GABA and the GUT

In light of yesterday’s post, I thought it would be fun to talk about GABA and the role it may play in gut health and digestion.

The gut is often called the “second brain” because it has its own extensive network of neurons. When we hear the word neuron, most of us immediately think about the brain. In reality, neurons are found throughout the body and the digestive tract has an entire nervous system of its own.

The enteric nervous system helps regulate motility, digestive secretions, blood flow and the movement of food through the gastrointestinal tract. It also communicates with the brain through the vagus nerve, immune signals, hormones and microbial metabolites. This communication travels in both directions. What happens in the brain can affect the gut and what happens in the gut can affect the brain.[1,2]

We see a dramatic example of this relationship following traumatic brain injury. Research has connected brain trauma with changes in intestinal motility, microbial balance, immune activity and intestinal barrier integrity. The stress response and inflammation created by the injury may affect the gut, while changes in the gut may send inflammatory signals back toward the brain.[3] GABA, or gamma-aminobutyric acid, is usually discussed as a calming neurotransmitter in the brain. It is the primary inhibitory neurotransmitter in the central nervous system. You can think of it as one part of the body’s braking system. It helps prevent neurons from becoming overly excited.

GABA is produced from glutamate with the help of the glutamic acid decarboxylase enzymes GAD1 and GAD2. Although we hear the most about GABA in relation to the brain, GABA receptors, transporters and signaling pathways are also present throughout the gastrointestinal tract.[4,5] This means GABA is involved in more than relaxation and sleep. It may influence gut motility, visceral sensation, intestinal secretion, barrier function and immune activity. The effects are complex and depend on the type of GABA receptor involved and where that receptor is located.[4–6]

How does this relate to digestion?

1. Stress and digestive symptoms

Stress is a common trigger for bloating, constipation, diarrhea, cramping and IBS symptoms. When the body shifts into a prolonged fight-or-flight response, digestion is no longer the priority. Blood flow, motility and digestive secretions may change. The gut can become more sensitive and normal digestive sensations may begin to feel painful or uncomfortable. Healthy GABAergic signaling helps regulate nervous system activity, but this does not mean that every digestive symptom is caused by low GABA. It is one part of a much larger gut-brain conversation.

2. Gut motility

GABA receptors are found within the enteric nervous system and gastrointestinal tissues. Research suggests that GABA signaling can affect smooth muscle activity, intestinal secretion and the neural pathways responsible for moving food through the digestive tract.[4,5] The effects are not always as simple as “more GABA creates better motility.” Different GABA receptors can produce different responses depending on the location and condition of the digestive tract. The goal is healthy regulation rather than simply trying to raise GABA as high as possible.

3. Visceral sensitivity

The gut contains sensory nerves that continuously send information to the brain. In conditions such as IBS, those signals can become amplified. Normal stretching, gas or movement may be perceived as painful. GABA receptors appear to participate in the regulation of these sensory signals. Altered GABAergic signaling has been studied in relation to visceral hypersensitivity and IBS, although much of the mechanistic research still comes from animal and laboratory models.[5,6]

4. Inflammation and immune activity

GABA receptors are also found on several types of immune cells. Experimental research suggests that GABA signaling may influence cytokine production and inflammatory responses.[7] This is interesting, but we should be careful with the interpretation. GABA is not an established treatment for Crohn’s disease, ulcerative colitis or autoimmune illness. Its immune effects appear to depend on the receptor, tissue and disease state. In some intestinal models, GABA receptor activation has produced different or even opposing effects.[7,8]

5. The gut microbiome

Certain intestinal bacteria can produce GABA by converting glutamate through their own glutamate decarboxylase systems. This ability is highly strain-specific. We cannot assume that every Lactobacillus, Bifidobacterium or probiotic formula produces meaningful amounts of GABA.[9,10] Microbial GABA may act locally on intestinal and enteric receptors. It may also influence gut-brain communication through the vagus nerve, immune system and microbial metabolites. Whether gut-produced GABA meaningfully increases GABA inside the human brain is still being studied.[9,11]

Supporting GABA naturally

After learning how GABA participates in both brain and gut function, it is tempting to look for ways to “boost” it. I think it is more accurate to talk about supporting healthy GABAergic signaling and nervous system regulation.

Food

Some fermented foods contain GABA-producing microorganisms or GABA created during fermentation. Examples may include certain preparations of kimchi, sauerkraut, kefir, miso and fermented grains. The actual amount of GABA varies according to the organisms used, preparation method and length of fermentation.[9,12] Fermented food is not automatically appropriate for everyone. Fermentation can also produce histamine and other biogenic amines. Someone with histamine intolerance or mast-cell reactivity may feel worse rather than better. The person’s response matters more than the fact that a food is labeled “healthy.”

A varied diet containing adequate protein, vegetables, minerals and complex carbohydrates supplies the nutrients needed for normal neurotransmitter and nervous system function. Magnesium and vitamin B6 are particularly relevant to GABA pathways, but more is not always better.

Oral GABA

GABA supplements are available in capsules and powders. Some human studies report modest benefits for stress or sleep, but the overall evidence remains limited. Researchers continue to debate how much oral GABA crosses the blood-brain barrier.[13,14] Oral GABA may still affect peripheral GABA receptors, the enteric nervous system or gut-brain communication without needing to enter the brain in large amounts. We simply do not have enough evidence to say that taking a GABA supplement directly corrects low brain GABA.

