Rest and Digest: Understanding Your Autonomic Nervous System
Science has shown that too much stress can negatively impact overall health, 1 but how does it all connect? Gaining a basic understanding of the body systems that control stress and learning some proven techniques to transition back to calm may inspire you to improve your long-term wellbeing.
A Simple Summary of the Autonomic Nervous System
The human nervous system is a network that allows our organs to communicate with each other. It’s made up of the brain itself and all the nerves it uses to connect to the body. 2
A major part of this system, the autonomic nervous system (ANS), oversees functions that happen automatically, without conscious thinking, even while you sleep. It regulates things like digestion, body temperature, heartbeat, breathing, blood flow, and blood pressure. 2
The ANS can be categorized into three major parts: sympathetic, parasympathetic, and enteric nervous systems. They all contribute to body communications in their own way. 2
The sympathetic nervous system (SNS) oversees your “fight or flight” response in times of high stress. This is the body’s alarm system that causes you to feel excited on a competition day, or to feel fear and panic if there’s a tiger chasing you. The SNS is what signals the body to send blood flow and energy to major muscle groups so that they can function well in their time of need. The SNS actions result in the delay of less urgent things like digesting your breakfast or going to the bathroom. 2
The parasympathetic nervous system (PNS) is in charge when your body is in a relaxed state and regulates your “rest and digest” processes. It’s responsible for taming your fight or flight functions, calming your body, and allowing more blood flow toward less critical activities. The PNS sends signals to the enteric nervous system, signaling that it’s okay to use energy to digest food. The vagus nerve is the major pathway for communication for the PNS. 2
The enteric nervous system (ENS) provides communication between the entire digestive system and the brain in both directions. It receives signals from the PNS vagus nerve when we don’t feel stressed, allowing normal digestion to take place. 2
When working properly, the components of the ANS complement each other to meet the body’s needs. However, sometimes with factors like too much stress, illness, aging, or an unhealthy microbiome, the ANS struggles to keep a normal balance. The body may stay amped up with stress hormones, which can negatively affect your body. [2,3,4,5]
The Invaluable Vagus Nerve
The vagus nerve is responsible for regulating the PNS and allows the body to switch from the “fight or flight” to a calming “rest and digest” mode. The word vagus means “wandering,” which makes sense because it is the longest nerve in the body, branching out to provide a means of communication with the major organs. 2
The nerve group promotes relaxation and digestion in several ways. It reduces the strength and vigor of the heart’s contractions and lowers the heart rate. It enables digestion by signaling the ENS to move involuntary esophagus, stomach, and intestinal muscles, and secretes salivary and digestive juices. It also helps regulate normal breathing. 2
Because the vagus nerve is involved with so many functions, its health, which is often termed “vagal tone,” can affect whole body wellness. Research shows that there are some simple things you can do to reduce chronic stress and maintain your vagal tonicity.
Reducing Stress and Increasing Vagal Tone
Today’s world full of work deadlines and negative news often puts us in a constant “fight or flight” SNS zone. We now know that chronic stress can lead to adverse health conditions. 1 Fortunately, there are conscious things we can do to help the vagus nerve return to a more relaxed, parasympathetic mode. Using these methods regularly may also improve your vagal tone. 6,7,8,9,10,11
Breathe deeply. There’s a lot of research that shows that the simple act of deep breathing can reduce stress and help activate your PNS. There are lots of deep breathing techniques you can try, but experts often recommend methods that expand your abdomen. 6
While sitting in a quiet place, take a deep breath slowly through the nose, allowing your chest and belly to expand, then slowly exhale as much air as possible through the mouth. You can also try deep breathing techniques while practicing yoga or meditation. 6,7
Eat a healthy diet. In case you needed one more reason to eat well, here it is. Studies show that taking care of your gut microbiome can be a contributor to managing stress.* Eating a diet high in prebiotic, high-fiber fruits, vegetables, and whole grains that feed your friendly gut microbes is a good place to start. 8,9,10
Regularly eating foods with active and live cultures can also contribute to a healthy microbiome.* Consider foods like yogurt, kefir, miso, and kimchi. 10
Omega-3 fatty acids are very important for nerve transmission. Great sources of omega-3s include salmon and sardines, walnuts, flaxseed meal, and chia seeds. 11
Move regularly. While physical activity generally stimulates your SNS, it can help your body practice switching from sympathetic to parasympathetic systems. Finding a form of movement you enjoy, like playing your favorite sport, can also take your mind away from the stress of the regular day. 12,13,14
Get a massage. This may be a favorite for many people. Some research shows that massage and myofascial self-care routines can reduce the signs and symptoms of chronic stress. Foot reflexology, a type of massage that applies pressure to certain areas of the feet, may be especially helpful for vagal tone.
Your autonomic nervous system is important for keeping you alert in times of stress and enabling normal body functions in times of rest. Maintaining your ANS balance with relaxation and therapeutic techniques can ultimately impact your overall health and feeling of wellbeing.
Resources:
1. “Chronic Stress Puts Your Health at Risk.” (2021). Mayo Clinic. mayoclinic.org.
2. Waxenbaum, Joshua A., Vamsi Reddy, and Matthew Varacallo. (2021). In StatPearls. Treasure Island (FL): StatPearls Publishing.
3. Bretherton, Beatrice, Lucy Atkinson, Aaron Murray, Jennifer Clancy, Susan Deuchars, and Jim Deuchars. (2019). Aging 11 (14): 4836–57.
4. Lieshout, J. J. van, W. Wieling, J. M. Karemaker, and D. L. Eckberg. (1991). Clinical Science 81 (5): 575–86.
5. “Vagus Nerve.” (n.d.). Cleveland Clinic. Accessed July 21, 2022. My.clevelandclinic.org.
6. Gerritsen, Roderik J. S., and Guido P. H. Band. (2018). Frontiers in Human Neuroscience 12 (October): 397.
7. “Relaxation Techniques: Breath Control Helps Quell Errant Stress Response.” (2020). Harvard Health. Health.harvard.edu.
8. Bonaz, Bruno, Thomas Bazin, and Sonia Pellissier. (2018). Frontiers in Neuroscience 12 (February): 49.
9. Fülling, Christine, Timothy G. Dinan, and John F. Cryan. (2019). Neuron 101 (6): 998–1002.
10. “Gut Insight.” (n.d.). Accessed July 21, 2022. gutinsight.com.
11. Christensen, Jeppe Hagstrup. (2011). Frontiers in Physiology 2 (November): 84.
12. Guiraud, Thibaut, Marc Labrunee, Kevin Gaucher-Cazalis, Fabien Despas, Philippe Meyer, Laurent Bosquet, Celine Gales, et al. (2013). Medicine and Science in Sports and Exercise 45 (10): 1861–67.
13. “Exercise and Stress: Get Moving to Manage Stress.” (2020). Mayo Clinic. Mayoclinic.org
14. Shimojo, Guilherme, Biju Joseph, Roshan Shah, Fernanda M. Consolim-Colombo, Kátia De Angelis, and Luis Ulloa. (2019). Brain, Behavior, and Immunity 75 (January): 181–91.
15. Lu, Wan-An, Gau-Yang Chen, and Cheng-Deng Kuo. (2011). Alternative Therapies in Health and Medicine 17 (4): 8–14
16. “Reflexology for Stress Relief.” (2020). Mayo Clinic. Mayoclinic.org.
