If you Google “GABA deficiency,” the only recognized medical condition you will find is GABA-transaminase deficiency, which is an extremely rare genetic disorder that is not survivable.  GABA deficiency is not a recognized deficiency like vitamin D or calcium deficiency that you can test for and correct with a GABA supplement. [2-4]
That being said, GABA is a very important chemical messenger in the brain and more research needs to be done to learn if GABA supplements could benefit people with conditions related to anxiety, stress, and sleep. [2-4]
What Is GABA?
GABA is an acronym for gamma-aminobutyric acid, an amino acid found in your brain. In the brain, GABA serves as the main inhibitory neurotransmitter. (A neurotransmitter is a chemical messenger in the brain.) GABA’s main message is to slow down some brain activities. You could think of it as a natural tranquilizer. [2-4]
Low levels of GABA in the brain may play a role in stress disorders, anxiety disorders, and sleep disorders like insomnia. GABA is made naturally in your brain, but it is also present in some foods and in bacteria. Supplements of GABA have been produced from fermenting bacteria. Because the idea of a natural brain tranquilizer is appealing, supplements are widely available and they claim to help people sleep and reduce stress or anxiety. [2-3]
Do GABA Supplements Work?
The jury is still out. One of the main problems is that researchers are still not sure if GABA can even get from your stomach to your brain. The blood vessels in your brain only allow a few substances to enter. They have tight junctions to protect the brain from toxins. This is called the blood brain barrier. So far there has not been any hard evidence that GABA crosses this barrier, so it would be hard for GABA in food or in a supplement to have any effect on the brain. [2,3]
There have been studies on GABA supplements in humans. Most of these have been for treatment of anxiety, stress, and insomnia. A recent review of human studies that were well-controlled and included a placebo was published in the journal Frontiers in Neuroscience. It included studies up through 2020. They found 14 studies that met their criteria for inclusion. Ultimately, the conclusion of the review was there is limited evidence for stress and very limited evidence for sleep. 
Researchers think that some GABA may get through the blood brain barrier or it may work through nerve endings in the gut that communicate with the brain, called the gut-brain access. In human studies, the dose range for sleep that might work was 100 to 300 milligrams. For stress, the dose range was 20 to 100 milligrams.  That said, there is not enough evidence to establish a safe or effective dose for GABA. Also, keep in mind that supplements are not regulated by the FDA, so you don’t really know what you are taking. [3,4]
What About GABA From Foods?
GABA is naturally present in some foods. These include fermented foods like kimchi, miso, and tempeh. GABA is also found in tea, tomato, soybean, rice, and spinach.  The problem with trying to increase GABA in your diet is that the amount of GABA in supplements is much higher than in food. For example, to get a dose equal to 100 milligrams of supplement, you would need to eat about five pounds of spinach. 
Could You Have GABA Deficiency?
If you don’t have enough GABA in your brain, it could lead to symptoms like stress, anxiety, or insomnia. However, these symptoms have many psychological and physical causes, so you should talk to your doctor before treating them with a supplement. 
There is no blood test to measure GABA deficiency. Although there may be measurable levels of GABA in your blood, that level may have nothing to do with GABA in your brain. For now, the only way to accurately measure brain GAMA is by studying the brain after death. 
The bottom line on GABA deficiency and GABA supplements is that we don’t know enough. we need more studies. The best advice is to talk to your doctor if you have symptoms that GABA supplements claim to help, and talk to your doctor before taking any supplements on your own. [2-4]
RECOMMENDED FOR YOU
- National Library of Medicine, GABA-transaminase deficiency, GABA-transaminase deficiency: MedlinePlus Genetics
- Frontiers in Neuroscience, Effects of Gama Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review, Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review (nih.gov)
- Frontiers in Psychiatry, Frontiers | Neurotransmitters as food supplements: the effects of GABA on brain and behavior | Psychology (frontiersin.org)
- Healthline, What Does Gamma Aminobutyric Acid Do? Gamma Aminobutyric Acid: Uses and Side Effects of GABA Supplement (healthline.com)