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(7) Mouthwash Can Disrupt Beetroot Juice Without Proving a Performance Cost

By Francesco//8 min read/Training science & durability

The mouth is part of the dose

Strong antibacterial mouthwash can reduce the conversion of beetroot-derived nitrate to nitrite, but current evidence does not show that this costs runners performance. A runner using beetroot juice can reasonably control antiseptic rinsing during a performance trial; they should not abandon necessary dental treatment for an unproven marginal gain.

The chemistry explains the concern. After nitrate is absorbed, roughly a quarter is concentrated back into saliva. Bacteria on the tongue reduce it to nitrite, which is swallowed and can then form nitric oxide in the stomach, blood and tissues. Humans lack their own nitrate-reductase enzyme, so the oral step is not decorative. Nitric oxide can affect vascular tone, muscle blood flow and contractile function, mechanisms behind beetroot juice's place among evidence-supported sports supplements. People also vary in oral nitrate-reducing capacity; Thomas and colleagues found that it correlated with peak oxygen uptake and power in 50 adults. That observational link cannot establish that manipulating the bacteria improves performance.

What antiseptic rinses change

The clearest evidence concerns biomarkers and blood pressure. In 2008, Govoni and colleagues gave seven healthy adults sodium nitrate. Chlorhexidine mouthwash abolished nitrate-to-nitrite conversion in saliva and markedly attenuated the rise in plasma nitrite. Kapil's group later studied 19 healthy volunteers using chlorhexidine twice daily for seven days: oral nitrite production fell by 90%, plasma nitrite by 25%, and blood pressure rose by 2–3.5 mmHg.

Formulation matters. Woessner's dose-response experiment found that chlorhexidine almost eliminated conversion after a nitrate load, while one essential-oil antiseptic rinse behaved similarly to water for plasma nitrite and blood pressure. “Mouthwash” is therefore too broad a category. Ingredient, antimicrobial strength, timing and repeated use may produce different effects.

Exercise also feeds this pathway. In a randomised crossover treadmill study of 23 adults, Clarke's team found that chlorhexidine used after exercise attenuated the normal fall in systolic blood pressure by 61% after one hour and abolished it after two. That experiment measured recovery haemodynamics and reactive-hyperaemia oxygenation, not pace, endurance or race performance.

The missing performance result

A 2022 meta-analysis of 123 nitrate trials found a very small overall performance benefit. Studies that instructed participants to avoid antibacterial mouthwash showed a benefit; studies without that instruction did not. This is suggestive, but it is a study-level comparison. Mouthwash avoidance travelled with other differences in methods and populations, so it cannot prove that rinsing erased the effect.

The strongest direct counterargument arrived in 2025. Gallardo and colleagues randomised 30 healthy young adults to seven days of cetylpyridinium or saline mouthwash. The antibacterial rinse reduced nitrite as a proportion of salivary nitrate plus nitrite from 25% to 17%, yet did not change knee-extension torque, maximal velocity or power. It was not a running test and did not combine mouthwash with a nitrate dose, but it shows why a disturbed pathway cannot be treated as a demonstrated performance loss. A registered 28-day study is now testing mouthwash, nitrate metabolism and maximal oxygen uptake directly; results are not yet available.

Dental treatment outranks a marginal gain

Antimicrobial mouthwash has legitimate uses. The American Dental Association describes chlorhexidine, cetylpyridinium and essential oils as therapeutic ingredients that can help control plaque and gingivitis alongside brushing and interdental cleaning. A Cochrane review of 51 trials found that chlorhexidine produced a large reduction in plaque, although longer use increased tooth staining and commonly altered taste.

That evidence makes the boundary straightforward. Do not stop a dentist-prescribed rinse to protect a speculative race benefit. Oral inflammation, infection or post-procedure care is not a supplement problem, and routine brushing should continue. Nor does the nitrate literature justify trying to cultivate particular bacteria with untested probiotics. The relevant choice concerns an optional antiseptic rinse, not oral hygiene as a whole.

A race-week control, not a new ritual

Beetroot juice itself offers a small and inconsistent advantage. Reviews find more reliable changes in exercise capacity than in time-trial performance, while highly trained athletes are less likely to respond. The IOC's commonly cited protocol is 5–9 mmol nitrate two to three hours before exercise, and both the IOC and Australian Institute of Sport treat nitrate as situational rather than compulsory.

If you test it, use a product with declared nitrate content, repeat the same session under similar conditions, and keep oral care consistent. When an antibacterial rinse is optional, omit it during the supplementation period and on test or race day, matching the control used in much of the research. When it is clinically indicated, keep using it and accept that the supplement response is uncertain. This is the practical place of the oral microbiome inside training science and durability: control what is easy, measure the outcome that matters, and do not trade dental treatment for a pathway diagram.

