As the topic of mental health has gained attention over the past several years, you’ve no doubt heard a couple of related phrases you’re not familiar with. One is the vagus nerve. The other is heart rate variability. Here, we’ll delve into the vagus nerve and what it’s all about.
What is the Vagus Nerve?
The vagus nerve, also known as the 10th cranial nerve or cranial nerve X, is the longest and most complex of the cranial nerves. It is also known as the “wanderer nerve” due to its long, winding course through the body, connecting various organs and systems. It is a key part of the parasympathetic nervous system, which controls involuntary body functions such as digestion, heart rate, and immune response.1“Vagus Nerve: What It Is, Function, Location & Conditions.” Cleveland Clinic, https://my.clevelandclinic.org/health/body/22279-vagus-nerve. Accessed 6 Feb. 2024.
The vagus nerve originates in the medulla oblongata, a part of the brain that connects to the spinal cord, and extends down through the neck to the vital abdominal organs.2Segal, Dayva. “Vagus Nerve: What to Know.” WebMD, https://www.webmd.com/brain/vagus-nerve-what-to-know. Accessed 6 Feb. 2024. It contains both motor and sensory fibers, which means it can send and receive information.3Kenny BJ, Bordoni B. Neuroanatomy, Cranial Nerve 10 (Vagus Nerve) [Updated 2022 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537171/
The vagus nerve carries signals between the brain, heart, and digestive system. It is responsible for various bodily functions, including digestion, heart rate, and breathing. It also plays a role in controlling mood, immune response, and the regulation of food intake, satiety, and energy homeostasis.4Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.
Vagus nerve stimulation (VNS) is a treatment method that uses electrical impulses to stimulate the nerve. It’s used to treat some cases of epilepsy and depression that don’t respond to other treatments.
Damage to it can lead to conditions like gastroparesis, where food does not move into the intestines, and vasovagal syncope, a condition where people faint from low blood pressure.
Vagal tone is often used to assess heart function, emotional regulation, and other processes that alter or are altered by changes in parasympathetic activity. A higher resting vagal tone means you have a reserve capacity for stress. You’re more stress resilient.5Laborde S, Mosley E, Thayer JF. Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research – Recommendations for Experiment Planning, Data Analysis, and Data Reporting. Front Psychol. 2017 Feb 20;8:213. doi: 10.3389/fpsyg.2017.00213. PMID: 28265249; PMCID: PMC5316555.
Vagal tone is typically measured indirectly by heart rate variability (HRV), which is the variation in time between each heartbeat. HRV is considered a marker of the body’s resilience and adaptability to stress, with higher HRV (indicating greater variability in the intervals between heartbeats) generally associated with better health and fitness, greater resilience to stress, and lower risk of disease.
The Vagus Nerve and the Gut-Brain Axis
The vagus nerve plays a pivotal role in the gut-brain axis, a complex communication network that links the central nervous system (CNS) with the gastrointestinal (GI) tract. This bidirectional pathway allows for the exchange of signals between the gut and the brain, influencing a wide range of bodily functions, including mood, immune response, digestion, and heart rate. Here’s how the vagus nerve affects the gut-brain axis:
Direct and Indirect Sensing
The vagus nerve can directly or indirectly sense a variety of signals from the intestinal environment and transmit these signals to the nucleus tractus solitarius (NTS) in the brain. This transmission is crucial for the regulation of behavior and the management of neurodegenerative diseases. The vagus nerve’s afferent fibers play a key role in this process, highlighting its importance in the gut microbiota-brain axis.6Han Y, Wang B, Gao H, He C, Hua R, Liang C, Zhang S, Wang Y, Xin S, Xu J. Vagus Nerve and Underlying Impact on the Gut Microbiota-Brain Axis in Behavior and Neurodegenerative Diseases. J Inflamm Res. 2022 Nov 9;15:6213-6230. doi: 10.2147/JIR.S384949. PMID: 36386584; PMCID: PMC9656367.
Modulation of the Brain-Gut Axis
As a major component of the parasympathetic nervous system, the vagus nerve modulates the brain-gut axis in psychiatric and inflammatory disorders. It regulates internal organ functions such as digestion, heart rate, and respiratory rate. In the intestines, it controls the contraction of smooth muscles and glandular secretion, affecting nutrient storage and mobilization. This modulation is significant for the control of food intake, regulation of satiety, gastric emptying, and energy balance.7Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.
