pairing has been studied in animals (Kim et al., 2019).

GABA vs L-Theanine: The Main Differences

The two are often mentioned together because both relate to a calmer state of mind, but they are very different substances. GABA is a messenger your brain already makes. L-theanine is an amino acid you take in from tea.

	GABA	L-theanine
What it is	The brain's main calming messenger	An amino acid found naturally in tea leaves
Reaching the brain	Debated; no human data yet show it crosses the blood brain barrier	Able to pass the blood brain barrier
Stress research	About 20 to 100 mg in trials; reviewers called the evidence limited	Eased heart rate response to a stressful task; lower stress-related symptom scores after 4 weeks
Sleep research	About 100 to 300 mg in trials; reviewers called the evidence very limited	200 mg at bedtime improved three sleep quality subscores over 4 weeks
Main safety note	Can cause a short, moderate drop in blood pressure	No adverse events seen in the 4-week trial

For a full profile of the amino acid, see our L-theanine ingredient page.

What GABA Is and the Blood Brain Barrier Question

GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the human cortex. Inhibitory means it quiets nerve signals. GABA supplements are sold widely (Boonstra et al., 2015), and research has looked at GABA made by fermentation, as in capsules and tablets, and at GABA found in foods such as GABA-enriched rice and tea (Hepsomali et al., 2020).

The key question is whether GABA you swallow reaches the brain. The blood brain barrier is a tight lining around the brain's blood vessels that controls what gets in. GABA was long thought unable to cross it, and studies on this point are often contradictory. A 2015 review found no definite answer for people yet, and suggested any effects of oral GABA might come from crossing the barrier or, more indirectly, through the nervous system of the gut (Boonstra et al., 2015).

A 2020 review noted that blood GABA rises after oral intake and that some brain wave recordings hint at effects in the brain, but found no data so far showing GABA crosses the blood brain barrier in humans (Hepsomali et al., 2020).

What L-Theanine Is

L-theanine is an amino acid found naturally in tea leaves. Unlike GABA, it is able to pass the blood brain barrier, where it exerts its relaxing effect, and it competes with glutamate, the brain's main excitatory messenger, for its receptors (Wang et al., 2022). It is known for supporting relaxation without sedation, so people describe feeling calmer while staying clear and alert. Our guide to L-theanine benefits covers the wider research.

GABA vs L-Theanine for Stress

L-theanine

In a double-blind study of 12 people doing a stressful mental arithmetic task, the rise in heart rate and in salivary immunoglobulin A, a stress marker, was smaller with L-theanine than with placebo, and heart rate variability suggested less activation of the fight or flight nervous system (Kimura et al., 2007).

Over a longer stretch, 30 healthy adults took 200 mg of L-theanine or placebo at bedtime for 4 weeks each. Scores on stress-related symptom questionnaires fell during the L-theanine period, and verbal fluency and executive function scores improved (Hidese et al., 2019).

GABA

The 2020 review of 14 placebo-controlled human trials looked at stress measures such as calmness ratings, heart rate variability, cortisol and brain wave activity. Stress trials used roughly 20 to 100 mg of GABA made by fermentation, and the reviewers described the evidence for stress as limited (Hepsomali et al., 2020). For more options in this area, see best supplements for stress and mood and our stress, mood and nervous system guide. If you are comparing GABA with an adaptogen herb, our guide to GABA vs ashwagandha covers stress, calm and sleep.

GABA vs L-Theanine for Sleep

In the 4-week trial, 200 mg of L-theanine at bedtime improved three parts of the Pittsburgh Sleep Quality Index more than placebo did: sleep latency (the time it takes to fall asleep), sleep disturbance and use of sleep medication (Hidese et al., 2019).

For GABA, sleep trials in the 2020 review used about 100 to 300 mg and measured sleep quality questionnaires, time to fall asleep and sleep recordings. The reviewers described the evidence for sleep benefits as very limited (Hepsomali et al., 2020). Our guide to L-theanine for sleep goes deeper on amounts and timing.

Taking GABA and L-Theanine Together

The pairing has been studied in animals. In mice and rats, a mix of GABA and L-theanine (100 and 20 mg per kg of body weight) shortened the time to fall asleep and lengthened sleep more than either one alone. In rats it also increased both REM and non-REM sleep compared with controls, and it increased the expression of GABA receptors and of a glutamate receptor subunit (Kim et al., 2019).

Animal doses do not translate directly to people. The idea behind the pairing is that L-theanine works on glutamate signaling while GABA is the calming signal itself. If you want to combine them, keep each at its label amount and check with your doctor first if you take any prescription medicine.

L-Theanine or GABA: How to Choose

• For calm during the day: L-theanine has human trials on stress responses and supports relaxation without drowsiness, so it suits work, travel or busy afternoons.
• For winding down at night: L-theanine at bedtime improved several sleep quality subscores over 4 weeks. Pairing it with melatonin is another option; see melatonin and L-theanine.
• If you are curious about GABA: know that research is still working out whether oral GABA reaches the brain, and ask your doctor first if you take blood pressure medicine.

