Titles like this one are straight clickbait, and I am truly sorry for using it. Worse, I hate top 10 lists, because people tend to skim them for the one or two items they care about and then ignore the rest. Please don’t do that here, because I am going to be providing lots of additional important information in each of these subtopics, and I think you’ll really miss out if you do jump around. So, without further ado, let’s get started.
- What is the vagus nerve?
The vagus nerve is a cranial nerve, which means that it is one of about a dozen large bundles of nerve fibers that relay between various spots in your body and your brainstem. These cranial nerves often interact with nerves that are part of your spinal cord (motor nerves that control mostly voluntary muscle action) and your sympathetic nerves (a chain of nerve bundles that follow the front of the spinal column that branch out at each spinal level) to provide control control over autonomic features of the body. Now, the truth is that very few of the other cranial nerves make it lower than the neck, and most are only involves in the face. For example, one really important cranial nerve is called the trigeminal nerve, and it has three pair of branches, the maxillary (in the jaw), facial (across the cheek), and supraorbital (just over your eyebrows). The maxillary branch of the trigeminal nerve is the one that the dentist numbs when you have dental work done.
The vagus nerve, on the other hand, wanders all around the chest and abdomen, gathering information from nearly all the organs, and transmitting it up to the brain so your central processing unit (your brain) can figure out the state of the system and then coordinate the messages to be sent back down the vagus, and out through the sympathetic nerves and even the spinal cord. That’s a lot for one nerve to do, and that’s because it really isn’t a single nerve, it is somewhere around 250-300,000 nerve fibers, and includes different types, some transmitting information up to the brain and others carrying signals from the brain back to the body. About 80% of the fibers actually bring information back up to the brain though, making it a really important sensory nerve.
The few last things to note before we move on to what key functions the vagus nerve is involved in are. First, when it couples to things in the body, it uses a neurotransmitter called acetylcholine (which used to be referred to as “vagusstuff” after being coined that by the German scientist who discovered the chemical associated with the vagus nerve … you’ve gotta love how the Germans just slam words together, but at least it is more descriptive than most neurotransmitter names … although I love that dopamine is the name of the neurotransmitter that gets released to keep people staring at their smart phones rather than stepping on the gas when the stoplight turns green … definitely dope-amine! The irony of that is just breathtaking!)
The second thing to remember is that the vagus nerve connects into the brain at an area called the nucleus of the solitary tract, or NTS, and exits the skull through two little holes on the lower part of the skull, descending through the neck inside the same sheath that holds the carotid artery, and then branches out to the organs and tissue of the chest and abdomen. In the NTS, signals from the vagus relay to REALLY important regions of the brain that cause the release of critical neurotransmitters, like serotonin, norepinephrine, GABA, dopamine, and, of course, acetylcholine (and greatly impacts glutamate levels as well). These are the “big 6” neurotransmitters of the brain, so you can imagine how important the signals in the vagus might be!
- What does the vagus nerve do?
History records that 10,000 years ago, our knowledge of medicine had already grasped the importance of the “fight or flight” versus “rest and digest” modes of our bodies. OK, the evidence really comes more from anthropology that actual historical records, but acupuncture, the yin and yang of ancient Chinese medicine, Ayurvedic and yoga practices, and the herbal concoctions of the ancient Egyptians were all based on the importance of these two states of the human (and animal) existence. We now know that the modes are driven by the sympathetic arm (“fight or flight” mode) and the parasympathetic arm (rest, digest, and restore) of the autonomic nervous system. The vagus nerve is the primary component of the parasympathetic arm.
Examples of the autonomic features that the sympathetic and parasympathetic exerts control over include the easy ones to think about, like heartbeat, digestion, and breathing, but they also have a lot of influence over some things that you might not think of as being controlled by your brain, including metabolism, insulin release, immune function, and even the clotting of blood. High level of vagal activity, and the release of acetylcholine, tends to slow heart rate and blood pressure, promote digestive movement, slow and deepen breathing (it even sounds like what would happen to your body while lying in a hammock). More recently, it has been discovered that high vagal tone is also associated with low inflammation levels, efficient energy utilization, and healthy insulin uptake.
