Beware of using mouthwash

I know, I know, mouthwash is no food and this is a blog about food. But bear with me and you will see the connection revealed at the end. Although mouth rinsing has been around for thousands of years it was not until the late 1960’s that effective antibacterial compounds started to be used. Since then commercial interest in mouthwashes has been intense.

New products have been developed that claim effectiveness in reducing bacteria and the associated build-up in dental plaque, a cause of gingivitis. They are also supposed to fight bad breath by controlling anaerobic bacteria that produce unpleasant volatile sulphur compounds.

The downside!

All good then? No, not so fast. Not only will mouthwash not live up to claims in expensive commercials and on product labels, but using a mouthwash can actually make your dental and oral health problems worse.

As the intake of oral antibiotics will disrupt the balance of bacteria in the gut, mouthwash will do the same with the important bacterial balance in the mouth. And just like we need our gut microbiome for general health, we need  our oral microbiome to protect against common issues like cavities, gingivitis and bad breath.

Contrary to popular belief, the common claim of killing “99.9% of germs” does not prevent cavity formation. The oral microbiome actually supports the natural teeth remineralisation and indiscriminately killing the constituent bacteria will eliminate a critical part of the repair mechanism.

Saliva, another key component of the remineralisation process, is typically reduced with mouthwash use. Saliva serves to disturb the oral bacteria that can cause decay, while also depositing important minerals like phosphorous and magnesium onto the teeth.

But there is more!

blood pressure1There is actually a connection between blood pressure and the oral microbiome. Exercise is known to reduce blood pressure, a pleasant bonus of the exertion. But the activity of bacteria in our mouths may determine whether we experience this benefit, according to new research.

Sounds far fetched but there is a plausible explanation.

It was already known that blood vessels open up during exercise, as the production of nitric oxide increases the diameter of the blood vessels, 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. It might be due to the magic of nitrate metabolism and the influence of the oral microbiome as the nitric oxide in the bloodstream is quickly converted to nitrate within 10 seconds.

Enterosalivary circulation of nitrate

Normally we ingest nitrate with the food we eat; green vegetables like spinach and rocket salad are particularly high in nitrate. In the gastro-intestinal system nitrate is released and enter the blood stream. And here comes the magic. Nitrate is excreted from the bloodstream into the oral cavity by the salivary glands.

Some species of bacteria in the mouth can use nitrate and convert it into nitrite. And when nitrite is swallowed, part of this molecule is rapidly absorbed into the circulation and reduced to nitric oxide. The nitric oxide helps to maintain a widening of blood vessels and a sustained lowering of blood pressure.

Thus the researchers asked the trial participants to rinse their mouths immediately after their exercise with either a mouthwash or water. And they showed that the blood pressure-lowering effect of exercise is significantly reduced when rinsing the mouth with an antibacterial mouthwash, rather than water.

Eating your greens

rucolaThis was new knowledge in relation to exercise but the overall relationship between the oral microbiome and nitrate metabolism was already well known. In 1998, three US scientists received the Nobel prize for their discoveries around the role of nitric oxide.

Several 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.

But in more general terms eating your greens and avoiding the use of a mouthwash will keep your blood pressure under better control, with exercise a bonus.

And there you have your food connection!

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