The Gut-Brain Axis: Improve your Gut with The Mind, and the Mind with The Gut

The “gut-brain axis” is all about how the gut and brain are interconnected. It’s much more tightly woven together than we previously thought— ongoing research is continuing to prove it. These discoveries have huge potential to help people with gut issues by addressing their brain. And help people with brain or mood issues by addressing their gut.

Imagine if eating differently could elevate your moods or improve your brain and mental health. (It can.) Or if reducing stress can also reduce gut symptoms. (It does.)

Sounds interesting? Learn all about the gut-brain axis and how you can leverage this new research to improve your gut and brain.

Your gut is (partially) controlled by your brain

Digestive disorders can cause pain, bloating, or other discomfort. They impact over 35% of people at some point in life—affecting women more than men. Many times, these gut issues don’t have an apparent or easily diagnosable physical cause, so they can be difficult to treat and find relief from. Often, people are told they have IBS, or Irritable Bowel Syndrome. But a “syndrome” doesn’t tell you anything about what the root cause is; it’s just a collection of symptoms.

We already knew that our brains control some of our digestive processes. For example, research has found that even thinking about eating can cause the stomach to release juices to get itself ready for food. (Think of Pavlov’s dog.) Your gut is also sensitive to emotions. You may recall a time when you felt anxious and nauseous or felt “knots” or “butterflies” in your stomach.

Athletes and runners are also susceptible to this connection – both because of the nerves before a big event; and because the physical act of running actually can cause a little extra strain on the gut lining itself.

Several studies show that stress may be an important—often overlooked—reason for gut issues. According to Harvard Health, “Stress can trigger and worsen gastrointestinal pain and other symptoms, and vice versa.”

This is why it’s so important to look at your stress and emotions if you have gut issues. Many studies have found that stress reduction techniques can lead to greater improvement in gut symptoms compared to conventional medical treatment alone.

Before we go over how to do this, let’s look at a bit more of the biology behind the gut-brain axis.

Your nervous systems

There are two main parts of your “main” nervous system. One is the part that we can consciously control, like when we move our muscles to walk around, chew our food, or go for a run. This is called the somatic nervous system.

The other part of our nervous system controls all of those things that we don’t typically consciously control, but need to survive. These include processes that happen automatically in the background: breathing, heart beating, sweating, or shivering. This part of the nervous system is called the autonomic nervous system (because it works automatically).

The autonomic system regulates our body’s functions by either speeding things up or slowing them down. When things are sped up, like when our “fight or flight” reactions kick in, this is done by the sympathetic part. We feel this happening when we sense danger (real or not) and get stressed. Our heart beats faster and we breathe heavier. We’re preparing to fight or flee, so our body focuses on ensuring our muscles get enough blood and oxygen to work hard.

Slowing things down, on the other hand, is done by the parasympathetic part. This happens when we’re relaxing or after the danger has passed and we start to calm down. Our heart, lungs, and muscles rest and our digestive systems do their jobs much better. In this phase, we’re secreting more digestive juices to break down food, we’re absorbing more nutrients, and we have lower levels of inflammation in our gut. That’s why this is called the “rest and digest” phase.

Both of these arms of the autonomic nervous system—the sympathetic and parasympathetic—interact with the gut. This means that when our body is stressed we can experience GI symptoms and when we’re relaxed our digestion does what it’s meant to do.

You cannot be in both “Fight or flight” and “rest and digest” at the same time – so staying stressed – even minimally with deadlines, lack of sleep, and more – can limit your healthy and natural processes of digestion and GI ease.

Your gut is your “second brain”

In addition to your “main” nervous system, your gut has its own nervous system called the enteric nervous system. The enteric nervous system spans your whole digestive tract from your esophagus, along your stomach, intestines, and colon. This nervous system is sometimes referred to as the “second brain” because it works in the same way that the “main” one does. It has 100 million nerve cells (called neurons) that communicate with each other using biochemicals called neurotransmitters.

Your enteric nervous system gets input from both the sympathetic and parasympathetic nervous systems, so it can speed up or slow down when it has to. It also has a “mind” of its own and can function independently of them.

This complex system is important because of how complex our digestive processes are. For example, after we eat, the neurons in our enteric system tell the muscle cells of the stomach and intestines to contract to move food along to the next part. As our digestive system does this, our enteric nervous system uses neurotransmitters to communicate with the Central Nervous System.

Your enteric nervous system is also very closely linked to your immune system. This is because a lot of bacteria can enter the body through the mouth and end up in the gut. You have a large immune presence there to help fight them off before they become a larger problem and infect other parts of the body. The cells of the immune system provide another path for the gut to communicate up to the brain. They relay information like when they detect an infection or when your stomach is bloated, so your brain knows, too.

Even the friendly gut bugs (gut microbiota) that help us digest and make certain nutrients play a role in communicating with the brain. They make neurotransmitters, some of which are known to influence our moods.

