This is Part 5 of our series on the fight-or-flight response. Here we will continue the conversation about nutrition and its relationship to chronic pain and inflammation, specifically in relation to the gut and our microbiome. If you missed previous parts of this series, check them out here: 

• Part 1: What is the Fight-or-Flight Response? 
• Part 2: What Happens During Fight or Flight and 4 Ways to Prevent It
• Part 3: Understanding Chronic Pain
• Part 4: Anti-Inflammatory Diet to Decrease Chronic Pain 

Check out the previous articles for a more in-depth breakdown of our body’s “fight-or-flight” response during times of acute and chronic stress. In this article, we’ll be talking about our gut and how stress affects our gastrointestinal system. 

Have you ever felt nauseous right before speaking or presenting to a crowd of people? 

Have you ever suddenly had to run to the bathroom before the start of an athletic competition or before a hard conversation? 

Don't worry! We’ve all been there. 

This is actually a normal event that the body triggers in the acute (short-term) “Fight-or-flight” response. During times of sudden stress, the body's focus is actually taken off of the digestive system, or temporarily disrupted and channeled towards other systems such as the cardiovascular system, endocrine system, etc. This will cause symptoms of functional gastrointestinal (GI) disorders such as abdominal pain, sudden bowel movement, or nausea. 

What happens to the gut during a long-term stress response? 
However, in addition to short-term disruption to the GI system and the digestive process, exposure to long-term stress causes alterations of the brain-gut interactions or "brain-gut axis," which can be more serious.

If you have ever heard that the gut is the second brain, here is why.  

Our brain’s emotional and cognitive center communicates with and receives feedback from our gut’s nervous system (called the “enteric nervous system”). Basically, what’s going on is that our gut picks up on our emotions. These alterations to the communication between the two during stress can lead to the following changes in the gut:

1. Altered composition of the gut bacterial composition, or microbiome. Over 70% of the cells of the immune system live in or around our GI tract. Because of that, a healthy immune system is largely dependent on a healthy intestine. Specifically, the bacteria that live in the gut help regulate the local intestinal protection system, but also the body’s systemic immune responses to disease. Prolonged use of antibiotics, steroids, and other drugs can have a profound effect on the gut microbiome. 
2. Changes in bowel movements. Many people who experience chronic pain experience chronic constipation or loose stools. This can also be influenced by the long-term use of pain medications such as opioids (morphine) and non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin. 
3. Increased GI upset. Stomach aches, nausea, bloating distention, or the feelings of needing to use the restroom can all be ongoing symptoms of stress on the gut. 
4. Increase in intestinal permeability. The tissue of our intestines has a tight barrier to protect the body from bad bacteria found in the food we eat. When the body is under prolonged periods of stress, this barrier can become weakened with inflammation and bacteria can enter the body. This can cause mild chronic symptoms of upset stomach and indigestion. 
5. Decreased ability for our gut mucosal cells to regenerate. The cells in our GI tract regenerate every 3-7 days. This is important for the effectiveness of digestion, absorption, and secretion of enzymes and fluids. Chronic inflammation and pain can slow the ability of these cells to regenerate, which can cause problems with digestion, absorption of nutrients, and elimination. 

Continuation of these changes in the gut’s function can lead to the development of chronic diseases such as: 

• Inflammatory bowel disease (IBD)
• Irritable bowel syndrome (IBS) 
• Food antigen-related adverse responses
• Peptic ulcers
• Gastroesophageal reflux disease (GERD) 
• Increased risk of autoimmune diseases
• Chronic constipation

(Note: Changes in the gut can also show up outside of the GI tract in symptoms such as: joint pain, disrupted sleep patterns, anemia, restless leg syndrome, fatigue, skin irritation.)

The connection to what we eat
There is a direct relationship between what we eat, the composition of the microbiome, and our immune system. The good news is that we can eat in a way that supports a healthy microbiome. We can also eat in a way that aids the motility of our gut (fiber and water). So, let’s offer some tips to help your gut during bouts of chronic pain and inflammation.  

Main ways to support optimal gut health in the presence of chronic pain

1. Address the stress: The most important step you can take is to address the root causes of the stress that led to your long-term stress response, and its negative effects on the body.  
2. Anti-inflammatory diet: Look at the foods outlined in Part 4 of this series and start incorporating more of these into your diet to decrease chronic pain and inflammation. 
3. Eat enough fiber: Especially if you are having trouble with your bowels moving or moving too quickly. Look for high-fiber carbohydrates and foods such as vegetables, beans, peas, rice, grains, quinoa, nuts, seeds, and fruits. 
4. Drink enough water: Make water your first choice beverage. Many times constipation can be resolved simply by drinking enough water. The amount of water you need to stay hydrated depends on a variety of factors, but for most people, drinking half their body weight in ounces (1 fluid ounce = ~30 mL) is adequate for their body’s needs. So, for a person who is 150 pounds (68 kilos), you would need approximately 75 ounces or 2.2 liters of water.
5. Supplement with probiotics and prebiotic foods: Both intake of yogurt and fermented milk products can prevent the alteration of the microbiota and promote a healthy balance of bacteria in the gut after chronic inflammation or imbalance in gut bacteria related to medications or an imbalanced diet. It is also an excellent way to counteract the inflammatory state that characterizes chronic pain.
6. Stay away from sugar alcohols: Many sugar alcohols (e.g., xylitol, erythritol, etc.) can disrupt the balance of the gut bacteria and cause bloating and cramping. Eliminating these (found in sugar-free beverages, desserts, gum, protein powder, etc.) can help the gut microbiome return to normal. 
7. Slow down: Eating and chewing slowly can help your body relax during meals and snacks and can ultimately allow time for the body to release the enzymes that are needed for digestion and allow smaller pieces of food into the GI tract, which is good for digestion. 

In summary 
Your gastrointestinal system is very sensitive to the brain's response to stress and emotion. Over time, the body’s digestive adaptations to stress can result in gastrointestinal distress and the development of chronic diseases. So, being both aware and proactive about how your body responds to stress is vital to a healthy lifestyle.

Inflammation and chronic pain are both significant hurdles to good nutrition and living a healthy, active lifestyle. We know there is so much difficulty when experiencing chronic pain and stress, but the good news is that there are things we can do to improve the situation. We hope this series has helped explain the connection between the body’s “fight-or-flight” response and the symptoms you might be experiencing. 

Share your experience with us by leaving a comment below. Have questions or want to learn more? Ask here; we're always listening! 

Revisit the whole series: 

• Part 1: What is the Fight-or-Flight Response? 
• Part 2: What Happens During Fight or Flight and 4 Ways to Prevent It
• Part 3: Understanding Chronic Pain
• Part 4: Anti-Inflammatory Diet to Decrease Chronic Pain 
• Part 5: Nutrition, Gut Health, and Ways to Tackle Chronic Inflammation (You are here!)

Written for Fitness Blender by Natalia Holguin, RDN LDN CPT 
Certified Nutrition Coach

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“Stress and Health.” The Nutrition Source, 15 Jan. 2021.

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