Have you ever had a strong “gut feeling?” Or did you feel too nauseous to eat right before taking an exam? These experiences demonstrate the connection between the gut and brain, or the “gut-brain axis.” The brain and gut are directly linked by a nerve called the “vagus nerve,” which allows signals to travel from the brain to the gut via millions of nerve endings. The vagus nerve is like a highway for messaging, flowing bidirectionally from both brain to gut and gut to brain.1 Other examples of this “messaging highway” include experiencing bowel irregularities when traveling (due to excitement, nervousness, or simply being out of your usual routine) or noticing the connection between the internal “tightness” of anxiety or nervousness and feeling constipated.
The Path from Brain to Gut
The gut-brain axis serves multiple purposes, many of which involve keeping us alive and safe. For example, anxiety is often felt because of a real or perceived threat of danger, leading to a “fight or flight” response as the body prepares to either fight or run from the threat. This message of “danger!” flows down the vagus nerve to the gastrointestinal system, alerts the gut that preparing to fight or flee means there’s no time to eat, and results in a diversion of blood and oxygen away from the gastrointestinal tract. This often leads to nausea, loss of appetite, and/or diarrhea.
The Path from Gut to Brain
The gut also communicates with the brain in a “bottom-up” messaging system. The small intestines contain trillions of healthy bacteria, which make up the microbiome. This community of microorganisms is responsible for digesting and absorbing micronutrients, creating brain messengers called neurotransmitters, regulating immune function, and influencing healthy metabolism.2 The microbiome is constantly communicating with the brain via the transmission of neurotransmitters, and some researchers are looking into the link between the gut microbiome and diseases such as Alzheimer’s and other various mental health disorders.3,4
Connecting the Dots
Millions of people are diagnosed each year with both gastrointestinal illnesses and mental health disorders. Mainstream efforts at reducing gastrointestinal discomfort typically revolve around food sensitivity tests, detoxes, supplements, elimination diets, and more. Learning how the gut and brain affect each other can give us better ideas for improving gut health and mental well-being.
FIVE WAYS TO SUPPORT A HEALTHY GUT-BRAIN AXIS:
1. EAT ENOUGH
Chronic restriction due to dieting, anxiety-related loss of appetite, disordered eating, or other reasons can lead to a slowed metabolism, reduced digestive capacity, and a less varied and healthy microbiome. As a result, both gut and brain health suffer with undernutrition. Eating adequate, consistent meals and snacks, including a wide variety of proteins, fats, and carbohydrates, will stimulate digestion, improve metabolism, and support a healthier and more diverse microbiome. For most people, this could look like eating three meals and two to three snacks daily at regular intervals (around two to four hours between each meal and snack).
2. VAGUS NERVE EXERCISES
Loss of appetite due to anxiety can make eating extremely difficult. Vagal tone exercises are designed to help calm the nervous system, which can help reduce feelings of anxiety-related nausea or loss of appetite. These exercises may include deep breathing, making certain sounds (humming, singing, gargling), cold exposure (holding a frozen orange in each hand/running cold water over your wrists), or gentle walking. Participating in these exercises can help calm your nervous system and intentionally send the message from the brain to the gut that you are not in danger and it’s ok to eat!
3. SUPPORT A HEALTHY MICROBIOME
Have you ever thought about feeding your gut? The healthy microbiome in your small intestines relies on a varied, diverse diet built on adequacy (Remember: Undereating will starve you AND your microbiome!). Eating lots of nutrient-dense foods within each food group supports a healthy microbiome, promoting brain health and a strong immune system. Specific foods that feed your microbiome include fiber-rich foods such as fruits, veggies, and whole grains, as well as probiotic-rich foods such as yogurt, kefir, or kimchi.
4. BE WARY OF FOOD SENSITIVITY TESTS
Food sensitivity tests are not reliable methods of determining whether you have an intolerance to specific foods. At-home food sensitivity tests use the presence of IgG antibodies to determine whether you have a sensitivity; however, IgG antibodies are typically produced after you have eaten any food, not necessarily foods that have caused a “reaction.” Because of this, IgG antibodies are often known as “memory antibodies” – an IgG response is essentially the “memory” of foods already eaten and signifies tolerance! As such, they are not reliable indicators of the presence of food sensitivities. Often, people mistakenly eliminate nonproblematic foods because of their food sensitivity test results, which could lead to under-eating or decreased quality of life.
If you strongly suspect a food allergy or intolerance, consider scheduling an appointment with a board-certified allergist or gastroenterologist to assess the need for more specialized testing such as IgE (immunoglobulin E) testing, which more reliably tests for the presence of an immune response with certain foods.
If you are experiencing food-related reactions, an elimination diet may not be the first line of defense. Consider asking for the support of a Registered Dietitian experienced in food allergies and sensitivities as you navigate this, as a dietitian can help by drawing connections between foods and symptoms, AND food and feelings. Emotions trigger strong physiological sensations in our bodies and are one of the many ways our bodies communicate with us, many of which are experienced in the gut. For example, common IBS symptoms include bloating, constipation, or diarrhea. A registered dietitian may start by helping connect the dots between symptom flares and other contextual factors and feelings (anxiety related to travel, being around certain friends/family members, depressive symptoms, etc.) to help identify both the trigger and ways to resolve symptoms.
5. CONSIDER THERAPY
Gut issues, such as diarrhea, constipation, nausea, or loss of appetite, are often due to the connection between the gut and the brain. Some studies have shown that functional gastrointestinal issues often show greater improvements with both psychologically based treatments and more traditional methods rather than conventional medical interventions alone.5 This may look like connecting with a therapist experienced in the treatment of anxiety, depression, trauma, or other mental health disorders. This is not to say that these symptoms are “all in your head” but rather that through the constant communication between the brain and gut, the body has unique ways of “talking to us” to get its needs met.
Understanding the intricate connection between the gut and brain opens the door for a more holistic approach to nurturing mental and physical health. For further support in understanding and navigating the gut-brain connection, reach out to the Registered Dietitians at Memphis Nutrition Group.
REFERENCES
1 What Is the Gut-Brain Connection? (clevelandclinic.org)
2 Regulation of Neurotransmitters by the Gut Microbiota and Effects on Cognition in Neurological Disorders – PMC (nih.gov)
3 The link between gut microbiome and Alzheimer’s disease: From the perspective of new revised criteria for diagnosis and staging of Alzheimer’s disease – Liang – 2024 – Alzheimer’s & Dementia – Wiley Online Library
4 The gut microbiome and mental health: advances in research and emerging priorities – PubMed (nih.gov) 5 The gut-brain connection – Harvard Health
Emily Gause, MA, RDN, LDN is a Nutrition Therapist at Memphis Nutrition Group, a nutrition and lifestyle counseling practice offering in-person and virtual nutrition therapy specializing in a non-diet, weight-neutral approach. The Registered Dietitians at Memphis Nutrition Group help individuals reconnect with their bodies, find confidence and clarity in their everyday choices. Contact Memphis Nutrition Group at 901.343.6146 or visit MemphisNutritionGroup.com for more information. You can also follow Memphis Nutrition Group on Instagram and Facebook.
By Emily Gause, MA, RDN, LDN
