The vagus nerve (cranial nerve ten) is the main nerve of the parasympathetic division of the autonomic nervous system. The autonomic nervous system (ANS) works largely autonomously, without your conscious effort to control the "automatic" functions of the body that you do not consciously think about, such as heart rate, blood pressure, digestion, dilation and constriction of the pupils of the eyes, kidney function, and temperature control.

The vagus nerve facilitates communication between the brain, cardiovascular, gut, and immune systems. This long and wandering nerve extends throughout much of the body, beginning in the medulla oblongata of the brainstem and then reaching every organ in the chest and abdomen and some skeletal muscles.

This article will discuss the importance of the vagus nerve tone and how it impacts so many aspects of health, including inflammation, digestion, and mood.

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What is the Vagus Nerve?

The vagus nerve (cranial nerve ten) is the main nerve of the parasympathetic (rest and digest) division of the autonomic nervous system (ANS). The vagus nerve is an essential communication route between the brain, cardiovascular system, gut, and immune system via the ANS.

This bi-directional nerve pathway travels from the brain stem down through the chest and into the abdomen, branching off to multiple organs. This wide-reaching pathway gave rise to its name, vagus, which means "wandering" in Latin.

Signals are sent from the brain to the organs of the chest and abdomen, as well as from the gut and organs back to the central nervous system. The vagus nerve helps orchestrate this communication network by signaling the brain to produce neurotransmitters and hormones, coordinating responses, regulating stress reactions, and helping to keep inflammation in check.

Some people have stronger vagus nerve activity than others, allowing their bodies to relax more quickly after stress. The strength of your vagus response is known as vagal tone and contributes to your overall resilience to stressors.

What is Vagus Nerve Stimulation?

Since the vagus nerve is a major control center for the body, the health and functioning of this nerve are of utmost importance to the health of your brain, immune system, and overall inflammatory state. Vagus nerve stimulation (VNS) includes techniques that stimulate the vagus nerve via manual or electrical means.

As far back as the 1880s, physicians noted that manual massage and compression of the carotid artery in the cervical region of the neck could stop seizures, an effect attributable to manual stimulation of the vagus nerve as it runs through this area of the neck. Later, implantable electrical VNS devices were developed and approved by the FDA to treat certain types of seizures/epilepsy, depression, and some impacts of stroke.

Electrical VNS often involves applying electrical impulses to the nerve via direct invasive stimulation with a surgically implanted device. When activated, this device sends electrical signals along the vagus nerve to the brainstem, which then sends signals to specific areas in the brain that change the way cells in the brain work, impacting seizures, mood, anxiety, and inflammation.

Newer indirect transcutaneous (across the skin) non-invasive devices have also been developed for stimulating the vagus nerve. These types of devices are approved in Europe to treat epilepsy, depression, and pain and FDA-approved in the US for cluster headaches. Transcutaneous stimulation can be done by attaching a vagal nerve stimulator to the ear to act on the auricular branch of the vagus nerve.

Ongoing research is exploring different types of VNS to help with other health issues like multiple sclerosis, migraines, stress, autoimmune disorders, and dementia.

There are also non-invasive strategies from lifestyle medicine that many practitioners recommend that have been shown to stimulate the vagus nerve. These treatments that target the vagus nerve increase the vagal tone, inhibit cytokine production, and improve resilience to stress.

How Does Vagus Nerve Stimulation Work?

Treatments that target the vagus nerve are believed to work through several methods:

• Improve blood flow in the brain
• Influence chaotic electrical patterns to stop seizures
• Alter levels of neurotransmitters (specifically norepinephrine and serotonin) in the brain that may control seizure development and influence mood
• Stimulate brain areas that control movement in areas of the body impacted by stroke

Stimulation of the vagus nerve aims to increase the vagal tone and balance neurotransmitter and cytokine production. Stimulating the vagus nerve fibers can influence serotonin, dopamine, norepinephrine, epinephrine, and histamine (monoaminergic) neurotransmitter systems in the central nervous system that play crucial roles in major psychiatric conditions, such as depression and anxiety disorders.

