Fitness buffs, don’t reach for that mouthwash

While mouthwash may be good for dental hygiene, it interferes with the exercise-related chemical process which promotes lower blood pressure and muscle oxygenation.                                                                          Image: Brian Jackson/123RF

If you want to enjoy the full benefit of your exercise regime, don’t use antibacterial mouthwash afterwards.

That may seem a highly unlikely piece of advice, but a team of English and Spanish scientists’ have found that while swirling a capful of antibacterial chemicals in your mouth may be good for dental hygiene, it interferes with the exercise-related chemical process which promotes lower blood pressure and muscle oxygenation. And it’s a timely reminder that not all bacteria are bad for us.

As reported in, when you exercise, your blood vessels open in response to the production of nitric oxide, which increases the diameter of blood vessels. It’s called vasodilation, and it increases blood flow circulation to active muscles.

“For a long time, researchers thought this only happened during exercise, but in more recent years, evidence has shown that circulation stays high — meaning blood pressure is lowered — even after exercise, thanks to how bacteria interact with a compound called nitrate, which forms when nitric oxide degrades.”

Raul Bescos, a physiology specialist at Plymouth University, is quoted as saying: “Research over the last decade has shown that nitrate can be absorbed in the salivary glands and excreted with saliva in the mouth.

“Some species of bacteria in the mouth can use nitrate and convert into nitrite — a very important molecule that can enhance the production of nitric oxide in the body.”

Once that nitrate is swallowed with saliva, it becomes absorbed into blood circulation and reduces back to nitric oxide, which keeps blood vessels wide and lowers blood pressure.

But antibacterial mouthwash messes with that process.

In an experiment, 23 healthy adults ran on a treadmill for 30 minutes. After the workout, they were asked to rinse their mouth with either an antibacterial mouthwash or a mint-flavoured placebo. They did that immediately after exercising, and again 30, 60, and 90 minutes after, their blood pressure being monitored every time.

The results showed that one hour after the treadmill session, average reduction in systolic blood pressure in the placebo group was significantly lower than that of the mouthwash-using group.

At the end of the monitoring window, two hours after the treadmill session, the mouthwash group showed no sign of blood pressure reduction from the exercise, whereas the placebo group still showed a significant reduction compared to their pre-exercise values.

“This is the first evidence showing that the nitrate-reducing activity of oral bacteria is a key mechanism to induce the acute cardiovascular response to exercise during the recovery period in healthy individuals,” the authors explained in their paper.

“While it’s only a small study, it serves as an important reminder of how not all bacteria are necessarily bad for us — and that ingesting antibacterial chemicals that indiscriminately terminate mouth-dwelling microbes could hamper important biological processes necessary for good health,” said.

*The findings were reported in Free Radical Biology and Medicine.

GET IN TOUCH: You can contact Wendy Knowler for advice with your consumer issues via e-mail: or on Twitter: @wendyknowler.



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