We know that exercise helps lower blood pressure, but you probably didn’t know how, because for years, scientists didn’t exactly know either. Now, researchers may have found the answer in the most unlikely place: your mouth.
Bacteria that live in the mouth help keep blood pressure low after exercise, and if you kill those helpful microscopic bugs with a mouthwash, you may be upsetting those rewards for your heart health by drainage, according to a new study .
Mouthwash is also likely to interfere with your performance goals due to this same issue.
This is how mouthwash affects your blood pressure after training
The researchers had 23 healthy men and women perform two 30-minute treadmill tests. During the first session, participants ran and then rinsed their mouths with an antibacterial mouthwash (0.2% chlorhexidine) or an inactive mint flavored rinse. For the second session, they repeated the treadmill test, changing the mouthwash they used. Neither the runners nor the researchers knew what liquid the runners were rinsing at any time.
The researchers measured the runners’ blood pressure and took blood and saliva samples before each session and again over a two-hour period after their exercise sessions.
When runners rinsed off the mint-flavored liquid placebo, their systolic blood pressure (the highest level of blood pressure when the heart squeezes and pushes oxygenated blood into the circulation) dropped by an average of 5.2 millimeters of mercury ( mm Hg) one hour later.
But when they were rinsed with the antibacterial mouthwash, the beneficial effect of exercise was less: blood pressure dropped 2mm / Hg during the same time period.
The blood pressure-lowering effects not only decreased by more than 60% during the first hour that the volunteers used the antibacterial mouthwash, but they also disappeared completely after two hours.
And here is the part that could be important: blood nitrate levels did not increase after exercise when runners used the antibacterial mouthwash; they only fired when they used the placebo rinse.
For the first time, oral bacteria have been shown to play a key role in the cardiovascular effects of exercise, specifically in vasodilation and lowering of blood pressure after training. When we exercise, the cells of the blood vessels and muscles produce nitric oxide, which widens the blood vessels to increase blood flow to the working muscles. That effect continues after the workout is over, so a blood pressure lowering response called hypotension occurs after exercise.
Think of the bacteria in your mouth as the “key” to opening your blood vessels. Without them, the body cannot produce the nitrite it needs to relax blood vessels and lower blood pressure.
Although this study examined the effect of using mouthwash immediately after exercise, previous research suggests that there is probably a chronic effect as well. A link has previously been found between antibacterial mouthwash and an increase in blood pressure while sleeping.
Can this mess affect performance too?
Although this study did not look at nitrates in the diet, there are some supplements (such as beet juice ) that many athletes use to increase endurance. The same effect that makes mouthwash with blood pressure also play a role in your performance.
If you use antibacterial mouthwash and take a dose of beet juice to ingest nitrates, you may not be getting the ergogenic benefit that increases circulation and muscle power that you are looking for. Mouthwash will reduce the ability of bacteria to convert nitrate to nitrite, and this has been shown by previous studies.
As for whether mouthwash can interfere with actual exercise performance, the researchers say more work is needed.
However, as long as antibacterial mouthwash decreases nitrite availability, this can affect exercise-related cardiovascular response, which in turn can have detrimental effects on training performance. However, more studies are needed to investigate this problem in more detail.
Meanwhile, experts recommend avoiding antibacterial mouthwashes unless a dentist has prescribed it for a specific condition and you practice good dental hygiene to maintain a healthy oral microbiome.
