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Exercise and Mouthwash

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This new study [1] along with the popular press article about it seem crazy at first, but it actually makes sense.

In a double blind, placebo-controlled, crossover trial, the researchers found that blood pressure was decreased and tissue oxygenation was increased for several hours after exercise on a treadmill. This is not surprising.

But when subjects gargled with an antibacterial mouthwash 30min after exercise, these beneficial post-exercise changes to blood pressure and tissue oxygenation were eliminated.

It is well known that bacterial in the mouth convert nitrate to nitrite which in turn gets converted into the vasodilator nitrous-oxide. This process seems to happen acutely after exercise with beneficial results. The authors conclude:

These findings show that nitrite synthesis by oral commensal bacteria is a key mechanism to induce the vascular response to exercise over the first period of recovery thereby promoting lower blood pressure and greater muscle oxygenation.

This confirms Dr. Greger's advice from this video to avoid antibacterial mouthwash and toothpaste because they can interfere with the elaborate way the body converts dietary nitrates (e.g. from beets) into cardioprotective nitrous oxide. 



[1] Free Radic Biol Med. 2019 Jul 29;143:252-259. doi:

10.1016/j.freeradbiomed.2019.07.035. [Epub ahead of print]

Post-exercise hypotension and skeletal muscle oxygenation is regulated by
nitrate-reducing activity of oral bacteria.

Cutler C(1), Kiernan M(2), Willis JR(3), Gallardo-Alfaro L(4), Casas-Agustench
P(1), White D(1), Hickson M(1), Gabaldon T(5), Bescos R(6).

Post-exercise hypotension (PEH) is a common physiological phenomenon leading to
lower blood pressure after acute exercise, but it is not fully understood how
this intriguing response occurs. This study investigated whether the
nitrate-reducing activity of oral bacteria is a key mechanism to trigger PEH.
Following a randomized, double blind and crossover design, twenty-three healthy
individuals (15 males/8 females) completed two treadmill trials at moderate
intensity. After exercise, participants rinsed their mouth with antibacterial
mouthwash to inhibit the activity of oral bacteria or a placebo mouthwash. Blood 
pressure was measured before, 1h and 2 h after exercise. The microvascular
response to a reactive hyperaemia test, as well as blood and salivary samples
were taken before and 2 h after exercise to analyse nitrate and nitrite
concentrations and the oral microbiome. As expected, systolic blood pressure
(SBP) was lower (1 h: -5.2 ± 1.0 mmHg; P < 0.001); 2 h: -3.8 ± 1.1 mmHg,
P = 0.005) after exercise compared to baseline in the placebo condition. This was
accompanied by an increase of circulatory nitrite 2 h after exercise (2h:
100 ± 13 nM) compared to baseline (59 ± 9 nM; P = 0.013). Additionally, an
increase in the peak of the tissue oxygenation index (TOI) during the reactive
hyperaemia response was observed after exercise (86.1 ± 0.6%) compared to
baseline levels (84.8 ± 0.5%; P = 0.010) in the placebo condition. On the other
hand, the SBP-lowering effect of exercise was attenuated by 61% at 1 h in the
recovery period, and it was fully attenuated 2 h after exercise with
antibacterial mouthwash. This was associated with a lack of changes in
circulatory nitrite (P > 0.05), and impaired microvascular response (peak TOI
baseline: 85.1 ± 3.1%; peak TOI post-exercise: 84.6 ± 3.2%; P > 0.05). Diversity 
of oral bacteria did not change after exercise in any treatment. These findings
show that nitrite synthesis by oral commensal bacteria is a key mechanism to
induce the vascular response to exercise over the first period of recovery
thereby promoting lower blood pressure and greater muscle oxygenation.

Copyright © 2019 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.freeradbiomed.2019.07.035 
PMID: 31369841 

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Yes, I was going to post this crazy thing, but you beat me to it, Dean. In general, I suspect it's again one of those cases where the more we know, the more we realize just how much we don't know. I remember a long-standing concern about mouthwashes has been disturbing the bacterial ecosystem in your mouth. When you brush your teeth, you are removing bacteria wholesale, all and sundry, but what if when you use mouthwash, you preferentially remove some strains more than others, thus disturbing the natural balance. When you change your diet, you too can affect the composition of the gut biome. 

Totally anecdotally, there was a period of time many years ago, where I used mouthwash, having read that various mouthwashes cut down on gingevitis bacteria by 13% over just brushing. I was using it systematically and had impeccable hygiene of brushing and flossing too. Despite this, my gums never felt - at that time - to be particularly awesome, just adequate. But then I stopped the mouthwashes over various concerns (cancer etc.), and on my next checkup, my dentist complimented me on the excellent state of my gums. I never used mouthwash again. 

