The Gut Brain Axis Connection: Why We Need to Be Paying More Attention

Josh Beaty

The Gut Brain Axis Connection: Why We Need to Be Paying More Attention

April 2, 2019

Did you know that there are between 200 and 600 million neurons in your gut?

These neurons line your gastrointestinal tract and are commonly called “the little brain” or Enteric Nervous System.

Believe it or not, there is a strong connection between your brain and the gut. It is called the gut-brain axis.

The expression “gut feeling” makes more sense now, right?

Let’s take a closer look at the brain-gut axis and see what it consists of.

The Vagus Nerve Connection

Your brain is home to approximately 100 billion neurons.

They are connected to the ENS using a complex nervous system called the Vagus Nerve. The Vagus Nerve sends signals both ways, so your brain communicates with your gut constantly.

Scientists discovered that the brain and the gut influence each other in numerous ways.

For example, people who experience severe episodes of anxiety and depression are more likely to develop irritable bowel syndrome (IBS).

IBS is a disease which affects the large intestine. Its symptoms are abdominal cramps, diarrhea, constipation and more.

In studies done on animals, excessive stress can cause stomach problems.  This happens because stress hormones affect the Vagus Nerve and this limits the interaction between the gut and the brain.

The Chemical Connection

The gut communicates with the brain through chemical compounds known as neurotransmitters.

Neurotransmitters help controlling emotions and they are produced in the brain and in the gut.

One of the most popular neurotransmitters is serotonin which gives you a feeling of happiness and pleasure.

The gut also produces neurotransmitters and sends them back to the brain. For example, the gamma-aminobutyric acid (GABA) neurotransmitter is produced by the microbes in the gut.

This neurotransmitter is responsible for reducing feelings of anxiety and fear. The more is produced, the less anxious you'll feel.

Studies done on rats show that administering probiotics can increase GABA production. Probiotics are known to improve gut health and general wellbeing.

Microbiome and Microbiota

A microbiome represents the totality of microbes living in a host. This host can be a human or animal.

Microbiota refers to the community of microbes found in a particular ecosystem. For example, there is gut microbiota (microbes found in the gut), skin microbiota (microbes found on the skin), etc.

Did you know that your gut contains ten times more microbes than the total number of cells in your body?

This shouldn’t scare you, the gut microbiota is responsible with food absorption. These are called healthy bacteria in the gut.

The gut microbiota also produces bile acids which influence the brain. When people are stressed or have certain social disorders, the production of bile acids is decreased.

This is just another way the gut-brain axis can influence your mood or state of mind in certain conditions.

Gut-Brain Axis and the Immune System

The immune system is responsible for fighting microbes and bacteria.

It does this helped by the lymphatic system which sends white blood cells to neutralize foreign body invaders.

These invaders can be new flu viruses, bad bacteria such as Candida and others.

The lymphoid tissue responsible for sending white blood cells is found in the gut. It represents approximately 70% of the entire immune system in the body.

We can say that most of our immune system is found in the gut. The healthier the gut, the less likely we are to get sick.

Cortisol is a hormone produced by the adrenal glands situated on top of your kidneys. It is also known as the “stress hormone”. It is usually produced when we are in a “fight or flight” situation.

When we experience social anxiety, a lot of cortisol gets secreted. This hormone is known to impair the function of the immune system. In other words, people get sick easier when they are stressed.

This is another proof of the brain gut axis and how stress can influence our moods and our health in general.

Tryptophan Metabolism Pathway

Tryptophan is a precursor of serotonin, one of the most important neurotransmitters in the body.

Almost all the serotonin in the body is produced in the gut. This neurotransmitter regulates mood and cognition and it’s responsible with pain perception.

The more serotonin your body produces, the better.

Studies have found out that the gut-brain axis can interfere with serotonin production by impairing the metabolism of tryptophan.

This can cause various symptoms such as moodiness, fewer feelings of pleasure and confidence, etc.

Stress and Gut Inflammation

When foreign invaders are detected in the body, the immune system starts a process known as acute inflammation.

