An intriguing new study is suggesting beneficial blood pressure reductions following exercise are kickstarted by molecules released by bacteria in the mouth. Led by scientists from the University of Plymouth, the research found antibacterial mouthwash can remove helpful oral bacteria, thus reducing positive post-exercise cardiovascular effects.
“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,” explains lead author of the study Raul Bescos. “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.”
When nitric oxide degrades in the human body it becomes a compound called nitrate. Prior research has revealed certain species of oral bacteria actively convert nitrate into a molecule called nitrite. This process is important as nitrite is absorbed across the gastrointestinal tract, entering the bloodstream, and is ultimately converted back into nitric oxide. So the new research set out to test a hypothesis asking whether this oral nitrate/nitrite pathway is what regulates the acute lowering of blood pressure seen in the hours following 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,” says Bescos.
The experiment involved 23 healthy adults running on a treadmill for half an hour. Following exercise the participants rinsed their mouths on four occasions over two hours with either an antibacterial mouthwash or a placebo. Blood pressure was measured before exercise and at one and two hours after, alongside saliva and blood samples being taken.
The compelling results revealed systolic blood pressure measurements were significantly lower one hour after the exercise in the placebo group. The mouthwash notably reduced the blood-pressure lowering effect of exercise by 60 percent, and nitrite blood levels were only identified in the placebo group, suggesting this molecule is key to generating post-exercise hypotension, and its production can be directly inhibited by disrupting the activity of bacteria in the mouth.
“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,” says Craig Cutler, co-author on the study. “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.”
The new research adds to some fascinating recent work finding regular use of antibacterial mouth wash can result in increases to resting systolic blood pressure. And this isn’t the only area of research finding connections between our overall health and the bacteria in our mouths. A study earlier this year found a common oral bacteria can release a molecule that accelerates the growth of colorectal cancers, while other more provocative studies have begun to uncover associations between oral bacteria and Alzheimer’s disease.
The new research does not imply one should stop using mouthwash altogether, but it does for the first time reveal strong associations between metabolites produced by bacteria in the mouth and acute blood pressure changes after exercise. As well as offering new insights into the broader systemic effects of our oral microbiome, the research points to novel new pathways for treating hypertension in the future.
“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,” says Cutler. “Long-term, research in this area may improve our knowledge for treating hypertension – or high blood pressure – more efficiently."
The new research was published in the journal Free Radical Biology and Medicine.
Source: University of Plymouth