Communication Through the Enteric Nervous System
The vagus nerve conveys sensory information about the conditions inside the gut from the enteric nervous system to the brain. In response, it conveys motor signals from the brain to the gut, mediating various reflexes within the gut in response to changing conditions. This highlights the complex and bidirectional nature of signals passing between the digestive system and the central nervous system, where health or disease in one can affect the other.
Influence of Gut Metabolites
Gut metabolites can signal directly to the vagus nerve through neuropods, indicating that the composition of the gut microbiome differs according to vagus nerve function. This suggests a direct biochemical interaction between the gut’s microbial environment and the vagus nerve, further emphasizing its role in the gut-brain axis.8Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.
How You Can Negatively Affect Vagus Nerve Function
The vagus nerve can be negatively impacted by a variety of factors, both physical and psychological.
Physical damage to the vagus nerve can occur due to surgery or disease. Certain conditions such as gastroparesis, where food does not move properly from the stomach into the intestines, can be caused by damage to the vagus nerve.9Vagus Nerve: Function, Stimulation, and More. https://www.healthline.com/human-body-maps/vagus-nerve. Accessed 6 Feb. 2024. Other conditions that can affect the vagus nerve include vasovagal syncope, which can cause fainting due to low blood pressure.10Vagus Nerve: Function, Stimulation, and More. https://www.healthline.com/human-body-maps/vagus-nerve. Accessed 6 Feb. 2024.
Infections, whether viral, bacterial, or parasitic, as well as exposure to mold and toxins, may also lead to vagus nerve dysfunction.
Diet can also impact the vagus nerve. For instance, both high-fat and high-carbohydrate diets have been shown to impair vagus nerve signaling of satiety.11Loper, H., Leinen, M., Bassoff, L. et al. Both high fat and high carbohydrate diets impair vagus nerve signaling of satiety. Sci Rep 11, 10394 (2021). https://doi.org/10.1038/s41598-021-89465-0
Psychological stress is another major factor that can negatively impact the vagus nerve. Chronic stress can lead to vagal nerve dysfunction, which can result in a variety of symptoms such as difficulty swallowing, bloating, nausea, vomiting, constipation, early satiety, diarrhea, and heartburn. Stress and anxiety can both trigger the vagus nerve, and when the vagus nerve is overstimulated, it can cause a number of symptoms including abdominal pain, vomiting, nausea, and dizziness.
Unresolved trauma or post-traumatic stress disorder (PTSD) can also impair vagus nerve function. Childhood events that may have been perceived as traumatic can impact vagus nerve function and related aspects of health well into adulthood.
In order to maintain a healthy vagus nerve, it is important to manage stress, maintain a balanced diet, and take care of one’s overall health.
Natural Ways to Support Vagus Nerve Function
You can support vagus nerve function through a variety of natural diet and lifestyle choices.
Mindfulness and Meditation
Mindfulness and meditation can increase vagal tone and heart rate variability (HRV), which are indicators of a well-functioning vagus nerve. These practices help balance the stress response and improve resilience by promoting relaxation and reducing the physiological effects of stress.
Regular physical activity, including moderate-intensity interval training, has been shown to increase vagus nerve activity. Exercise leads to increased sympathetic tone during the activity, but post-exercise, there is an enhancement in vagus nerve activity as the body returns to baseline, which is beneficial for heart health and metabolic regulation.12Kai S, Nagino K, Ito T, Oi R, Nishimura K, Morita S, Yaoi R. Effectiveness of Moderate Intensity Interval Training as an Index of Autonomic Nervous Activity. Rehabil Res Pract. 2016;2016:6209671. doi: 10.1155/2016/6209671. Epub 2016 Nov 10. PMID: 27957342; PMCID: PMC5121464.
Cold exposure, such as cold water face immersion or applying cold to the neck region, activates the vagus nerve by triggering the diving reflex. This reflex is a physiological response that optimizes respiration by redistributing oxygen stores and is associated with increased parasympathetic activity, which is mediated by the vagus nerve.13Jungmann M, Vencatachellum S, Van Ryckeghem D, Vögele C. Effects of Cold Stimulation on Cardiac-Vagal Activation in Healthy Participants: Randomized Controlled Trial. JMIR Form Res. 2018 Oct 9;2(2):e10257. doi: 10.2196/10257. PMID: 30684416; PMCID: PMC6334714.,14Richer R, Zenkner J, Küderle A, Rohleder N, Eskofier BM. Vagus activation by Cold Face Test reduces acute psychosocial stress responses. Sci Rep. 2022 Nov 10;12(1):19270. doi: 10.1038/s41598-022-23222-9. PMID: 36357459; PMCID: PMC9649023.
