Common Personal Product Use Could Interfere With Exercise Benefits



Exercise is known to reduce blood pressure—but the use of a popular personal
care product can disrupt the important benefits exercise provides.  Researchers recently discovered the activity
of bacteria in our mouths may determine whether we experience this benefit.

An international team of scientists has shown that the blood pressure
-lowering effect of exercise is significantly reduced when people rinse their
mouths with antibacterial mouthwash, rather than water—showing the importance
of oral bacteria in cardiovascular health.

The researchers now suggest that health professionals should pay attention
to the oral environment when recommending interventions involving physical
activity for high blood pressure.

The study was led by the University of Plymouth in collaboration with the
Centre of Genomic Regulation in Barcelona (Gabaldon’s lab), Spain, and was
published in the journal Free Radical Biology and Medicine.

Why did the research take place?

Lead author Dr. Raul Bescos, Lecturer in Dietetics and Physiology at the
University of Plymouth, said: “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.

“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 has suggested that nitric oxide was not involved in
this post-exercise response—and only involved during exercise—but the new study
challenges these views.

“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.

“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. And when nitrite in saliva is swallowed, part of this
molecule is rapidly absorbed into the circulation and reduced back to nitric
oxide. This helps to maintain a widening of blood vessels which leads to a
sustained lowering of blood pressure after exercise.

“We wanted to see whether blocking nitrate’s ability to convert into
nitrite by inhibiting oral bacteria would have any effect on post-exercise
hypotension.”

What did the study involve?

Twenty-three healthy adults were asked to run on a treadmill for a total of
30 minutes on two separate occasions, after which they were monitored for two
hours.

On each occasion at one, 30, 60 and 90 minutes after exercise they were
asked to rinse their mouths with a liquid—either antibacterial mouthwash (0.2%
chlorhexidine) or a placebo of mint-flavoured water. Neither the researchers
nor the participants knew which liquid they were rinsing with.

Their blood pressure was measured and saliva and blood samples were taken
before exercise and at 120 minutes after exercise. No food or drink except
water was allowed during exercise and the recovery period, and none of the
study participants had any oral health conditions.

What did the science show?

The study found that when participants rinsed with the placebo, the average
reduction in systolic blood pressure was -5.2 mmHg at one hour after exercise.
However, when participants rinsed with the antibacterial mouthwash, the average
systolic blood pressure was -2.0 mmHg at the same time point.

Systolic blood pressure refers to the highest blood pressure level when the
heart is squeezing and pushing the blood round the body.

These results show that the blood pressure-lowering effect of exercise was
diminished by more than 60% over the first hour of recovery, and totally
abolished two hours after exercise when participants were given the
antibacterial mouthwash.

Previous views also suggested that the main source of nitrite in the
circulation after exercise was nitric oxide formed during exercise in the
endothelial cells (cells that line the blood vessels). However, the new study
challenges this. When antibacterial mouthwash was given to the participants, their
blood nitrite levels did not increase after exercise. It was only when
participants used the placebo that nitrite levels in blood raised, indicating
that oral bacteria are a key source of this molecule in the circulation at
least over the first period of recovery after exercise.

What the authors say

Craig Cutler, study co-author who conducted the research as part of his
Ph.D. at the University of Plymouth, said: “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.

“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.

“The next step is to investigate in more detail the effect of exercise
on the activity of oral bacteria and the composition of oral bacteria in
individuals under high cardiovascular risk. Long-term, research in this area
may improve our knowledge for treating hypertension—or high blood pressure—more
efficiently.”

Sources:

C. Cutler et al, Post-exercise hypotension and skeletal
muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria, Free
Radical Biology and Medicine
(2019). DOI:
10.1016/j.freeradbiomed.2019.07.035