The Importance of the Vagus Nerve for Nervous System Balance and Optimizing Physical and Psychological Health

The tenth cranial nerve, the vagus nerve, has gotten a lot of attention recently. This is for good reason. Having an optimally functioning vagus nerve is vital for balancing many critical functions in the body.

In this post, I’ll discuss what the vagus nerve is, its roles and functions, signs of vagal dysfunction, vagal response triggers, measuring vagal tone, and ways to balance your vagus nerve.

In a future post, I’ll explore how the vagus nerve provides a new way of dealing with PTSD (post-traumatic stress disorder), based on the polyvagal theory. I’ll also touch on how essential oils can support this therapeutic application.

What is the Vagus Nerve?

The vagus nerve is the 10^th cranial nerve (CN X). It is the most complex and longest of the twelve cranial nerves. This nerve is predominately associated with the parasympathetic division of the autonomic nervous system (ANS), the part of our of nervous system that subconsciously controls the smooth muscles of all our organs.

The parasympathetic nervous system (PNS) is often referred to as the “rest and digest” part of the nervous system. The PNS works in synergy with the sympathetic nervous system (SNS), which helps prepare the body for an emergency and assists with “fight and flight” responses.

The left and right vagal nerves (collectively known as the vagus nerve) contain 75% of your parasympathetic nervous system’s nerve fibers, therefore, the vagus nerve is often attributed to calming the body.

Yet, the vagus nerve is a mixed nerve that carries both afferent and efferent fibers with some sympathetic influence. This means it carries sensory and motor information to the organs it innervates and carries the information back to the central nervous system for interpretation.

Think of it as a superhighway in which this “vagrant,” or wondering nerve, expands from the brainstem in the medulla oblongata and has many branches throughout the body.

What Does the Vagus Nerve Do?

The vagus nerve has connections primarily within your neck, chest, heart, lungs, and abdomen. Its fibers receive and send information from the brain, heart, and digestive system.

As a result, it influences your blood vessels and cardiovascular system, liver, and gut and respiratory functions. Furthermore, it also innervates the skull and plays a role in sensory processes such as hearing. Consequently, the vagus nerve has many crucial tasks including regulating heart rate, blood pressure, breathing, and digestion.

What are the Functions of the Vagus Nerve?

Below is an overview of the vagus nerve’s functions.

These include regulating:

• Digestion
• Heart rate, blood pressure, and respiration (breathing)
• Immune system responses
• Inflammation (via the hypothalamic pituitary axis, the enteric nervous system (ENS) in the gut, and the splenic sympathetic nerve)
• Mood
• Mucus and saliva production
• Skin and muscle sensations
• Speech
• Taste
• Urine output
• Reflex actions (coughing, sneezing, swallowing, gagging, and vomiting via its skin and muscle sensory innervation)
• Communication between the gut and brain via the gut-brain axis (impacting emotions and psychiatric disorders, such as depression)

Vagal Response Triggers

There are various triggers that can impact a vagal response (stimulation to the vagus nerve that leads to symptoms). They can be internal or environmental factors.

Some common triggers of the vagus nerve include:

• Psychological stress or fear
• Gastrointestinal disorders
• Having a bowel movement (this is part of the “rest and digest” function)
• A blood draw or seeing blood (physical or emotional reaction)
• Change of positions or standing in one position too long
• Heat
• Pain
• Trauma

Signs of Vagal Dysfunction

Damage to the vagus nerve can lead to issues with involuntary body functions. This is referred to as autonomic dysfunction or dysautonomia.

Vagal nerve damage can occur from things such as physical trauma, viruses, chronic inflammation, diabetes, cardiovascular system compromise, stress, and other factors. It can lead to:

• Digestive issues: difficulty swallowing (dysphagia), acid reflex, and gastroparesis (where food is not effectively moving through the intestines)
• Vasovagal syncope: fainting due to a sudden drop in blood pressure from a fright
• Irregular heart rate (arrhythmias)
• Orthostatic hypotension: dizziness or fainting from a drop in blood pressure when changing position
• Laryngeal issues affecting the voice

Vagal Tone

Vagal tone is a term that refers to how well the vagus nerve is functioning.