Sources

Nitrate pathway and the oral microbiome

  1. Lundberg, J. O., Weitzberg, E. & Gladwin, M. T., "The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics" https://pubmed.ncbi.nlm.nih.gov/18167491/

  2. Kapil, V. et al., "The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway" https://doi.org/10.1124/pr.120.019240

  3. Hezel, M. P. & Weitzberg, E., "The oral microbiome and nitric oxide homoeostasis" https://pubmed.ncbi.nlm.nih.gov/23837897/

  4. Govoni, M. et al., "The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash" https://pubmed.ncbi.nlm.nih.gov/18793740/

  5. Kapil, V. et al., "Physiological role for nitrate-reducing oral bacteria in blood pressure control" https://pubmed.ncbi.nlm.nih.gov/23183324/

  6. Woessner, M. et al., "A stepwise reduction in plasma and salivary nitrite with increasing strengths of mouthwash following a dietary nitrate load" https://doi.org/10.1016/j.niox.2016.01.002

  7. Vanhatalo, A. et al., "Nitrate-responsive oral microbiome modulates nitric oxide homeostasis and blood pressure in humans" https://pubmed.ncbi.nlm.nih.gov/29807159/

  8. Tribble, G. D. et al., "Frequency of Tongue Cleaning Impacts the Human Tongue Microbiome Composition and Enterosalivary Circulation of Nitrate" https://pubmed.ncbi.nlm.nih.gov/30881924/

  9. Burleigh, M. et al., "Dietary nitrate supplementation alters the oral microbiome but does not improve the vascular responses to an acute nitrate dose" https://pubmed.ncbi.nlm.nih.gov/31051259/

  10. Thomas, B. et al., "The oral nitrate-reducing capacity correlates with peak power output and peak oxygen uptake in healthy humans" https://pubmed.ncbi.nlm.nih.gov/30853629/

  11. Bryan, N. S., Burleigh, M. C. & Easton, C., "The oral microbiome, nitric oxide and exercise performance" https://pubmed.ncbi.nlm.nih.gov/35636654/

  12. Moran, S. P. et al., "The effects of nitrate on the oral microbiome: a systematic review investigating prebiotic potential" https://pubmed.ncbi.nlm.nih.gov/38420038/

  13. Senkus, K. E. & Crowe-White, K. M., "Influence of mouth rinse use on the enterosalivary pathway and blood pressure regulation: A systematic review" https://pubmed.ncbi.nlm.nih.gov/31542940/

Mouthwash and exercise outcomes

  1. Clarke, C. et al., "Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria" https://pubmed.ncbi.nlm.nih.gov/31369841/

  2. Gallardo, E. J. et al., "Pilot randomized trial of the effect of antibacterial mouthwash on muscle contractile function in healthy young adults" https://pmc.ncbi.nlm.nih.gov/articles/PMC11819566/

  3. Silva, K. V. C. et al., "Factors that Moderate the Effect of Nitrate Ingestion on Exercise Performance in Adults: A Systematic Review with Meta-Analyses and Meta-Regressions" https://pubmed.ncbi.nlm.nih.gov/35580578/

  4. UMIN Clinical Trials Registry, "Effects of mouthwash on oral nitrate metabolism and exercise performance" https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000069350

Dietary nitrate and exercise performance

  1. Bailey, S. J. et al., "Dietary nitrate supplementation reduces the O₂ cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans" https://pubmed.ncbi.nlm.nih.gov/19661447/

  2. Lansley, K. E. et al., "Acute dietary nitrate supplementation improves cycling time trial performance" https://pubmed.ncbi.nlm.nih.gov/21471821/

  3. Wylie, L. J. et al., "Beetroot juice and exercise: pharmacodynamic and dose-response relationships" https://pubmed.ncbi.nlm.nih.gov/23640589/

  4. McMahon, N. F., Leveritt, M. D. & Pavey, T. G., "The Effect of Dietary Nitrate Supplementation on Endurance Exercise Performance in Healthy Adults: A Systematic Review and Meta-Analysis" https://pubmed.ncbi.nlm.nih.gov/27600147/

  5. Gao, C. et al., "The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis" https://pubmed.ncbi.nlm.nih.gov/34243756/

  6. Wong, T. H., Sim, A. & Burns, S. F., "The effects of nitrate ingestion on high-intensity endurance time-trial performance: A systematic review and meta-analysis" https://pubmed.ncbi.nlm.nih.gov/35892115/

  7. Poon, E. T.-C. et al., "Dietary Nitrate Supplementation and Exercise Performance: An Umbrella Review of 20 Published Systematic Reviews with Meta-analyses" https://pubmed.ncbi.nlm.nih.gov/40085422/

  8. Cai, C. et al., "Effectiveness of beetroot juice on aerobic and anaerobic exercise performance: systematic review and meta-analysis" https://pubmed.ncbi.nlm.nih.gov/42445795/

Sport and oral-health guidance

  1. Maughan, R. J. et al., "IOC consensus statement: dietary supplements and the high-performance athlete" https://pmc.ncbi.nlm.nih.gov/articles/PMC5867441/

  2. Australian Institute of Sport, "Group A" https://www.ausport.gov.au/ais/nutrition/supplements/group_a

  3. National Institutes of Health Office of Dietary Supplements, "Dietary Supplements for Exercise and Athletic Performance — Health Professional Fact Sheet" https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/

  4. Cochrane, "Chlorhexidine mouthrinse to reduce gingivitis and plaque build-up" https://www.cochrane.org/evidence/CD008676_chlorhexidine-mouthrinse-reduce-gingivitis-and-plaque-build

  5. American Dental Association, "Mouthrinse (Mouthwash)" https://www.ada.org/resources/ada-library/oral-health-topics/mouthrinse-mouthwash

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