We have many nerves in our bodies and you can think of them as cables that transmit electrical impulses between the brain and the body. Some have a specific function, for example, to move a muscle, and others help us to see and smell. The largest nerve in our body is the vagus nerve. It has been scientifically proven that stimulating the vagus nerve and its “vagal tone” can improve physical and mental health. Before we look at how it can promote well-being and counteract the fight or flight response, let’s take a closer look at the vagus nerve.
The word vagus is Greek and means “traveller” or “wanderer”. This name describes the 10th cranial nerve very well, as it travels throughout the body. It is a fundamental part of the autonomic system, which consists of the enteric nervous system, the sympathetic nervous system, in charge of stress and survival control functions, and the parasympathetic nervous system, responsible for rest, digestion and recharging. The vagus nerve is the most important nerve of the parasympathetic branch and starts at the brainstem and runs through the neck and then down to the abdomen.
It passes through the cardiovascular system, the digestive system, the reproductive system and many other organs. As the nerves send information to the brain and vice versa, the vagus transmits messages from all the areas it covers to the brain. The vagus nerve is afferent, passing information from the internal organs such as the intestines, liver, heart and lungs to the brain. A small percentage of functionality relays information from the brain to the organs (1).
Many people experience stress in their daily lives, which leads to physical and psychological problems. When the body is exposed to severe stress, it reacts with a fight-or-flight response. This means that functions in the body that are essential for survival are activated, such as a faster heartbeat, a slowing down of digestion and the provision of energy for the muscles instead of organ functions. It doesn’t matter if there is a tiger to fight or a deadline approaching. The body does not know the difference. Throughout high stress, the body is overflown with stress hormones such as cortisol and adrenaline, exhausting the body and mind.
As mentioned above, the vagus nerve is an important messenger of the parasympathetic nervous system between the body and the brain. When it is activated, it can lead to a relaxation reaction in the body. This means that increased vagal activity can counteract a fight or flight stress response from the sympathetic nervous system. Vagal activity slows the heart rate and shuts down the immune system by triggering calming chemicals. This chemical acetylcholine is a tranquilliser resulting in slow, long, deep breaths.
The vagus nerve sends information between the brain and the gut. The gut has its nervous system, the Enteric Nervous system, that communicates with the brain via the vagus nerve. Stimulating the activity of the vagus nerve can also send calming signals to the gut resulting in healthy digestion and a reduction of inflammatory response. You might have experienced some tummy issues caused by stress before. Working with the vagus nerve can relieve the symptoms.
When the body is under stress, pro-inflammatory chemicals are released. An activated vagus nerve can sense the chemicals in the body and counteract them with anti-inflammatory chemicals. This requires stimulation though.
Studies found that the vagus nerve can lead to better access to memory (2). This comes from a release of norephedrine when stimulated. You probably experienced the issue of remembering where you put your key while under stress. Calming down the nervous system leads to better memory.
The vagus nerve promotes well-being by triggering various reactions and chemicals in the body to feel calm, safe and relaxed. When the vagus nerve is activated, breathing and heartbeat are slow, pro-inflammatory chemicals are low and the gut can digest in peace. This is the result of constant communication between the brain and the organs that the vagus connects to. And we all have it in our power to stimulate the vagus nerve to enhance our well-being. There are many ways to activate it, such as breath work, cold exposure, slow diaphragmatic breathing, meditation, humming, singing, laughing, yoga and meditation.
The parameter used to measure vagal activity is the vagal tone. It tells us how well the vagus nerve is functioning. High vagal tone is when there is a slight increase in heart rate after inhalation and a slight decrease in heart rate after exhalation. Low vagal tone, on the other hand, is associated with a high heart rate, inflammation and an overall poor sense of well-being.
In recent years, more and more studies have been done on the vagus nerve, and there is still much to learn about it. One thing is clear: the vagus nerve plays an important role in our mental and physical well-being.
(1) Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in psychiatry, 9, 44. https://doi.org/10.3389/fpsyt.2018.00044
Sahar T, Shalev AY, Porges SW. Vagal modulation of responses to mental challenge in posttraumatic stress disorder. Biol Psychiatry. 2001 Apr 1;49(7):637-43. doi: 10.1016/s0006-3223(00)01045-3. PMID: 11297721.
(2) Sun L, Peräkylä J, Holm K, Haapasalo J, Lehtimäki K, Ogawa KH, Peltola J, Hartikainen KM. Vagus nerve stimulation improves working memory performance. J Clin Exp Neuropsychol. 2017 Dec;39(10):954-964. doi: 10.1080/13803395.2017.1285869. Epub 2017 Feb 19. PubMed PMID: 28492363
Written by Zoe Levit 
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