Why nasal breathing?

Somewhere along the way, breathing through the mouth became ordinary — unremarked, unremarkable. We do it when stressed, when sleeping, when sitting at a screen. The nose, by contrast, is not simply an alternate route. It does things the mouth cannot.

What the nose does.

The nasal passages filter, warm, and humidify incoming air before it reaches the lungs. That much is standard anatomy. Less commonly known is that the paranasal sinuses — the air-filled cavities surrounding the nasal cavity — produce a gas called nitric oxide in substantial quantities. In 1995, Lundberg and colleagues at the Karolinska Institute showed that nitric oxide concentration in sinus air is orders of magnitude higher than in the lower airways [Lundberg et al. 1995]. The gas has nowhere to go during mouth breathing. Breathe through your nose, and it travels down with each inhale.

Why does that matter? Nitric oxide is a vasodilator and bronchodilator — it widens blood vessels and relaxes airway muscle. A follow-up study by the same group demonstrated that nasally derived nitric oxide measurably modulates pulmonary function in humans [Lundberg et al. 1996]. There are also antimicrobial properties, which is part of why researchers suspect the sinuses produce so much of it. None of this means the effect is large or clinically decisive. But the mechanism is real and well-characterized.

The nose is not decoration. It is the first part of the respiratory system — and in most quiet moments, it is meant to do the work.

Resistance and rhythm.

Nasal passages create airflow resistance — noticeably more than the open mouth. That resistance is not a flaw. Cross-sectional research has found that habitual mouth-breathers show lower diaphragmatic amplitude compared to nasal breathers; accessory muscles compensate instead [Trevisan et al. 2015]. Breathing more slowly, more deeply, with the primary muscle of respiration doing its job — this tends to be the nasal pattern. How consequential that difference is over a lifetime is genuinely unknown.

The broader cardiovascular picture is murkier than popular accounts suggest. A small 2023 trial found that nasal breathing acutely lowered diastolic blood pressure and shifted heart rate variability toward greater parasympathetic tone in resting young adults [Watso et al. 2023]. Twenty participants. Five minutes per condition. The authors described their findings as “modest, but potentially clinically relevant.” That is an honest characterization. We quote it that way.

What the evidence does — and doesn't — say.

The mechanistic case for nasal breathing is solid. The sinus-to-lung pathway for nitric oxide, the filtration and humidification advantages, the diaphragm data — these are grounded in reproducible physiology. The larger claims circulating in popular wellness writing — that nasal breathing transforms sleep, reverses cardiovascular risk, meaningfully enhances athletic performance — rest on thinner ground. Most trials are small. Many are short. The enthusiastic extrapolations arrive faster than the controlled trials that would support them.

If you can breathe comfortably through your nose, doing so is almost certainly the better default for ordinary, quiet breathing. That is the reasonable conclusion from what we have. We are not suggesting you tape your mouth shut.

Evidence tier: peer-reviewed. The mechanistic evidence (nitric oxide pathway, filtration, airflow resistance) is well-established. Clinical evidence for broader cardiovascular and performance outcomes is preliminary — small trials, short durations. Claims in the popular literature often outrun the data.

A reasonable default.

breathe with me is built around nasal breathing. Not because the evidence demands it with certainty, but because the physiology points in a clear direction, and because returning attention to how you breathe — slowly, through the nose, with the body doing the work it was built to do — is, on its own, a worthy practice.

Sources

• Lundberg et al. 1995 - Lundberg JO, Farkas-Szallasi T, Weitzberg E, Rinder J, Lidholm J, Anggaard A, Hokfelt T, Lundberg JM, Alving K. High nitric oxide production in human paranasal sinuses. Nature Medicine. 1995;1(4):370–373.
• Lundberg et al. 1996 - Lundberg JO, Settergren G, Gelinder S, Lundberg JM, Alving K, Weitzberg E. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans. Acta Physiologica Scandinavica. 1996;158(4):343–347.
• Trevisan et al. 2015 - Trevisan ME, Boufleur J, Soares JC, Haygert CJP, Ries LGK, Correa ECR. Diaphragmatic amplitude and accessory inspiratory muscle activity in nasal and mouth-breathing adults: a cross-sectional study. Journal of Electromyography and Kinesiology. 2015;25(3):463–468.
• Watso et al. 2023 - Watso JC, Cuba JN, Boutwell SL, Moss JE, Bowerfind AK, Fernandez IM, Cassette JM, May AM, Kirk KF. Acute nasal breathing lowers diastolic blood pressure and increases parasympathetic contributions to heart rate variability in young adults. American Journal of Physiology — Regulatory, Integrative and Comparative Physiology. 2023;325(6):R797–R808.