Everything You Need to Know About the Gut-Brain Axis
The gut and brain are interconnected more than we previously thought—new research is proving it. These discoveries have huge potential to help people with gut issues with help from their brain. And help people with brain or mood issues with help from their gut.
Imagine if eating differently could elevate your mood or improve your brain and mental health (it can). Or if reducing stress could also reduce gut symptoms (it does).
Sound 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, and other forms of discomfort. They impact over 35 percent of people at some point in life. 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.
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. 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.
Several studies show that stress may be an important and 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 digestive 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 exercise. This is called the somatic nervous system.
The other part of our nervous system controls all of those things that we can’t control, but that we 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 digestive system. This means that when our body is stressed, we can experience digestive symptoms, and when we’re relaxed, our digestion does what it’s meant to do.
Your digestive system is your “second brain”
In addition to your “main” nervous system, your digestive system has its own nervous system called the enteric nervous system. The enteric nervous system spans your whole digestive tract, from your esophagus through to 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 brain” 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 and other pathogens 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 with 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 microbes (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 mood.
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 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 you’re stressed about a looming deadline. This disruption of the digestive process can cause pain, nausea, and other related issues.
Meanwhile, it’s known that experiencing strong or frequent digestive issues can increase your stress levels and disrupt your mood. 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, anxiety and depression are often felt in the digestive system. When they cause our digestive system to speed up (or slow down) too much, this can influence pain and bloating. It can also allow germs to cross the lining of the gut and get into the bloodstream, activating our immune system. 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 digestive issues such as Crohn’s disease, colitis, irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD), and food allergies or sensitivities. These gut issues are then communicated to the brain, increasing the stress response and affecting our mood. 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 digestive and brain health
What you eat can have a huge impact on your health. This is particularly true when it comes to the microbiome. Your gut health improves when you make smart choices that specifically target your digestive diagnosis or condition. That’s because nutrition that works for you 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 red meat 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 digestive 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
● Wild caught fish
● Poultry
● Extra virgin olive oil
● Organic whole milk yogurt
● Sauerkraut
● Kimchi
● Miso
Eat less:
● Added sugar
● Processed red meat
● Vegetable and seed oils
● Fried and oily foods
What about stress? Evidence suggests 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:
● Deep breathing
● Mindfulness
● Relaxation
● Prayer
● Yoga
● Targeted stretching
● Massage
Your gut, brain, and mood will thank you!
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/nutritionist who can provide personalized research-based nutrition advice for your health, lifestyle, and goals.
I can help. Schedule a Discovery Call with me (on my Services Page) to talk about your goals and learn how I can help you optimize your gut brain axis for better digestive balance and mental health.
References
Cleveland Clinic. (2016, October 6). Gut-Brain Connection. Retrieved from
https://my.clevelandclinic.org/health/treatments/16358-gut-brain-connection
Harvard Health. (n.d.). The gut-brain connection. Retrieved from
https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection
Harvard Health. (2019, August 21). Stress and the sensitive gut. Retrieved from
https://www.health.harvard.edu/newsletter_article/stress-and-the-sensitive-gut
Harvard Health. (2019, April 11). Brain-gut connection explains why integrative treatments can help relieve digestive ailments. Retrieved from
University of Calgary. (2018, December 1). Can a meal be medicine? How what we eat affects our gut health, which affects our wellness. Retrieved from
https://explore.ucalgary.ca/gut-health-microbiome-and-our-wellnes