In part one of this series on improving vagal tone, I explained that the vagus nerve is the information superhighway of your autonomic nervous system. It connects your brain to organs and glands throughout the body and acts as the main conduit of your parasympathetic (“rest-and-digest”) nervous system. Vagal nerve activity touches just about every system in the body, including respiration, immunity, cardiovascular activity, digestion, and the gut microbiome.
The term “vagal tone” refers to how active your parasympathetic nervous system is. Ideally, we want high vagal tone, because that indicates a generally relaxed state where the body can focus on growth and repair. When vagal tone is low, the sympathetic (“fight-flight-freeze”) nervous system is dominant. That’s no good. The sympathetic nervous system should kick in when we need to respond to an acute threat or stressor, but we don’t want it running in the background all the time.
Unfortunately, a chronically stressed, sympathetic-dominant state is the norm for most people nowadays. Scientists are always on the hunt for ways to alleviate that stress and reduce the medical burden associated with it. Some researchers are investigating pharmaceutical means of improving vagal tone, along with protocols for using electrostimulation. You don’t need these high-tech procedures, though. Once you start digging into the science of the vagus nerve, you realize something cool: Most of the things we promote in the Primal community probably improve vagal tone.
Mark wasn’t thinking about the vagus nerve when he formulated the 10 Primal Laws. Yet, I suspect that vagus nerve stimulation is a common underlying thread connecting them. It’s an awesome example of science confirming what we already know: a Primal lifestyle reduces stress, builds resilience, and is an all-around better way to live. Here are some examples of popular Primal practices that are linked empirically to improving vagal tone.
Are you one of those Primal folks, like our own Brad Kearns, who absolutely loves their ice baths? Well, there’s a reason that it “hurts so good.” When you plunge into cold water, blood vessels constrict, and blood is redirected to your core. This triggers an increase in parasympathetic and a decrease in sympathetic activity. If you were measuring, you’d see your HRV rise as you chill (literally) in cold water.12 Friends who have managed to incorporate daily ice baths into their routine tell me that they start to crave it. When they skip a day, they feel off somehow. That’s probably because they aren’t getting the parasympathetic stimulation their bodies have come to expect.
Can’t quite bring yourself to immerse yourself in cold water? Try ending your normal shower with a blast of cold water. You’ll even get some of the same benefits from splashing cold water or applying ice packs to your face.3 Whole-body cryotherapy is another option.4
Interacting with other people and building strong social bonds is fundamentally human. We are meant to be in community with other people.Loneliness and social isolation are detrimental to both mental and physical health. Many large-scale research studies show that lonely or socially isolated folks are at greater risk for cardiovascular disease, chronic inflammation, suppressed immune function, and death.5
The autonomic nervous system likely plays a significant role in this process.6 Numerous studies have documented lower vagal tone among
Students studying abroad with few social connections in their host country8
Unmarried individuals, compared to married individuals9 (even better if you’re happily married10)
Lonely individuals aren’t able to buffer stress as well as their socially connected brethren. They are at greater risk of getting sick due to outside stressors or pathogens. A recent study even found that lonely participants with lower HRV also had shorter telomeres, a marker of cellular aging.11 The researchers concluded that when loneliness leads to decreased parasympathetic activity, we actually age faster!
It doesn’t take a whole village to be healthy, though it’s great if you have one. Psychologists believe that even one close relationship can make a big difference.
Can Social Connection Create an Upward Spiral of Health and Happiness?
In one study, researchers had participants engage in a loving-kindness meditation for one hour each week for six weeks.12 Loving-kindness meditation entails offering messages of love, compassion, and support to yourself and others—for example, the people closest to you, your community, your country, and all humanity. Results showed that the loving-kindness practice increased participants’ positive emotions and perceived social connection, which in turn improved vagal tone.
According to these findings, you don’t need actual social interactions to reap the benefits. Even thinking about meaningful social connections can raise vagal tone. Furthermore, the authors posit that this becomes a self-perpetuating cycle: social connection improves vagal tone, which increases positive emotions, which leads people to feel more connected, further boosting vagal tone, and on and on.
Some limited research also suggests that laughing,1314 chanting,15 and singing16—all activities that would traditionally be social in nature but which you can also do on your own—promote cardiovascular health, possibly by way of improved vagal tone.
Primal Blueprint Law #3 urges us to avoid being sedentary. Our ancestors would have moved frequently throughout the day by necessity, carrying out the everyday business of staying alive. Heart disease is relatively rare among traditionally living societies in part because they engage in so much consistent, low-level activity.17
One of the reasons exercise improves insulin sensitivity, cardiovascular health, and neurological function is that it increases brain-derived neurotrophic factor, or BDNF.18 BDNF has widespread effects throughout the body, and it just so happens to stimulate the vagus nerve.19
Any type of movement is probably beneficial as long as it doesn’t veer into chronic cardio territory. Small studies have documented HRV improvements with walking, especially in nature,20 Qigong,21 yoga,22 and tai chi.23 Some of the benefits might not be due to the movement per se, though. These practices all involve a breathwork component, and we know that slow and nasal breathing improve vagal tone independent of exercise.
Intermittent fasting yields well-documented health benefits, especially for cardiovascular disease risk factors, insulin sensitivity, inflammation and oxidative stress, and other markers of metabolic health. Many of these benefits are probably mediated at least in part by vagal activity. The vagus nerve communicates information between the brain and the body, facilitating the physiological response to fasting.24
As with exercise, intermittent fasting also stimulates BDNF production. Experts suggest that BDNF increases parasympathetic (vagal) activity in neurons connected to the gut, arteries, and heart.2526 Alternate day fasting and caloric restriction both raise HRV in rats.27 Fasting also suppresses sympathetic nervous system activity, and fasted rats are less stress reactive.2829 More research is needed in humans.
Although intermittent fasting does not necessarily imply caloric restriction, in practice, the two often go hand in hand. Caloric restriction by itself can increase HRV and parasympathetic activity.3031
Getting Your Omega-3s
Primal folks appreciate the myriad benefits of omega-3 fatty acids for reducing inflammation and improving immune function. That’s why we’re all eating plenty of small, oily fish and supplementing as needed, right?
Awesome, because omega-3s also elevate HRV and improve other cardiovascular health markers. Research has linked omega-3 intake to HRV in infants, healthy adults, dialysis patients, elderly individuals, and people with coronary heart disease and type 2 diabetes.32
Vagal tone is only one pathway by which omega-3s improve health, but hey, it’s as good a reason as any to whip up a batch of sardine butter, right?
Lindsay Taylor, Ph.D., is a senior writer and community manager for Primal Nutrition, a certified Primal Health Coach, and the co-author of three keto cookbooks.
As a writer for Mark’s Daily Apple and the leader of the thriving Keto Reset and Primal Endurance communities, Lindsay’s job is to help people learn the whats, whys, and hows of leading a health-focused life. Before joining the Primal team, she earned her master’s and Ph.D. in Social and Personality Psychology from the University of California, Berkeley, where she also worked as a researcher and instructor.
Lindsay lives in Northern California with her husband and two sports-obsessed sons. In her free time, she enjoys ultra running, triathlon, camping, and game nights. Follow along on Instagram @theusefuldish as Lindsay attempts to juggle work, family, and endurance training, all while maintaining a healthy balance and, most of all, having fun in life.