Mouthwash Cancels Out Blood Pressure-Lowering Benefits of Exercise

Mouthwash might seem like an innocuous aspect of oral hygiene but a new study warns that it could, sometimes, raise your blood pressure. Or rather, could prevent the blood-pressure-lowering effects of things like exercise. 

It is a pretty common understanding—and has been for awhile—that exercise lowers your blood pressure.  This is mostly the result of the body producing more nitric oxide which, in effect, opens up and dilates the blood vessels.  After exercise, though, we stop producing nitric oxide, but the reduction effect on blood pressure remains for at least the next few hours. This is a biological phenomenon called hypotension; and while there are many theories for why this happens, we still don’t fully understand. 

And that is what makes the results of this new study so interesting. Lead study author Raul Bescos explains that his team had a theory that this process might have something to do with the natural microbial environment of the mouth.  Apparently nitric oxide has a natural byproduct called nitrite that is commonly consumed by bacteria of the mouth. This nitrite is then re-absorbed into the body when we swallow (as in, the saliva); some of which getting transformed, again, back into nitric oxide.

The theory suggests that our bodies do this to help restore nitric oxide into the body after we exercise as a means to regulate this lower blood pressure.  A means for testing this, then, was presented to Bescos—and team—in the form of mouthwash. Antibacterial mouthwash, of course, contains the potent antiseptic chlorhexidine, which could be provide a simple, but effective, means to test this theory.  

The University of Plymouth (UK) nutritional physiologist explains this method appears to be an effective way to easily inhibit the activity of oral bacteria and, specifically, nitrite synthesis in the mouth. 

Recruiting a team of only 23 healthy adults, the experiment had volunteers run on a treadmill for a half-hour on two different occasions. This, of course, would simulate normal exercise for the average person.  Monitoring blood pressure, each person was randomly assigned to periodically use mouthwash or a placebo, switching their method between the two sessions. 

Sure enough, the team found that blood pressure was not lowered as much when monitored after mouthwash use. The researchers note that this is an acute effect: that it did not change the diverse microbiome of the mouth at all: it just had the strange effect on blood pressure. 

The results of this study have been published in the journal Free Radical Biology and Medicine.