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Learn more about the results we get at Within

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How the gut and brain are connected

Medical experts have long been exploring the relationship between the gut and your physical health, mental health, and overall well-being. Evidence shows that the gut affects the rest of the body, but the rest of the body affects the gut as well. This interconnected and two-way link is often called the gut-brain connection.

Continue reading to learn more about the gut-brain axis and connection, how it affects mental health, and how eating disorders can disrupt their typical functioning.

Last updated on 
December 27, 2023
The gut-brain connection
In this article

What is the gut-brain connection?

Gut-brain communication refers to the bidirectional communication that takes place between the gut and the brain. When people talk about the gut, they are referencing the trillions of microorganisms that live in the large intestine. The colony of gut microbes is established at birth, but diet, genetics, and environmental factors can change the gut throughout your life.7

If a person could combine all the organisms in their gut, they would weigh as much as six pounds.1 This community of microorganisms, called a microbiome, is made up of:6

  • Bacteria, making up the largest part
  • Fungi
  • Parasites
  • Viruses

Those microorganisms communicate back and forth to the brain via the central nervous system through the 100 million nerve cells that stretch through the digestive tract. Sometimes called the enteric nervous system (ENS), the gut is mainly involved with digestion, but it can send and receive messages from the brain and spinal cord. It can act as a secondary brain function by influencing thoughts, feelings, and behaviors.1,2

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How the gut and brain are connected

The gut and the brain are connected by a network of neurons in the brain (brain-gut axis), the microbiome, and nerve cells throughout the gastrointestinal tract (GI tract).2 Researchers found that some bacteria even contain neurotransmitters like GABA. These chemical messengers communicate messages to the brain and regulate behavior and emotions.1

The idea of a link between the gut and the brain is nothing new. The connection is part of the daily language with sayings like:

  • Go with your gut
  • Trust your gut
  • Gut-wrenching decision
  • Butterflies in your stomach

It seems that the gut-brain connection may affect other functions of the body as well. The gut and brain connection influences the nervous, endocrine, and immune systems.3

Is the brain-gut connection linked to mental health issues?

The gut-brain connection is linked to mental health issues in a bidirectional relationship. Gut health affects mental health, and mental health affects the digestive system. Mental health issues are more likely when there is dysbiosis or an imbalance of the microorganisms in the gut.3

Anxiety

The clearest example of this two-way relationship is between GI symptoms and anxiety. Having GI problems, like diarrhea, gas, constipation, and nausea, can cause higher stress and anxiety levels. Likewise, high levels of anxiety can trigger these GI symptoms.4,5 

At the core of these symptoms is the balance of gut microorganisms. If the system is out of balance, it can create GI and anxious symptoms, creating a greater imbalance in the gut and producing more mental and physical health symptoms. Symptoms worsen in an endless cycle.

Anxiety is just one condition that illustrates the gut-brain connection. Two other mental health concerns linked to the gut-brain relationship are depression and autism spectrum disorder (ASD).3

People with these mental health concerns tend to have a "less diverse" microbiome, which means they lack the variety of healthy microorganisms needed for balance. Although it is impossible to say that gut health causes mental health conditions, there is surely a link between them.7

Gastrointestinal symptoms from eating disorders

As a group of mental health issues, eating disorders greatly influence gut health. Overall, having an eating disorder, like anorexia nervosa (AN), bulimia nervosa (BN), or binge-eating disorder (BED), seems to disturb the balance of the microbiome by allowing certain bacteria to grow.6

AN symptoms will encourage the growth of bacteria that only thrive in a low-energy environment. BN and BED will promote the growth of other forms of gut bacteria (gut microbiota). Ultimately, these conditions upset the essential balance of the gut. With the gut out of balance, the person may experience various unwanted and uncomfortable symptoms.7

Up to 98% of people with an eating disorder have functional bowel problems, such as IBS.

