Talk of the vagus nerve has become ubiquitous across social media and is referenced often in wellness communities. If you are swimming through a sea of information overload then you are certainly not alone. Moreover, if the details of exactly what the vagus nerve is and why it is important for your health are not well understood, hopefully this article will help to fill in the blanks.
The vagus nerve is instrumental in many autonomic functions in the body, and has become well known as the pathway toward relaxation. While this is one of many of the vagus nerve functions, it is not the only one. Ultimately, stimulating the vagus nerve through certain practices increases heart rate variability (HRV), which is very important in the prevention of many cardiac diseases as well as for stress reduction.
So, where does sauna use come into play in this conversation? A recent longitudinal study using human subjects found that sauna use stimulated the vagus nerve in a positive way that resulted in increased heart rate variability. This could mean that in the long run it may be possible to prevent many common and deadly diseases by augmenting heart rate variability through sauna use.
Find out what the vagus nerve is and garnish clarity amid the whirlpool of information so that you can proceed in fostering its health in an effective way. Additionally, examine the details of the study that led to the realization that sauna use can massage the tender vagus nerve and in doing so ultimately improve heart rate variability.
The Vagus Nerve as a Pathway for the Brain-Gut Axis and the Parasympathetic Branch of the Autonomic Nervous System
Central to the brain-gut axis is the vagus nerve, and along this freeway of bidirectional biological pathway many crucial autonomic functions occur. If there is a breakdown of any portion of the vagus nerve pathway then diseases ranging from gastrointestinal, to psychiatric, or mood disorders, and even issues with the wellbeing of the heart can occur. (1)
The vagus nerve is a very long pathway through the body beginning in the base of the brain, into the brain stem, neck, and all the way down into the gut and slightly beyond. Due to its length it has also been called the ‘wanderer nerve’. (1)
The National Library of Medicine published an article entitled ‘Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders’ (1). In this article the authors write this about the vagus nerve’s anatomy and function.
“The vagus nerve carries an extensive range of signals from the digestive system and organs to the brain and vice versa. It is the tenth cranial nerve, extending from its origin in the brainstem through the neck and the thorax down to the abdomen.” (1)
The vagus nerve is the primary pathway of the parasympathetic branch of the autonomic nervous system, and therefore plays an important role in relaxation among many other functions. The autonomic nervous system is divided into two primary branches: Sympathetic and parasympathetic which pivots between both branches depending upon internal and environmental factors.
Sympathetic dominance is associated with an external presentation of readiness to take action in the outside world, and at its peak is the cause for states of fight or flight. At a less extreme aspect it allows for proper vigilance when driving or performing tasks in the outside world that require a wakeful state of being. On the other hand, parasympathetic dominance is associated with states of restfulness, calm, and ultimately sleep. The vagus nerve is an intrinsic aspect of the parasympathetic branch of the nervous system.
As stated by the authors of the aforementioned article:
“The vagus nerve is the main contributor of the parasympathetic nervous system.” (1)
When the vagus nerve is damaged or under-performing many illnesses of the body ensue. In stimulating the vagus nerve either through electrical impulses, or in less intrusive ways many diseases may be healed. (1)
For example, a study performed on 60 treatment resistant patients of depression found that vagus nerve stimulation was able to relieve symptoms in many cases, and is now an FDA approved method of treating depression. (1) Why is this?
As it turns out the brain is not the only place where serotonin is produced, but in fact the gut produces the neurotransmitter serotonin responsible for mood regulation as well. By opening up the brain-gut freeway, the vagus nerve serotonin is released, and therefore mood is improved. (1)
This is only one example of how vagus nerve stimulation can heal different aspects of human health. Now, the important point here is that saunas can play a critical role in stimulating the vagus nerve, and there is now peer reviewed evidence that even one sauna session can dramatically improve the health of the vagus nerve and specifically improve heart rate variability as a result.
Find out the details of the study that sauna uses as a major player in the stimulation of the vagus nerve by reading on.
How Can Sauna Use Effect Positive Changes For the Vagus Nerve?
The vagus nerve is the pillar of the parasympathetic branch of the autonomic nervous system, and by stimulating this pathway it is possible to bring balance to the body, gut, and brain. An effective way of measuring the health of the autonomic nervous system, and thus the vagus nerve is by measuring heart rate variability.
A study was conducted to find out if exposure to a sauna session could positively affect the autonomic nervous system in a measurable way for heart health.
The study entitled ‘Recovery from sauna bathing favorably modulates cardiac autonomic nervous system’ was published in both journals, Science Direct, as well as by the National Library of Medicine. (2,3)
The goal of the study is stated by its authors here.
“…we hypothesized that immediately after a single sauna exposure, it is possible to identify favorable cardiac autonomic responses. In this context, we conducted an experimental study to investigate cardiac autonomic nervous system responses, by using HRV measurements, during and immediately after sauna bathing among participants with at least one cardiovascular risk factor.” (2)
The study included 93 participants who had at least one cardiac risk factor. All of the participants were Finnish men with an average age of 52 years. A traditional steam sauna was used for 30 minutes and the temperature was set to 73 degrees Celsius (163 degrees Fahrenheit). (3)
The authors discuss the style of their study as longitudinal here.
“We conducted a single-group, longitudinal study utilizing a pre-post design to examine acute effects of sauna bathing on the autonomic nervous system as reflected by HRV.” (3)
A longitudinal study is important and gives a study more weight because it examines human subjects over a period of time. This is significant in measuring long lasting health effects, and often makes a study more credible.