Poor vagal tone can also occur without damage to the nerve based on the triggers listed above. Symptoms include:

• Poor emotional regulation
• A heightened stress response
• Being in flight-or-fight mode
• Lowered attention span
• Increased inflammation
• Pain

Low vagal tone is also associated with various conditions. These include:

• Gastrointestinal problems: IBS (irritable bowel syndrome) and Crohn’s (R, R, R)
• Neurological conditions such Parkinson’s disease (R)
• Depression, anxiety, and PTSD (R)
• Metabolic disorders such as Type 2 diabetes (R, R)
• Cardiovascular disease, hypertension, and irregular heartbeat (atrial fibrillation) (R)

Measuring Vagal Tone

Vagal tone can be measured indirectly by heart rate variability (HRV). HRV measures the amount of time between heartbeats which is caused by the flux of SNS and PNS stimulation and dominance. It provides more insight into the functioning of the ANS including its regulation of blood pressure (BP), gas exchange, digestion, heart rate, and vascular tone.

According to an article in Frontiers in Public Health, an optimal HRV measurement reflects self-regulatory capacity, adaptability, resilience, and cognitive performance. The authors state:

…Higher levels of resting vagally-mediated HRV are linked to performance of executive functions like attention and emotional processing by the prefrontal cortex (1). Afferent information processing by the intrinsic cardiac nervous system can modulate frontocortical activity and impact higher-level functions (7).

HRV is also used in fitness to assess how well one recovers from exertion and to avoid overtraining. There is no baseline for what is considered “normal”. It is individual and the variance over time is what one uses to track changes in the ANS.

Although it is true that HRV most accurately predicts cardiac vagal tone, it is often used as a correlative to the function of overall ANS performance.

Ways to Improve Vagal Tone

The good news is there are ways to care for our vagus nerve.

Lifestyle factors such as stress reduction, nutrition, and exercise have all been shown to modulate vagal tone.

For example, nutrients can be used to support the brain-gut axis, which is mediated by the vagus nerve. These include foods that contain neurotransmitter precursors that influence calming, such as:

1. foods high in b vitamins (whole grains and veggies)
2. foods rich in magnesium (veggies, chocolate, nuts, and seeds)
3. foods for feeding the microbiome (such as eating fermented foods like sauerkraut and yogurt and consuming high polyphenol-containing foods, which are beneficial plant compounds digested by gut bugs)

Other techniques and interventions that have also been shown to modulate HRV in human studies, indicating better vagal tone. Many were reviewed in this article and include:

• Fish intake and omega-3 supplementation
• Probiotics
• Breathing techniques
• Chanting
• Laughter
• Positive emotions and social connections (promoting feelings of safety)
• Mindfulness
• Practicing forgiveness
• Exercise: aerobic, stretching, resistance training, and yoga
• Music therapy
• Massage
• Gag reflex stimulation (a role that the vagus nerve plays in)
• Cold water facial immersion
• Sleeping on the right side (According to the review, one study with subjects with coronary artery disease showed that the highest parasympathetic tone was achieved when lying for five minutes on the right side. Alternately, parasympathetic activation was the lowest when lying on the back, the supine position.)
• Essential oils (my addition) – essential oils can modulate the stress response and vagal tone (Learn more in my podcast interview.)

Conclusion: What to Know About the Vagus Nerve

The vagus nerve deserves its popularity in integrative medicine. It impacts all vital functions in the body and regulates our psychology. We can indirectly assess our vagal tone based on fluctuations in our HRV and by the symptoms we are experiencing.

Lifestyle practices such as diet, movement, mindfulness, social connection, and music therapy can help to optimize our vagal tone and enhance our resilience.

In an upcoming post, I’ll discuss more about applying what we know about the vagus nerve into therapeutic applications for psychological disorders and the potential of incorporating this theory with essential oils.

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