Stomach and Brain Connection:
A Complete Guide

If you've ever felt "butterflies in your stomach" when nervous or "gone with your gut" when making a decision, you're getting signals from an unexpected source: Your second brain. Masked behind the walls of your digestive system, this "gut-brain" helps us understand our mood, health, and digestion.  

The human body's stomach and brain connection is a truly remarkable feature. To learn more about this, see the comprehensive guide below:  

How does the stomach and brain connection work? 

The stomach and brain connection operates through the gut-brain axis (GBA), which is a bidirectional link between the enteric nervous system (ENS) and the central nervous system (CNS).  

Throughout this bidirectional link, it has direct and indirect routes between emotional and cognitive centres in the brain with peripheral intestinal functions. To increase its influence on our brain, it also has complex crosstalk between the immune (cytokine and chemokines), endocrine (hypothalamic-pituitary-adrenal axis), and autonomic nervous system (ANS). 

The GBA primarily combines the parasympathetic and sympathetic arms of the autonomic nervous system (ANS), driving efferent and afferent neural signals from the gut to the brain. Located in the ANS is where the nerve connecting the stomach to the brain is located. This is called the vagus nerve.  

With help from the vagus nerve, it facilitates feedback from the intestinal end to the brain system. Having this enables us to engage the limbic and hypothalamus system, which is responsible for regulating emotions. For this reason, the gut can trigger happiness, stress, and anxiety, depending on its health. 

When the nerve connecting the stomach to the brain is healthy, it triggers a positive response. What makes an impact on this is the gut's microbiome.  

Gut microbiome 

The term "microbiome" refers to every microorganism in or on its host and its genetic makeup. Contrarily, the microbiota describes the bacterial populations found in a particular ecosystem, such as those in the gut microbiota or the skin microbiota. 

There are around 10 times as many cells in the intestine as there are in the human body. Some scientists have referred to the microbiome as a "superorganism" since it contains genetic material about 150 times larger than the human genome. 

About 75% of the gut microbiota is made up of the bacterial phyla Firmicutes and Bacteroidetes, both of which are highly sensitive to change. The incidence of allergies, autoimmune diseases, metabolic problems, and neuropsychiatric disorders that plague today's society is increasingly linked to microbiome disruptions. 

The stomach and brain connection 

There are seven major parts in the stomach and brain connection cycle. Each area utilises the microbes of gut microbiota, which then interact with the GBA. Here's a brief overview of how they react to the GBA and their purpose.  

1. The Vagus Nerve 

  • The brain stem receives feedback from the intestine end via spinal and vagal: emery neurons, which then activate the limbic and hypothalamus system (responsible for the regulation of emotions) 
  • The limbic system's descending projections, which are stimulated by stress, impact the gut's autonomic activity. 


2. Neuroendocrine (gut hormone) signalling 

  • Bacterial products induce enteroendocrine cells (EECs) to produce several neuropeptides, including substance P, peptide YY, and neuropeptide Y (NPY). 
  • These neuropeptides subsequently affect the enteric nervous system after they enter the bloodstream. 


3. Interference with tryptophan metabolism 

  • Gut mucosal enterochromaffin cells produce 95% of the serotonin (5-HT) in the body. 
  • In the body, 5-HT controls motility (smooth muscle contraction and relaxation), GI secretion and pain perception; in the brain, 5-HT is thought to control mood and cognition. 
  • Additionally, the gut microbiota is crucial for the metabolism of tryptophan, which is a precursor to serotonin. 


4. The immune system 


5. Altered intestinal permeability 

  • Leaky gut syndrome, which is connected to low-grade inflammation and has been functionally linked to psychiatric diseases, including depression, has been demonstrated to be altered by chronic stress. 
  • Lipopolysaccharides (LPS), bacterial endotoxins that circulate in the blood, significantly contribute to illness risk in many of these situations. 
  • Alternately, some research has indicated that the gut microbiome can create neuroactive chemicals that could affect the primary symptoms of neuropsychiatric diseases. 
  • This alternate theory might indicate that the gut microbiota plays a significant and pertinent role in the pathophysiology of various diseases, such as schizophrenia, autism, anxiety, and depression. 


6. Production of microbial metabolites

  • Numerous species of Bifidobacterium and lactobacillus produce gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain. 
  • Additionally, some bacillus species have been demonstrated to create dopamine, whereas candida, Escherichia, and enterococcus produce serotonin. 
  • Short-chain fatty acids (SCFAs), such as butyric acid, propionic acid, and acetic acid, are also produced by bacteria. These SCFAs can stimulate the sympathetic nervous system and mucosal serotonin production, which can have an impact on memory and learning. 


7. HPA Axis involvement 

Although chronic stress may result in a clinically significant imbalance in the microbial community, acute stress has no impact on the gut microbiota. 

  • A leaky gut resulting from increased gut permeability brought on by elevated cortisol levels subsequently promotes a systemic inflammatory response. 
  • The pro-inflammatory state caused by a leaky gut is demonstrated by elevated levels of TNF-, interferon-, and IL-6 in the blood. 
  • The HPA axis is known to be activated by IL-6, which also gradually downregulates glucocorticoid receptors. These receptors provide a feedback mechanism that inhibits the HPA axis, but when downregulated, the HPA axis becomes overactive and sensitive. 

What does this mean for our health? 

After reading the above, you should better understand the stomach and brain connection process. As you can see, our gut carries emotional responses. Therefore, it can trigger mental and physical problems or benefits based on how it's feeling.  

Because of this, it's important to maintain good gut microbiota health. If you implement the below, you can create a healthy gut that'll prevent and treat disease:  

  • Consume probiotics  
  • Eat a healthy diet  
  • Exercise regularly  

These alone are enough to boost gut microbiota health, allowing you to live a much healthier and sturdy lifestyle.  

How can Nu Mind Wellness help? 

At Numind Wellness, we've created the UK's first all-in-one stress supplement that includes a high-strength probiotics blend of 20 billion CFU. The supplement comprises 15 different bacteria strains that support a healthy gut microbiome.  

With our supplement, you can obtain a wide range of health benefits. Including:  

  • Rebuild poor gut health  
  • Reduce feelings of stress and anxiety  
  • Improve sleep quality and duration  
  • Enhance mental clarity and focus  
  • Boost overall wellbeing  

Order today and step closer to a healthier second brain to start receiving these benefits.  

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