Your Mouthwash Might Be Working Against You
The bacteria your body actually needs
Your mouth is home to over 700 species of bacteria. Some cause cavities. Some cause gum disease. But others do something pretty remarkable — they help produce nitric oxide, a molecule your heart and blood vessels depend on to work properly.
Here is how that works:
- You eat vegetables rich in nitrate. Think spinach, beets, arugula.
- Your body absorbs those nitrates and concentrates them in your saliva at levels 10 to 20 times higher than in your blood.
- Specific bacteria living on your tongue convert those nitrates into nitrites.
- Your body then turns those nitrites into nitric oxide — a molecule that relaxes blood vessels, lowers blood pressure, and supports healthy circulation to every organ.
About half of your body's nitric oxide comes from this pathway. Without the right oral bacteria, it simply shuts down.
The bacteria responsible — Rothia, Neisseria, Haemophilus, and Veillonella — are the same ones Cnvrg measures in your Oral Microbiome Assessment.
What antiseptic mouthwash actually does
It does not just kill bad bacteria. It kills the ones making nitric oxide too.
Dr. Vikas Kapil and his team at Queen Mary University of London studied what happens when you use chlorhexidine mouthwash — the most common prescription-strength antiseptic rinse — for just seven days.
Here is what they found:
- Oral nitrite production dropped by 90%
- Plasma nitrite levels fell by 25%
- Systolic blood pressure went up by 2 to 3.5 mmHg within a single day
- The rise in blood pressure directly tracked with the drop in nitrite
(Kapil et al., Free Radical Biology and Medicine, 2013, n = 19)
To put that in perspective, even a 2 mmHg bump in systolic blood pressure is associated with a 10% higher risk of stroke mortality and a 7% higher risk of dying from heart disease in middle-aged adults.
In a follow-up study, Kapil's group used 16S rRNA gene sequencing — the same technology Cnvrg uses — and showed that chlorhexidine caused a major shift in the oral microbiome. Diversity dropped, saliva became more acidic, and nitrite availability fell significantly.
(Kapil et al., Free Radical Biology and Medicine, 2018)
It is not just prescription rinses
A three-year study of more than 1,200 adults found that people who used any over-the-counter mouthwash twice a day or more had:
- 55% higher risk of developing prediabetes or diabetes
- 85% higher risk of doctor-diagnosed hypertension
...compared to people who used mouthwash less often or not at all. The likely reason? Chronic suppression of the oral pathway that produces nitric oxide.
(Joshipura et al., San Juan Overweight Adults Longitudinal Study)
A 2025 analysis from the same group confirmed it. Frequent mouthwash users had significantly lower serum nitrite levels — the direct marker of disrupted nitrate reduction in the mouth.
(Guo et al., Frontiers in Oral Health, 2025)
Why this matters — Dr. Nathan Bryan
Dr. Nathan Bryan, one of the world's leading nitric oxide researchers, has spent years studying this connection.
"Nitric oxide is one of the most important signaling molecules produced in the human body. Yet the very first thing over 200 million Americans do each day is use an antiseptic mouthwash, which destroys the good bacteria that helps to create it."
"Mouthwash does to the oral microbiome what antibiotics do to bacteria in the gut. It wipes out the good and the bad alike."
Bryan's work comes down to a simple point: you cannot make enough nitric oxide without a healthy oral microbiome. And without nitric oxide, blood pressure regulation, circulation, wound healing, and even exercise performance all take a hit.
A clearer way to think about rinses
Not all rinses act the same way on your microbiome. The published evidence supports thinking about them in three tiers, based on how they work:
Tier 1 — Prebiotic rinses. These don't kill bacteria. They feed the right ones. Nitrate-containing rinses fall in this category, as do L-arginine rinses. Both shift your community toward health-associated species without collateral damage.
Tier 2 — Microbiome-neutral antimicrobials. These prevent cavities or other problems without significantly altering your bacterial community. Sodium fluoride rinses are the cleanest example — proven to prevent enamel demineralization without disrupting the microbiome.
Tier 3 — Broad-spectrum bactericidal rinses. These kill bacteria indiscriminately — the bad along with the good. Chlorhexidine, alcohol-based rinses, and CPC fall here. They have legitimate clinical uses (post-surgical care, acute infections) but real costs when used daily.
The goal isn't to stop caring for your mouth. It is to choose rinses that don't destroy the bacteria your body needs in the process.
