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How Stress Affects Our Gut Health

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How Stress Affects Our Gut Health

According to the American Institute of Stress, 55% of Americans report feeling stressed daily. Stress can be caused by various factors, including work, finances, family, health, and more. Most people know that stress induces physical changes in our bodies, including a faster heartbeat, sweating, and tense muscles, but some may not realize its profound effect on our gut health.  

This article will discuss gut health, how stress can affect it, functional medicine labs to assess stress and gut health, and treatment options to get to the root causes.


What is Gut Health?

Gut health is the layman's term for optimal gastrointestinal (GI) functioning. The GI tract's main function is digestion, which encompasses six processes: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation (excretion). Essentially one long tube, these processes begin in the mouth and end in the rectum.

Digestion begins in the mouth, where saliva breaks down food and wards off pathogens with its antimicrobial properties. Food then continues down through the esophagus and into the stomach, which contains acids and enzymes that aid in the breakdown of food. Intrinsic Factor, a hormone necessary for B12 absorption, is produced in the stomach and some substances, such as alcohol and aspirin, are absorbed in the stomach.

Next is the small intestine, where vitamins, minerals, and other food substances are absorbed into the bloodstream. Accessory digestive organs also play a role, including the liver, which produces bile (an important substance for fat breakdown), the gallbladder, which stores excess bile, and the pancreas, which produces and releases enzymes important for protein and carbohydrate breakdown. It's important to emphasize that absorption is a specific process; in a healthy gut, only foods that are properly broken down can be transferred into the bloodstream.

The remaining food products then move into the large intestine, which houses the microbiome: a collective group of microbes that aid in digestion, immune function, hormone synthesis, and more. The microbiome will process food in the final step of digestion before food is excreted out of the body. Gut health describes healthy digestion at every step, including a healthy and robust microbiome.

How Does Stress Affect Gut Health?

It is thought that stress can induce the onset of or make the following GI conditions worse: Inflammatory Bowel Disease (IBD), including Crohn's disease and Ulcerative colitis, Irritable Bowel Disease (IBS), Gastroesophageal Reflux Disease (GERD), Peptic Ulcer Disease (PUD) and other gastrointestinal conditions. Here we will explore a few mechanisms that may cause this to happen.

Hypothalamic Pituitary Adrenal (HPA) axis

The Hypothalamic-Pituitary-Adrenal (HPA) axis is the body's stress system. The hypothalamus, the main regulatory center of the brain, senses stress. When it does, it releases a hormone to the pituitary gland, a gland in the brain that controls hormone function in the body. The pituitary gland will then release a hormone that signals the adrenal glands that we are under stress. The adrenal glands release several hormones to help combat stress, including cortisol. Cortisol affects various metabolic functions, including blood pressure and blood sugar. It also has a profound effect on the gastrointestinal system, leading to decreased stomach (gastric) emptying, increased colonic contractions and transit (diarrhea), and increased sensitivity in the GI, leading to heartburn symptoms without an increase in stomach acid.

Microbiome-Gut-Brain Axis (MGBA)

In addition, there is another pathway of great importance when talking about stress and gut health: the microbiome-gut-brain axis (MGBA). The microbiome is a group of bacteria, viruses, and fungi inhabiting our large intestine. We have a symbiotic relationship with these microbes in that they benefit from us by living in us, and we benefit from them as they have an essential role in digestion and absorption, immune function, hormone production, and more. It is thought that the HPA is one way the MGBA is modulated. Studies have shown stress-induced alternations in the microbiome's composition, leading to dysbiosis or an imbalance in the good and bad microbes within the gut. This can significantly affect the microbiome's functioning.  

