Mouthwash can increase your blood pressure by disrupting an unexpected symbiosis!

March 4, 2016 | Bob T. Rosier
Mouthwash can increase your blood pressure by disrupting an unexpected symbiosis!

Imagine you’re on your first date and you’ve just arrived at the restaurant. What do you think has happened to your blood pressure? You wouldn’t be surprised if it’s slightly higher than normal. The common explanation for this would be that you are extremely nervous or excited. However, you probably also used a little extra mouthwash to keep your breath minty fresh. Did you know that mouthwash can increase your blood pressure?

In order to understand the relationship between mouthwash and blood pressure, we have to go back to 2006. This is when researchers discovered that a compound present in many different vegetables, called ‘nitrate’ (NO3), reduces blood pressure [1]. For instance, beetroot juice, which is particularly high in nitrate, acutely lowers blood pressure in healthy individuals [2]. Surprisingly, an anti-bacterial mouthwash completely abolishes this effect of nitrate. This is strange, because mouthwash does not affect the nitrate directly, so what is really going on here?

Only recently, researchers from the Queen Mary University of London found firm evidence of the missing link between nitrate, mouthwash and blood pressure [3]. You may be surprised to hear that this link is actually formed by the millions of tiny inhabitants in your mouth, the so-called ‘oral microbiome’. These inhabitants include bacteria that reduce nitrate (NO3) to nitrite (NO2). Nitrite, in turn, is further reduced to nitric oxide (NO) in your body, which is a vasodilator (i.e., a compound that widens your blood vessels). To illustrate the entire process [4], here is what normally happens when you drink a glass of nitrate-rich beetroot juice:


Figure 1: The effect of beetroot juice on blood pressure
1. You swallow the beetroot juice.
2. The nitrate (NO3) content is taken up by your intestine into your blood and transported to your salivary glands.
3. Your salivary glands actively fish out the nitrate of your blood and concentrate it to high levels (4-8 mM) into your saliva.
4. The bacteria in your mouth reduce the nitrate in your saliva to nitrite (NO2).
5. (a) Your saliva, which is now nitrite rich, is swallowed. (b) This nitrite enters your blood via the gut.
6. In our blood and tissues, there are several processes that further reduce nitrite into nitric oxide (NO).
7. One of the many effects that nitric oxide has on the body is vasodilation. This means that nitric oxide expands your blood vessels thereby decreasing your blood pressure.



When you use mouthwash and sterilize your mouth, the nitrate reduction by your oral bacteria (step 4 in the figure above) is temporarily lost. This means that the final result, vasodilation (step 7), is also lost and your blood pressure increases!

So before overusing mouthwash, you might want to think twice. Because this same mouthwash that makes your breath smell so fresh, could kill too many of your oral bacteria, hereby disrupting your body’s symbiosis with the oral microbiome. This symbiotic relationship, which developed over millions of years of co-evolution, contributes to the normal functioning of your body. It should be noted that regular tooth brushing does not have any effect on blood pressure. Oral hygiene is very important, but everything in moderation!


Author: Bob T. Rosier (Illustration Lab), MSc Biomolecular Sciences
Illustrator: Justin C. Burford (Illustration Lab)


Note: consult your dentist or physician before changing recommended or prescribed mouthwash usage.


References:

  1. Larsen et al., 2006: Effects of dietary nitrate on blood pressure in healthy volunteers. Journal: the New England Journal of Medicine. Link to Pubmed.
  2. Webb et al., 2008: Acute blood pressure lowering, vasoprotective and anti-platelet properties of dietary nitrate via bioconversion to nitrite. Journal: Hypertension. Link to Pubmed.
  3. Kapil et al., 2013: Physiological role for nitrate-reducing oral bacteria in blood pressure control. Journal: Free Radical Biology & Medicine. Link to Pubmed.
  4. Hezel & Weitzberg, 2015: The oral microbiome and nitric oxide homoeostasis. Journal: Oral Diseases. Link to Pubmed.

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Mouthwash can increase your blood pressure by disrupting an unexpected symbiosis!
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