The Gut-Brain Connection

Have you ever used the terms “gut feeling,” “butterflies in the tummy,” or “gut-wrenching experience”? They indicate you are getting signals from your second brain, your gut.

While we know that the brain controls the entire body, including your gut, recent studies have shown that your gut can affect your brain’s health.

This gut-brain connection is known as the gut-brain axis. Just like the brain has billions of neurons, your gut has millions. And the vagus nerve is one of the biggest nerves that sends signals both ways.

Keep reading to learn more about the vagus nerve’s role, neurotransmitter production, chronic inflammation, and pain perception in the gut-brain connection.


The Vagus Nerve And Neurotransmitter Production

There are many players in the feedback loop of the gut-brain axis. The communication between the gut and the brain involves immune, endocrine, and neural communications. The most important of them is the vagus nerve signaling.

The vagus nerve is a part of the nervous system involved in involuntary actions like pumping of the heart, breathing, and digestion. It also plays a crucial role in influencing feelings, behaviors, and thoughts.

The vagus nerve is the connecting link between the gut and the brain. It is the fastest and most direct way for the gut microbiota to communicate with the brain. It connects through the gut-brain axis and communicates through neurotransmitters.

Doctors discovered the importance of nerves in the early twentieth century through studies and while treating patients. When treating patients with peptic ulcers with partial or complete stomach removal (gastrectomy), the individuals showed ablation of vagus nerve activity. This resulted in an increased occurrence of psychiatric-related disorders in such patients.

Studies have found that the inhibition of the signal of the bidirectional nerve can lead to gastrointestinal problems. Another study has found that patients with Crohn’s disease or irritable bowel syndrome have reduced vagal tone.

This proves that the vagus nerve plays a key role in the gut-brain connection.

Importance Of Neurotransmitters

Since the vagus nerve communicates through neurotransmitters, they are the chemical link between the gut and the brain.

Neurotransmitters are produced in the brain and play crucial roles in pain, mood, stress, hunger, and sleep.

But many neurotransmitters are also produced in our gut, confirming their importance in the gut-brain connection. Some bacterial strains can also produce neurotransmitters, thus regulating the vagus nerve.

Here are a few important neurotransmitters and their functions:


The cells in the epithelial lining of the gut produce around 90% of our serotonin. It is an important chemical that plays a role in processing pain, happiness, appetite, sleep, peristalsis, regulating the body clock, and inducing vomiting and nausea.

Interactions between serotonin and the vagus nerve are important in psychological well-being. One study found that a lack of the amino acid tryptophan (precursor of serotonin) can induce symptoms of depression.


Dopamine is a feel-good chemical that is important for both your brain and your body. It plays crucial roles in memory, learning, behavior, regulating blood flow, and movement control.

It is synthesized in the gut, and the brain releases it during pleasurable activities. It is an integral part of the reward system of the brain.

Drugs that regulate dopamine levels can treat Parkinson’s disease, addiction, depression, anxiety, bipolar disorder, and other conditions.

Gamma-aminobutyric Acid (GABA)

GABA is the primary inhibitor of the central nervous system. It helps in controlling the feeling of anxiety and fear, reducing them and depressive behavior.

It is a mood regulator that, if not present adequately, can lead to depression, anxiety, and even schizophrenia. By increasing the action of GABA, they can help treat anxiety attacks.

Types Of Supplements

Leaky Gut And Chronic Inflammation

The leaky gut has been linked to many health issues, including chronic inflammation. 

Our gut is semi-permeable. This means that it selectively allows the passage of certain substances while forming a barrier for others. The mucous lining of the intestine has small gaps known as tight junctions. These allow nutrients and water to pass through but block toxins, bacteria, and other harmful substances from entering the bloodstream. 

This is known as intestinal permeability. But when the tight junctions become loose, they can no longer control the passage of harmful substances, and the gut is now called “leaky.” 

When the intestinal barrier is impaired, it may allow undigested food and toxins into the bloodstream. This can cause various diseases, including widespread inflammation. 

A leaky gut is one of the major causes of chronic inflammation. The lymphocytes of the small intestine trigger systemic inflammatory processes to respond to toxins from the leaky gut. 

Inflammation is usually good for the body. It is a response to harmful and irritating substances that must be removed from the body. However, sometimes the body recognizes self-cells as foreign objects, leading to chronic inflammation and chronic inflammatory diseases like ulcerative colitis, Crohn’s disease, psoriasis, and rheumatoid arthritis. Also, as mentioned above, a leaky gut too results in chronic inflammation. 

Persistent chronic inflammation is very damaging. It affects both your brain and your body. Chronic inflammation in the gut can lead to the breakdown of barriers. This results in the disruption of the blood-brain barrier, allowing toxins to enter the brain. This results in inflammation of the brain, known as neuroinflammation. 