Increased Intestinal Permeability, aka "Leaky Gut"

Increased intestinal permeability, also referred to as "leaky gut," may be another result of stress. Under normal conditions, the passage of certain nutrients and signaling molecules from the small intestine into the bloodstream occurs under significant regulation. However, if there is increased permeability in the small intestine, unwanted particles may enter the bloodstream, causing the creation of inflammatory markers, amongst other things. It is thought that increased permeability is the result of an inflammatory marker, too. Lipopolysaccharide (LPS) is a product of harmful bacteria within the microbiome and, when elevated, can cause increased intestinal permeability.

Functional Medicine Labs For Stress Related Gut Issues

Cortisol Testing

Cortisol is one of the main hormones the body produces when under stress. Cortisol is essential to life and, in proper amounts, can be highly beneficial. However, large amounts of cortisol for prolonged periods can be detrimental. Additionally, cortisol is released according to our circadian rhythm. Prolonged stress can affect our circadian rhythm, affecting the timing of cortisol release and negatively impacting health. Testing cortisol levels throughout the day can give insight into the production and timing of cortisol release, which can aid in evaluating stress-related gut health issues. The Cortisol Awakening Response (CAR) test by Precision Analytical will show cortisol levels throughout the day, including the important morning release, which sets the tone for the rest of the day. In addition, this test shows cortisone levels, the inactive form of cortisol. It's essential to look at both cortisol and cortisone as they can interchange depending on genetics and environment.

Comprehensive Stool Analysis

Comprehensive Stool testing will give great insight into the microbiome. The GI-MAP by Diagnostic Solutions analyzes fecal samples for various microbes within the GI tract, including pathogens or harmful microbes. It will also give the level of calprotectin, the gold standard marker of inflammation in the GI. Additionally, zonulin, a marker of increased intestinal permeability, can be added to this test.  

Small Intestine Bacterial Overgrowth (SIBO)

As its name implies, SIBO is a condition when the microbes from the microbiome in the large intestine move into the small intestine. Although beneficial in the large intestine, these microbes create problems in the small intestine, such as impaired digestion and absorption. High stress levels, or cortisol, can be an attributing cause of the development of SIBO. A Breath Test is the best way to test for this condition.    

Functional Medicine Treatment to Support Stress Levels and Gut Health

Anti-inflammatory Diet

Since stress can cause inflammation, an anti-inflammatory diet can be beneficial for supporting gut health when stressed. The anti-inflammatory and Mediterranean diets are similar: both high in fruits, vegetables, whole grains, fish, and poultry. Probiotic-rich foods such as yogurts, sauerkraut, and kimchi can also play a beneficial role in supporting the microbiome.  


Exercise can positively impact gut and GI functioning. Exercise has been shown to increase the microbiome's diversity and enhance the number of beneficial microbes. There is also evidence to suggest exercise can increase the production of prebiotic byproducts, short-chain fatty acids (SCFAs). SCFA can play a significant role in health as they enter the bloodstream and affect numerous body systems. Exercise can modulate intestinal motility or movement by increasing blood flow to the intestines. The intensity of exercise is important, as regular to moderate exercise seemed to be the most beneficial, while high intensity seemed to impact stress and GI markers negatively.

Complementary and Alternative Medicine

Adaptogenic Herbs

Adaptogenic herbs are herbs that help the body adapt to stress. One of the most common adaptogens is Ashwagandha somnifera. Ashwagandha has been shown to modulate cortisol levels and lower inflammation, making it an excellent choice for stress-induced gastrointestinal problems.


Probiotics are supplements that contain various strains of beneficial gut microbes. A study published in Neurogastroenterology and Motility assessed probiotic supplementation in medical students in Japan. They found that the probiotic group had lower cortisol levels and fewer abdominal symptoms compared to controls.


The connection between stress and gut health is important, especially since more than half of Americans report being stressed daily. Stress affects the GI in multiple ways, including the effects of cortisol, the microbiome, and intestinal permeability. Functional medicine testing can assess all of these mechanisms, allowing for great insight into the impact of stress on the individual. It also allows for a personalized, comprehensive treatment plan to be created to alleviate the effects of stress while aiding in lowering the stress itself.  

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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