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Stress and Gut Health: How The Gut-Brain Axis Causes Your Digestive Symptoms

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Has a doctor ever told you your gut symptoms are “all in your head”?

Many conventional doctors attribute unexplainable gut conditions to “psychosomatic” causes, meaning their symptoms are primarily due to negative emotions or stress.

Suffering patients are usually diagnosed with IBS, which is often accompanied with an “it’s all in your head” response from their doctor. Patients are sick and tired of their doctors making them feel like they are crazy or depressed and minimizing their GI pain.

While these “all in your head” sentiments are an apathetic oversimplification of gut dysfunction, they do highlight the strong connection between how we think and how we feel.

That’s not to say that GI pain associated with stress is a figment of your imagination.

The pain, discomfort and dysfunction is very real.

Emotional and physical stress has a strong connection with our digestive function. This connection has been dubbed the “gut-brain axis.”

The gut-brain axis is a bi-directional relationship that allows the brain to manage digestive function, regulate the gut’s immune system, and coordinate the emotional and physical well-being of a person with the activity in the gut.

The gut-brain connection explains why we feel like our stomach is in knots before we give a public speech or when we watch scary movies.

Due to this highly connected gut-brain axis, physical and emotional stress can have a profound effect on GI function.

Rethinking Stress

In our society today, stress is most often associated with emotional and psychological causes, like worrying about a big presentation at work or how you are going to pay the bills.

Some other common emotional stressors include:

  • starting a new job
  • ending a relationship
  • coping with a sick family member
  • moving to a new unfamiliar city
  • loss of a pet

Stressors don’t necessarily have to be negative either. Sometimes even positive life changes like a new relationship or new baby can bring extra stress into your life. (Or maybe planning a wedding like me!)

While stress is most commonly seen as an emotional/psychological condition, stress can also be physical. Many patients claim that they have de-stressed their life, but still have health symptoms.

I usually discover that these patients, though they are focused on removing emotional stressors, fail to recognize and remove the more elusive physical causes of stress in their lives.

Some common physical stressors that are often overlooked are:

  • Over-exercising or training
  • Under eating
  • Food intolerances
  • Lack of sleep
  • Hidden infections
  • Inflammatory diseases like autoimmune diseases, heart disease or diabetes
  • Poor circadian rhythm entrainment

Both physical and emotional stress trigger the release of cortisol, our “fight or flight” hormone. Cortisol activates our sympathetic nervous system sounding the alarm in your body to prepare for battle.

This stress response is great for dealing with an acute stressor (like when you are being chased by a tiger) but chronic activation when you have a stressful job or don’t get enough sleep causes deeper problems.

Cortisol directly inhibits digestion through its activation of the sympathetic nervous system. We must be in “rest and digest” mode and under the control of our parasympathetic nervous system in order to properly digest and absorb food.

The sympathetic and parasympathetic nervous systems cannot both be active at the same time.

So, if you are chronically stressed you lose your ability to rest and digest fully. This disabled digestion causes symptoms like stomach pain, malabsorption, reflux, bloating, constipation and diarrhea. It can even lead to infections like SIBO as stomach acid and gut motility drops.

How do these stressors affect the gut?

We have established that stress directly affects our ability to digest and absorb foods. In addition, stress contributes to inflammation in the gut in a number of ways.

Let’s look at a few different problems that chronic stress can cause for our digestive health.

Intestinal Permeability (Leaky Gut)

Preserving the integrity of your gut lining is essential to maintaining good health and preventing disease. Your gut lining is a single layer of cells responsible for preventing food particles, toxins and microbes from entering the body.

In between each of these cells are tight junctions, which are responsible for holding these cells tightly together to properly seal the gut to prevent particles from moving between the cells and into the body.

Both physical and emotional stressors have been shown to induce intestinal permeability. Research suggests that stress-induced leaky gut is dependent on the activation of the HPA axis that secretes corticotropin releasing hormone (CRH) from the hypothalamus.

An increase in CRH not only stimulates cortisol release from adrenal glands, but CRH also appears to mediate leaky gut through its signaling to the mast cells found in the gut lining. Once activated, these mast cells can produce leaky gut by releasing proteases and tumor necrosis factor alpha.

As the gut lining becomes compromised by stress, a vicious cycle of inflammation can occur. Food particles, bacteria and lipopolysaccharides seep into the bloodstream. These foreign invaders raise the alarm, and an overzealous immune system kicks off an inflammatory response thinking that you are under attack.

Lipopolysaccharides (LPS) – endotoxins released by gram negative bacteria – are especially problematic and can trigger systemic inflammation in the body. LPS even has the ability to cross the blood brain barrier, leading to inflammation in your brain!

