What’s the connection between Nitric Oxide (NO) and mouth breathing?


Recently discovered (1998) Nitric Oxide (NO) is produced in the nasal mucosa and to a greater degree, the paranasal sinuses – underlining the importance of nasal over mouth breathing. NO has several important functions within the body.

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In 1998 Robert F. Furchgott, Louis J. Ignore and Ferid Murad were jointly awarded the Nobel Prize for their discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system.

 Nitric Oxide (NO) producing enzymes are found in the nasal mucosa and to a greater degree, the paranasal sinuses underlining the importance of nasal over mouth breathing. NO has several functions within the body including

Regulator of oxygen bonding to haemoglobin – see, Nitric oxide effect on the hemoglobin-oxygen affinity.

Signalling molecule in multiple body systems – see, NO as a signalling molecule in the nervous system .

A vasodilator, it decreases BP and increases tissue perfusion – see, Role of Nitric Oxide in the Cardiovascular and Renal Systems.

As a free radical itself, it acts as an intra-arterial anti-oxidant and coagulant – see, Inflammation-induced endothelial dysfunction involves reduced nitric oxide bioavailability and increased oxidant stress.

Shown (likely through respiration) to increase neurological and cognitive function – see, Impaired cognitive function and mental performance in mild dehydration.

A regulator of smooth muscle (bladder), hormones, erectile function and digestive health. – see, erectile dysfunction.

Nasal breathing acts as a flow limiter, increasing air flow resistance by up to 200% assisting the uptake of oxygen.

Mouth breathing disrupts orofacial muscular balance leading to abnormal developmental and jaw growth disturbance. It can lead to chronic hyperventilation, reduced perfusion, oxygen lowering and vasoconstriction.

Some surgical increases in “nasal cavity volume” can equally lead to problems for the same reason. “Empty nose syndrome is an effect form over treatment.

Mouth breathing can also cause sleep difficulties, causing  people to wake in the night, if they aren’t getting enough oxygen.

 In children, lack of sleep may reduce their ability to pay attention and concentrate at school, which may be mistaken for attention deficit disorder.

 Mouth breathing can be related to sleep apnea, causing people to wake frequently at night and excessive daytime sleepiness.

Think of these things next time you watch a child playing or watching something at rest with their lips apart, mouth breathing. If they sit without their lips together at rest, there is something wrong. Chances are this is a child that will end up having orthodontics as the teeth won’t fit the distorted dental arches.

Unfortunately, up until now the teeth have been straightened (‘ortho’ teeth – ‘dontia”teeth’). This results in straight (although unstable) teeth requiring retainers (it becomes your fault if you don’t wear them), rather than a functional (that’s the magic word) oral condition allowing adequate breathing.

Nitric oxide formation – increase you antioxidant intake.

Nitric oxide is an unstable molecule that degrades quickly in the bloodstream, so it must be constantly replenished – Nitric oxide metabolism and breakdown

One way to increase Nitric oxide stability and limit its breakdown is by consuming antioxidants,



Antioxidants are molecules that neutralize free radicals, which contribute to the short life of nitric oxide, see, Role of oxidative stress and nitric oxide in atherothrombosis.

These antioxidants are found in all foods but primarily those of plant origin, such as fruits, vegetables, nuts, seeds and grains. It is sometimes necessary to supplement such a diet with appropriate supplementation.

A few important antioxidants include:

Vitamin C: This antioxidant helps your body form connective tissues, including skin, bones, tendons and cartilage. It also produces brain chemicals that help nerve cells communicate.

Vitamin E: This antioxidant protects cells from the damaging effects of free radicals, which are thought to contribute to aging and disease. It also plays an important role in keeping the immune system strong – see,

Polyphenols: This category of antioxidants is associated with several health benefits, including a reduced risk of cancer and cardiovascular disease.

Glutathione: coined “the mother of all antioxidants,” glutathione is the master antioxidant and detoxifier of basically every cell in your body.

Several studies have found that ingesting nitric oxide precursors, such as nitrate or citrulline, with antioxidants maintains greater levels of nitric oxide in your body by helping reduce its breakdown.

See also, Tetrahydrobiopterin, l-Arginine and Vitamin C act synergistically to decrease oxidative stress, increase nitric oxide and improve blood flow after Induction of hindlimb blood flow reduction in the rat.

Long-term vitamin C treatment increases vascular tetrahydrobiopterin levels and nitric oxide synthase activity, improving blood flow and the positive effect of ascorbic acid supplementation on nitric oxide metabolites and systolic blood pressure in rats when exposed to certain poisons – eg. lead.

Vegetables that are high in nitrate are also inherently high in antioxidants, which is likely why vegetables are so effective at increasing and maintaining optimal levels of nitric oxide.


Good sleep is crucial to good health and longevity.


Dr. Stephen Bray 2019

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