Your Gut Can Influence How You Feel: It All Starts with GABA and Serotonin

In the most recent issue of Psychology Today, Dan Hurley explores the fascinating connection between the brain and the gut – and what this connection implies.

For the past several decades, researchers and scientists have known about the direct line of communication that is found between the brain and the gastrointestinal tract. In fact, the nervous system as we know it first began in the gut. The central nervous system (CNS), which is found in the brain and in the spinal cord, evolved from what is called the enteric nervous system (ENS), or the nerve tissue and neurotransmitters belonging to the gastrointestinal tract.

Because both the brain and the gut share much of the same tissue, there is an uncanny relationship between the nervous system and the digestive system.

This is why, for example, SSRIs (selective serotonin reuptake inhibitors) are sometimes prescribed for bouts of irritable bowel syndrome (IBS). SSRIs are typically used to treat depression. However, physicians have discovered that when treating depression in patients with IBS, that these patients also find relief from irritable bowel symptoms when they take an SSRI drug. These findings have been confirmed with MRI imaging: there is a clear relationship between gut function and brain function.

What exactly is going on? For starters, serotonin is a neurotransmitter. It is responsible for regulating things in the body like mood, appetite, and sleep. The right amount of serotonin in the brain produces a relaxed and positive feeling.

As it turns out, approximately 90% of the serotonin in the body is located in the gut.
Do you want to get happy? Boosting your gut health with beneficial bacteria will not only improve digestion, but it can benefit your mood!

The remaining 10% is synthesized in the central nervous system (CNS). The neurotransmitter serotonin can actually modulate motility in the gut. When levels of serotonin are skewed, this can cause either constipation or diarrhea.

Gut bacteria have also been found to play a significant role in the communication that goes on between the brain and the gut.

When most people talk about gut bacteria, they are referring to the friendly and beneficial microorganisms housed in the digestive tract. These microorganisms come together and form a community, or what is otherwise known as a microbiome. A microbiome is strong in both numbers and in structure. Gut bacteria and other organisms, whether beneficial or not, adhere together and coat themselves with a protective film.

Within your gut is a large, bustling community of mostly beneficial microorganisms. These microorganisms have evolved with us over the centuries. This is one of the reasons why they have turned out to be so helpful, furnishing our bodies with certain vitamins and supporting our digestive function.

Because the tissue in the gastrointestinal tract is largely nerve tissue, it follows that the friendly microorganisms in the gut would not only benefit the digestive system but also the nervous system.

Just recently scientists have discovered that certain bacteria have the special ability to generate that “feel good” mood.

Some beneficial bacteria that have taken up residence in the gut will actually increase GABA receptors in the brain. When there are more GABA receptors in the brain, more GABA is being put to good use. This is a good thing, especially since a decrease in GABA receptors has been associated with mood disorders, like chronic depression.

To give you a better idea what GABA receptors do in the body, consider substances like:

  • Alcohol
  • Benzodiazepines
  • Barbiturates

What do alcohol, benzodiazepines, and barbiturates have in common? They all stimulate the GABA receptors. Which, according to scientists, is exactly what certain beneficial bacteria do. (1)

Bacteria not only interact with neurotransmitters, they can also produce their own.

As we mentioned, some beneficial bacteria can influence GABA receptors in the brain. Other bacteria in the gut can prompt or inhibit inflammation in the gut and also elsewhere in the body. The latest? Some gut bacteria will actually produce neurotransmitters.

What is a neurotransmitter? Serotonin is one example. Others are:

  • Dopamine
  • Aceytlcholine
  • GABA
  • Norepinephrine
  • Oxytocin

Professor Mark Lyte from the Texas Tech University Health Sciences Center speculates that the discovery of neurochemical-producing bacteria could have profound implications in the field of gastrointestinal health and psychology – which Donna Gates has been teaching since the inception of the Body Ecology Diet. (2)

For example, if you have ever taken an anti-depressant, you may know that the body eventually builds up a resistance to SSRI medication. In psychiatric care, it may turn out that instead of treating depression with an SSRI medication, physicians could just as easily prescribe a specific probiotic supplement. This would benefit not only gut health but also brain health.

As Canadian neuroscientist Jane Foster reminds us in Hurley’s article, “The cross talk between the gut biome and the brain is continual. That’s the important take-home message. These are not two separate systems; they are two parts of a single system.” (3)

What to Remember Most About This Article:

Scientists have discovered in the past several decades that there is direct communication between the brain and the gastrointestinal tract. In fact, 90% of the serotonin produced in the body is found in the gut, a neurotransmitter responsible for regulating appetite, mood, sleep, and relaxation.

Gut bacteria significantly influences the communication between the brain and the gut. When the gut is full of healthy bacteria, it has the potential to regulate mood and positive feelings. Beneficial bacteria in the gut will increase GABA receptors in the brain to alleviate mood disorders like chronic depression.


  1. Javier A. Bravo, et al. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. PNAS 2011 : 1102999108v1-201102999.
  2. Lyte, M. Probiotics function mechanistically as delivery vehicles for neuroactive compounds: Microbial endocrinology in the design and use of probiotics. Bioessays. doi: 10.1002/bies.201100024.
  3. Hurley, Dan. Your Backup Brain. Psychology Today. Dec 2011. 80 – 86
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