Stress effects everything, instantaneously. When in “fight and flight”, our whole physiology and psychology shifts quickly to survive. Thankfully, once the stress is gone, the mind and body can enter into recovery.

However, if there is no respite, long-term stress can be detrimental. Chronically, either the perception and continued rumination of emotional stressors, or, experiencing legitimate dangerous, stressful situations, can lead to physical and mental illnesses.

One area that is heavily impacted by stress is our gut. Unless you were born a spiritually serene guru, you’ve probably experienced firsthand the influence of stress on digestion. Furthermore, you’ve probably noticed becoming a bit more irritable when your gastrointestinal (GI) tract was misbehaving.

The relationship between stress (physical, environmental, and/or psychological) and digestive function is complex and bidirectional. This means stress can trigger GI distress and gut imbalances can cause stress. In fact, they are so intricately linked that psychological therapies are often used solely, or with other treatments, to address functional gastrointestinal disorders.

If you are struggling with digestive issues, and constantly overwhelmed, it’s important to understand how stress can sway your symptoms.

In this article, we will explore how stress can affect the gut.

Topics include:

• Our nervous system’s connection to our “second brain” in the gut
• The gut-brain connection
• An overview on how stress influences gut physiology (the “gut-stress” axis)
• How stress impacts:
  • gut immunity
  • the microbiome
  • intestinal permeability (“leaky gut”)
• An overall summary and two tips to support a stressed-out gut

In a follow up article, I’ll highlight more naturopathic and functional medicine modalities to support optimal gut-brain health.

Let’s get started.

Your Nervous System and Your “Second Brain” in the Gut

Physiological functions, such as breathing, heartbeat, blood pressure, and body temperature, are regulated through the autonomic nervous system (ANS). The ANS has two major divisions. The first is the sympathetic nervous system (SNS), which triggers the “fight, freeze, or flee” response. The other is the parasympathetic nervous system (PNS), which calms the body down. Both extend from the brain to all major organs of the body.

The SNS and PNS also interact with a third, less recognized component of the autonomic nervous system — the enteric nervous system, located in the gut. This is known as the “second brain” because it relies on neurons and neurotransmitters similarly as the brain to function.

In fact, most of our serotonin is produced in our gut. Along with its affect on mood, it also influences intestinal contractions and appetite. In addition, other signaling molecules in the GI tract also play a role in digestion and regulating our physiology through communication with the central nervous system. This interaction is known as the “gut-brain” connection.

This gut’s influence on your brain and body includes how it interplays with:

1. The immune response – Our gut houses over 70% our immune system.
2. Tryptophan metabolism – This amino acid is a precursor to the “feel-good” neurotransmitter, serotonin, melatonin, and a modulator of inflammation.
3. The vagus nerve – This nerve extends from our brain into our GI tract. It is akin to a gut-brain “highway” that “transports” communication via signaling information back and forth. The vagus nerve plays a role in mood, inflammation, digestion, and other crucial bodily processes.
4. The metabolites of microbes (e.g., short-chain fatty acids (SCFAs), branched-chain amino acids, and peptidoglycans) – These act as signaling molecules that effect health outcomes.
5. The enteric nervous system – As mentioned above, these neurons and supporting cells of the “second brain” influence systemic processes.

Stress on the Gut

Stress has both short- and long-term effects on the gastrointestinal tract. It can modify the communication between the gut and brain and influence the “rest and digest” branch of the nervous system. As a result, when stressed the digestive process is hindered and discomfort in the GI tract can be exacerbated. Furthermore, gut issues can cause physical stress and perpetuate the cycle of symptoms.

Specifically, stress has the following impacts on the gut:

• it affects gut motility
• it increases pain sensation in the organs (inducing proinflammatory cytokines and neurotransmitters)
• it alters intestinal secretions
• it influences gut permeability
• it negatively effects GI mucosa regeneration and mucosal blood flow
• it shifts the microbiota

Stress has been linked to the development of many gastrointestinal disorders. These include:

• inflammatory bowel disease (IBD)
• irritable bowel syndrome (IBS) and other functional gastrointestinal diseases
• food antigen-related adverse responses
• peptic ulcer
• gastroesophageal reflux disease (GERD)

How Stress Signals Alter the Gut’s Immune Response (The Gut-Stress Axis)

When stress signals (CRF, ACTH, and glucocorticoids) are released from the central nervous system the parasympathetic nerves are activated. These innervate the enteric neurons and not only lead to the shifts in gut function mentioned above, but also in the immune response.

It is believed that CRF (corticotropin-releasing hormone), the initial hormonal signal of the stress cascade, has neural connections to the enteric nerves, mast cells, and enterocytes (gut cells). This signal leads to inflammation and alters gut motility and secretion.

For example, mast cells (MC) are a type of immune cell that interplay with the gut-stress axis. They are initiated by stress signals and release a wide range of neurotransmitters and proinflammatory cytokines in response. These chemicals can profoundly affect gastrointestinal physiology and have been linked to pain and immune deregulation.

Stress and the Gut Microbiome

Our GI tract is home to 10¹⁴ cells of thousands of different species of microbiota. These critters have been found to influence our physical and emotional health in many important ways.

These include:

• synthesizing, assimilating, and absorbing nutrients
• metabolizing and excreting toxins and wastes
• housing over 70% of our immune cells
• producing 90% of our serotonin and other vital neurochemicals
• regulating hormone excretion
• communicating with our brain to help supervise many bodily processes through the gut-brain axis
• skin health (yes, there’s even a gut-skin axis)

According to the 2011 article on stress and the gut, stress shifts the microbiota contributing to changes in pain sensation and immune modulation. The authors also note how probiotics may modify this for the better:

Stress causes changes in the composition of the microbiota; induces changes in neurotransmitter and proinflammatory cytokine levels, which could affect directly or indirectly the microbiota.