The gut-brain axis

This intimate and complex connection between your gut and brain is called the gut-brain axis. And we now know that the signals go in both directions: from your brain down to your gut, and from your gut up to your brain.

This is where we see the link between digestive issues and brain, stress, and mood issues.

When someone is stressed enough that they get into the “fight or flight” reaction, digestion slows right down to allow the muscles to fight or flee. The same physical reaction appears whether the stress is from a real threat or a perceived one. This means that your body reacts the same whether you’re facing a real life-threatening situation or whether you’re super-stressed about a looming deadline. This disruption of the digestive process can cause pain, nausea, or other related issues.

Meanwhile, it’s known that experiencing strong or frequent digestive issues can increase your stress levels and moods. People with depression and anxiety have more GI symptoms, and vice versa.

How stress and emotions affect your gut

Because of these strong connections between the gut and brain, it’s easy to see how stress and other emotions can affect the gut. Things like fear, sadness, anger, or feeling anxious or depressed are often felt in the gut. When they cause our digestive systems to speed up (or slow down) too much, this can influence pain and bloating, constipation or diarrhea. It can also allow germs to cross the lining of the gut and get into the bloodstream, activating our immune systems. It can increase inflammation in the gut or even change the microbiota.

This is why stress and strong emotions can contribute to or worsen a number of GI issues such as Crohn’s disease, colitis, irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), or food allergies or sensitivities.

Then, these gut issues are communicated to the brain, increasing the stress response and affecting our moods.

This loop of stress and gut issues and more stress and more gut issues becomes a vicious cycle.

New research shows that changes to the gut’s inflammation or microbiome can strongly affect many other parts of the body as well—not just the brain and mood. They’re also associated with depression and heart disease.

How to eat and de-stress for better gut and brain health

The good news is that you can control some of this! What you eat has a huge impact on your health.

This is particularly true when it comes to the microbiome. Your gut health improves when you eat a higher-fiber, plant-rich diet. That’s because it provides your friendly gut microbes with their preferred foods so they can grow and thrive. Probiotic foods that include health promoting bacteria are also recommended. Reducing the amount of sugar and processed foods you eat can also help. These can lead to a healthier microbiome by helping to maintain a diverse community of many species of microbes to maximize your health. They can also lower levels of inflammation, as well as reduce the risk of depression and heart disease.

For better gut and brain/mental health, eat more:

  • Fruits and vegetables
  • Nuts and seeds
  • Whole grains
  • Yogurt (not sugar loaded!)
  • Sauerkraut

Eat less:

  • Sugar
  • Processed Snacks
  • Condiments with hidden sugars, like ketchup, sauces, and more
  • Soda/Energy drinks
  • Processed carbs like baked goods

**Want a comprehensive food list? Check out the free 7 Day Challenge for a crash course on healthy eating for your gut, complete with an extensive food list!**

What about stress?

Evidence shows that some stress reduction techniques or psychotherapy may help people who experience digestive issues. They can lower the sympathetic “fight or flight” response, enhance the parasympathetic “rest and digest” response, and even reduce inflammation.

Some of the stress-reduction techniques I love and recommend are:

  • Meditation
  • Box breathing
  • Mindfulness
  • Relaxation
  • Sitting in nature
  • Slow walks
  • Yoga

Essentially, anything that causes you to quiet your mind, and slow your breathing – it will change your heart rate, which changes your brain patterns, which lowers cortisol and stress.

Your gut, brain, and mood will thank you!

If you want some help with that, check out this video from a past program that discusses proper breathing for health.

Bottom line

Our bodies are complex and interact with other parts on so many different levels. The gut-brain axis is a prime example. Research shows that what we eat not only improves the gut and overall health, but also brain and mental health. Not to mention that several stress-reduction techniques have been shown to reduce digestive illness and distress as well.

If you want a plan to help you eat—and enjoy—more of the foods that help your gut, brain, and moods, consult a registered dietitian or functional nutritionist who can provide personalized research-based nutrition advice for your health, lifestyle, and goals.

Need some help with fresh gut-supporting recipes and menu plans? Check out the Menus or VIP Accountability programs here.

Or have a medical issue to address with a more individualized approach? Check out The Empowered Healing Program, or click here to set a free Discovery Call to discuss the best options for you and your goals.

In health,


PS – interested in even more on how the mind affects our health? If you missed it, check out The Gut Check Podcast from Monday! Dr. Thomas Morse and Steffany Morse share about their work, bridging their work as doctor and occupational therapist with functional medicine and mental health work!

PPS – my Instagram has changed! As I shift away from “Dublin Dietitian,” my new Insta handle is @NutritonAndGutHealth – come say hello!


Published by Kate Cline, RD

Registered Dietitian with a focus on Gut Health, Inflammation, and Functional Nutrition. Personal Trainer with a focus on corrective exercise. Yoga teacher, traveler, empowerment coach.

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