Mouthwash May Block Blood Pressure Benefit Triggered By Exercise

Exercise is known to trigger a blood pressure-lowering effect in the hours after getting physical activity, but that benefit may be greatly reduced by the use of commonly available antibacterial mouthwash. The findings come from a study out of the University of Plymouth, where researchers studied two groups of people who exercised, one given antibacterial mouthwash and the other given ordinary mint-flavored water.

Lowering high blood pressure is vital for good health, being a key preventative measure to help protect against cardiovascular disease and a number of other potential conditions. A number of lifestyle changes may be recommended as a way to address high blood pressure, including reducing salt intake and getting physical activity, according to the American Heart Association.

The newly published study explains how exercise triggers this 'post-exercise hypotension,' which is the fancy term for the drop in blood pressure experienced after exercise. Nitric oxide causes blood vessels to dilate, which increases blood flow to the muscles being used while exercising. Nitric oxide degrades into nitrate, which, it turns out, may play an important role in the blood pressure effects triggered by exercise.

The salivary glands in one's mouth may absorb the nitrate produced by the degradation of nitric oxide. The nitrate ends up in the saliva where it is exposed to certain beneficial bacteria found in one's mouth. These bacterial species are able to convert the nitrate back into nitrite, after which point it is swallowed. The molecules then work their way back into circulation as nitric oxide, increasing blood vessel dilation and lowering blood pressure.

The researchers behind this study worked to determine whether using antibacterial mouthwash may harm the bacteria that convert nitrate into nitrite sufficiently enough to impact the blood pressure benefits of exercise. To determine this, the team tasked 23 healthy adults with running on a treadmill for half an hour on two occasions.

After each session, the researchers monitored the participants for two hours during which time they were told to either rinse their mouth with an antibacterial mouthwash containing 0.2% chlorhexidine or regular water flavored with peppermint.

Blood and saliva samples were taken before exercise and again two hours after exercising; blood pressure measurements were also taken. The scientists found that participants who were given mouthwash experienced a -2.0 mmHg average decrease in systolic blood pressure an hour after exercising. However, the participants who were given mint-flavored water experienced a greater -5.2 mmHg average decrease.

The study's co-author Craig Cutler explained:

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. Existing studies show that, exercise aside, antibacterial mouthwash can actually raise blood pressure under resting conditions, so this study followed up and showed the mouthwash impact on the effects of exercise.