You’ve heard the old phrase “trust your gut,” I am sure you have gotten a “gut feeling” about something before. These are not just sayings; the gut and the brain have a communication network called the gut-brain axis. The link between these two systems can significantly impact our well-being and impact you in ways you did not recognize.
What is involved in the Gut-Brain Axis?
The gut-brain axis requires various bodily systems to work together. Some important terms to keep in mind throughout this post include:
- Central Nervous System: It is the processing center of the body, embedded in the brain and spinal cord.
- HPA (Hypothalamus- Pituitary- Adrenal) Axis: Controls our body’s response to stress by releasing hormones.
- Autonomic Nervous System: It controls heart rate, blood pressure, respiration, the involuntary bodily functions – which contain the enteric, sympathetic, and parasympathetic nervous systems.
- Enteric Nervous System: Found in the gut. The nervous system is specific to the gastrointestinal tract.
- Sympathetic Nervous System: Triggers the “fight or flight” reaction during danger, distress, or anxiety.
- Parasympathetic Nervous System: Activates the “rest and digest” response and helps the body return to a calm state.
- Vagus Nerve: The largest of our 12 cranial nerves and connects to the brain, spinal cord, and various vital organs (including our gastrointestinal tract). The main part of the parasympathetic nervous system. It helps the body get out of the “fight or flight” response and into “rest and digest mode.” (Breit et al., 2018)
- Immune System: Immune cells are connected to the enteric nervous system and can recognize and communicate information about the GI tract. For example, the immune cells would help communicate this back to the brain if inflammation is present.
- Microbiome: Consists of the trillions of bacteria, fungi, and viruses (microbes) within our bodies. These microbes are mainly found within our intestines and our skin.
The gut-brain axis links the central nervous and enteric nervous systems to allow for bidirectional communication between the brain and the gut. The enteric nervous system is extensive, consisting of two layers of over 100 million neurons, and is commonly called the “second brain.” Neurons are cells that help communicate information between the brain and different body parts. The brain and the gut communicate through the sympathetic and parasympathetic nervous systems. This communication can impact how food digests, GI tract inflammation, and nutrients are absorbed. Communication between the brain and the gut is through the vagus nerve and the HPA axis.
All of these systems work together to allow the brain to impact gastrointestinal functions and the gut to impact the brain, including mental health symptoms such as mood and anxiety. The vagus nerve carries many of the signals between our brain and gut. Because of this, vagal nerve stimulation is being studied as a potential way to treat mood, anxiety, and gastrointestinal disorders.
How does the microbiome relate to the Gut-Brain Connection?
Research has found that microbiota within the enteric nervous system significantly influences the gut-brain connection (Margolis et al., 2021). While some microbes can be harmful, most are necessary to maintain our health and provide important bodily functions. We are first exposed to microbes at birth; however, our microbiome grows and diversifies over time, positively impacting our health. Microbes play a role in producing serotonin, the “feel-good” chemical, which can decrease depressive symptoms in our bodies. Interestingly, 90% of our body’s serotonin is produced in the gut (Barandouzi et al., 2022). Because the gut and brain connect through many nerves, the microbiota plays a part in helping to control the messages sent to the brain through the nerves. An imbalanced microbiome can negatively impact weight and cause inflammation, heart health, blood sugar, and the brain.
Impact of the Gut-Brain Connection on Mental Health
It was previously thought that gastrointestinal problems such as irritable bowel syndrome, constipation, diarrhea, and/or other frequently experienced GI problems were worse by anxiety, depression, and other mental health conditions. However, recent studies have suggested that communication between the brain and the gut goes both ways (Carabotti et al., 2015). The gut can communicate messages to the brain, and the brain can communicate messages to the gut. It means that gastrointestinal issues communicate signals to the central nervous system, which can trigger emotional and mood changes, so GI problems may cause specific mental health symptoms.
For example, have you ever felt butterflies or knots in your stomach before speaking in front of a crowd? Or, have you ever felt very anxious and noticed you immediately needed to use the bathroom? Due to the connection and communication between the brain and the gut, if a person has gastrointestinal issues, this will be signaled to the brain, which could cause distress. On the other hand, if a person has mental health struggles, stress, anxiety, or depressive symptoms, this may also be transmitted to the gut causing physical reactions. It means that gastrointestinal issues can be either a cause or product of anxiety, stress, depression, or other health symptoms.
Ways to Improve the Gut-Brain Connection:
Integrative techniques can be helpful to utilize in order to improve the gut-brain connection and improve GI symptoms and anxiety/depression that seem to be linked. Techniques should aim to soothe that sympathetic “fight or flight” response and increase that “rest and digest” parasympathetic response.
Mind-Body Techniques:
- Vagus Nerve Stimulation Exercises
- Mindfulness and Meditation
- Yoga
- Deep Breathing Exercises
- Progressive Muscle Relaxation
- EFT tapping
- Managing and Coping with Anxious/Distressing Thoughts
Healthy Diet:
- Low FODMAP Diet:
- Our diet has a significant impact on the microbiome of the gut. Studies have shown that diets low in FODMAPS (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyol) can potentially reduce irritable bowel syndrome symptoms. FODMAPS are not absorbed well by the gut and include certain wheat products, specific lactose or dairy products, foods containing high levels of fructose, etc. (Liu et al., 2020).
- Probiotics:
- Probiotics contain live microorganisms that help to increase or maintain the healthy microbiota in the body. Probiotics are in certain foods or supplements, including yogurt, kombucha, apple cider vinegar, miso, and kimchi.
- Prebiotics:
- Prebiotics are contained in certain foods and act as food for the healthy microbiota in the gut – foods that are high in fiber, including almonds, bananas, whole grains, etc.
If improving your diet is an area you could improve upon, consulting with a registered dietician or nutritionist can be a beneficial step.
Exercise:
- Studies have suggested that moderate physical exercise can improve gut microbiota diversity and gut-brain communication by producing neurotransmitters involved in thinking, behavior, and functioning within the brain (Friere-Royes, 2020).
It is important to remember that mental health symptoms can often manifest themselves in a physical way, and physical ailments can also have mental health manifestations. While there is still much research to achieve on the gut-brain axis, there is a clear connection between the two and various ways to improve your gut-brain connection immediately.
References
Barandouzi, Z.A., Lee, J., del Carmen Rosas, M. et al. (2022). Associations of neurotransmitters and the gut microbiome with emotional distress in the mixed type of irritable bowel syndrome. Scientific Reports, 12(1).
Breit, S.; Kupferberg, A.; Rogler, G.; Hasler, G. (2018). Vagus nerve as a modulator of the brain-gut axis in psychiatric and inflammatory disorders. Frontiers in Psychiatry, 44(9).
Carabotti, M.; Scrirocco, A.; Maselli, M.A.; Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central, and enteric nervous systems. Ann Gastroenterol, 28(2).
Freire- Royes, L.F. (2020). Cross-talk between gut and brain elicited by physical exercise. BBA-Molecular Basis of Disease, 1866(10).
Liu J., Chey W.D., Haller E., Eswaran S. (2020). Low-FODMAP Diet for Irritable Bowel Syndrome: What We Know and What We Have Yet to Learn. Annu Rev Med, 71:303-314.
Margolis, K.G., Cryan, J.F., Mayer E.A. (2021). The Microbiota-Gut-Brain Axis: From Motility to Mood. , Gastroenterology, 160(5).1486-1501.