For amounts used in studies, see our L-theanine dosage guide.

Safety and Who Should Check First

L-theanine. In the 4-week trial, no participant dropped out, no adverse events were apparent, and body mass index and blood chemistry measures did not change significantly (Hidese et al., 2019). Our guide to L-theanine side effects covers the rest of the safety picture.

GABA. A United States Pharmacopeia safety review found no serious adverse events, with intakes studied up to 18 g a day for 4 days and 120 mg a day for 12 weeks. Some studies saw a short, moderate drop in blood pressure, so taking GABA with blood pressure medicines might raise the risk of blood pressure falling too low. No studies were available in pregnancy or breastfeeding, and the reviewers advise caution there (Oketch-Rabah et al., 2021).

Talk to your doctor before taking either one if you are pregnant or breastfeeding, take blood pressure medicine, or take sleep medicine or sedatives.

Where Our Theanine Products Fit

We do not make a GABA product. Our Theanine Nasal Spray gives 36 mg of L-theanine in every 2-spray serving, with alkaline water as the only other ingredient, used as needed. It is made with third-party tested ingredients and absorbed through the lining of the nose instead of being swallowed like a capsule, so some of each dose skips digestion.

For nights, our Melatonin Nasal Spray pairs 200 mcg of melatonin with 17 mg of L-theanine in every 2-spray serving, with alkaline water as the only other ingredient. It is designed to support your natural sleep timing and a calmer wind down before bed. Use 2 sprays before your intended bedtime, as the label directs. For the bigger picture, see our sleep health guide.

Frequently Asked Questions

Is GABA or L-theanine better for sleep?

L-theanine has the clearer human research. In a 4-week trial of 30 healthy adults, 200 mg at bedtime improved sleep latency, sleep disturbance and sleep medication use scores more than placebo. A 2020 review of oral GABA trials, which used about 100 to 300 mg, described the evidence for sleep as very limited.

Is GABA or L-theanine better for stress?

In human studies, L-theanine eased the rise in heart rate during a stressful mental task and lowered stress-related symptom scores over 4 weeks. GABA trials for stress used about 20 to 100 mg, and a 2020 review described that evidence as limited.

Can you take GABA and L-theanine together?

They have been studied together in animals: in mice and rats, a GABA and L-theanine mix shortened the time to fall asleep more than either alone. Animal doses do not carry over to people, so keep each at its label amount. Talk to your doctor first if you take blood pressure medicine, sleep medicine or any other prescription medicine.

Does oral GABA reach the brain?

This is still being worked out. GABA was long thought unable to cross the blood brain barrier, and studies on the question are often contradictory. A 2020 review found that blood GABA rises after oral intake but that there are no data yet showing it crosses into the brain in humans.

Does L-theanine make you sleepy?

Not usually. L-theanine is known for supporting relaxation without sedation, so most people feel calmer while staying clear and alert. That makes it usable during the day as well as before bed. In one trial, bedtime use improved several sleep quality subscores over 4 weeks.

Can you take L-theanine every night?

In a trial of 30 healthy adults, 200 mg of L-theanine every night at bedtime for 4 weeks caused no apparent adverse events, and no one dropped out. Follow your product's label, and talk to your doctor first if you are pregnant, breastfeeding or take prescription medicine, including sleep medicine.

Can you take L-theanine with melatonin?

Yes. L-theanine supports a calmer state, while melatonin supports your natural sleep timing, so the two fit together in a bedtime routine. Our Melatonin Nasal Spray pairs 200 mcg of melatonin with 17 mg of L-theanine per 2-spray serving. Talk to your doctor before using melatonin if you are pregnant, breastfeeding or take prescription medicine.

Sources

• Boonstra E, de Kleijn R, Colzato LS, Alkemade A, Forstmann BU, Nieuwenhuis S. Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Frontiers in Psychology, 2015. https://doi.org/10.3389/fpsyg.2015.01520
• Hepsomali P, Groeger JA, Nishihira J, Scholey A. Effects of oral gamma-aminobutyric acid (GABA) administration on stress and sleep in humans: a systematic review. Frontiers in Neuroscience, 2020. https://pubmed.ncbi.nlm.nih.gov/33041752/
• Wang L, Brennan M, Li S, Zhao H, Lange KW, Brennan C. How does the tea L-theanine buffer stress and anxiety. Food Science and Human Wellness, 2022. https://doi.org/10.1016/j.fshw.2021.12.004
• Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biological Psychology, 2007. https://pubmed.ncbi.nlm.nih.gov/16930802/
• Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients, 2019. https://pubmed.ncbi.nlm.nih.gov/31623400/
• Kim S, Jo K, Hong KB, Han SH, Suh HJ. GABA and l-theanine mixture decreases sleep latency and improves NREM sleep. Pharmaceutical Biology, 2019. https://doi.org/10.1080/13880209.2018.1557698
• Oketch-Rabah HA, Madden EF, Roe AL, Betz JM. United States Pharmacopeia (USP) safety review of gamma-aminobutyric acid (GABA). Nutrients, 2021. https://doi.org/10.3390/nu13082742

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.