• For example, norepinephrine increases the virulence of some, bacteria like E. coli or C. jejuni.
• Gut microbiota may modulate the sensation to pain and some probiotics may inhibit the hypersensitivity and perhaps the intestinal permeability caused by the body’s exposure to stress.

Stress and Leaky Gut

In a healthy gut, the inner lining of the intestinal wall is an intact barrier which selectively filters through helpful molecules and prevents access of potentially dangerous compounds. It allows water and nutrients to cross it, while it inhibits undigested food, toxins, bacteria, and viruses to enter the bloodstream.

This makes our intestinal barrier one of the major players in our immune response. It helps to maintain gut and immune tolerance by separating gut microbiota and human immune cells.

A healthy digestive tract has multiple layers of defense to do this job. They include:

1. The external mucus layer. It is composed of microbiota on the outside and an inner layer of sparse bacteria and peptides (components of proteins) with antibacterial functions.
2. The middle intercellular junctions. A thin layer of intestinal cells with three sets of intercellular junctions. These support the brush border of the intestinal barrier and regulate its function and transport between cells.
3. The outer gut vascular barrier (GVB). The final defensive shield is the GVB which regulates the release of microbial metabolites into the portal circulation (via the liver).

A breakdown in the intestinal barrier can occur in any one of these three places: the mucus layer, tight junctions, or the GVB.

Causes of Leaky Gut

Various triggers can cause the inner lining of the intestinal wall to “leak,” aka the term “leaky gut.” In the broadest sense, all these factors can be considered stresses on the body.

Specifically, intestinal permeability can be fueled by the following stressors:

• certain medications
• emotional stress
• excessive exercise
• non-nourishing lifestyle habits
• toxic exposures
• inflammatory dietary components (which are related to individual responses)
• alcohol
• infections
• food sensitivities (related to the lack of specific enzymes or due to digestive disorders)

“Leaky gut” is a symptom, not a diagnosis.

Intestinal permeability (leaky gut) is currently gaining more attention in research and in clinical applications. This is related to a rise in awareness of how gut health impacts all diseases. Decreasing the stressors that cause “leaky gut” can help to decrease gut and systemic symptoms.

For example, there have been associations with leaky gut to chronic inflammatory health conditions such as Celiac disease, Crohn’s disease, autoimmune disorders, neurological disorders, and mood disorders.

Summary

Our emotions impact our whole physiology, not just our brain and mood. Stress has system-wide effects and negatively influences gut function including its immune response, microbiome, and defensive intestinal lining. Furthermore, digestive distress perpetuates stress symptoms.

If you’re having intestinal issues and are stressed out, it’s important to understand how much this could be impacting your symptoms and support all aspects of the gut that are impacted.

From this article, we already learned that probiotics and preventing certain stressors on the gut’s lining could decrease negative impacts on the gut-stress axis.

In the next post, we’ll explore more on how to use naturopathic and functional medicine modalities to soothe and support optimal gut-brain health.

Is stress messing with your gut?

If you can’t get to the bottom of your chronic gut issues, a naturopathic and/or functional medicine doctor can support you in remediating the contributors to a stressed-out gut and supporting your emotional health.

Naturopathic Medicine and Holistic Resources for Hormonal, Mood, and Digestive Support

• Free resources and more education on essential oils and mind-body wellness are available to you here.
• An Integrative Mental Health and Stress Resource Guide.
• Tools for coping with isolation and separation.

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Many blessings.

References:

1. https://www.health.harvard.edu/newsletter_article/stress-and-the-sensitive-gut
2. https://consumer.healthday.com/stress-stomach-pain-2659717087.html
3. https://www.health.harvard.edu/newsletter_article/stress-and-the-sensitive-gut
4. https://pubmed.ncbi.nlm.nih.gov/31460832/
5. https://pubmed.ncbi.nlm.nih.gov/33803407/
6. https://www.frontiersin.org/articles/10.3389/fpsyt.2018.00044/full
7. https://pubmed.ncbi.nlm.nih.gov/31460832/
8. https://www.sciencedirect.com/topics/neuroscience/enteric-nervous-system
9. https://www.webmd.com/digestive-disorders/what-to-know-short-chain-fatty-acids
10. https://pubmed.ncbi.nlm.nih.gov/33470191/
11. https://pubmed.ncbi.nlm.nih.gov/22314561/
12. https://www.pnas.org/doi/10.1073/pnas.0503092102
13. https://www.jpp.krakow.pl/journal/archive/12_11/pdf/591_12_11_article.pdf
14. https://naturalpath.net/body/pediatrics/the-unsterile-start/
15. https://pubmed.ncbi.nlm.nih.gov/33670115/
16. https://pubmed.ncbi.nlm.nih.gov/22314561/
17. https://www.rupahealth.com/post/what-is-leaky-gut
18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4253991/
19. https://www.journal-of-hepatology.eu/article/S0168-8278(19)30604-X/fulltext
20. https://pubmed.ncbi.nlm.nih.gov/31076401/
21. https://my.clevelandclinic.org/health/diseases/21688-food-intolerance
22. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8427160/
23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4253991/
24. https://www.health.harvard.edu/blog/leaky-gut-what-is-it-and-what-does-it-mean-for-you-2017092212451