Who knows what other common practices that we think of as healthy today, are actually midly (or not so mildly) detrimental. There's a bacterial ecosystem on your skin, in fact different environments on different parts of your skin over your body - antibacterial soaps and wipes are suspect. And so on, endlessly.

But to balance all this off - my blood pressure is about as low as is healthy I think (I started a whole thread about it), and any lower would probably be not optimal. So, I'm not all that excited to have my blood pressure lower yet. Of course, perhaps there are other consequences of disturbing the bacterial ecosystem, so who knows.  

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Interesting study.

My dentist has always advised against mouthwash, suggesting using salt water solution instead (which presumably kills bacteria just as indiscriminately).

Funny enough, I had been researching oral probiotics, as I just got my Nebula Genomics saliva results, which show that I have a relatively high level of Porphyromonas (which is associated with gingivitis).

After some comparisons, I realized that my current probiotic of choice has the same bacteria which is commonly found in the much more expensive, and also less potent, oral probiotics. So I started opening a capsule of NewRhytm 20 Strains and dissolving its content in water, with which I rinse my mouth at night (and swallow it, too).

I do this about 20-30 minutes after I brush my teeth and rinse with salt water solution. Is it beneficial? I have no idea, but it makes sense that it should be, at least to me. I'll see what my dentist says in a few months

Edited by Ron Put
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I am also wondering if it's worth trying something like a probiotic toothpaste, like PeriBiotic, which contains dead Lactobacillus paracasei. Found a very small study which seems to indicate benefits:

"Background: Probiotics are live microorganisms which when administered in adequate amounts confer health benefits on the host. Commonly, most of the organisms ascribed as having probiotic properties belong to the genera Lactobacillus and Bifidobacterium and milk is the most commonly used vehicle. Objectives: The study was aimed at analyzing the biofilm formation by plaque regrowth method upon the usage of a probiotic toothpaste containing Lactobacillus paracasei by measuring the optical density using a spectrophotometer.Materials and Methods: A commercially available probiotic toothpaste, PerioBiotic (spearmint flavored) from the company Designs for Health, has been tested. The toothpaste contains the strain L. paracasei, which has been found to co-aggregate with Streptococcus mutans (MS). The Plaque Glycolysis and Regrowth Method (PGRM) was used for the evaluation of the antimicrobial effects on plaque metabolism in vivo. PGRM is based on the observation that natural fasted dental plaque, sampled from different quadrants of the dentition, exhibits similar metabolic and regrowth properties when suspended at equal “biomass” in standardized media. Conclusion: The results suggest that L. paracasei-based toothpaste, PerioBiotic, is effective in the reduction of MSmonospecies biofilm, but the activity appears short lived when high sucrose exposure is administered."


The lack of fluoride is a bit of a problem for me, but I guess I can use fluoride toothpaste in the morning and probiotic toothpaste in the evening. 🙂

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The lack of fluoride is a bit of a problem for me, but I guess I can use fluoride toothpaste in the morning and probiotic toothpaste in the evening

Eh? Why is the lack of fluoride a problem? What exactly is fluoride supposed to accomplish wrt. oral health? If it is to prevent caries by stronger mineralization, then there's an easy fix - get fluoride treatment every few years - it only takes a few minutes at the dentist and is super effective. 

Personally, I have not used toothpaste in brushing my teeth for a few years now - I use an electric toothbrush without toothpaste. I read a study somewhere showing that toothpaste far from helping actually slightly decreases the effectivness of toothbrushing, and but also that in fact fluoride is the most useful part of toothpaste - sadly I can't find the study at the moment, so you're fully entitled to dismiss it. Still, anecdotally, despite not using any toothpaste for years now, I have not had a single cavity (so far) or any gum problems. Be that as it may, if the sole benefit of toothpaste is fluoride then there are other ways of getting it (including treatments, as mentioned). 

But the most important consideration for me, was the fact that I consume very large amounts of tea daily - this gets me fluoride systemically, but also topically. Now, probably on balance my tea choices have less fluoride than the average tea (young green and white), but considering the quantities, I suspect I still get plenty of fluoride anyway. Anyhow, I've not felt any negative consequences of not using fluoridated toothpaste so far. YMMV, and to each his own. 


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Well, there are plenty of studies in support of using fluoridated toothpaste. On the other hand, I use tap water, which contains about 1mg per liter, so technically I should be covered even without fluoridated toothpaste (I have been filtering much of my water lately (Britta charcoal filter) to remove the chlorine (microbiome and all), but luckily, this method of filtration leaves most of the fluoride alone.

I am also wondering how the effect found on biofilm in the study above would compare to the effect of using a regular toothpaste, or no toothpaste at all.

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