The link between stress, digestion, and your gut microbiome has received significant attention in recent years. Our bodies have a remarkable response to stress known as the “fight or flight” response. When activated, our adrenal glands will release a variety of stress hormones, including cortisol. While cortisol is crucial for short-term stress responses, ongoing chronic stress, can lead to high levels of cortisol, and that spells trouble for digestion.

In today’s article, I will explain exactly how stress and high cortisol cause various digestion-related problems. I will explain how stress and cortisol can negatively affect the gut microbiome, how it can cause leaky gut, how it can cause Small Intestinal Bacterial Overgrowth (SIBO). I will review the relationship between cortisol and acid reflux and lastly, I will review some important nutritional and lifestyle tips to help alleviate the impact that this stress and high cortisol have on your digestion and your gut microbiome.

The Consequences of High Cortisol on Digestion

We’ve all experienced that feeling when we’re nervous: an upcoming interview, a school presentation in front of our peers, where we feel like we are being judged, those jitters that we feel in the pit of our stomach are proof that our brain and gut are connected. It’s no surprise that the gut is often referred to as the second brain because it has a nervous system with more neurotransmitters than the brain’s central nervous system.

The Centers for Disease Control and Prevention of the United States estimates that stress accounts for around 75% of all doctor visits (*) and this level of stress extends to primary care doctors. Studies show that stress and burnout among primary care doctors is 50% to 80%.(*)

These patients and primary care doctors report having heart problems, an upset stomach, ulcers, insomnia, fatigue, back pain, and headaches, among other complaints. Stress also increases your risk of diabetes, especially in overweight individuals.

One of the biggest problems I see with my patients who have Leaky Gut, IBS, or IBD, and SIBO is a history of a lifetime of stress and anxiety. Those are always the common denominators. “When we’re stressed, our brain activates the sympathetic nervous system.

The sympathetic nervous system is our flight-or-fight response: it prepares the body to protect itself against imminent danger by conserving functions that aren’t immediately needed for survival. That makes sense right? Our innate wisdom of the body prioritizes what needs to be done here and now.

As part of this fight or flight response, under stress, your brain will send a signal to your adrenal glands instructing them to pump out a hormone called Cortisol and adrenaline. During this fight or flight response, (Stress response) If it doesn’t help you run faster, run longer, or fight harder, it will take a back seat and that includes almost every aspect of digestion. Digestion does not take center stage when you are under stress. You see our Digestion, is run by another part of our nervous system known as “Rest and Digest” It’s better known as our Parasympathetic Nerve System.

How High-Stress and Cortisol Alter The Gut Microbiome

High cortisol can induce negative changes in the gut microbiome, the community of microorganisms living in our intestines(*). Remember when our body perceives stress, our adrenal glands begin to secrete Cortisol. High cortisol levels can alter the balance of gut bacteria, favoring the growth of harmful microbes like Streptococcus, and Escherichia coli while reducing the populations of beneficial bacteria like Lactobacillus and Bifidobacterium.(*)

This imbalance in the gut microbiome, known as dysbiosis, can further compromise the integrity of the intestinal barrier and exacerbate a Leaky Gut.

The combination of increased gut permeability due to changes in tight junction function and alterations in the gut microbiome composition can create a vicious cycle in which stress contributes to Leaky Gut, and Leaky Gut, in turn, can perpetuate chronic stress and inflammation in the body.(*) The consequences of stress-induced leaky gut extend beyond digestive issues and can have far-reaching effects on overall health, including immune dysfunction, systemic inflammation, and the development or exacerbation of various chronic diseases.

High Cortisol, Stress, And Leaky Gut

Stress can significantly impact the integrity of the intestinal barrier and contribute to the development of a Leaky Gut.(*) When we experience stress, whether it be acute or chronic, our bodies respond by releasing cortisol, the primary stress hormone. High levels of cortisol in the body can lead to changes in the gut environment that affect the tight junctions between cells in the intestinal lining. These tight junctions act as gatekeepers, regulating the passage of molecules and substances into the bloodstream.

Under conditions of chronic stress, the continuous presence of high cortisol levels can disrupt the normal functioning of the intestinal barrier. Cortisol has been shown to increase gut permeability by affecting the proteins that make up the tight junctions, making the barrier more permeable.

Normally, the intestinal barrier acts as a selectively permeable membrane, regulating the passage of nutrients while keeping harmful compounds out of circulation. However, under conditions of chronic stress and sustained elevation of cortisol, the integrity of this barrier can become compromised.

This increased permeability allows for the passage of larger molecules, such as toxins, undigested food particles, and bacteria, from the gut into the bloodstream. As these substances leak into the circulatory system, they can trigger an immune response and system inflammation throughout the body.

Learn more about common causes of Leaky Gut here.

