Did you know that CO2 isn’t just a byproduct, but it’s both a narcotic gas and hormone? “Take a big deep breath,” is what I was taught to do in order to calm my nerves. While this is a great first start, it is a gross under representation of the power of breath.

Now scientists like Stephen Porges and Sue Carter are explaining the connection between breath, health, social behavior, human evolution, and ancient religious and spiritual practices. Extreme athletes like Wim Hof have shined a light on how breath manipulation can have seemingly superhuman effects, while author James Nestor’s New York Times bestselling book Breath takes an in-depth look at breathing throughout the ages. All of this, it turns out, is really just manipulation of the autonomic nervous system.

I recently closed the gap in my knowledge on this topic when I watched David Blaine discuss hypercapnia on the Joe Rogan Experience. I also discovered that The Journal of Yoga and Physical Therapy has an in-depth review article on hypercapnia and the nervous system. What is actually going on physiologically between the breath and the body? It’s all about carbon dioxide. Let me try to explain…

Breathing is the first life or death challenge babies face when entering this world. It’s the first program you download to survive. It’s so primal, so basic, and so foundational that your subconscious (a.k.a. the body) absorbed it long ago and you probably didn’t think about it again until maybe one day when you realized that your heart was racing, your body was tense, and you couldn’t think straight. Sound familiar? I was totally in denial about my anxiety disorder for years and I eventually developed an autoimmune disease. This is how the subconscious functions. It streamlines automations to free up consciousness for other things. In this case, fear was my body’s automation. Over time, it adjusted to a nervous state and forgot how to settle back into homeostasis.

So what’s actually happening on the inside? It turns out that the tenth cranial nerve, a.k.a. the vagus nerve, is responsible for switching you into a rest and digest mode (parasympathetic) or a fight-flight-freeze mode (sympathetic). This system is completely involuntary, however, it is influenceable. Breath is the only way to effect the autonomic nervous system and CO2 is the mechanism! Steven Porges’ polyvagal theory debunks Darwin’s competition-based “survival of the fittest” mantra by suggesting that our health and evolution favors a calm physiological state. It is actually our ability to love that has evolved the part of our brain which makes us unique as primates, Dr. Porges suggests. Our prefrontal cortex has the ability to calm down the limbic system, which is responsible for the fight-flight-freeze response.

Carbon dioxide is uniquely metabolized in every cell in the body and signals physiological and behavioral changes. In other words, by definition, CO2 is a hormone. Carbon dioxide doesn’t just chemically trigger breathing, it acts as a switch that regulates the autonomic nervous system. Increased CO2 in the blood facilitates parasympathetic physiology while decreased CO2 in the blood facilitates sympathetic physiology.

Before learning this, my paradigm for breathing was focused on oxygen, not carbon dioxide. Hmm. So… when we gasp for air, we are not actually gasping for oxygen, we are gasping to remove a build-up of CO2 from our system? Yes, because you can learn to ease this gasp reflex without running out of oxygen.

When we are stressed or in fear, our breathing shallows and quickens. This is known as chest breathing. This quick exhale pattern causes carbon dioxide to be expelled at a faster rate. The dorsal vagal pathway (sympathetic) is stimulated and triggers the production of hormones like cortisol and adrenaline to help escape danger.

On the contrary, when we prolong the exhale, CO2 builds up in the blood stream. Extreme build-up is called hypercapnia and is classified as 45 mmhg. Receptors in the brain stem sense the carbon dioxide in the blood stream and trigger a gasp reflex that travels through the vagus and glossopharyngeal nerves. With practice, it is possible to extend the period of time that passes between the pause (or extended breath) and the gasp reflex. Training the body to tolerate higher levels of carbon dioxide allows the vagus nerve to slow the heart rate and lowers the body’s ph. Carbon dioxide then acts as a mild tranquilizer on your brain and body. Too much CO2 will eventually make you pass out, but there is a vast, pliable threshold before this mechanism takes place.

It is possible to build-up CO2 in the blood by holding the breath on the inhale, however, it does not elicit the same calming response from the nervous system. The exhalation phase is the natural state of rest, characterized by a loop where movement integrates chemistry and visa-versa.

What does this all mean? Chest breathing causes the nervous system to push energy to the extremities in response to a low CO2 signal. Sub-diaphragmatic breathing causes energy to flow towards the internal organs in response to a high CO2 signal. Think about it this way, if you don’t have access to oxygen, your body needs to become as efficient as possible to survive. Carbon dioxide tells your brain to send all of it’s energy to the vital organs.

So literally when the parasympathetic pathway is dominant, your heart and organs have the energy needed to feel, sense, remember, work, and radiate a positive electronic frequency. Moreover, this parasympathetic state allows the organs to signal production of hormones like oxytocin, (a.k.a. the love hormone). Our health thrives on these hormones, which are triggered and strengthened by positive social interaction, and bodily sensations such as touch, smell, and sound. The expression “love heals all” is finally being scientifically understood! It takes a lot of energy for the body to be in a constant fight or flight mode and evolutionarily, it’s totally unsustainable. Compassion and social interaction is what lowers entropy, building order out of chaos. Our survival literally depends on it.

Researcher Steven W. Cole has identified that there are at least two physiological states associated with the sympathetic nervous system. The first happens when someone feels just slightly worried and fearful. This sets off a series of chemical reactions in the body. The more severe state happens when someone experiences complete disconnection with themselves and humanity, as is the case in physical and emotional trauma. This has been coined the defeat-withdrawal response. If not corrected, the body carries itself in a way that reflects this altered physiological state, which can set the stage for opportunistic pathogens, cancer, and auto-immune diseases to take the lead.

A lowered mental, emotional, and physiological state is often accompanied by a caving inward, slouching forward, clenching the buttocks, and tilting the pelvis. This structural change makes it nearly impossible to relax the neck and chest to be able to breath into the lower diaphragm. This creates a situation where the structural body is now reinforcing the chemical body that was caused by the emotional body. Then doctors and physical therapists play wack-a-mole with symptoms that arise from an emotional state, never addressing the root cause. The reality is that there is a delicate interplay between our minds, bodies, and emotions.

Breath has been the subject of Yogis and Chi Gong practitioners for centuries. They teach us that in order to release emotions and tensions that keep us locked into neurological pathways, it is necessary to practice surrendering to gravity at the bottom of the exhale. For instance, holding a pose during the exhalation phase allows the prefrontal cortex to calm down the sympathetic nervous system. It also re-wires the brain/gut access towards regeneration and strengthens core muscles, making it easier to maintain a controlled breath outside of practice. The key is a deep, long exhale that transcends the length of the inhale and fully engages the lower diaphragm. Learning to exhale a bit more will allow carbon dioxide to act as natures’ medicine.