GI disorders are extremely common in people with eating disorders. As many as 98% of people with an eating disorder have functional bowel problems, including irritable bowel syndrome (IBS). The influence of eating disorders on the gut-brain connection may trigger other mental health symptoms.8

How can I improve my gut health?

Since gut health involves a combination of mental and physical health issues, you must address your mind and body to improve gut health. Fortunately, many changes are simple, low-cost, and widely accessible.

Changing your diet can have a significant impact on your gut health. But always consult your doctor, dietitian, or eating disorder specialist before making any changes. Some physical tips for improving gut health are:9

  • Eat more fiber, just not too much all at once
  • Eat smaller meals slower to aid digestion
  • Limit what you eat at night. Your gut is more active during the day, so overeating at night can trigger an imbalance.
  • Try to eat around the same times each day.
  • Experiment with probiotics. Talk to your doctor about supplementing healthy bacteria and gut microbiome into your system.

When your well-being is boosted, your gut health will benefit. Some psychological tips for improving gut health are:4

  • Practice relaxation techniques. From deep breathing and guided imagery to progressive muscle relaxation and meditation, anything you can do to relax your body and mind will help your gut.
  • Biofeedback. Biofeedback is a type of therapy that increases as you track and change your body’s automatic responses. You can improve your gut health by managing your breathing and heart rate.
  • Explore therapy. Evidence-based therapies can help you address the damaging mental health effects. Cognitive behavioral therapy (CBT) is one option that can positively impact your mood and your gut.

Your gut has an enormous effect on how you feel mentally and physically. Working to support your gut through lifestyle changes that increase relaxation could significantly improve your health and well-being and make the gut-brain connection work for you.

Disclaimer about "overeating": Within Health hesitatingly uses the word "overeating" because it is the term currently associated with this condition in society, however, we believe it inherently overlooks the various psychological aspects of this condition which are often interconnected with internalized diet culture, and a restrictive mindset about food. For the remainder of this piece, we will therefore be putting "overeating" in quotations to recognize that the diagnosis itself pathologizes behavior that is potentially hardwired and adaptive to a restrictive mindset.

Disclaimer about weight loss drugs: Within does not endorse the use of any weight loss drug or behavior and seeks to provide education on the insidious nature of diet culture. We understand the complex nature of disordered eating and eating disorders and strongly encourage anyone engaging in these behaviors to reach out for help as soon as possible. No statement should be taken as healthcare advice. All healthcare decisions should be made with your individual healthcare provider.

Resources

  1. US Department of Health and Human Services. (n.d.). 4 fast facts about the gut-brain connection. National Center for Complementary and Integrative Health. Retrieved February 10, 2023.
  2. Johns Hopkins Medicine. (n.d.). The Gut-Brain Connection. Retrieved February 10, 2023.
  3. Carabotti, M., Scirocco, A. et al. (2015, April). The Gut-Brain Axis: Interactions between Enteric Microbiota, Central, and Enteric Nervous Systems. Annals of Gastroenterology, 28(2), 203-209.
  4. Gut-Brain Connection. (2020, December 3). Cleveland Clinic. Retrieved February 10, 2023.
  5. Harvard Health Publishing. (2021, April 19). Pay Attention to Your Gut-Brain Connection – It May Contribute to Your Anxiety and Digestion Problems. Retrieved February 10, 2023.
  6. Glenny, E. E., Bulik-Sullivan, E. C., et al. (2017, August). Eating Disorders and the Intestinal Microbiota: Mechanisms of Energy Homeostasis and Behavioral Influence. Current Psychiatry Reports, 19(8), 51.
  7. Powder, J. (2021, September 21). The Gut Microbiome and the Brain. Hopkins Bloomberg Public Health. Retrieved February 10, 2023.
  8. Janssen, P. (2010, December). Can Eating Disorders Cause Functional Gastrointestinal Disorders? Journal of Neurogastroenterology and Motility, 22(12), 1267-1269.
  9. National Institutes of Health. (2017, May). Keeping your Gut in Check. Retrieved February 10, 2023.

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