The air we breathe in through our nose passes through tiny little hairs called cilia. The cilia help filter out small particles in the air like pollen as well as humidify and warm or cool the air before entering the lungs. It’s estimated that the cilia in our nose protect us from 20 billion particles every day.
Also, as air passes through our nose it gets mixed with nitric oxide. Nitric oxide helps in two ways: it’s a vasodilator, so it helps open the airways, arteries and capillaries so oxygen-rich blood can flow more easily; and nitric oxide is antifungal, antiviral, antiparasitic and antibacterial so it helps your immune system to fight off infections.
Once the air passes through your nose, it goes through your windpipe, which also helps trap unwanted particles from entering your lungs.
When you breathe through your mouth, you bypass all of these natural defenses your body has created and let unfiltered air straight into your lungs.
Additionally, because inhaling and exhaling through your nose takes longer than breathing through your mouth, nose breathing can reduce hypertension and stress literally forcing you to “slow down and take a deep breath.”
In addition to reducing snoring and apneaic episodes (sleep apnea), nose breathing also helps activate the parasympathetic nervous system, producing a relaxed feeling in the body that leads to deeper sleep.
This is because when you breathe through your nose, you take fuller and deeper breaths that stimulate the lower lungs which are full of parasympathetic nerve receptors.
Mouth breathing on the other hand stimulates the upper lungs which are full of sympathetic nerve receptors that trigger our fight or flight response, leaving us in a constant state of stress and leading to poor sleep quality.
Think Dr. Seaman is crazy for taping his mouth shut and then running up a mountain? He’s not alone in his belief that nose breathing can increase performance.
A recent study of 10 runners found that while nasal breathing didn’t increase the amount of oxygen they could consume, it did lower their respiratory rate and breaths per minute. This was found to allow the oxygen in each breath more time to be absorbed by the body before being expelled, letting more oxygen reach each cell.