Stress, High Cortisol, And Vagus Nerve Function

Stress and high cortisol impact many areas of digestion and we can’t talk about the effect of stress on digestion without talking about the Vagus Nerve. If you never heard of the Vagus Nerve here is a little refresher on why it’s important for digestion. The vagus nerve plays a crucial role in the bidirectional communication between the gut and the brain, forming a key component of the gut-brain axis and it plays a major role in digestion(*).

As the longest cranial nerve, the vagus nerve extends from the brainstem to various organs in the body, including the heart, lungs, and most importantly, the gastrointestinal tract. Its intrinsic connection to the gut makes it a vital player in regulating digestion, gut motility, immune responses, and overall gut health.(*)

One of the primary functions of the vagus nerve concerning gut health is its role in modulating the parasympathetic nervous system, which is responsible for promoting rest, relaxation, and digestion.

The Mighty Vagus Nerve

The vagus nerve helps to stimulate the release of

• Stimulates organs of digestion to release enzymes
• Stimulates or increases gut motility,
• Stimulates and plays a role in appetite,
• Regulates intestinal inflammation-maintain a balance between pro-inflammatory and anti-inflammatory pathways
• Enhances nutrient absorption.

All of these functions are essential for maintaining a healthy digestive system (*).

By activating the parasympathetic response, the vagus nerve promotes optimal gastrointestinal function and supports overall gut health.

Additionally, the vagus nerve regulates gut-brain communication, influencing mood, emotions, and stress responses. Through its connection to various brain regions, the vagus nerve can transmit signals related to gut health and overall well-being. This communication pathway is pivotal in linking gut dysfunction with conditions such as anxiety, depression, and mental health disorders, highlighting the interconnectedness of the gut and brain in maintaining holistic health.(*)

Research has shown that the vagus nerve can sense and respond to signals from the gut microbiota, influencing brain function and behavior.(*) The vagus nerve is activated by several neurotransmitters produced by the gut microbiota. This highlights the importance of a healthy gut microbiome in promoting optimal vagus nerve function and overall gut-brain axis balance.

Enhancing vagus nerve tone can be accomplished by correcting intestinal dysbiosis, and improving short-chain fatty acids, prebiotics, and probiotics. If you have gut issues you will want to learn ways to stimulate this vagus nerve to support your gut microbiome, digestion, and motility. You can do this with specific exercises known as vagal nerve exercises.

Stress and High Cortisol Can Shut Down The Vagus Nerve 

Remember the Vagus nerve represents the main Nerve of the parasympathetic nervous system, and this parasympathetic nerve system, everything from our mood oversees, immune response, heart rate, and yes digestion! Think of your Vagus nerve as the connection between the brain and the gut. When stress hormones like cortisol run high, they put a block on the Vagus nerve.

High levels of Stress hormones, like cortisol and adrenaline, decrease blood flow to the digestive system including the stomach… this in turn causes less Hydrochloric acid production in the stomach. Well….. (HCL) Hydrochloric acid is needed to digest fats and proteins.

If you decrease Hydrochloric acid (HCL) production in the stomach, this is going to put the brakes on the digestion of proteins and fats. Now stop for a moment and think, “What might be the consequence of putting the breaks on the digestion of proteins and fats?”

If you said bloating, gas, belching, feeling full all the time, food allergies, skin conditions, SIBO and toxicity,  you would be exactly right!.

When stomach acid is decreased, due to high cortisol levels, the overall pH of the stomach rises, in other words, it becomes more alkaline, and bacteria that are normally killed by acid, begin to proliferate and colonize not only our stomach but also the small intestines and large intestines. This is one of the ways people get infected with H.pylori, SIBO and other pathogenic disease causing bacteria.

Follow these 5 tips to improve low stomach acid

Stress, High Cortisol, And Acid Reflux

While we are on the topic of bacteria let’s review how stress can cause or exacerbate Acid reflux. Once these bacteria begin to take over and colonize your gut, you can get an enormous amount of gas that builds up pushing against a sphincter called the lower esophageal sphincter, or the LES for short.

The LES prevents the contents of the stomach from coming back into the esophagus. This is what we call acid reflux. Acid reflux is caused by a LES (lower esophageal sphincter) that’s not working the way it’s supposed to. It’s not creating a nice tight seal between the stomach and esophagus.

If you have acid reflux you most likely have an infection with H.pylori, you could have a problem with not enough acid in your stomach, you could have a problem with LES and you could have too much cortisol shunting blood away from your stomach and reducing acid production.

High cortisol can slow down the emptying of the stomach, causing food and stomach acid to remain in the stomach for a prolonged period. This delay can increase the pressure in the stomach, leading to the reflux of acid into the esophagus.