L-theanine

L-theanine is an amino acid found naturally in tea. Animal research suggests that it may influence GABA, glutamate, dopamine and serotonin signaling. Human studies provide some support for relaxation and stress reduction, but the exact GABA-related mechanism in people is not fully established.[15] L-theanine is one of the tools I may consider when someone feels tense, overstimulated or unable to settle. I would describe it as supporting nervous system balance rather than promising that it directly raises brain GABA.

Magnesium

Magnesium is involved in normal nerve signaling and helps regulate excitatory and inhibitory activity. It may be useful when someone is deficient or when muscle tension, constipation, sleep difficulty or nervous system irritability is present.

The form and amount matter. Too much supplemental magnesium can cause diarrhea and cramping. Magnesium also needs to be used cautiously with impaired kidney function and separated from certain medications.

Probiotics

Some probiotic organisms can produce GABA, but this is a strain-specific function. A general probiotic label does not tell us whether the organisms in the product produce GABA or how they will behave in a particular person.[9,10] I prefer to choose probiotics according to the person and the problem rather than assuming that every probiotic is good for every gut.

Mind-body practices

Quiet time, prayer, meditation, deep breathing, grounding and walking in nature can help move the body away from a constant fight-or-flight response. These practices do not work because symptoms are imaginary. They work by changing real autonomic and neurological signaling. Some human imaging studies have found differences in brain GABA following yoga and other mind-body practices, although this area of research is still developing.[16]

Physical activity

Exercise can influence GABA and glutamate activity in the brain. Human magnetic resonance spectroscopy studies have found temporary changes in regional brain GABA after exercise.[17,18] That does not mean harder exercise is always better. For someone with central sensitization, chronic illness or post-exertional symptoms, movement should be matched to the person’s capacity. Gentle and consistent activity may be more helpful than repeatedly pushing the body into a flare.

GABA is not only a calming neurotransmitter in the brain. GABAergic signaling is woven throughout the enteric nervous system, immune system, microbiome and gut-brain axis.

It may influence motility, visceral sensation, stress responses and immune communication. At the same time, we need to resist reducing every digestive problem to “low GABA.” The gut-brain axis is a network. Histamine, serotonin, glutamate, hormones, immune mediators, microbial metabolites and the autonomic nervous system are all part of the conversation.

The goal is not to force one neurotransmitter higher. It is to help the nervous system and digestive system communicate more effectively and return to a healthier rhythm.

Citation Guide

1. Carabotti M, Scirocco A, Maselli MA, Severi C. The gut-brain axis: Interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology. 2015;28(2):203–209.Read the review

2. Mittal R, Debs LH, Patel AP, et al. Neurotransmitters: The critical modulators regulating gut-brain axis. Journal of Cellular Physiology. 2017;232(9):2359–2372.Read the review

3. Dysregulated brain-gut axis in the setting of traumatic brain injury: Review of mechanisms and anti-inflammatory pharmacotherapies. 2024.Read the review

4. Auteri M, Zizzo MG, Serio R. GABA and GABA receptors in the gastrointestinal tract: From motility to inflammation. Pharmacological Research. 2015;93:11–21.View the article

5. Hyland NP, Cryan JF. A gut feeling about GABA: Focus on GABA-B receptors. Frontiers in Pharmacology. 2010;1:124.Read the review

6. Lambiase C, et al. Targeting gamma-aminobutyric acid pathways in irritable bowel syndrome. 2025.Read the review

7. Bhat R, Axtell R, Mitra A, et al. Inhibitory role for GABA in autoimmune inflammation. Proceedings of the National Academy of Sciences. 2010;107(6):2580–2585.Read the study

8. Ma X, Sun Q, Sun X, et al. Activation of GABA-A receptors in colon epithelium exacerbates acute colitis. Frontiers in Immunology. 2018;9:987.Read the study

9. Conn KA, et al. Implications of microbe-derived gamma-aminobutyric acid in the microbiota-gut-brain axis. Gut Microbes. 2024.Read the review

10. Otaru N, Ye K, Mujezinovic D, et al. GABA production by human intestinal Bacteroides species: Prevalence, regulation and role in acid stress tolerance. Frontiers in Microbiology. 2021;12:656895.Read the study

11. Jiang C, et al. From the gut to the brain: Mechanisms and clinical implications of gut-derived GABA. 2025.Read the review

12. Braga JD, et al. Gamma-aminobutyric acid as a potential postbiotic mediator in the microbiota-gut-brain axis. 2024.Read the review

13. Hepsomali P, Groeger JA, Nishihira J, Scholey A. Effects of oral GABA administration on stress and sleep in humans: A systematic review. Frontiers in Neuroscience. 2020;14:923.Read the review

14. Boonstra E, de Kleijn R, Colzato LS, et al. Neurotransmitters as food supplements: The effects of GABA on brain and behavior. Frontiers in Psychology. 2015;6:1520.Read the review

15. Nathan PJ, Lu K, Gray M, Oliver C. The neuropharmacology of L-theanine. Journal of Herbal Pharmacotherapy. 2006;6(2):21–30.View on PubMed

16. Govindaraj R, Karmani S, Varambally S, Gangadhar BN. Effect of yoga on cortical inhibition in healthy individuals. 2018.Read the study

17. Maddock RJ, Casazza GA, Fernandez DH, Maddock MI. Acute modulation of cortical glutamate and GABA content by physical activity. Journal of Neuroscience. 2016;36(8):2449–2457.Read the study

18. Coxon JP, Cash RFH, Hendrikse JJ, et al. GABA concentration in sensorimotor cortex following high-intensity exercise and relationship to lactate levels. Journal of Physiology. 2018;596(4):691–702.Read the study