Recently, there has been growing discussion about mouth breathing versus nose breathing. Is it actually bad to breathe through your mouth? And why does yoga place so much emphasis on breathing through the nose?
For yoga teachers, understanding the physiology behind breathing can help clarify why nose breathing is commonly encouraged in practice.
This article is adapted from an excerpt from my book The Physiology of Yoga.
Why the nose exists for breathing
The benefits of nasal breathing have been described in scientific literature since at least the 1950s (Cottle et al. 1958). The nose performs numerous protective and regulatory functions for the respiratory system.
Compared with mouth breathing, breathing through the nose helps to:
• warm and humidify inhaled air
• filter airborne particles, allergens, and pathogens
• slow the breathing rate
• support lung expansion and breathing mechanics
• support healthy development of the teeth and jaw
• reduce the risk of snoring and sleep apnoea
Nasal breathing also adds natural resistance to airflow. Air moving through the nose experiences roughly 50% more resistance than air moving through the mouth.
At first glance this might seem inefficient, but the resistance actually supports respiratory function. It tends to slow the breath, encourages deeper diaphragmatic breathing, and can increase oxygen uptake by approximately 10 to 20% due to improved breathing mechanics (McKeown, O’Connor-Reina, and Plaza 2021).
Slower breathing also helps maintain healthy levels of carbon dioxide, which plays an important physiological role in regulating blood pH, circulation, and oxygen delivery to tissues.
The nitric oxide advantage
Another fascinating feature of nasal breathing involves a molecule called nitric oxide, which is produced in the nasal sinuses.
Sometimes referred to as “the mighty molecule” (Chang 2011), nitric oxide contributes to several beneficial physiological processes. When we inhale through the nose, nitric oxide mixes with incoming air before it reaches the lungs.
Research suggests that nitric oxide may:
• improve oxygen uptake in the lungs
• enhance oxygen transport throughout the body
• support blood vessel dilation through relaxation of vascular smooth muscle
• provide antimicrobial effects against viruses, bacteria, fungi, and parasites
This means that nasal breathing may influence both respiratory efficiency and immune defence.
Nasal breathing and the nervous system
Emerging research also suggests that nasal breathing may interact with the nervous system.
The lining of the nasal cavity contains sensory receptors that may influence brain activity and autonomic regulation. Both animal and human studies suggest that nasal breathing could contribute to some of the regulatory effects observed in slow breathing practices (Zaccaro et al. 2018).
This area of research is still developing. However, it highlights an idea that yoga traditions have long emphasised: how we breathe can influence how we feel and function.
What about mouth breathing?
Mouth breathing is associated with several potential health concerns, including:
• increased allergic responses to airborne allergens
• asthma symptoms
• bad breath
• tooth decay and gum inflammation
• snoring and sleep disturbances
• altered dental or jaw development
Because of these associations, encouraging nasal breathing during yoga practice is often sensible.
A useful reminder for yoga teachers
Like most aspects of physiology, breathing is context dependent.
Nasal breathing tends to be beneficial at rest, during slow breathing practices, and during many forms of yoga. However, during high intensity exercise, the body may require a larger airflow than the nose alone can comfortably provide.
In those situations, mouth breathing may simply be the body’s natural way of meeting increased oxygen demand.
For yoga teachers, a helpful approach is to encourage nasal breathing when it is comfortable and sustainable, while recognising that breathing patterns may naturally change during more demanding activity.
For people who habitually breathe through the mouth, the slower and more mindful breathing practices often found in yoga can provide a valuable opportunity to gradually reintroduce nasal breathing.
References:
Chang, H.R. (2011). Nitric oxide, the mighty molecule: Its benefits for your health and well-being. Mind Society.
Cottle, M.H., Loring, R.M., Fischer, G.G., and Gaynon, I.E. (1958). The maxilla-premaxilla approach to extensive nasal septum surgery. AMA Archives of Otolaryngology, 68(3), 301–313.
McKeown, P., O’Connor-Reina, C., and Plaza, G. (2021). Breathing re-education and phenotypes of sleep apnea, a review. Journal of Clinical Medicine, 10(3), 471.
Zaccaro, A., Piarulli, A., Laurino, M., et al. (2018). How breath-control can change your life, a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience, 12, 353.