g-aminobutyric acid (GABA)

Optimal Result: 0 - 0.04 qmol/dL.

Gamma-aminobutyric acid (GABA) is an amino acid that functions as an inhibitory neurotransmitter. It serves one-third of brain neurons and is involved in depression and mania.

GABA is known for producing a calming effect. It’s thought to play a major role in controlling nerve cell hyperactivity associated with anxiety, stress and fear.

Although there are some dietary supplement and food sources for GABA (cruciferous vegetables, spinach, tomatoes, beans, and rice), the primary source may be endogenous prodution. Nervous tissue, the gut microbiome, the liver, pancreas, and endothelial cells are important sources for production.

Endogenous GABA is produced by the decarboxylation of the excitatory neurotransmitter glutamic acid. It can also be produced from the diamine putrescine using diamine oxidase (DAO). Also, the gut microbiome is capable of synthesizing various hormones and neurotransmitters. For example, Lactobacillus and Bifidobacterium species can produce GABA.

In general, plasma GABA may reflect brain GABA activity, however urine GABA levels are felt not to correlate with CNS levels.


- Petty F. Plasma concentrations of gamma-aminobutyric acid (GABA) and mood disorders: a blood test for manic depressive disease? Clin Chem. 1994;40(2):296-302.

- Briguglio M, Dell’Osso B, Panzica G, et al. Dietary Neurotransmitters: A Narrative Review on Current Knowledge. Nutrients. 2018;10(5):591.

- Brandes RP. A Buttery Taste to Vascular Biology: Endothelial Cells Generate and Release γ-Aminobutyric Acid. Circ Res. 2016;119(5):577-579.

- Lee H, Doud EH, Wu R, et al. Mechanism of inactivation of γ-aminobutyric acid aminotransferase by (1S,3S)-3-amino4-difluoromethylene-1-cyclopentanoic acid (CPP-115). J Am Chem Soc. 2015;137(7):2628-2640.

- Hardt J, Larsson LI, Hougaard DM. Immunocytochemical evidence suggesting that diamine oxidase catalyzes biosynthesis of gamma-aminobutyric acid in antropyloric gastrin cells. J Histochem Cytochem. 2000;48(6):839-846.

- Nicholson-Guthrie CS, Guthrie GD, Sutton GP, Baenziger JC. Urine GABA levels in ovarian cancer patients: elevated GABA in malignancy. Cancer Let. 2001;162(1):27-30.

- Galland L. The gut microbiome and the brain. J Med Food. 2014;17(12):1261-1272.

- Dhossche D, Applegate H, Abraham A, et al. Elevated plasma gamma-aminobutyric acid (GABA) levels in autistic youngsters: stimulus for a GABA hypothesis of autism. Med Science Mon. 2002;8(8):Pr1-6.

- Griffiths JA, Mazmanian SK. Emerging evidence linking the gut microbiome to neurologic disorders. Genome Med. 2018;10(1):98.

What does it mean if your g-aminobutyric acid (GABA) result is too low?

Decreased protein intake, GI maldigestion, and malabsorption can contribute to lower levels. Also, since GABA can be made endogenously from glutamic acid and other pathways, low glutamic acid levels, issues with enzymes like DAO, or an altered microbiome should also be considered.

Reduced GABA levels are known to exacerbate seizures.

What does it mean if your g-aminobutyric acid (GABA) result is too high?

High intake of protein and GABA-containing foods can contribute to elevated levels.

The metabolism and degradation of GABA requires a vitamin B6- dependent enzyme; therefore vitamin B6 deficiency can contribute to elevated GABA levels.

Elevated plasma GABA levels have been observed in autistic children.

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