A new study has found a strange connection between the bacteria in our mouth and post-exercise 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. It was published in the journal Free Radical Biology and Medicine.
Exercise is known to reduce blood pressure. Even when we finish exercising, the blood pressure remains low. Unless we use mouthwash that is. Why? Because the oral bacteria we killed using mouthwash was the ‘key’ to opening up the blood vessels. How so? They convert a molecule called nitrate into nitrite, which when swallowed and absorbed into the bloodstream turns into nitric oxide, which is what causes vasodilation – an increase in the diameter of blood vessels.
During exercise, our body produces this nitric oxide that causes vasodilation to increase blood flow circulation to active muscles. However, what keeps this nitric oxide production going well after the exercise is finished (something known as post-exercise hypotension) is the oral bacteria. If they are removed, nitrite can’t be produced meaning nitric oxide also stops being produced, and the vessels return to their normal state.
Lead author Dr. Raul Bescos, Lecturer in Dietetics and Physiology at the University of Plymouth, said:
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.
The Study
- 23 healthy adults participated.
- They all ran on a treadmill for 30 minutes and then were monitored for two hours. Two sessions of this took place.
- They all had to rinse their mouths with a liquid at 1, 30, 60 and 90 minutes after exercise. The liquid was either antibacterial mouthwash (0.2 percent chlorhexidine) or a placebo of mint-flavored water. Both the researchers and the participants didn’t know which liquid they were rinsing with.
- Before and 120 minutes after exercise, the participants’ blood pressure was measured and saliva and blood samples were taken.
- No food or drink except water was allowed during exercise and during the recovery period.
- None of the study participants had any oral health conditions.
The Results
- When participants rinsed with the placebo, the average reduction in systolic blood pressure was -5.2 mmHg at one hour after exercise.
- When participants rinsed with the antibacterial mouthwash, the average systolic blood pressure was -2.0 mmHg at the same time point.
- Overall, 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.
Conclusion
These findings do not mean you shouldn’t use mouthwash… unless it’s a couple of hours after a good cardio session at the gym of course. Mouthwash use aside, what the research really wanted to show was that there is a strong association between metabolites produced by bacteria in the mouth and acute blood pressure changes after exercise. Meaning, it’s highly likely there could be a way to treat hypertension – or high blood pressure – more efficiently, orally.
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.