- What bad can happen to the vagus nerve?
Just like any other tissue in the body, the vagus nerve can be physically damaged. There are viral infections that can also cause vagal tone to become erratic. Two big factors that can also weaken vagal tone (render it dysfunctional or chronically low in some capacity) are microbiome dysbiosis (screwing up the microbes in the digestive system, since the vagus nerve is the brain gut axis) and chronically elevated blood glucose levels (such as is common in type-2 diabetes). In truth, the latter factor is really the worst of a group of chronic inflammatory conditions that weaken vagal tone.
The vagus nerve is just like muscles or connective tissue in that it needs to be limber and resilient. Now, the flexibility we are talking about isn’t the range of motion that muscle, tendons and ligaments have to maintain in order to prevent strains, pulls, or tears. In this case, we are talking about the ability to rapidly cycle between firing frequencies. A great way to gauge this resilience is through heart rate variability (HRV), which is a measurement of the spacing between the beats of the heart. It turns out that being really healthy and relaxed means that the interbeat spacing (the time between contractions) has a high degree of variation and still the beats are smooth and stable. Under stress, i.e., sympathetic dominance, that HRV drops and the heart beats with very little time variability. Under chronic stress that leads to disease and heart attacks, the heart stops having that healthy variability and starts to beat like a metronome. It has been said that when HRV drops to zero, you are within 24 hours of a heart attack. (I remember watching the movie GATTACA with Ethan Hawke, who wanted desperately to be an astronaut, but had a heart condition. In the movie, he assumes the identity of a foreign athlete, but in order to keep up pretenses has to run on a treadmill wearing an EKG harness. He manages to fake being in fabulous shape by concealing wires that supposedly projected a healthy heartbeat which was, quite wrongly, described as steady as a metronome. Mistakes like these tends to destroy my ability to suspend disbelief and enjoy an otherwise good movie.)
- What are ways to protect and support it?
So, what are things we can do to enhance the health and function of the vagus nerve? If you’ve read my blogs before, or frankly anyone’s blogs about how to maintain your health, you know about exercise, good diet, microbiome health, sleep, and a low stress life. I’ll leave it to others to describe the details of those strategies, as well as meditation and yoga breathing techniques. (I will just emphasize that vagus nerve function really, really requires taking care of the gut microbiome.) Techniques that people don’t typically talk about when discussing heart rate variability and vagal health are things like positive social engagement, mindfulness, spirituality, gratitude and compassion. I know what you are thinking … and trust me, there is a part of me that still thinks “give me a break, how ‘woo-woo’ is this” when I hear this. Stick around for one more page, and then we’ll move on to other stuff that is completely practical and actionable.
Do you like it when someone is nice to you? Of course, who wants to be cut off and left flipping people the bird, body tingling with adrenaline and feeling a cold sweat? What you want is for people to slide to the left as you merge onto the highway, to move out of the left lane if they are going to drive 55 mph, and to move quickly through the crosswalk when you are trying to make a right on red. You want people to wait to take a lunch break until after they’ve taken care of you at the bank, to let you leave for home a half hour early on your birthday (and every Friday), and to give you a free refill on fountain drinks … at least during the Summer. What happens when you have positive experiences like these? You guessed it. Your vagus nerve takes notice and it shifts the balance of your autonomic nervous system against the pro-inflammatory sympathetic activation, in favor of rest, digest, and restore. Remember that the central nervous system is part of the immune system inasmuch as it is the proactive arm that recognizes danger and risks of injury so you can avoid it. That goes beyond recognizing rotten food and catching the eyeballs of alligators floating just below the waterline. It means recognizing rotten people and stressful situations when you’re up to your elbows in alligators and barely keeping your nose above the waterline. That wonderful third arm of the immune system is fully capable of recognizing emotional and mental risks as much as the physical, and those events have the ability to trigger inflammation just as effectively as physical trauma. For several decades, childhood trauma, especially emotional abuse and neglect, has been known to be associated with adult diagnoses of fibromyalgia. What is now being recognized is that life experiences of emotional mistreatment is as impactful on