What to use instead
Sodium fluoride (NaF) rinses
The most microbiome-friendly antimicrobial rinse with clinical evidence. NaF at standard concentrations completely prevented enamel demineralization in lab studies without affecting biofilm composition or bacterial growth. It works by inhibiting acid production rather than killing bacteria. A 2023 review concluded that fluoride-containing oral hygiene products may have beneficial effects on the oral microbiome for caries prevention without causing dysbiosis. (Thurnheer & Belibasakis, Archives of Oral Biology, 2018; Moran et al., Toxicology Letters, 2023)
Nitrate-containing rinses (the prebiotic concept)
The most actively pro-microbiome approach in the research. In lab studies, a single dose of nitrate increased Neisseria by 3.1× and Rothia by 2.9× within 5 hours, while reducing cavity-associated and periodontitis-associated genera in the same biofilm. A nitrate-and-antioxidant mouthwash tested in animals raised nitrate-reducing bacteria and lowered blood pressure. These aren't yet widely commercial, but they represent the direction the science points. (Rosier et al., Scientific Reports, 2020; Senkus et al., Scientific Reports, 2025)
L-Arginine rinses
Arginine works through a prebiotic mechanism — it's metabolized by the protective oral streptococci (S. sanguinis, S. gordonii) to produce ammonia, which raises pH and suppresses cavity-causing S. mutans without killing bacteria. In one clinical study, an arginine-containing dentifrice normalized the oral microbiome of cavity-prone individuals to look like cavity-free controls. (Agnello et al., Journal of Dental Research, 2017)
Hydroxyapatite rinses
Hydroxyapatite is the mineral your teeth are made of. In one in situ study, hydroxyapatite mouthwash reduced biofilm coverage comparably to chlorhexidine but without killing bacteria — it works by blocking adhesion rather than disrupting your microbiome. The evidence is mixed, though: a separate 48-hour study found no anti-adherent effects. The category is promising but not yet definitively validated. (Kensche et al., Archives of Oral Biology, 2017; Schestakow et al., Archives of Oral Biology, 2022)
Xylitol and erythritol
These natural sugar alcohols target cavity-causing bacteria like Streptococcus mutans while leaving beneficial species alone. A 2025 study found that erythritol combined with nitrate actually increased the abundance of Neisseria subflava and Haemophilus parainfluenzae — the exact nitrate-reducing bacteria you want more of. (Journal of Oral Microbiology, 2025)
Oral probiotics
Probiotic lozenges with strains like L. salivarius and L. rhamnosus help recolonize beneficial species and crowd out harmful bacteria — without the collateral damage of antiseptic rinses.
Salt water
The simplest option. Alkalizing, gentle, and recommended by Dr. Bryan's own N1O1 platform as a safe everyday alternative.
What to avoid for daily use
| Ingredient | Why |
|---|---|
| Chlorhexidine (CHX) | Reduces nitrate-reducing capacity by 78–85%; depletes Rothia, Neisseria, Haemophilus |
| Alcohol-based rinses | Kills bacteria indiscriminately; dries out your mouth |
| Cetylpyridinium chloride (CPC) | Recently shown to block oral nitrate conversion |
| Monofluorophosphate (MFP) | Less microbiome-friendly than sodium fluoride; reduces diversity |
These products have their place — your dentist might prescribe them for a short time after surgery or for an acute infection. But using them every day comes with a cost your mouthwash bottle does not mention.
A 2025 dental practitioner update in the British Dental Journal put it directly: mouthwashes "may not be of much value in those with good periodontal health or low caries risk." Sometimes the best rinse is no rinse at all. (Brookes et al., British Dental Journal, 2025)
How Cnvrg connects the dots
This is exactly what Cnvrg was built to measure. Our Oral Microbiome Assessment uses the same 16S DNA sequencing found in the research above to identify the bacteria in your mouth — including the nitrate-reducing species that produce nitric oxide.
When we pair that data with your blood biomarkers — like high-sensitivity CRP, an inflammation marker — and your sleep patterns, we can see how your oral health connects to your whole-body health in ways no single test can.
Oral. Blood. Sleep. Longevity. Three signals. One measure of resilience.
---
Sources
- Kapil V, et al. Physiological role for nitrate-reducing oral bacteria in blood pressure control. Free Radical Biology and Medicine. 2013. PMID 23183324
- Kapil V, et al. Sex differences in the nitrate-nitrite-NO pathway. Free Radical Biology and Medicine. 2018. PMID 30031863
- Bryan NS, et al. Tongue microbiome and resting blood pressure. Frontiers in Cellular and Infection Microbiology. 2019.
- Guo K, Joshipura K, et al. Association of over-the-counter mouthwash use with markers of nitric oxide metabolism. Frontiers in Oral Health. 2025.
- Rosier BT, et al. Nitrate as a potential prebiotic for the oral microbiome. Scientific Reports. 2020. PMID 32737394
- Thurnheer T, Belibasakis GN. Effect of sodium fluoride on oral biofilm microbiota and enamel demineralization. Archives of Oral Biology. 2018.
- Agnello M, et al. Arginine improves pH homeostasis via metabolism and microbiome modulation. Journal of Dental Research. 2017.
- Moran GP, et al. Does fluoride exposure impact on the human microbiome? Toxicology Letters. 2023.
- Senkus KE, et al. Functional mouth rinse containing inorganic nitrate and antioxidants bolsters the enterosalivary pathway and lowers blood pressure in Wistar rats. Scientific Reports. 2025.
- Brookes Z, et al. An update on mouthwashes: advice for dental practitioners. British Dental Journal. 2025.
- Kensche A, et al. Efficacy of a mouthrinse based on hydroxyapatite to reduce initial bacterial colonisation. Archives of Oral Biology. 2017.
- Schestakow A, et al. Influence of a hydroxyapatite suspension on 48-h dental biofilm formation in-situ. Archives of Oral Biology. 2022.
- N1O1 Education: Oral Health and Nitric Oxide. https://n1o1.com/education/oral-health-and-nitric-oxide/