I was reading about the differences between mouth and nose breathing, and it seems that nitric oxide is beneficial to cardiovascular health, but that only breathing through one’s nose produces it. I couldn’t seem to find a simple explanation for it.
Edit to add: I thought this was a genuine question about something I didn’t understand but wanted to. So much(passive) aggression in the comments. Apologies. I was just trying to learn.
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**ELI5**: Nitric oxide is made all throughout your airways including your nose, mouth, trachea, and lungs. NO helps to keep your blood vessels open so they can absorb oxygen and get rid of CO2.
**More in-depth:** Nitric oxide (NO) is synthesized by NOS enzymes that are present throughout your nasal, oral, tracheal, and lung epithelium. NO is also used by the nervous system for signal transduction and the immune system in response to infection. NO is a potent vasodilator (opens blood vessels) which is why it’s commonly used to prevent heart attacks as the pro-drug nitroglycerin (Nitrostat). The NO pathway is also used by the erectile dysfunction drug sildenafil (Viagra) which enhances the effects of NO to increase blood flow to certain tissues.
Most studies on NO inhalation is in the context of treating disease (eg pulmonary hypertension, coronary artery stenosis) or detecting disease (eg asthma, cystic fibrosis). Some studies have found that nasal breathing generates more NO than oral breathing but the mechanism isn’t clear. Furthermore, it’s not clear whether these differences would have an affect on someone who is already healthy. The studies I read (and linked below) found increased oxygenation but the effect size was sometimes small (~5%) and the samples sizes were always small (<20 per study). At this point, we don’t have enough information to say whether or not nasal vs oral breathing has an affect on normal healthy people.
My personal opinion is that the benefits of nasal vs oral breathing are often overblown in pop science. We often do not have the evidence to back the claims many make on social media. That being said, there’s no harm to trying it out to see if it works for you.
Physiology of NO – [https://pubmed.ncbi.nlm.nih.gov/30342580/](https://pubmed.ncbi.nlm.nih.gov/30342580/)
More NO produced in nasal breathing than oral breathing (n = 10) – [https://pubmed.ncbi.nlm.nih.gov/12030725/](https://pubmed.ncbi.nlm.nih.gov/12030725/)
Increased lung oxygenation from nasal breathing (n = 15) – [https://pubmed.ncbi.nlm.nih.gov/19875719/](https://doi-org.ezproxy.library.tufts.edu/10.1152/japplphysiol.00285.2009)
Better exercise economy for nasal breathing (n = 10) – [http://www.journals.aiac.org.au/index.php/IJKSS/article/view/4400](http://www.journals.aiac.org.au/index.php/IJKSS/article/view/4400)
I never knew this. Is this why it’s recommended to inhale through the nose and exhale through the mouth when doing cardio workouts? Or is that just for the purpose of regulating your breaths?
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Looks like this been answered but you can increase the production of NO 20x by humming.
https://pubmed.ncbi.nlm.nih.gov/16406689/
If you take 5 mins of your day and do this, it’s meditative and you really feel a difference in your body. I usually do 5 deep breathes exhaling from my mouth to get rid of excess co2 and oxygenate my blood. Then I do deep inhales through my nose, with slow controlled hums out until you empty your lungs.
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Mouth breathing can’t allow contact with the enzymes because that also exposes those enzymes to your saliva (which will break them down) and when you swallow it will wash them down into your stomach. Thus you can’t have them between your oropharynx and your glottis.
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