25 October 2019

Skip Mouthwash After Exercise

Welcome back. You might recall my blog post Salt in Mind. Though I wrote about my dislike of salty food, the takeaway was salt’s link with increased risk of dementia and diseases of the brain and blood vessels, at least in mice.

Salt was being blamed because a study found: [E]xcess salt suppressed functioning of cells lining blood vessels to the brain (endothelial cells). This caused a reduction of nitric oxide, a gas the cells produce to relax the blood vessels and increase blood flow.

Reading blood pressure (from
OK, so what has this got to do with mouthwash and exercise, the subject of this post? I’m going to tell you. Just don’t forget that nitric oxide relaxes blood vessels and increases blood flow. In other words, it affects blood pressure. 

Post-Exercise Hypotension
International collaborators led by an investigator from the UK’s University of Plymouth conducted a study that demonstrated the importance of oral bacteria in cardiovascular health.

Their work built upon earlier research that showed exercise reduces blood pressure. How? Exercise produces nitric oxide, which (as you know) dilates blood vessels (“vasodilation”), increasing blood flow to active muscles.

The question addressed by the recent study was how blood circulation stays higher after exercise--how does exercise cause a blood-pressure lowering response known as post-exercise hypotension?

Nitric Oxide, Nitrate, Nitrite, Nitric Oxide
To answer the question, the investigators focused on nitric oxide and a compound that nitric oxide degrades to, nitrate.

Nitrate was of interest because research has shown it can be absorbed in the salivary glands and excreted with saliva in the mouth. Some species of oral bacteria can use the nitrate and convert it into nitrite.

If it seems we’re going in circles, we are. When the nitrite in saliva is swallowed, it’s partly absorbed into the circulation and reduced to nitric oxide, which could be responsible for post-exercise hypotension.

Testing the Importance of Oral Bacteria
How could the researchers prove this? By interfering with the oral bacteria. If those critters don’t convert nitrate to nitrite, blood circulation won’t stay higher and blood pressure lower after exercising.

In two separate sessions, the researchers had 23 healthy adults run on a treadmill for 30 minutes, then be monitored at rest for two hours. Only water was allowed during exercise and recovery.

Blood pressure was measured before exercise and at 1 hour and 2 hours after exercise. To analyze nitrate and nitrite concentrations and oral bacteria, other testing included blood and salivary samples taken before and 2 hours after exercise. 

Mouthwash and exercise,
here with my stationary bike
rather than a treadmill.
To gauge the importance of oral bacteria, the runners rinsed their mouths periodically during the recovery with either an antibacterial mouthwash (0.2% chlorhexidine) or a placebo of mint-flavored water.

The Mouthwash Effect
The study found that rinsing with antibacterial mouthwash after exercise reduced the  blood-pressure lowering effect by 61% at 1 hour into the recovery period and completely by 2 hours.

In contrast, the average blood pressure of participants that rinsed with the placebo remained lower than the baseline throughout the 2-hour recovery period.

Supporting the researchers’ expectation, the measured levels of circulatory nitrite at 2 hours after exercise increased for participants that rinsed with the placebo and remained constant for those that rinsed with the antibacterial mouthwash.

Wrap Up
The researchers concluded that nitrite synthesis by oral bacteria is a key mechanism to induce the vascular response to exercise over the first period of recovery thereby promoting lower blood pressure and greater muscle oxygenation.

Though I stand by my earlier comments on the virtues of antibacterial mouthwash to control the evil tooth decay-causing micro-creatures that slosh around in your mouth (Dental Check-Up Time), you may want to adjust the timing of your rinse. Thanks for stopping by.

Study of mouthwash and post-exercise hypotension in Free Radical Biology and Medicine journal: www.sciencedirect.com/science/article/abs/pii/S0891584919307610
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