The vagus nerve plays a central role in coordinating the parasympathetic relaxation response, helping to slow down breathing and heart rate, promote relaxation, stimulate digestion, and bring about a sense of peace and calm. To help coordinate this relaxation response, the vagus nerve releases the neurotransmitter acetylcholine, which seems to give a significant brake on inflammation in the body. These functions allow vagus nerve stimulation to influence immune responses and inflammation.

Research Behind Vagus Nerve Stimulation

Emerging research suggests that the vagus nerve may be an effective target in treating various psychiatric, inflammatory, and gastrointestinal disorders. Stimulating the vagus nerve acts as a natural anti-inflammatory and tranquilizer since it reduces the production of pro-inflammatory cytokines and calms the nervous system. Therefore vagal nerve stimulation has been studied as an adjunct treatment for treatment-refractory depression, posttraumatic stress disorder, and inflammatory conditions.

Gut/Brain Axis

The nervous system and digestive system are closely intertwined in what is sometimes called the brain-gut axis. The vagus nerve establishes one of the primary connections between the brain and the gastrointestinal tract. It acts as a communication pathway that sends information about the state of the inner organs of the abdomen to the brain via afferent fibers and conveys signals from the brain and central nervous system back to the digestive tract. This is why your gut is sometimes called your second brain.

The gut microbiota also influences these communications to regulate the gastrointestinal tract and connect emotional and cognitive areas of the brain with gut functions.

Given this essential role that the vagus nerve plays in the gut-brain axis and intestinal health, VNS has been shown to reduce intestinal inflammation and benefit inflammatory conditions like Crohn's disease and ulcerative colitis.

Stress

You have likely experienced this brain-gut connection before when you sense a "gut feeling," "butterflies in your stomach," or anxiety-induced nausea. Since the vagus nerve and digestive system are closely intertwined in this way, the digestive system is particularly vulnerable to the presence of stress, especially when it becomes chronic. Stimulating the vagus nerve to increase vagal tone has been shown to help regulate stress.

The vagus nerve modulates systems involved with the symptoms of most stress-related psychiatric disorders that seem to include changes in how the brain and body respond to stress. VNS has beneficial effects on brain systems and autonomic nervous system functions that help address stress and the processing of emotional stimuli.

Depression

VNS is sometimes considered for people who have not responded to other intensive depression treatments, such as antidepressant medications, psychological counseling, or electroconvulsive therapy (ECT). Non-invasive direct vagus nerve stimulation through the skin of the ear produces an effect similar to an implantable electrical VNS for reducing depressive symptoms without the risks of surgery.

Anxiety

Given the significant impact that the vagus nerve has on autonomic functions like heart rate and blood pressure, vagal nerve function is essential for adapting to stress and modulating fear, trauma, and anxiety. VNS shows promise in helping treat anxiety, fear, and trauma. Activation of the vagus nerve helps to counteract the sympathetic stress response, reducing heart rate and blood pressure.

Another way the vagus nerve influences anxiety is via its impact on the gut microbiome. A healthy balance of gut bacteria can benefit mood and anxiety, partly through its influence on vagus nerve activity. When your gut has a healthy balance of microbes, you have less intestinal permeability, improved resistance to illness, and better psychological and gastrointestinal health.

Inflammatory Conditions

Low vagal tone has been associated with chronic inflammation. Inflammation lies at the root of most chronic diseases. While acute inflammation can be useful as part of the immune and healing responses, inflammation can damage the body when it becomes chronic or imbalanced. Chronic, systemic, and low-grade inflammation significantly contributes to aging, allergies, and chronic diseases like type 2 diabetes, dementia, atherosclerosis, and arthritis.

Research shows that those with inflammatory conditions, such as rheumatoid arthritis and other autoimmune diseases, often have decreased heart rate variability, a marker of reduced vagal tone. This reduced vagal tone triggers the production of pro-inflammatory cytokines (substances secreted by inflammatory cells and affect other cells) and leads to an increase in sympathetic nervous system activity and stress hormones, contributing to systemic inflammation. VNS may help to balance inflammation and address these types of conditions.

How to Stimulate The Vagus Nerve

There are many non-invasive ways to help improve vagal tone, balance the stress response, reduce chronic stress, boost resilience, and improve digestive health. These approaches are based on mindfulness, stress management, functional nutrition, and lifestyle medicine approaches. Be sure to work with your healthcare provider to find an appropriate approach to vagus nerve stimulation for your unique needs.

