Mouth and body
Some of the bacteria on your tongue are part of how your body uses dietary nitrate.
Researchers are studying how oral nitrate metabolism relates to vascular biology, including blood pressure. Here's the pathway, and what the studies have found so far.
Nitric oxide is a signaling molecule involved in how blood vessels widen and narrow. The body makes it two ways. One runs on an enzyme in your own cells. The other starts with nitrate from food — leafy greens, beets — which is absorbed, concentrated into saliva, and delivered back to the tongue, where bacteria reduce it to nitrite. Human cells do not perform that reduction efficiently, so this step depends on the microbial community. Studies that suppressed oral bacteria with antibacterial rinses found nitrite levels fell, and several reported measurable changes in vascular readings. The pathway is well described. How much it matters for any one person is still being worked out.
Blood pressure is regulated by many systems at once
Kidney handling of sodium and water, the renin–angiotensin system, the autonomic nervous system, hormones, vessel wall structure and stiffness — all of it contributes, continuously.
Nitric oxide signaling is one input among those. Keeping that proportion in mind is the difference between reading this page correctly and reading it as more than it is.
Nitric oxide and vascular tone
Nitric oxide diffuses into the smooth muscle of vessel walls and triggers relaxation. That relaxation is part of how vessels adjust their diameter moment to moment.
It is a short-lived molecule produced locally where it acts, which is why the supply routes for it are studied closely.
Dietary nitrate
Nitrate is abundant in leafy green vegetables and beets. Eaten, it is absorbed in the small intestine and enters the circulation.
Here the biology turns odd. Rather than being cleared, a substantial share is taken up by the salivary glands and concentrated into saliva at levels well above those in blood — an active process, which is generally a sign something is being done on purpose.
The enterosalivary cycle
Nitrate is swallowed, absorbed, concentrated into saliva, and delivered back to the mouth. On the tongue, bacteria reduce it to nitrite. The nitrite is swallowed, and further conversion downstream yields nitric oxide.
Human cells do not perform the nitrate-to-nitrite reduction efficiently. The loop runs through bacteria, which is the part worth sitting with. The full pathway is set out on the nitric oxide page.
The role of oral bacteria, and where they live
The reduction happens largely on the tongue's dorsum, in the deeper parts of the coating where oxygen is low — conditions that favor organisms which use nitrate as an alternative electron acceptor.
Veillonella, Actinomyces, Rothia and Neisseria are among the genera involved. They are ordinary residents of a healthy mouth, not unusual organisms.
What happened when oral bacteria were suppressed
This is where the pathway was tested rather than described. Investigators used antibacterial rinses, chlorhexidine among them, to suppress the oral community, then measured what followed.
Salivary and plasma nitrite fell. In studies that also recorded vascular readings, including one in treated hypertensive participants, measurable changes in blood pressure accompanied the drop. These are small experimental studies, and they are the most direct evidence that the oral step carries physiological weight.
Human evidence to date
What exists is a set of small, mostly short-term studies: rinse suppression experiments, dietary nitrate studies measuring nitrite and vascular responses, and observational work relating oral community composition to those readings.
They are consistent with a pathway that matters. They are not large trials with clinical endpoints, and nobody involved describes them that way.
Why effects vary between people
Oral communities differ, and so does nitrate-reducing capacity between individuals. Diet determines how much nitrate arrives. Periodontal disease has been associated with reduced nitrate-reduction capacity. Antibacterial rinse use, smoking and saliva flow all change conditions on the tongue. Age appears in this picture too, as does the structure of the community as a whole rather than any single organism.
Which is why a group-level finding does not transfer cleanly to an individual.
What is still being studied
Whether differences in oral nitrate-reducing capacity between people translate into differences in vascular readings over time. Whether changing that capacity changes anything durably. How the community as a system, rather than a species count, governs the conversion. All of it is open.
Where the research is
Where the relevant findings sit.
Nitrate from food is concentrated into saliva and delivered back to the mouth — the enterosalivary cycle.
Oral bacteria reduce nitrate to nitrite; human cells do not perform this step efficiently.
Nitric oxide is involved in the regulation of vascular tone.
Suppressing oral bacteria with antibacterial rinses lowers salivary and plasma nitrite.
In rinse-suppression studies that recorded vascular readings, measurable changes in blood pressure accompanied the fall in nitrite.
