What Is the Gut-Brain Connection, and Why Does It Matter?
Key takeaways:
The gut-brain connection refers to the way your brain and gut talk back and forth through a network of nerves and chemical messengers.
Your digestion can affect your mood and mental health. And your mental health can lead to stomach and digestive problems.
There are several common intestinal and neurological conditions that are associated with the gut-brain connection.
Have you ever had an upset stomach before a big event? Or heard someone say, “My stomach is in knots” when they are stressed? As it turns out, there’s a scientific explanation behind these experiences.
Scientists sometimes refer to the millions of nerves that run through the gut as the body’s “second brain.” The brain and gut are in constant communication with each other and have the power to affect your health.
What is the gut-brain connection?
The brain and gut communicate through a network of nerves and chemical messengers. These pathways help them influence each other in different ways.
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Research shows that the nerve cells in the gut influence more than just digestion. They can also affect things like your mood and immune response.
When a person’s gut is irritated or sluggish, it can trigger mental health symptoms like anxiety or low mood. Likewise, when someone is anxious, their brain can send signals that cause gastrointestinal (GI) symptoms like nausea or diarrhea. This is the gut-brain connection in action.
There are a few ways the brain and the gut talk to each other.
Vagus nerve
The vagus nerve is one of the primary nerves that helps your brain and gut communicate. It’s a large nerve that runs from the brain, down the body, and through the chest and abdomen. It regulates important bodily functions — including breathing, heart rate, and digestion.
Chemical messengers
The gut produces neurotransmitters — important chemical messengers that are often linked to mood and anxiety. But they also play an important role in regulating gut function. They include:
Serotonin: The gut produces about 90% of the body’s serotonin. Serotonin can affect things like mood, sleep, libido, and digestion time.
Dopamine: The gut produces almost half of the body’s dopamine. Beyond mood and digestion, dopamine can affect behavior, movement, memory, and attention.
GABA (gamma-aminobutyric acid): This chemical controls GI function and also plays a big role in stress, anxiety, and sleep.
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Gut microbiome
Your intestinal tract is home to trillions of microorganisms. Many are good bacteria that play important roles in digestion and immune system function. This diversity of microorganisms makes up the gut microbiome.
Much like your fingerprint, your body’s microbiome is uniquely yours. But unlike your fingerprint, your body’s microbiome changes in response to different factors.
Research suggests that the gut microbiome may have the power to influence emotions and behavior. As we review below, there are multiple neurological and mental health conditions associated with disruptions in the gut microbiome.
How does stress affect your gut health?
Stress can activate the body’s fight-or-flight response. Here’s how this can affect the gut:
The vagus nerve has a hard time doing its job.
Blood gets directed away from the gut to other body parts, like the muscles. Reduced blood flow to the gut can lead to symptoms like indigestion, heartburn, stomach pain, and nausea.
You can have more cravings for comfort foods, which often have high sugar or fat content. This can lead to changes in the gut microbiome and inflammation.
Stress can also worsen GI conditions such as:
Irritable bowel syndrome (IBS)
What conditions involve the gut-brain connection?
The term “disorders of gut-brain interaction” (DGBI) refers to health conditions with ongoing GI symptoms without a clear physical cause. Symptoms can include:
Heartburn
Abdominal bloating
Belching
Diarrhea
Constipation
Stomach pain
IBS is the most common DGBI, and it affects 10% to 15% of people in the U.S. But studies have found possible links between a disrupted gut-brain axis and various health conditions, such as:
People with DGBI have higher levels of anxiety and depression compared to people without DGBI. And treatments that help the anxious or depressed brain also seem to calm and regulate the gut. Antidepressants and a specific type of talk therapy called cognitive behavioral therapy (CBT) can improve GI and mental health symptoms in certain people with DGBI.
How can you improve your gut-brain connection?
There are two main ways to improve the relationship between your brain and gut.
Maintain a healthy gut microbiome
There are many ways to support a healthy gut microbiome. You can nourish good gut bacteria by:
Eating prebiotic foods: Prebiotics are foods that have a type of fiber that your body can’t digest. But the good bacteria in your gut can digest them. Prebiotic, fiber-rich foods include fruits, vegetables, and whole grains. The fiber in nuts and seeds can also enhance gut health.
Eating probiotic foods: Probiotics are foods that contain living microorganisms. These foods introduce good bacteria into your gut. Probiotic-rich foods include sauerkraut (fermented cabbage), tempeh (fermented soybeans), yogurt, kefir, and kombucha.
Reducing processed foods and foods high in sugar: These foods can create an environment where harmful gut bacteria thrive and beneficial gut bacteria decline. These foods can also trigger inflammation in the body.
Practice stress reduction and relaxation techniques
A calm mind and body can also help maintain a healthy gut-brain axis. Try working these activities into your daily routine:
Exercise: Even a short walk can increase blood flow and help deliver oxygen and nutrients to the brain. And movement helps with digestion as well.
Deep breathing: Take slow, deep breaths for 2 to 5 minutes. Focus on making your belly rise and fall with each breath (rather than your chest). Repeat several times a day as needed to activate your body's relaxation response.
Meditation: Sit in a quiet place with your eyes closed. Clear your mind and focus on your breathing. Observe any distracting thoughts without judgment and let them pass. Return your attention to your breathing. Continue for 5 minutes.
The bottom line
A balanced gut-brain connection can enhance your physical and mental well-being. Scientists are exploring how different parts of the gut-brain axis interact to enable or improve different health conditions. You can keep your gut-brain axis functioning at its best by creating a healthy environment for the trillions of friendly microorganisms living in your gut. By helping them flourish, you can help your brain and body flourish as well.
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References
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Alpert, O., et al. (2021). The brain-gut axis in gastrointestinal cancers. Journal of Gastrointestinal Oncology.
American College of Gastroenterology. (n.d.). Irritable bowel syndrome.
Bennett, E. J., et al. (1998). Level of chronic life stress predicts clinical outcome in irritable bowel syndrome. Gut.
Bernstein, C. N., et al. (2010). A prospective population-based study of triggers of symptomatic flares in IBD. The American Journal of Gastroenterology.
Evrensel, A., et al. (2015). The gut-brain axis: The missing link in depression. Clinical Psychopharmacology and Neuroscience.
Kowalski, K., et al. (2019). Brain-gut-microbiota axis in Alzheimer's disease. Journal of Neurogastroenterology and Motility.
Lackner, J. M., et al. (2018). Improvement in gastrointestinal symptoms after cognitive behavior therapy for refractory irritable bowel syndrome. Gastroenterology.
Ley, R., et al. (2006). Human gut microbes associated with obesity. Nature.
Li, S., et al. (2021). The gut microbiome is associated with brain structure and function in schizophrenia. Scientific Reports.
Pellissier, S., et al. (2014). Relationship between vagal tone, cortisol, TNF-alpha, epinephrine and negative affects in Crohn's disease and irritable bowel syndrome. PloS One.
Radjabzadeh, D., et al. (2022). Gut microbiome-wide association study of depressive symptoms. Nature Communications.
Satokari, R. (2020). High intake of sugar and the balance between pro- and anti-inflammatory gut bacteria. Nutrients.
Tan, A. H., et al. (2022). The microbiome-gut-brain axis in Parkinson disease — From basic research to the clinic. Nature Reviews Neurology.
For additional resources or to connect with mental health services in your area, call SAMHSA’s National Helpline at 1-800-662-4357. For immediate assistance, call the National Suicide Prevention Lifeline at 988, or text HOME to 741-741 to reach the Crisis Text Line.