This mobilizes white blood cells to neutralize the invaders and prevent the virus from replicating. Once the foreign invader is taken care of, body inflammation is reduced.

When the level of body inflammation stays up too long, this can lead to chronic inflammation.

Stress can be a major contributor to chronic inflammation and it can lead to numerous diseases. For example, chronic stress can influence intestinal permeability which causes the “leaky gut syndrome”.

When the leaky gut syndrome develops, toxins can pass into the bloodstream and cause inflammation into the body.

One of those toxins is the lipopolysaccharide. It is produced by the gut microbiota and it is an important risk for diseases such as cardiovascular disease, diabetes type 2 and even cancer.

Gut-Brain Axis and Probiotics

As mentioned earlier, probiotics improve the health of the gut. They are represented by healthy bacteria which digest foods eaten and help to absorb the nutrients.

Some probiotics can influence the brain directly and they might reduce the risk of developing neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease.

Studies show that certain probiotics can improve the symptoms of people with IBS or severe depression.

Prebiotics are represented by fibers and they are also healthy for the gut-brain axis. Prebiotics might help reduce the cortisol hormone and improve general health.

Probiotics and Depression in Animal Studies

Studies performed on rats revealed the importance of probiotics in alleviating symptoms such as depression and anxiety.

A study performed by Desbonnet treated depression in rats using a combination of probiotics and citalopram.

The rats were separated from their mother and this caused depression-like symptoms. Some of these symptoms include increased inflammation biomarkers and a reduction of the norepinephrine neurotransmitter.

Upon administering a combination of probiotics and citalopram, the symptoms of these rats have been improved.

Scientists have also found out that administering these two substances separately had no effect on rats.

Foods that Improve the Gut-Brain Axis

There are certain types of foods which can improve the signaling process between the gut and brain.

These foods contain minerals and nutrients which improve the health of the gut-brain axis.

For example:

  • Dairy products: Foods like yogurt, kefir, and cheese contain probiotics which are live bacteria that help improve the health of the gut
  • Foods containing polyphenols: Polyphenols are plant-based chemicals. They are preferred by the gut bacteria and are contained by olive oil, coffee, green tea, and other drinks
  • Foods containing fiber: High-fiber foods contain prebiotics, which start the fermentation process in the gut. Some of these foods are whole grains, apples, vegetables, nuts, and seeds
  • Foods containing omega-3 fatty acids: Studies show that omega-3 fatty acids can improve brain function and the number of healthy bacteria in the gut. Omega-3 fatty acids are found in sardines, tuna, and mackerel

Diet, Lifestyle and Gut Health

Apart from introducing “gut-friendly” foods in your diet, you can also make additional changes to improve gut health.

For example, you can minimize the consumption of gluten or eliminate it altogether.

Gluten is a protein commonly found in grains. It acts as a glue, adding consistency to foods and ingredients and keeping them together.

The bad thing is that gluten tends to stick to intestinal walls. This is detected by the immune system which sends white blood cells to eliminate it.

In other words, the immune system sees gluten as a foreign invader. By trying to neutralize it, the immune system does damage to the gut itself.

This can lead to gluten intolerance and it causes stomach problems. If not treated, gluten intolerance can develop into the celiac disease which is a life-threatening problem.

By minimizing gluten consumption, you can avoid such health conditions and the symptoms associated with them.

Limiting antibiotics consumption will also improve gut health.

Antibiotics tend to kill bacteria, including healthy ones. This is a bad thing because it gives bad bacteria a chance to develop, causing various health conditions.

Studies performed on mice showed that antibiotics might cause memory impairment. Although studies on humans haven’t yet been performed, it’s safe to assume that too many antibiotics are dangerous for health.


The gut-brain axis provides valuable insights on how our bodies work and how we feel.

Best of all, it is possible to influence it in a positive way by increasing the consumption of probiotics and gluten-free products.

Want to find out more about your gut? Check out this article on gut health and intestinal lining. You’ll be amazed by how complex and interesting your gut is!


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