Is Your Mouthwash Blocking Your Workout Benefits?
Exercise helps lower blood pressure, but using antibacterial mouthwash can blunt that effect, a study published in Free Radical Biology and Medicine shows.
Bacteria in your mouth helps recycle nitrates produced during exercise into nitric oxide, which helps widen blood vessels and lower blood pressure.
It is also possible that antibacterial mouthwash can reduce the effectiveness of nitrate supplements you take for performance benefits.
You know exercise helps lower blood pressure. But you probably didn’t know how, because for years, scientists didn’t fully understand it either. Now, researchers may have found the answer in the most unlikely place: your mouth.
The bacteria that live in your mouth help keep your blood pressure low after exercise—and if you kill those helpful microscopic bugs with mouthwash, you might just be swirling those heart-health rewards down the drain, a new study published in Free Radical Biology and Medicine suggests.
It’s also likely that the mouthwash can mess with your performance goals due to the same mechanism at hand. Here’s what you need to know.
How Antibacterial Mouthwash Affects Your Postexercise Blood Pressure
Researchers had 23 healthy men and women perform two 30-minute treadmill tests. During the first session, the volunteers performed the run and then rinsed their mouths with either an antibacterial (0.2 percent chlorhexidine) mouthwash or an inactive, mint-flavored rinse. For the second session, they repeated the treadmill test, switching which mouthwash they used. Neither the runners nor the researchers knew which liquid the runners were rinsing with either time.
The researchers measured the runners’ blood pressure and took blood and saliva samples before each session and again during a two-hour period following their exercise bouts.
When the runners rinsed with the mint-flavored placebo liquid, their systolic blood pressure (the highest blood pressure level when the heart is squeezing and pushing oxygenated blood into circulation) was reduced by an average of 5.2 millimeters of mercury (mm Hg) one hour later.
But when they rinsed with the antibacterial mouthwash, the beneficial effect of exercise was smaller: Their blood pressure just fell by 2 mm Hg over that same time period.
Not only were the blood pressure-lowering effects diminished by more than 60 percent during the first hour when the volunteers used they antibacterial mouthwash, but also they completely disappeared after two hours.
And here’s the part that might be key: Their blood nitrate levels did not increase after exercise when the runners used the antibacterial mouthwash—it only spiked when they used the placebo rinse.
“For the first time we have showed that oral bacteria play a key role in the cardiovascular effects of exercise, specifically the vasodilation and lower blood pressure after exercise,” lead author Raúl Bescós, Ph.D., lecturer in dietetics and physiology at the University of Plymouth in the U.K. told Bicycling.
Here’s how it works: When you exercise, cells in your blood vessels and muscles produce nitric oxide, which widens your blood vessels to increase blood flow to your working muscles. That effect continues after you’re done working out, and you enjoy a blood pressure lowering response called postexercise hypotension.
“We hypothesized that nitrate formed during exercise could be absorbed by the salivary glands and secreted in the mouth [where oral bacteria could reduce it to nitrite] during the recovery period after exercise,” he said. “Once nitrite is swallowed, a small portion is rapidly absorbed into the bloodstream and can form new nitric oxide that helps to sustain the blood supply to the previously active tissues.”
Think of the bugs in your mouth as the “key” to opening up the blood vessels, study coauthor Craig Cutler said in a press release. Without them, your body can’t produce the nitrite it needs to relax your blood vessels and lower blood pressure.
Though this study examined the acute effect of using mouthwash immediately after exercise, previous research suggests that there is likely a chronic effect as well. As Cutler said in the release, prior studies have even found a link between antibacterial mouthwash and a rise in blood pressure while you’re resting.
Can This Mess With Nitrates You Take for Performance, Too?
While this study didn’t look at dietary nitrates—say, beet juice supplements—that cyclists may take for an endurance boost, the same mechanism at hand that makes mouthwash mess with your blood pressure may be at play with your performance, too.
If you use antibacterial mouthwash and take a beetroot juice shot for nitrates, you might not get the vessel-widening, circulation-boosting ergogenic benefit you’re looking for.
“The mouthwash will lower the ability of bacteria to convert nitrate into nitrite. This has been shown by previous studies,” Bescós said.
[Find 52 weeks of tips and motivation, with space to fill in your mileage and favorite routes, with the Bicycling Training Journal.]
As to whether mouthwash can interfere with your actual exercise performance, the researchers say more work is needed.
“We don’t have enough evidence to say this to date,” Bescós said. “However, as long as antibacterial mouthwash lowers nitrite availability, this may impair the cardiovascular response associated with exercise, which in turn may have detrimental effects on exercise performance. We need more studies to investigate this question more in detail.”
In the meantime, they recommend avoiding antibacterial mouthwashes unless you’ve been prescribed one by a doctor or dentist for a specific condition and practicing good dental hygiene to maintain a healthy oral microbiome.
“A healthy diet and exercise are the best approaches,” he said. “Avoiding smoking and alcohol and sugar consumption can also substantially help.”
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