physical medical state as physical trauma. (Seriously … I’m not kidding … Mieko Yoshiyama and colleagues conducted a study of over 1300 women and showed that emotional and physical abuse were significantly associated with other medical problems, but also found that “there were no significant differences between those that reported emotional abuse only and those that reported emotional abuse plus physical or sexual violence.”) Now, I’m a big believer that old truisms are based on keen observations over countless examples and generations, and thus are most likely to actually be true. To my way of thinking, we simply have to spend the time to figure out the science to confirm them. However, I think the old saying that “sticks and stones may break my bones but words will never hurt me” looks like it is one that needs to be shot down. In fact, there are studies that actually suggest how this emotional neglect and abuse can cause long term physical problems. It looks like emotional stress and abuse, if it is chronic and severe, causes epigenetic changes in DNA methylation states (more on that in a separate blog) that literally alters gene expression levels and whether certain proteins are manufactured. There is also evidence that emotional abuse leads to changes non-coding RNAs that prevent the translation of messenger RNA into proteins, and modifications of histones that affect the accessibility of genes to be transcribed. (both important epigenetic factors).
- What are the ways the vagus nerve can be activated?
The vagus nerve can be stimulated by many of the same mechanisms that support its proper function, e.g., exercise, meditation, and deep breathing. There are also some ways to mechanically activate it (mini-versions of the original deep carotid massage concept) that include gargling, humming, and chanting … Gregorian style. Ice baths have also been shown to activate the vagus nerve, and some people swear by them, but to be honest, I really don’t think that would be my preferred way to activate my parasympathetic nervous system.
Despite the million ways that modern society has for activating our sympathetic nervous systems (and driving us into inflamed states by keeping us in sympathetic overdrive for our entire adult lives), modern technology has provided us all with a very easy way to increase parasympathetic tone, which is called vagus nerve stimulation, or VNS. VNS is a neuromodulation therapy, i.e., an electrical stimulation, of the key fibers within the vagus nerve. The fibers that are activated are the ones that increase stress resilience, provide better sleep quality (more deep sleep), enhance cognitive functions, and even reduce the inflammatory signals that come from excessive stress, sleep deprivation, and chronic sympathetic overdrive.
The original VNS devices were implanted, but over the past decade, non-invasive devices have made it to the market. One that was recently released is called Truvaga, and it is produced by the same company that received FDA clearances for the gammaCore medical device for the treatment and prevention of migraines and cluster headaches. Truvaga is a hand-held, non-invasive device that stimulates the vagus nerve through the skin for brief treatments of two minutes. Generally, I find that two minutes of “stim” in the morning is great for maintaining my stress resilience I need to get through the day (as a father of 4 kids between the ages of 11 and 16!), and another two minutes in the evening helps me fall asleep more peacefully and sleep more deeply than I was before.
- What does stimulation do?
Stimulation of the vagus nerve, if done at the right frequency and with the right strength, causes an activating signal to enter the brainstem to promote the release of some important neurotransmitters, including serotonin and norepinephrine. Both of these brain chemicals are targets of medications for depression, headache, fibromyalgia, anxiety, and other conditions. Those medications are designed to enhance the effects of the low serotonin and norepinephrine levels, because serotonin is important for both mood and pain perception (elevating the first and quieting the second), and norepinephrine is also important for enhancing pain thresholds. Instead of trying to keep the little that is naturally produced around for longer, VNS increases the production and release of them.
In addition to the release of serotonin and norepinephrine, vagus nerve stimulation triggers the release of acetylcholine from the nucleus basalis of Meynert. This neurotransmitter has remarkable anti-inflammatory effects throughout the brain and body. Studies have shown how quickly (within minutes) the innate immune cells of the brain begin to change their shape and activity. This is critical because these immune cells play vital roles in the maintaining cognitive function, i.e., learning, memory formation, and efficient recall and application of knowledge. When they are distracted by inflammation, they become destructive to the normal functioning off the brain.