Nitrate-reduction capacity is reduced in periodontitis.
Whether between-person differences in oral nitrate-reducing capacity relate to vascular readings over time.
How the community as a whole, rather than any single organism, governs the conversion.
In context
The rest of blood-pressure regulation
Kidneys, hormones, the nervous system and vessel structure are all involved. Nitric oxide signaling is one input among several.
Diet
The pathway starts with nitrate from food. Without it arriving, the microbial capacity has nothing to act on.
The tongue
This is where the reduction happens, in the low-oxygen depth of the coating. What disturbs that surface changes the conditions.
Your physician
Blood pressure is measured with a cuff, over time, by someone who can interpret it. That measurement has nothing to do with this one.
How OraPath measures this
The Oral Balance Test targets the narG gene, which encodes part of the enzyme that performs the nitrate reduction. Detecting the gene indicates the capability is present — which is a different question from whether a related species happens to be there.
Those detections feed the Nitric Oxide System reading. It describes the oral step of the pathway: what your mouth can do with nitrate. It is a measurement of your oral microbiome, and it says nothing about your blood pressure.
Measure your nitrate-reducing capacity.
Curious what your oral microbiome looks like? The Oral Balance Test measures targeted organisms and microbial functions from a saliva sample processed in our Norman, Oklahoma laboratory.
Common questions
Do oral bacteria affect blood pressure?
Certain oral bacteria perform a conversion the body uses in nitric oxide production, and studies that suppressed those bacteria reported falls in nitrite alongside measurable changes in vascular readings. How much this matters for any one person is still being studied.
Does mouthwash raise blood pressure?
Experimental studies using antibacterial rinses to suppress oral bacteria reported lower nitrite and measurable changes in blood pressure readings. These were small, short-term studies designed to test the pathway.
What is the enterosalivary cycle?
Nitrate from food is absorbed, concentrated into saliva by the salivary glands, and delivered back to the mouth, where bacteria reduce it to nitrite before it is swallowed again.
Which bacteria reduce nitrate?
Veillonella, Actinomyces, Rothia and Neisseria are among the genera involved. They are ordinary residents of a healthy mouth.
Does the Oral Balance Test measure my blood pressure?
No. It measures the narG gene in a saliva sample, which indicates the oral capacity to reduce nitrate. Blood pressure is measured with a cuff, by your physician.
Why measure a gene rather than a species?
A species list says who is present. The gene says the capability is there. Related organisms do not all carry it, which is why presence and function are different questions.
References
- Lundberg JO, Weitzberg E, Gladwin MT. The nitrate–nitrite–nitric oxide pathway in physiology and therapeutics. Nat Rev Drug Discov. 2008;7(2):156–167.
- Hezel MP, Weitzberg E. The oral microbiome and nitric oxide homeostasis. Free Radic Biol Med. 2015;105:48–57.
- Kapil V, Haydar SM, Pearl V, et al. Physiological role for nitrate-reducing oral bacteria in blood pressure control. Free Radic Biol Med. 2013;55:93–100.
- Bondonno CP, Liu AH, Croft KD, et al. Antibacterial mouthwash blunts oral nitrate reduction and increases blood pressure in treated hypertensive men and women. Am J Hypertens. 2015;28(5):572–575.
- Vanhatalo A, Blackwell JR, L'Heureux JE, et al. Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans. Free Radic Biol Med. 2018;124:21–30.
- Vanhatalo A, L'Heureux JE, Kelly J, et al. Network analysis of nitrate-sensitive oral microbiome reveals interactions with cognitive function and cardiovascular health across dietary interventions. Redox Biol. 2021;41:101933.
- Tribble GD, Angelov N, Weltman R, et al. Frequency of tongue cleaning impacts the human tongue microbiome composition and enterosalivary circulation of nitrate. Front Cell Infect Microbiol. 2019;9:39.
- Rosier BT, Takahashi N, Zaura E, Krom BP, Marsh PD. The importance of nitrate reduction for oral health. J Dent Res. 2022;101(8):887–897.
- Rosier BT, Moya-Gonzalvez EM, Corell-Escuin P, et al. Nitrate reduction capacity of the oral microbiota is impaired in periodontitis. Int J Oral Sci. 2024;16:3.
Laboratory developed test · for adjunctive clinical use · not FDA cleared.