The Gut-Brain Connection: How Stress Affects Digestion

Have you ever experienced a “pit in your stomach” – that moment when an uncomfortable realization makes you feel as if your stomach is tightening into a knot or dropping down to your feet?

Maybe you’ve been excited or anxious and felt the fluttering of “butterflies” in your belly.

Or perhaps you were “chewing something over” when you were thinking about it deeply…or something was so awful that it was “gut wrenching”…or a situation made you so angry that you could feel your “bile rising.”

Our everyday language reveals that we intuitively understand the connection between our emotions and our digestive system. Now, science can help us explain how connected our brains and our guts really are.

The Gut-Brain Connection

The highway between our emotions and our digestive system is called the gut-brain connection.

In recent years, research has revealed why and how our gut is so closely linked to our emotions and stress response. To understand this, you must understand a bit about your nervous system.

The Autonomic Nervous System (ANS) is a part of the nervous system that controls our involuntary (automatic) physiological reactions. The ANS is divided into three systems which enable your brain and digestive system to remain in constant communication.

The Sympathetic Nervous System controls our “fight or flight” state. It kicks-on in response to stress and stimulates blood-flow to the major muscles and the brain. 

The Parasympathetic Nervous System controls our “rest and digest” mode. In this state, energy is conserved, heart rate slows down, blood flows to the digestive tract and intestinal activity increases.

The Enteric Nervous System, which is referred to by scientists as our “second brain,” is a largely independent system that lies in the walls of the gastrointestinal tract and controls many digestive functions.

Take a look at the picture of the brain and the digestive tract. Can you see the similarity in their structure?

Did you know that:

• You have more neurons (the cells that send and receive messages between the body and the brain) in your gastrointestinal tract than in your spinal cord?
• Your gut contains the same neurotransmitters (chemical messengers such as serotonin, dopamine and GABA) that are found in your brain?
• The vagus nerve (cranial nerve ten) sends information about the state of the inner organs of the abdomen to the brain and conveys signals from the brain and central nervous system back to the digestive tract?

This means that your gut is literally wired to sense and feel!

Stress & Modern Lifestyle

When we experience stress, our bodies switch into a sympathetic state. In this “fight or flight” response, pupils dilate, sweating increases, heart rate rises, and the peristaltic movement normally seen through our digestive system is decreased. This happens because our body is trying to ensure our survival.

By shunting blood and energy to the muscles and brain, we can react faster to our threats. By shunting blood and energy away from the digestive system, we slow down the functions that are not essential to our immediate survival. In a life-or-death matter, digesting our last meal is not very high on that list!

However, in our modern lives we are exposed to stress that is not truly life-or-death and is typically not remedied by either fighting or fleeing. The problem is that our bodies don’t know the difference. The persistent stress of our jobs, families, traffic, deadlines, finances, politics, interpersonal conflict, and numerous other issues, can repeatedly activate our stress response.

Simply put, modern living puts us in a constant state of “fight or flight” and many of us are living in chronic sympathetic activation. To our bodies, it feels like we are “running” and “fighting” off a threat—even when the stress has passed, and often without even knowing that we are doing this.

When our bodies get stuck in this sympathetic, stressed state it can take its toll on our health and impact our digestive function. There have been many studies that explore the relationship between an over-activated stress response and digestive disorders.

How Stress Affects Digestion

Chronic stress has been shown to lead to increased inflammation in the body, decreased gastric fluids, and decreased bowel motility. A study from 2018 explains that our stress response affects our bowel movements, which can alter our microbiome and gut permeability. This may lead to IBS and obesity in some people.

Stress may also contribute to small intestinal bacterial overgrowth (SIBO) through several mechanisms, including the reduction of gastric acid production, impairment of GI motility and gut mucosal immunity, enhanced bacterial growth and virulence, and the formation of biofilms. 

Ultimately…

Chronic Stress = Prolonged Sympathetic Activation = Unhappy Digestion

Stress may lead to symptoms that interfere with healthy digestion, such as:

• Irregular contractions and spasms of the muscles along the digestive tract
• Decreased secretions (pancreatic, gallbladder) necessary for proper digestion
• Imbalanced acid in the stomach, resulting in indigestion
• Increased inflammation
• Increased intestinal permeability (“leaky gut”)
• Unhealthy gut flora 
• Lack of appetite and nausea
• Altered bowel movements, such as diarrhea or constipation
• Increased likelihood of IBS and/or SIBO

Harnessing Your Parasympathetic (“Rest & Digest”) State

As if any of us needed another reason to learn how to relax, we can potentially avoid some digestive distress by learning to manage our stress levels! Here are a few simple ways to improve digestion by utilizing the gut-brain connection in your favor.

Choose whole foods

A balanced microbiome is more resilient to the negative effects of stress. Encourage healthy intestinal flora by eating an unprocessed, whole foods diet. Choose an abundance of seasonal vegetables, lean animal and vegetable proteins, complex carbohydrates, and seasonal fruits (organic whenever possible). Minimize refined sugar, alcohol and caffeine.

Eat in a relaxed state

If your day has been busy or rushed, assist your body into a parasympathetic state before you eat. Firmly plant your feet on the floor and take five deep, belly breaths to help you to relax before you begin your meal.

Chew your food well

Chewing is the first step in the digestive process—and one that is often skipped! When you take the time to chew your food well, you are helping your body breakdown the foods with the enzymes in your saliva. Adequately chewing slows down your eating and helps to activate the digestive process.

Eat mindfully

Let eating be an experience. Chew each bite of food thoroughly before you swallow. Put your fork down between bites. Taste your food. Put on some music. Relax. Enjoy.

Learn ways to manage your stress

It is essential to understand your personal stress response and learn effective techniques to manage emotions such as anger, despair, guilt and fear. Utilize practices such as therapy, meditation, yoga, tai chi and breathing exercises to counterbalance the negative effects of stress on your body.

Live at your own pace

Find the routine and rhythm that works best for your body. Be intentional about what you allow to consume your attention. Consciously cultivate more positive life experiences and remove yourself from toxic situations and people whenever possible. Learn when to say no. 

Re-wire your brain

An overactivated stress response can happen to anyone at any time in their life – and to different degrees of severity. However, research has clearly demonstrated that early childhood trauma causes this nervous system activation to begin at a young age.

The ACE (adverse childhood experiences) study showed that early childhood stress and adversity is not only associated with, but actually predictive of, adult health outcomes. This means that the more adverse childhood experiences a person has, the more health problems they are likely to suffer from.

I have found this to be true for myself and many of my clients who struggle with chronic, unrelenting digestive complaints. In these cases, brain-based programs that are geared towards calming the limbic system and/or re-wiring a brain that is stuck in a high-alert (sympathetic) response can be very helpful. 

In closing, the more you can connect with your life experiences and cultivate healthy ways to manage your stress and adversity, the more efficiently you will be able to “digest” both your emotions and your food.

Sources

https://pubmed.ncbi.nlm.nih.gov/32572435/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5859128/

https://www.gastrojournal.org/article/0016-5085(94)90775-7/pdf

https://www.sciencedirect.com/science/article/pii/S2352345X18300602

https://kresserinstitute.com/how-stress-contributes-to-sibo/

https://www.blackmores.com.au/digestive-health/how-stress-affects-your-digestion