Acetylcholine is also released by the vagus nerve throughout the chest and abdomen, where it wanders from one place to the next, sensing and influencing the behavior of peripheral organs and tissues. As in the brain, this acetylcholine release binds to receptors on immune cells and reduces their inflammatory activity, restoring them to their housekeeping tasks that maintain the system in its healthy state. As a result, VNS optimizes the body’s healthiest orientation as a system in homeostatic equilibrium.
- What can I hope to gain from VNS?
Even if you are a healthy person, you have undoubtedly experienced some degree of sickness, stress, trauma, and sleep deprivation in your life. You have likely, also, either eaten poorly for some portion of your life, or avoided exercise when you should have. If not, then you are a role model most of us don’t ever get to fully emulate. For the rest of us, we are carrying some percentage of our innate immune cells in an inflammatory posture that is not optimally maintaining our organs and other tissue (from the brain to bones, heart, lungs, liver, kidneys, and even reproductive organs). We have some of our cells under oxidative stress, some of them harboring disrupted DNA methylation states, and other dysregulated epigenetic factors. We may even have been primed by maternal inflammation that we were exposed to in the womb! Vagus nerve stimulation is a good way to optimize everything from inflammation state to protecting oxidative phosphorylation cycles in our mitochondria, to ensuring proper gene and protein expression.
What will a healthy person experience? More stress resilience and a feeling of relaxation should be a very quick response. Feeling mentally clearer, more alert, and more well rested after a night of sleep should be recognized within the first week to ten days.
- How can I get one?
There are a variety of devices that purport to stimulate the vagus nerve. The FDA approved implanted devices have preclinical studies and clinical trials that have demonstrated their effectiveness in activating the vagus nerve through electrodes physically wrapped around the vagus nerve. These require surgery and a prescribing physician (usually a neurologist treating epilepsy or a psychiatrist treating depression) willing to pass you along to a neurosurgeon because he or she has exhausted all medical treatments for your condition. The same is true of the gastroenterologists and endocrinologists who have to prescribe and then refer their patients for surgery to implant sub-diaphragmatic gastric pacing devices and so-called V-blocks for treating gastroparesis and obesity, respectively.
Of course, non-invasive options are far preferable for those who either don’t want surgery, or who just want to optimize their health by aligning their autonomic nervous system and innate immune system in a parasympathetically dominant and anti-inflammatory state (and why isn’t that everyone on the planet?). There are two main ways to non-invasively stimulate the vagus nerve. The first is at the neck, where the main branch of the vagus nerve travels inside the carotid sheath. The second is by activating a small branch of afferent-only nerves called the tragus nerve that exists in and around the ear canal. The latter appears to be a viable way to stimulate at least some of the benefits of vagus nerve stimulation, although a strict anatomical analysis suggests that this path has only 1-2% of the fibers of the overall vagus (which it actually merges with), and the tragus doesn’t take a direct path into the brainstem the way the primary branch of the vagus does (right into the nucleus tractus solitarius). Use of these ear stimulators, which are generally referred to as auricular stimulators, is generally recommended for at least 20-30 minutes per treatment, and some treatment regimens from Europe have patients using 5 to 6 hours of stimulation per day for treating epilepsy.
Now, an alternative that I have long preferred (and not just because I helped to develop it), is called cervical non-invasive VNS. It is available in a prescription strength version, called gammaCore, with FDA clearances to acutely treat and even prevent migraines, cluster headaches, and other really nasty headache conditions. It is also being studied in a number of other serious medical conditions, ranging from PTSD and Parkinson’s Disease, to auto-immune conditions and opioid withdrawal. The company that makes the gammaCore has just recently released a wellness version of the device called Truvaga. It is available online at truvaga.com.
[As an aside … Given that gammaCore and Truvaga are covered by dozens and dozens of U.S. patents (along with dozens outside the U.S. as well), and the company that makes them has been around for close to 20 years and it is publicly traded, it is very likely that any other device you find that claims to stimulate the vagus nerve at the neck is either a hoax, or is violating the inventors’ patents. Buying products that rip off the inventions of others isn’t just stealing, it makes inventors less interested in doing good for other people and make things.]
