No spit! Mouthwash can hinder benefits of exercise, study finds

PLYMOUTH, England — Here’s some advice you probably didn’t expect to get today: Don’t use mouthwash on days you work out. It sounds odd at first, but a team of researchers from the University of Plymouth say that antibacterial mouthwash can seriously hinder the blood pressure-lowering benefits of exercise.

Now, no one is saying you should throw out your toothbrush, dental floss, and mouthwash all together. However, these findings illustrate that oral bacteria is a necessary and important part of each person’s overall, and more specifically cardiovascular, health.

It’s fairly common knowledge that exercise can lower blood pressure, but researchers say that whether or not a person experiences this benefit depends on their oral bacteria activity. The study’s authors believe that cardiologists and other health professionals should keep an individual’s oral bacteria in mind when prescribing exercise for patients suffering from high blood pressure.

“Scientists already know that blood vessels open up during exercise, as the production of nitric oxide increases the diameter of the blood vessels (known as vasodilation), increasing blood flow circulation to active muscles,” explains lead author Dr. Raul Bescos in a release. “What has remained a mystery is how blood circulation remains higher after exercise, in turn triggering a blood-pressure lowering response known as post-exercise hypotension.”

Previous research had indicated that nitric oxide is not involved in post-exercise hypotension, but Dr. Bescos says this new study is challenging that notion.

“It’s all to do with nitric oxide degrading into a compound called nitrate, which for years was thought to have no function in the body. But research over the last decade has shown that nitrate can be absorbed in the salivary glands and excreted with saliva in the mouth,” Dr. Bescos continues.

According to researchers, certain types of mouth bacteria use that nitrate to produce nitrite, a molecule that promotes enhanced production of nitric oxide in the body. So, when that nitrite in saliva is swallowed, it gets absorbed back into the blood stream and turns back into nitric oxide — which widens blood vessels and lowers blood pressure.

In summation, the oral bacteria found in the mouth helps create a cycle of nitric oxide production that extends the cardiovascular benefits of exercise, ultimately resulting in post-exercise hypotension and lower blood pressure.

Upon drawing these conclusions, the research team decided to conduct an experiment on the effect mouthwash, and a subsequent reduction in oral bacteria, would have on post-exercise hypotension. A total of 23 adult participants took part in the study, and each person was asked to run on a treadmill for 30 minutes on two separate occasions. Participants were monitored for two hours after each treadmill session.

At one, 30, 60, and 90 minutes after each treadmill session participants were asked to wash their mouths with a liquid. That liquid was either legitimate antibacterial mouthwash or mint-flavored placebo water. Additionally, blood pressure was measured, and blood and saliva samples were taken both before and after exercise sessions. Participants weren’t allowed to eat or drink anything else during the entire process, and researchers were sure to select study subjects with no oral health problems or conditions.

The results showed that those who rinsed with a placebo had an average reduction in blood pressure of -5.2 mmHg one hour after exercising. Meanwhile, those who rinsed with a real mouthwash only saw an average reduction of -2.0 mmHg after one hour. These numbers clearly indicate that the blood pressure-lowering benefits of exercise were hampered by the use of mouthwash following a work out.

Researchers say that mouthwash cut the blood pressure benefits of exercise by 60% over the first hour of recovery, completely negated any benefits when participants used mouthwash two hours after a workout.

It was also noted that participants who were given real mouthwash did not see their nitrite levels increase after exercise, which means that oral bacteria must play an even larger role in the creation and circulation of nitrite than previously thought.

“These findings show that nitrite synthesis by oral bacteria is hugely important in kick-starting how our bodies react to exercise over the first period of recovery, promoting lower blood pressure and greater muscle oxygenation,” study co-author Craig Cutler comments. “In effect, it’s like oral bacteria are the ‘key’ to opening up the blood vessels. If they are removed, nitrite can’t be produced and the vessels remain in their current state.”

Moving forward, the research team would like to investigate the effect of exercise on oral bacteria more thoroughly.

“Long-term, research in this area may improve our knowledge for treating hypertension – or high blood pressure – more efficiently,” Cutler concludes.

The study is published in the scientific journal Free Radical Biology and Medicine.

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About the Author

John Anderer

Born blue in the face, John has been writing professionally for over a decade and covering the latest scientific research for StudyFinds since 2019. His work has been featured by Business Insider, Eat This Not That!, MSN, Ladders, and Yahoo!

Studies and abstracts can be confusing and awkwardly worded. He prides himself on making such content easy to read, understand, and apply to one’s everyday life.

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