LPS also perpetuates the stress response by stimulating the release of cortisol. Once stress opens the intestinal floodgates, LPS can make re-establishing your gut’s integrity a difficult feat by continuing to provoke the stress response.

You are essentially stuck in the fight or flight state and your gut continues to stay permeable to toxins, food particles, and microorganisms.

Immune System Dysfunction

Stressors have a profound effect on our immune system. Chronic stress suppresses the immune system, leaving your body (especially your gut) susceptible to opportunistic infections. After all, about 70% of our immune system is found in the gut!

Cortisol suppresses the immune system directly by preventing the proliferation of T-cells, which are important in modulating cellular immunity. So, if you find yourself battling a cold or chronic infection, it is important to de-stress and relax to allow your immune system to work its magic.

With the majority of your immune response residing in your digestive tract, it is no surprise that the brunt of the dysfunction from high cortisol occurs there. When stress-induced leaky gut occurs, your immune system loses its ability to distinguish between harmful and harmless compounds.

This disability leads to the development of food sensitivities, allergies, autoimmunity and other inflammatory conditions.

Bacterial Imbalance

Stress also seems to play an important role in regulation the microbial populations in the GI tract. There have been numerous animal studies that have demonstrated stress-induced changes in the microbiota.

One particular study showed a decrease in Lactobacillus species of bacteria in infant monkeys after a 3-day separation from their mothers. These changes in gut microbiota usually coincide with an increase in intestinal permeability.

Brain-gut connection is not a one-way street. Gut bacteria communicate back to the brain as well. Probiotics like Lactobacillus helveticus and Bifidobacterium longum have been shown to prevent HPA axis activation.  So, resilience to stress relies on a diverse and healthy microbiome.

Suppresses Thyroid Function

Thyroid hormones are essential for optimal digestion and motility of food through the GI tract.

Increased cortisol inhibits the conversion of the T4, the inactive thyroid hormone, to T3, the active thyroid hormone. Low T3 can cause symptoms like bloating, water retention, constipation and abdominal pain.

How to optimize the connection between your gut-brain axis

Focusing on proper stress management, nutrition, sleep, and exercise will make your gut-brain axis far more resilient to the challenges it faces on a daily basis to protect your body from the outside world.

Reducing the unnecessary stress from your life is an important step in optimizing your health. Finding a different job or ending a stressful relationship will improve your health. Surrounding yourself with caring and supportive people whenever possible will also reduce stress.

Stress is not completely avoidable, but doing daily stress reduction practices can make you resilient to unexpected stress. Meditation, yoga, hiking and even taking time to pet your dog can be great ways to build your stress tolerance every day. Find what techniques work best for you and stick with it.

Supporting your microbiome will help as well. As we have discussed above, good gut bugs can make us more resilient to stress, while pathogenic bacteria can stimulate a stress response. To ensure that you have a robust and diverse microbiome, you should eat fermented and prebiotic-rich foods to foster your microbiome.

Interestingly, one of the best ways to minimize your stress response and to build a strong gut-brain axis is to stimulate your vagus nerve. Humming, singing, gagging and gargling exercise excite the vagus nerve and activates your parasympathetic nervous system allowing you to rest and digest.

Here is a great video that explains how to exercise your vagus nerve to improve gut function.

And of course, you should work on getting plenty of sleep! Lack of sleep makes you less resilient to stress. To make matters worse, high cortisol can lead to insomnia and sleep disturbances. Stress management is essential for establishing a healthy  sleep pattern.

Aim for 8-10 hours of sleep a night in order to ensure you are resilient to the stressors that may come up the following day.

And of course, eating  a wide-variety of nutrient dense foods while limiting inflammatory processed foods and seed oils will raise your stress tolerance by nourishing your body and your microbiome. Cortisol can rise on a low carb diet, so I don’t usually recommend very low carb diets for individuals struggling to manage high stress levels.

Finally, be cautious not to overtrain, which can supress immunity and potentially contribute to deficits in the gut-brain axis. Be sure to take at least one day off from intense exercise per week, and cut down on your volume of training if you are struggling with significant gut symptoms.

To learn more tips on lowering stress, download my free guide to developing a Fear-Free Diet and learn how to take the stress out of your eating and lifestyle habits!

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Your Friend and Business Mentor

I'm a women's health expert and a registered dietitian (RD) with a passion for helping goal-oriented people fuel their purpose.

I help nutrition entrepreneurs grow their income and their impact by packaging their brilliance into transformative coaching and consulting programs, and get crystal clear on their marketing strategy.

I'm on a mission to help nutrition business owners drop the hustle and come into alignment with their ideal business goals, so they can work from a sense of ease and abundance, and build the online business of their dreams. 

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