Inflammation also irritates nerves, sending pain signals to the brain. It sensitizes the peripheral nerve terminals, which initiates inflammatory pain, as seen in arthritis. In the case of acute inflammation, signals are sent to the brain to induce a sickness response, which increases pain and other negative effects. But in the case of chronic inflammation, the sickness response gradually transitions into depression and chronic pain. 

Chronic inflammation can also be manifested as many other diseases like obesity, arthritis, fibromyalgia, asthma, migraines, food sensitivities, chronic fatigue syndrome, diabetes, multiple sclerosis, autism, skin conditions, thyroid abnormalities, and mood swings. 

The Impact Of Fiber And Blood Sugar Levels On Pain Sensations

Fiber is the non-digestible carbohydrate obtained from fruits and vegetables. It offers multiple benefits, like lowering cholesterol levels, helping control blood sugar levels, and helping achieve a healthy weight. But it is most beneficial for the gut. 

Dietary fiber is also referred to as roughage or bulk. It is not digested but rather passes relatively intact from your stomach to your small intestine to your colon and finally out of your body. 

A high-fiber diet helps achieve the right consistency of stools. It increases the size and weight of your stool, making them easier to pass. It improves gut motility and prevents constipation. Additionally, if the stools are watery, fiber helps solidify it by absorbing water. 

Dietary fiber was beneficial in five out of seven chronic constipation studies and all three IBS-associated constipation studies. Hence, it is easy to conclude that dietary fiber is beneficial for gut motility and for treating and preventing constipation. 

Dietary fiber has been used for the treatment of many gastrointestinal conditions. One review stated the inadequate dietary fiber intake was the primary cause of IBS. 

Also, much evidence in the literature shows an association between fiber intake and insulin sensitivity. One study found that participants on a High Cereal Fiber (HCF) diet had a 25% higher insulin sensitivity than participants on a High Protein (HP) diet. 

Imbalanced blood sugar levels is a health condition associated with some pain syndromes. One study found that chronic pain symptoms were significantly more common in diabetic and prediabetic patients. 

While the benefits of fiber for gut health are tremendous, an unhealthy or compromised gut cannot handle fiber in the first place. Several inflammatory gut conditions like IBS, ulcerative colitis, and Crohn’s disease make a person extra sensitive to fiber. Fiber will only aggravate the symptoms in these patients. In these cases, probiotic foods have been found to decrease 20+ inflammatory markers and increase the microbiome’s diversity in the gut, both of which enable the gut to handle the increased fiber intake more appropriately.

The Role Of The Microbiome And Importance Of Probiotics

The Role Of The Microbiome And Importance Of Probiotics

Your body contains approximately 40 trillion microbes, most of which inhabit your gut. They constitute the gut microbiome and are essential for proper digestion. 

They aid the gut in metabolizing food and keeping it healthy. They digest fiber and convert it into beneficial short-chain fatty acids. These fatty acids are acetate, propionate, and butyrate, all of which help the body in several ways. 

Propionate reduces anticipatory reward responses in the brain. Butyrate improves brain health by forming the blood-brain barrier. 

Gut microbes also metabolize bile acids produced in the liver. While they are primarily involved in the absorption of dietary fats, they can also affect the brain. 

However, the gut microbiome is a fight between good and bad bacteria. And if the bad bacteria overtake the good ones, complications ensue.

Hence, it is important to maintain the gut microbiota so that opportunistic organisms do not inhabit it. One way you can improve your gut health is by increasing the consumption of probiotics


Probiotics are live strains of specific bacteria that establish themselves in the gut and replace the bad bacteria when ingested. They prevent their overgrowth, maintain the gut lining, and restore gut barrier function. 

Probiotic foods include fermented foods like yogurt, kefir, kimchi, sauerkraut, miso, kombucha tea, tempeh, and pickled vegetables. 

Most foods contain live lactobacillus, a common and beneficial gut bacteria. People who have more yogurt have fewer Enterobacteriaceae in their gut. Enterobacteriaceae have been associated with many chronic conditions and chronic inflammation. Yogurt consumption has also been associated with decreased symptoms of lactose intolerance.


Understanding the gut-brain connection is vital for overall health and can help modify pain. 

We now know that the vagus nerve acts as a bidirectional commuter between the gut and the brain, communicating through neurotransmitters. These neurotransmitters are vital for regulating sleep, mood, pain, stress, hunger, sleep, and more.

When gut health is compromised, it can lead to chronic inflammation, affecting the body and the brain. It can also lead to “leaky gut syndrome”, where toxins and bacteria leak out of the gut and enter the bloodstream, activating inflammation. 

An inflamed body is more sensitive to pain and more likely to develop secondary illnesses. 

A high-fiber diet increases gut motility and prevents chronic constipation and irritable bowel syndrome (IBS). Ingesting probiotic foods can restore the gut microbiome so that it can handle a high-fiber diet more appropriately. 

Understanding the gut-brain axis alone will help understand many chronic conditions, improve overall health, and modify pain.