Recently, a lot of attention has been paid to mouth breathing versus nose breathing. Is it bad to breathe through your mouth? Why is there such a focus on nose breathing in yoga? Read on to find out more, in an exclusive excerpt from The Physiology of Yoga.

The benefits of nose breathing have been explored and described in the scientific literature since at least the 1950s (Cottle 1958). The nose has at least 30 health-protecting functions, and nose breathing, as opposed to mouth breathing, is understood by McKeown, O’Connor-Reina, and Plaza (2021) to

• warm and humidify inhaled air;

• filter air, reducing exposure to foreign substances and pathogens;

• increase oxygen uptake and circulation;

• slow down breathing rate;

• improve lung volume;

• support the correct formation of the teeth and mouth; and

• lower your risk of snoring and sleep apnoea (a disordered, stop–start breathing condition).

Nose breathing also imposes approximately 50% more resistance to the air stream than mouth breathing. While air resistance might not sound like a good thing for breathing, such resistance results in 10 to 20% more oxygen uptake because of the biomechanics of slowed breath. Additionally, sufficient nasal resistance during inhalation allows the diaphragm to work more efficiently and maintains elasticity of the lungs. Furthermore, this resistance to breathing slows the breathing rate, allowing our bodies to retain an ideal amount of carbon dioxide, which is not just a waste product but serves several important roles in the body.

Nasal breathing also allows for the mixing of inhaled air with a gas called nitric oxide, which is produced in the nasal sinuses. Called “the mighty molecule” by Chang (2011), nitric oxide improves the lungs’ ability to absorb oxygen; increases our ability to transport oxygen throughout the body; allows blood vessels to dilate through the relaxation of vascular smooth muscle; and serves antifungal, antiviral, antiparasitic, and antibacterial purposes.

Meanwhile, mouth breathing is associated with a number of problems, including increased allergic reactions to allergens, asthma, bad breath, tooth decay, gum inflammation (gingivitis), snoring, and teeth or jaw abnormalities. Truly, the benefits of nose breathing seem manifold, and breathing through the nose during a yoga practice is a good idea. However, as is often the case with physiology, there are exceptions to this rule. Because nose breathing is slower, it might not be sufficient for high-intensity exercise when oxygen needs are much greater than at rest. In such cases, it is best to let your body decide how it needs to breathe. For chronic mouth breathers, though, the slow and mindful breathing practices of yoga can be very powerful.

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References: 

Chang, H.R. 2011. “Nitric Oxide, the Mighty Molecule: Its Benefits for Your Health and Well-Being.” Mind Society.

Cottle, M.H., R.M. Loring, G.G. Fischer, and I.E. Gaynon. 1958. “The Maxilla-Premaxilla Approach to Extensive Nasal Septum Surgery.” AMA Archives of Otolaryngology 68 (3): 301-313.

McKeown, P., C. O’Connor-Reina, and G. Plaza. 2021. “Breathing Re-Education and Phenotypes of Sleep Apnea: A Review.” Journal of Clinical Medicine 10 (3): 471.