Endless books could be written on the science and importance of nose breathing. In fact, they have been. Around 1500 BCE, the Ebers Papyrus, one of the oldest medical texts ever discovered, offered a description of how nostrils, not the mouth, were supposed to feed air to the heart and lungs. From there, countless texts have outlined this idea and the science behind it. While I am no expert on the subject, I have become fascinated with a book that has helped bring this subject to my attention, and which goes into great details on the subject of nose-breathing and breath in general. I highly recommend reading or listening to this book, which is appropriately called Breath, by James Nestor.
Despite my hearty recommendation, I understand that some of you will not have the desire to invest your time into this book. While I cannot pretend to know as much as Nestor and his sources, I will do my best to touch on just a few of the most important takeaways from the book and those that helped create it.
Breathing through the nose is essential for innumerable reasons. To begin with, when breathing correctly through our noses, our bodies naturally switch between breathing through the right and left nostrils. This nasal cycle generally occurs every four hours, and plays a critical role in the balance of our biomarkers, hormones, and even brain function. When you're inhaling primarily through the right nostril, circulation speeds up, your body gets hotter, and cortisol levels, blood pressure, and heart rate all increase. This happens because breathing through the right side of the nose activates the sympathetic “fight-or-flight” nervous system. Breathing through the right nostril will also feed more blood to the opposite side of the brain, specifically to the prefrontal cortex, which has been associated with logical decisions, language, and computing. The left nostril is more deeply connected to the parasympathetic “rest-and-relax” nervous system, which lowers body temperature and blood pressure and reduces anxiety. Left-nostril breathing shifts blood flow to the opposite side of the prefrontal cortex, which plays a role in creative thought, emotions, formation of mental abstractions, and negative emotions.
Another extremely motivating reason to breathe through your nose is that mouth breathing can literally change the shape of your face, and not in a good way. There is no lack of research showing that consistently breathing through the mouth will eventually narrow the shape of the face as well as the dental arches. This means that there’s less room in the mouth to accommodate the tongue, which drops down to the floor of the mouth (instead of resting against the roof of the mouth). Aside from contributing to sleep disorders such as sleep apnea, the tongue dropping down into the floor of the mouth hinders mid-face development, which normally is pushed outward by the tongue when correctly positioned. Those who breathe through the mouth are more likely to develop facial structures that are long and narrow, which causes dental crowding and disfigurement. Narrow facial structures can also cause people to have less prominent jaws and a retracted chin.
If these facts aren’t fascinating and incentivizing enough, dentists and sleep researchers alike have also found that mouth-breathing contributes to bad breath and periodontal disease, and is believed by many to be the primary cause of cavities - yes, even more damaging than sugar consumption, bad diet, or poor hygiene. These professionals have also found that mouth-breathing while sleeping is both a cause of and a contributor to snoring and sleep apnea.
Lastly, and perhaps of most interest to those with an athletic focus, nasal breathing can boost nitric oxide sixfold compared to mouth breathing. Nitric oxide is a molecule that plays a critical role in increasing circulation and delivering oxygen into cells. Immune function, weight, circulation, mood, and sexual function can all be heavily influenced by the amount of nitric oxide in the body.
To take a quote from the book Breath of Life by George Catlin, "And if I were to endeavor to bequeath to posterity the most important Motto which human language can convey, it should be in three words— SHUT-YOUR-MOUTH... Where I would paint and engrave it, in every Nursery, and on every Bedpost in the Universe, its meaning could not be mistaken."