GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in your brain. Think of it as the brakes on your nervous system. When GABA binds to its receptors, it reduces neuronal excitability, which translates to feelings of calm and relaxation.

Your brain makes GABA from glutamate, an excitatory neurotransmitter that does the opposite job. The balance between these two determines a lot about how you feel: too much glutamate activity relative to GABA and you might feel anxious, wound up, unable to sleep. Too much GABA (which is rare naturally) and you’d feel sedated.

This explains why GABA supplements have become popular. The logic seems straightforward: if GABA calms the brain, taking more GABA should make you calmer, right? The reality is more complicated, and I’ll get into that shortly.

The blood-brain barrier problem

Here’s something most GABA supplement marketing conveniently ignores: there’s genuine scientific doubt about whether orally taken GABA can actually reach your brain.

The blood-brain barrier is a selective membrane that protects your brain from potentially harmful substances in your bloodstream. GABA molecules are polar and relatively large, which means they don’t cross this barrier easily. Most research suggests only trace amounts, if any, make it through.¹

So why do some people report feeling calmer after taking GABA supplements? A few possibilities:

Placebo effect. Never underestimate it. If you believe something will relax you, that expectation alone can trigger real physiological changes.
Gut-brain axis. GABA receptors exist throughout the enteric nervous system (the network of neurons in your gut). Some researchers think oral GABA might work through this pathway rather than by reaching the brain directly.¹
Stress hormone effects. One small study found that GABA affected salivary immunoglobulin A and cortisol levels, suggesting it might influence the stress response through peripheral mechanisms.²

I should be honest here: we don’t have a definitive answer. The question of how (or whether) oral GABA supplements produce their reported effects remains open. What we can do is look at what clinical trials have actually found.

What are the benefits of GABA?

1. GABA derivatives for nerve pain after shingles

This one needs clarification upfront. The studies showing benefits here used GABA derivatives like gabapentin (sold as Neurontin) and pregabalin (Lyrica), which are prescription medications. These are chemically related to GABA but modified to cross the blood-brain barrier. They’re not the same as GABA supplements you’d buy in a health shop.

Shingles (herpes zoster) occurs when the chickenpox virus, which stays dormant in your nerve cells, reactivates. About 20 to 30 percent of people experience this at some point in their lives. The most dreaded complication is postherpetic neuralgia, a persistent burning, stabbing pain that can last months or years after the rash heals.

A meta-analysis of three randomised controlled trials (297 patients total) found that GABA derivatives given during acute shingles significantly reduced the incidence of postherpetic neuralgia compared to placebo.³

The bottom line: prescription GABA derivatives have evidence for nerve pain. Over-the-counter GABA supplements? That’s a different story entirely.

2. GABA may modestly lower blood pressure

High blood pressure rarely causes symptoms, which makes it dangerous. The damage accumulates silently in your blood vessels, heart, kidneys, and brain until something goes wrong.

One small double-blind study tested GABA-enriched rice (containing 11.2 mg GABA per 100g) in 39 people with mild hypertension over 8 weeks. The GABA rice group showed improvements in morning blood pressure measurements compared to placebo, though other blood pressure readings throughout the day weren’t significantly different.⁴

I wouldn’t call this conclusive. One small study with modest effects in one time-of-day measurement isn’t compelling evidence. The researchers themselves noted the results were preliminary and needed confirmation in larger trials.

If you have high blood pressure, medication and lifestyle changes (less salt, more exercise, maintaining healthy weight) have far stronger evidence behind them. GABA supplements might be a small piece of the puzzle, but I wouldn’t rely on them.

3. GABA may reduce stress and improve focus

Chronic stress affects roughly three-quarters of people seeking medical care for physical symptoms. Prolonged emotional dysregulation is associated with heart disease, high blood pressure, digestive problems, weakened immunity, and depression.

A small study found that oral GABA supplementation reduced markers of stress and anxiety as measured by electroencephalogram (EEG) readings. Interestingly, when subjects were under stress, GABA increased salivary immunoglobulin A levels, which is considered a physiological marker of relaxation and immune function.²

The catch? This was a small study. The effects, while statistically significant, weren’t dramatic. And there’s still that nagging question about how GABA is producing these effects if it can’t cross the blood-brain barrier.

For stress management, I’d look at options with stronger evidence first: regular exercise, adequate sleep, and for supplements, magnesium and valerian have more research behind them.

4. GABA for sleep problems

Here’s where GABA gets more interesting for many people. Insomnia affects a substantial portion of adults, and sleep problems tend to worsen with age.

Brain GABA levels appear to matter for sleep. Research has found that people with insomnia have about 30% lower GABA levels in certain brain regions compared to good sleepers.⁵ This doesn’t prove that taking GABA supplements will help, but it suggests the system is worth targeting.