- How do I use it?
I’ll let the manufacturers of the auricular stimulators tell you how to use their devices, but as I understand them, it generally involves putting an earbud with an electrode on it in the ear, along with some gel or salt water to allow the signal to get through the skin.
The Truvaga is pretty simple to use. It involves placing a small amount of that same sort of gel described above on the rounded metal surfaces that are the stimulation heads of the device, and then placing them against the neck generally aligned along the notch between the trachea and the muscle at the side of the neck (called the sternocleoidomastoid, or SCM, for the anatomy geeks out there). That’s where you feel your pulse as well, which makes sense, since that’s where the vagus nerve runs. Once in place, the Truvaga has a pair of buttons that allow you to turn the device on and off. By pressing the button closer the stimulation heads, the device will turn on and then beep a few times as the chip inside boots up and displays the number of doses left (Truvaga devices are programmed to provide 300 two-minute doses, based on the reliable lifespan of the battery). By continuing to press down on the same button, the intensity of the stimulation increases steadily. At first, there is a mild tingling sensation, not unlike the feeling when your arm falls asleep. That becomes more intense until that SCM muscle in the neck starts to vibrate and flex. About 4 out of 5 people will start to feel a downward tug at the corner of their mouths. The company has done multiple studies top show that when that level is met, the stimulation is being transmitted into the vagus nerve. Two minutes is all that is needed per treatment for nearly everyone, and the company recommends twice per day for optimal wellness benefits. (I suggest in the morning and evening when you brush your teeth; or keep it on your nightstand for when you wake up and go to sleep. Others like to carry it with them during the day as well.) Other than a quick wipe of the gel from the neck, there is nothing else that is needed.
- How quickly will I experience results?
Everyone is different. Some people experience immediate benefits that range from relaxation in the neck, shoulders, and back to a feeling of pressure being lifted from their heads and neck. Others will experience a feeling of breathing more freely and deeply, both in the lungs and through the sinuses. Some will even experience a lift in mood as well. Studies show that inflammation levels will drop quickly, but the benefits of that drop may be difficult for many to perceive. This means that for others, the benefits may be better sleep, starting within a few days, or a feeling of more flexibility in the joints. Very interesting data from DARPA suggests that VNS will provide the users with more energy and clearer thinking and processing of information. That energy comes from an optimization of mitochondrial function and renewed oxidative phosphorylation activity. Changes in glucose tolerance and insulin sensitivity have also been reported, along with reductions in HbA1c measures. While not approved for diabetes, or hypertension, individuals with pre-diabetes may find benefits that heklp them avoid the diagnosis of diabetes.
The benefits of VNS are broad and extensive. The side effects of non-invasive stimulation are mild, transient, and inherently self-limiting, after all, if you want, you simply remove the earbud or pull the device away from your neck. The only significant issue that has been reported is that implanted vagus nerve stimulators, which deliver nearly three hundred 30-second to 2-minute stimulations, day and night, can exacerbate sleep apnea. Non-invasive devices simply aren’t used during sleep (although it is possible for someone to fall asleep with a stimulating earbud still on), and no clinical experiences that have been gathered over the past decade have suggested that a few doses, two minutes in duration, cause any risks associated with sleep disorders. To the contrary, sleep benefits are some of the most widely hailed benefits that accrue from use of VNS.
1 Yoshiyama, et al., The Role of Emotional Abuse in Intimate Partner Violence and Health Among Women in Yokohama, Japan, American Journal of Public Health, Vol 99, No. 4, p 647-653 (2009)
2 Yang, et al., Child Abuse and Epigenetic Mechanisms of Disease Risk, Am J Prev Med, Vol. 44(2) p. 101–107 (2013). doi:10.1016/j.amepre.2012.10.012.
3 Hollins, et al., MicroRNA: Small RNA mediators of the brains genomic response to environmental stress, Progress in Neurobiology, Vol., 143, p. 61–81 (2016)