The study found that the increase of temperature experienced in a sauna initially targets the sympathetic branch of the nervous system, with a rapid switch of the rails back into parasympathetic dominance. This can be measured by an initial increase in heart rate followed by a decrease in heart rate, and this is experienced as a sense of relaxation coming over the body, as many individuals can testify to after a sauna session.
The movement from sympathetic dominance and back on to the vagus nerve pathway in parasympathetic dominance is one way to stimulate this incredible portion of the body.
The authors of the study explain why measuring heart rate variability is a reliable marker of autonomic nervous system health here.
“Heart rate variability (HRV) is a marker of autonomic nervous system balance, which is a measure of heart rate (HR) fluctuations around the mean HR and has been used to indicate the balance between parasympathetic and sympathetic function of the autonomic nervous system. Higher HRV is indicative of a greater capacity of the cardiovascular system to respond to changes in stressful conditions. A reduced HRV is associated with an increased risk for hypertension, CVD, sudden cardiac death (SCD), and cardiac arrhythmias; indeed, autonomic nervous system imbalance with an increased sympathetic or reduced vagal tone has been implicated in the pathophysiology of SCD.” (2)
This suggests that as saunas activate heart rate variability through the use of heat it may be possible to increase resiliency to stressful life events as well, and all of this is a result of a healthy vagus nerve.
The study writes this regarding the vagus nerve stimulation that occurs during just a single sauna session.
“A sauna session transiently diminished the vagal component, whereas the cooling down period after sauna decreased low frequency power (p < 0.001) and increased high frequency power in HRV (p < 0.001), favorably modulating the autonomic nervous system balance.” (3)
An individual who can seamingless move between states of vigilance to the outside world back into states of deep relaxation indicates that this individual will be less vulnerable to blood pressure related illness, as well as many other diseases that result from ongoing stress. The study makes their final concluding remarks when they write this.
“This study demonstrates that a session of sauna bathing induces an increase in HR. During the cooling down period from sauna bathing, HRV increased which indicates the dominant role of parasympathetic activity and decreased sympathetic activity of cardiac autonomic nervous system.” (2)
Now that you understand how saunas stimulate the vagus nerve to increase heart rate variability you may be wondering if heat rate variability is healthier than a steady heart rate.
Why Does Heart Rate Variability Matter?
Heart rate variability matters because it is an indicator of the body’s overall stress load and ability to move into states of relaxation that elicit sleep and calm, additionally this means lowered blood pressure. All humans should aim to have significant heart rate variability to promote overall health.
HRV is, very crudely put, the measurement of time between heart beats. For most individuals it is important to have this variability present. There are some exceptions for specific abnormalities of the heart, and in this case individuals should work directly with a medical practitioner.
According to a publication from Harvard Medical School in an article entitled ‘Heart rate variability: How it might indicate well-being’ (4)
“The brain is constantly processing information in a region called the hypothalamus. The ANS (Autonomic Nervous System) provides signals to the hypothalamus, which then instructs the rest of the body either to stimulate or to relax different functions. It responds not only to a poor night of sleep, or that sour interaction with your boss, but also to the exciting news that you got engaged, or to that delicious healthy meal you had for lunch. Our body handles all kinds of stimuli and life goes on. However, if we have persistent instigators such as stress, poor sleep, unhealthy diet, dysfunctional relationships, isolation or solitude, and lack of exercise, this balance may be disrupted, and your fight-or-flight response can shift into overdrive.” (4)
The authors of this article also suggest that perhaps HRV is an indication of a more well adapted mind and body when they write this.
“..heart rate variability (HRV) as a possible marker of resilience and behavioral flexibility.” (4)
Given that we now know that many illnesses of the body and brain are a result of ongoing toxic stress it is important to stimulate the vagus nerve by drawing the body out of sympathetic dominance back into parasympathetic dominance where relaxation and healing can occur. The evidence is apparent that even a single sauna session can induce heart rate variability by massaging the autonomic nervous system out of states of arousal and back into states of calm.
How Should You Use Your Sauna to Activate the Vagus Nerve?
The exciting aspect of the studies examined in this article is that it is possible to stimulate the vagus nerve through a single sauna session. While the study performed on the men in Finland used a low heat traditional steam sauna, the authors of the same study believe that a variety of heat stimulation methods could be effective. Here is what they write.
“A number of studies have shown that other passive heat therapies (eg. infrared-ray sauna, Waon therapy, etc) improve cardiac function and autonomic nervous activity in patients with pre-existing conditions such as heart failure and chronic respiratory disease.” (3)
If you plan on using a sauna to stimulate the vagus nerve and improve heart rate variability it does not seem to matter what type of heat source that you use. If you are working with an infrared sauna or a steam room instead it appears that the most important aspect is that you are able to increase internal temperature for as close to 30 minutes as you possibly can. If you are able to rest after your sauna session and really allow your body temperature to drop this will heighten your experience.
If you have any pre-existing heart conditions please consult with your doctor before using an infrared sauna to improve vagus nerve function and heart rate variability.
You do not need to head to a lab to have your vagus nerve stimulated electronically, but rather enjoy yourself in a sauna and improve your resiliency to life for your physical, emotional, and mental health!
Sources Cited:
- https://my.clevelandclinic.org/health/body/22279-vagus-nerve
- https://pubmed.ncbi.nlm.nih.gov/31331560/#:~:text=A%20sauna%20session%20transiently%20diminished%20the%20vagal,favorably%20modulating%20the%20autonomic%20nervous%20system%20balance.
- https://www.sciencedirect.com/science/article/abs/pii/S0965229919301943?via%3Dihub
- https://www.health.harvard.edu/blog/heart-rate-variability-new-way-track-well-2017112212789