A small randomised controlled study found that oral GABA supplementation reduced the time needed to fall asleep, increased non-REM sleep (the deeper, more restorative phase), and improved overall sleep efficiency compared to placebo.⁶

The researchers proposed that even if GABA doesn’t cross the blood-brain barrier in significant amounts, it might improve sleep through other mechanisms: activating the parasympathetic nervous system (the “rest and digest” branch), lowering core body temperature, or signalling through the enteric nervous system.

For nocturia (waking to urinate at night) or other bladder conditions that disrupt sleep, addressing the underlying urological issue directly is probably more effective than trying to sleep through it with supplements. But for general difficulty falling asleep, GABA might be worth trying alongside good sleep hygiene practices.

Related reading: Melatonin benefits and side effects

What are the side effects of GABA?

At typically recommended doses (100-750 mg), GABA supplements appear fairly safe for short-term use. Side effects, when they occur, tend to include:

Drowsiness (which might be the point if you’re taking it for sleep)
Tingling or flushing sensation in the skin
Shortness of breath (rare, usually with higher doses)
Nausea or stomach upset
Headache

These side effects seem more common at higher doses. Single doses exceeding 3000 mg, or combining GABA with other sedating substances, increases the likelihood of problems.

The NHS notes that supplements like GABA are not subject to the same rigorous testing as medicines, so quality and actual content can vary between products.⁷

Safety precautions (5 contraindications)

1. Pregnancy, breastfeeding, and children

No adequate safety studies exist for these groups. The precautionary approach is to avoid GABA supplements during pregnancy and breastfeeding, and not to give them to children unless specifically advised by a doctor.

2. Liver or kidney problems

GABA is processed through these organs. Without safety data in people with impaired liver or kidney function, it’s best avoided or used only under medical supervision.

3. Operating machinery or driving

GABA can cause drowsiness. Don’t take it before driving, operating heavy machinery, or doing anything requiring alertness. This applies especially when you’re first trying it and don’t know how it affects you personally.

4. Combining with sedatives or alcohol

GABA supplements may amplify the effects of:

Benzodiazepines (like diazepam or lorazepam)
Sleep medications (like zolpidem)
Anticonvulsants (some work through GABA pathways)
Alcohol

The combination could cause excessive sedation. If you’re taking prescription sedatives or anti-anxiety medications, talk to your doctor before adding GABA supplements.

5. Bipolar disorder or depression

Some concern exists that GABA supplements might affect mood in unpredictable ways in people with mood disorders. The evidence here is limited, but caution is warranted. If you have bipolar disorder or depression, discuss any supplements with your psychiatrist first.

Dosage and how to take GABA

Typical doses in studies range from 100 mg to 750 mg daily. Most people start at the lower end to see how they respond.

For sleep, taking GABA 30-60 minutes before bed makes sense. For daytime anxiety or stress, smaller doses throughout the day might work better, though be aware of the drowsiness potential.

GABA supplements come in various forms: capsules, tablets, powders, and combination products (often mixed with L-theanine, melatonin, or other calming ingredients). There’s no strong evidence that one form absorbs better than another.

The bottom line

GABA is a genuinely important neurotransmitter for calm and sleep. The supplements are probably safe for most healthy adults in normal doses. Some people report benefits for stress and sleep.

But I have reservations. The blood-brain barrier question remains unresolved. The clinical evidence consists mostly of small studies. And for conditions like overactive bladder or neurogenic bladder that might disrupt sleep, treating the underlying problem makes more sense than layering on sleep supplements.

If you want to try GABA, start with a low dose, don’t combine it with other sedatives, and pay attention to how you actually feel rather than how you expect to feel. And if sleep problems persist, see a doctor. Chronic insomnia can have many causes, some of which need proper medical evaluation.

References

Boonstra E, et al. Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Front Psychol. 2015;6:1520. PubMed ↩ ↩²
Abdou AM, et al. Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans. Biofactors. 2006;26(3):201-8. PubMed ↩ ↩²
Dworkin RH, et al. Prevention of postherpetic neuralgia by gabapentin and pregabalin: a systematic review and meta-analysis. Pain Med. 2020;21(11):2637-2643. PubMed ↩
Nishimura M, et al. Effects of white rice containing enriched gamma-aminobutyric acid on blood pressure. J Tradit Complement Med. 2016;6(1):66-71. PubMed ↩
Winkelman JW, et al. Reduced brain GABA in primary insomnia: preliminary data from 4T proton magnetic resonance spectroscopy (1H-MRS). Sleep. 2008;31(11):1499-506. PubMed ↩
Yamatsu A, et al. Effect of oral gamma-aminobutyric acid (GABA) administration on sleep and its absorption in humans. Food Sci Biotechnol. 2016;25(2):547-551. Link ↩
NHS. Herbal medicines. NHS ↩