Hopefully, you can now see that simply taking antibiotics and antacids does not fix the root cause of Acid reflux. If you don’t ask the right questions, you will never get the right answers.

High Cortisol And SIBO

High cortisol, caused by prolonged stress, can also have dire consequences on your gut microbiome. These changes often show up as Small Intestinal Bacterial Overgrowth (SIBO). SIBO is a condition characterized by the overgrowth of bacteria in the small intestine. High cortisol levels can also cause Small Intestinal Bacterial overgrowth (SIBO).

Normally the small intestines do not have the same kind of bacteria that the large intestines do. But once the bacteria from the large intestines move up and colonize the small intestines, they begin to rob nutrients from you, while producing hydrogen or methane gas.

There are many factors behind SIBO. Some of the factors include a high FODMAP diet, a bout of food poisoning, motility issues, hormone imbalances, neurotransmitter imbalances, and certain medications that can disrupt this balance, allowing bacteria to proliferate in the small intestine. S

SIBO can manifest through symptoms such as gas, bloating, diarrhea, fatigue, and skin issues like rosacea. But let’s talk about bloating and SIBO.

Being bloated all the time causes a malfunction in another valve called the Ileocecal valve.

The Ileocecal valve is another valve- This one is between the small intestines and the large intestines. If you are bloated all the time, your IC valve stays open, and this is how we develop bacteria overgrowth in the small intestines. When the IC valve stays open, bacteria from the large intestines, move up and take residence in the small intestines.

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Fight or Flight Digestion and Our Gut Microbiome

There are a few more things I want you to know about stress, high cortisol, and the microbiome. When the HPA axis is we get a surge of cortisol and adrenaline released into our system. Let’s review the consequences.

1. Stress But more specifically high cortisol affects your gut microbiome
2. High Cortisol causes changes in the permeability of the gut- The gut becomes more leaky, and this can be a biological door into colorectal cancer, autoimmune diseases, and several chronic health problems caused or exacerbated by a Leaky Gut. (*)
3. High cortisol causes thinning of the gut barrier (*)
4. Decreased mucous production is also a consequence of high cortisol levels. Mucous not only forms a physical barrier the mucous layer of the gut is the home for a major part of the immune system. (*)
5. High cortisol levels decrease your SIgA Levels making your more prone to infection, candida overgrowth and food sensitivities and food allergies(*)

Sadly, early events in our life that kept us in this fight or flight state, program the HPA axis- for all these consequences. This becomes one big problem that snowballs into even bigger problems. This is the connection between stress, and how high cortisol affects digestion and various problems in the gut.

Tips To Alleviating Stress, Improve Digestion, and Improving Your Gut Microbiome

Whether you have been diagnosed with anxiety, panic disorder, or some other condition, it should be quite clear that balance needs to be reestablished between your sympathetic and parasympathetic nervous system

To have a positive impact on digestive symptoms, we want to activate the parasympathetic nervous system, which is the body and brain’s rest and digest response—it undoes what the sympathetic nervous system does.

When the parasympathetic nervous system is activated, your body becomes calm, your heart rate goes down, and your gastrointestinal system functions as it should.

If this is something you want to learn more about “How to activate your Vagus Nerve” I recommend that you read the article I wrote on Vagus Nerve Exercises.

Remember This About The Effects Of Stress on Gut Health, Digestion the Microbiome and Motility

So a few things to remember and a few recommendations when it comes to dealing and understanding the relationship between stress, high cortisol and its impact on the microbiome and digestion. High cortisol can have numerous implications for our digestive health. I talked about high cortisol and SIBO, High cortisol and leaky gut and how High cortisol can cause acid reflux. Remember High cortisol shuts down many areas of the digestion process.  Gut related symptoms that might indicate you have high cortisol levels include things like bloating, constipation, heartburn, stomach pain.

If you have gut infections that keep coming back, SIBO that doesn’t improve, Food sensitivities that just continue to get worse, Candida overgrowth that you cant get rid of or a leaky gut that never heals, you may be missing the link between high cortisol and your microbiome. If you’re not healing (based on retesting) it might be time to look at your adrenal glands and specifically your cortisol levels. If you

Well, there you go! I hope today’s video, helped you understand another piece of the health puzzle on how stress affects the microbiome and perhaps why you’re not getting better despite changes in your diet, medications, and or supplements. You need to know the “WHY”

Check out These Articles Next 

1. Exercises To Activate Your Vagus Nerve for Better Gut Function
2. How to Improve Your Vagus Nerve When Suffering with IBS and SIBO
3. The Migrating Motor Complex- Why It’s Important When You Have SIBO and 7 Steps to Improve its Function
4. The Gut-Brain Connection- Learn How to Harness this Powerful Connection.
5. How To Raise Dopamine Levels Naturally- 7 Ways To Improve Your Mental Health Naturally