Deep, slow belly breathing stimulates the vagus nerve by activating specific neurons that detect blood pressure changes. These neurons signal to the vagus nerve to lower heart rate and blood pressure, which induces a state of relaxation.
Singing, Humming, or Gargling
These activities activate the muscles at the back of the throat, which are connected to the vagus nerve. When these muscles are activated, the vagus nerve is stimulated, which can improve its tone and function.
Massage, particularly foot massage, can stimulate the vagus nerve through gentle or firm touch. The sensory receptors in the skin send signals to the brain via the vagus nerve, which can induce relaxation and improve vagal tone.
A diet rich in probiotics and omega-3 fatty acids can support vagus nerve health by improving gut health and reducing inflammation, which can positively affect brain function and vagus nerve activation.
This yoga breathing technique can help strengthen the vagus nerve by promoting relaxation and reducing stress, which in turn can improve vagal tone.
To support vagus nerve function, certain dietary supplements can be beneficial due to their roles in neurotransmitter synthesis, nerve health, and anti-inflammatory effects. Here are some supplements with scientific references supporting their potential benefits for the vagus nerve:
- Choline: Choline is a precursor to acetylcholine, a neurotransmitter that the vagus nerve uses to communicate. Adequate choline intake is essential for proper vagus nerve function.15Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.
- Vitamin B12: Vitamin B12 is crucial for maintaining the health of neurons and is involved in the synthesis of neurotransmitters. Deficiency in B12 can lead to neurological and psychiatric disorders.
- Magnesium: Magnesium is involved in numerous physiological functions, including nerve transmission and muscle contraction. It has a calming effect on the nervous system and can influence the activity of the vagus nerve.
- Omega-3 Fatty Acids: Omega-3 fatty acids, particularly those found in fish oil, have anti-inflammatory properties and are important for brain health. They may enhance vagus nerve function by improving heart rate variability (HRV), a marker of vagal tone.16Ano, Y., Ohya, R., Yamazaki, T. et al. Hop bitter acids containing a β-carbonyl moiety prevent inflammation-induced cognitive decline via the vagus nerve and noradrenergic system. Sci Rep 10, 20028 (2020). https://doi.org/10.1038/s41598-020-77034-w
- Probiotics: Probiotics can influence the gut-brain axis and may enhance vagus nerve function. Certain strains of probiotics have been shown to affect the brain via the vagus nerve in animal studies.17McVey Neufeld, KA., Bienenstock, J., Bharwani, A. et al. Oral selective serotonin reuptake inhibitors activate vagus nerve dependent gut-brain signalling. Sci Rep 9, 14290 (2019). https://doi.org/10.1038/s41598-019-50807-8
- Zinc: Zinc is important for the immune system and has been shown to influence vagus nerve activity. Zinc deficiency can impair the function of the vagus nerve.18Ano, Y., Ohya, R., Yamazaki, T. et al. Hop bitter acids containing a β-carbonyl moiety prevent inflammation-induced cognitive decline via the vagus nerve and noradrenergic system. Sci Rep 10, 20028 (2020). https://doi.org/10.1038/s41598-020-77034-w
- Adaptogens: Adaptogens are a class of herbs that help the body adapt to physical and emotional stress. Some well-known examples include eleuthero, reishi mushroom, Lion’s Mane, and astragalus. Ashwagandha, often referred to as the queen of Ayurveda, has been used for over 6000 years to enhance resilience to stress. Rhodiola Rosea, another adaptogen, is a mild antidepressant and a stimulant that has been found helpful in addressing anxiety and supporting cognitive function. Adaptogens like reishi, astragalus, and ashwagandha are helpful when taken over time to build stamina and bring your body back into balance, which can better protect your body from the negative effects of stress.
While it’s possible to treat the vagus nerve directly, and is necessary when treating some dysfunctions, there’s a lot you can do through intelligent diet and lifestyle choices to enhance the function of your vagus nerve, and thereby enhance your overall health and wellbeing. With is vagus nerve primer in mind, we’ll delve deeper into some of those choices in future articles.