You've heard about good and bad gut bacteria, but did you know that the mouth has its own microbiome? An increasing amount of research has been coming out about the oral microbiome and its relationship to overall health.

The foods we eat along with our oral hygiene habits can significantly affect the bacteria in our mouths. Tooth brushing, flossing, chewing gum, and gargling mouthwash keep your breath fresh, but they may also interfere with certain physiological processes of the body.

A Clean Mouth Could Come at a Cost

A paper published at the University of Plymouth in 2019 suggests that mouthwash usage post-workout may hinder your gains. The researchers tested 23 healthy individuals, assessing a variety of health markers ranging from height and weight to blood pressure. They also collected blood and saliva samples.

Then participants did a treadmill workout consisting of four sets of seven-minute runs at 65% of their VO2 peak interspersed with three minutes of recovery between rounds.

Over a two-hour period after their training session, the participants rinsed their mouths with mouthwash every 30 minutes. One week later, they were all asked to return to the lab to repeat the treadmill test. This time, however, the group did not gargle with mouthwash and were only provided water to drink.

Without mouthwash, the participants' systolic blood pressure had an average reduction of -5.2 mmHg at one hour after exercise. When the group gargled an antibacterial mouthwash, however, the average systolic blood pressure had an average reduction of -2.0 mmHg at the same time point (more than a 60% difference). The researchers also noted that the participants had significant increases in salivary lactate and in salivary nitrate after using mouthwash.

Effectively, this study shows that mouthwash usage after an intense workout can prevent both the blood-pressure lowering benefits that we'd normally get post-exercise and the tissue oxygenation that comes with it.

The changes noted in the participants after rinsing with mouthwash suggests that the oral microbiome may be a key component in initiating post-workout recovery. If the blood vessels cannot fully dilate during this two-hour window, other successive physiological processes (such as muscle oxygenation) will be stunted.

Another study found a similar effect on blood pressure with chewing gum. The researchers had the participants cycle at 80 revolutions per minute for 20 minutes while chewing gum (both hard and soft varieties) on their dominant side.

Ten minutes post-workout, the researchers noted a heart rate that was elevated by 11 beats per minute compared with the control group. Furthermore, the systolic blood pressure was 14 mmHg higher, and the diastolic blood pressure was 11 mmHg higher in the group that chewed the harder type of gum.

Cardiovascular Effects of Mouthwash

Several other studies have corroborated these findings, going so far as to suggest that mouthwash could pose a potential risk for cardiovascular health.

More than 100 million Americans suffer from hypertension (high blood pressure), and something seemingly benevolent like mouthwash may actually increase it. Several other studies have found significant elevations in plasma and salivary nitrite concentrations in addition to elevations in resting blood pressure.

Tying It All Together

These studies shine light on how the oral microbiome affects other systems of the body. With these findings in mind, within the two-hour post-workout window, opt out of the minty-fresh hygiene.

And if you already suffer from hypertension, you may unknowingly experience a greater elevation in blood pressure when using mouthwash or chewing gum. If you do choose to chew gum post-workout, opt for softer chewing gum to mitigate the deleterious effects.

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Works Cited

  1. Bondonno, C. P., Liu, A. H., Croft, K. D., Considine, M. J., Puddey, I. B., Woodman, R. J., & Hodgson, J. M. (2015). Antibacterial mouthwash blunts oral nitrate reduction and increases blood pressure in treated hypertensive men and women. American Journal of Hypertension, 28(5), 572-575.
  2. Cutler, C., Kiernan, M., Willis, J. R., Gallardo-Alfaro, L., Casas-Agustench, P., White, D., ... & Bescos, R. (2019). Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria. Free Radical Biology and Medicine, 143, 252-259.
  3. Govoni, M., Jansson, E. A., Weitzberg, E., & Lundberg, J. O. (2008). The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric oxide, 19(4), 333-337.
  4. Woessner, M., Smoliga, J. M., Tarzia, B., Stabler, T., Van Bruggen, M., & Allen, J. D. (2016). A stepwise reduction in plasma and salivary nitrite with increasing strengths of mouthwash following a dietary nitrate load. Nitric oxide, 54, 1-7.