Mindfulness Meditation

Several mindfulness and meditation techniques have been shown to modulate the vagus nerve with therapeutic effects. Techniques like progressive muscle relaxation, visualization, and mindfulness meditation are effective ways to shift into a more parasympathetic state which favors relaxation and healthy digestion. For example, self-generated positive emotions via loving-kindness meditation increase vagal tone.

Breathwork

Relaxation and focused breathing exercises increase vagal tone to provide greater autonomic balance. Deep slow breathing triggers the parasympathetic nervous system, which activates processes involved in rest, repair, and digestion.

When the body is in parasympathetic mode, blood flow and oxygenation to the digestive tract increase, making digestion more efficient. Various forms of paced breathing can influence brain electrical activity by stimulating the vagus nerve arising from the diaphragm. This type of vagus nerve stimulation explains some of the positive emotional and cognitive benefits of breathwork.

Yoga

Some yoga postures and pranayama breathing practices can directly stimulate the vagus nerve to increase vagal tone and improve autonomic regulation, mood, and cognitive function. Yoga practices that coordinate the breath with movement are especially effective at reducing the state of constant hyperarousal, which is detrimental to digestion, stress, and mood.

Massage

An emerging technique for reducing inflammation and toning the vagus nerve is a type of self-abdominal massage. Moderate pressure massage has been shown to stimulate the vagus nerve, increase the movements of the digestive system and contents, and improve insulin secretion to help balance blood sugar in preterm infants (studies on adults have yet to be done).

Similarly, reflexology or massaging points on the foot can increase vagal tone and balance blood pressure.

Singing, Humming, Chanting, and Gargling

Since the vagus nerve is connected to the muscles of the back of the throat and vocal cords, singing, humming, chanting, and gargling aggressively can stimulate the vagus nerve. These methods to engage the muscles of the back of the throat may increase heart-rate variability and improve vagal tone.

Cold Exposure

Acute cold exposure activates the vagus nerve. For example, exposing the side of the neck (where the vagus nerve runs through) to cold improves heart rate variability, a maker of better stress resiliency and vagal nerve function. Similarly, exposing the body to cold regularly, such as with cold showers or cold applied to the face, may lower the sympathetic "fight or flight" response and increase parasympathetic activity by stimulating the vagus nerve.

Omega-3 Fats

Omega-3 fatty acids are essential fats your body cannot produce and must obtain from the diet or via supplementation. Foods rich in omega-3s include cold-water fish like mackerel and salmon, walnuts, flaxseeds, and chia seeds. These fats are necessary for the normal electrical functioning of your brain and nervous system. Studies show that omega-3 fats increase vagal tone and vagal activity and, therefore, help to reduce heart rate and increase heart rate variability.

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Summary

The vagus nerve (cranial nerve ten) is a key communication route between the brain, heart, lungs, and abdominal organs. It is the main nerve of the parasympathetic nervous system that influences many bodily functions like breathing, heart rate, and digestion. Therefore, this nerve helps to regulate balance in the body by influencing heart rate, gastrointestinal motility and secretion, pancreatic function, blood sugar balance, and other organ functions.

Optimal functioning of the vagus nerve can impact many aspects of health. Healthy vagal tone or functioning of the nerve allows the body to return to calm after stress and helps to regulate important functions like heart rate, blood pressure, and digestion. The vagus nerve helps us maintain calm when we are not in danger, engage in "rest and digest" functions, and regulate mood, anxiety, and stress.

Vagal nerve stimulation includes techniques that help increase the vagus nerve's activity. This can be done with lifestyle approaches like meditation, yoga, breathing exercises, massage, singing, humming, gargling, or cold exposure. Some devices can be implanted into the neck or used across the skin to provide electrical stimulation of the nerve.

VNS is effective for epilepsy, depression, headaches, and other forms of pain. Further studies of applications of VNS for treating inflammation, stress, multiple sclerosis, migraines, autoimmune disorders, and dementia are also ongoing. Given the broad reach of the vagus nerve and its many functions, vagal nerve stimulation shows excellent potential for metabolic, psychological, and cerebrovascular impacts.