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Can Mouthwash Increase Blood Pressure? An Unusual Interaction

Antibacterial mouthwash is supposed to kill germs. What if it has an unexpected side effect? Could mouthwash increase blood pressure by killing good germs?
Can Mouthwash Increase Blood Pressure? An Unusual Interactio...
Close-up Of A Man’s Hand Pouring Mouthwash Into Cap

If you think about bacteria in the mouth you probably consider bad breath. But oral bacteria are crucial for good health. They are part of your microbiome (the organisms that live in and on your body). These “good” bacteria appear to play an important role in facilitating blood vessel flexibility and lowering blood pressure. Could disrupting the bacterial balance in the mouth with mouthwash increase blood pressure?

Bacteria and Blood Pressure?

Get ready for a little biochemistry lesson. But don’t worry, this isn’t that challenging. It all starts with green leafy vegetables such as spinach, kale, Swiss chard, oak leaf lettuce, butter leaf lettuce, cilantro, and arugula. These veggies contain substantial amounts of inorganic nitrate. Beet greens and beet roots are also high in natural nitrates.

As you chew foods high in nitrates the bacteria in your mouth start converting those nitrates to nitrites. They use enzymes called nitrate reductases. The nitrites that are formed in the mouth are swallowed and end up in the stomach. Some are turned into nitric oxide (NO for short) in the stomach and some are absorbed directly into the blood stream where they circulates throughout the body. This nitrite is converted to NO in the tissues lining blood vessels and in other organs (Free Radical Biology and Medicine, July, 2019). 

Here’s the bottom line: NO (Nitric Oxide) is your friend! By relaxing blood vessels it naturally lowers blood pressure. Anything that interferes with the conversion of nitrate to nitrite and nitrite to NO is problematic.

Mouthwash Can Increase Blood Pressure in Rats:

Could some mouthwash have an unintended consequence? People use antibacterial rinses to control bad breath and gum disease.

Scientists have discovered that antibacterial mouthwash might be undermining the blood pressure benefits that result from the conversion of nitrate to nitrite to NO. A study in rats concluded (Free Radical Biology and Medicine, April 15, 2009): 

“We show here that if the oral microflora is suppressed by an antiseptic mouthwash, both the gastroprotection and the blood pressure lowering effect of dietary nitrate are abolished.

“The acute gastric injury caused by a nonsteroidal anti-inflammatory drug is markedly reduced by dietary nitrate but as shown here this protection is completely lost by the mouthwash treatment.

“In summary, when a commercial antibacterial mouthwash is administered to rats daily for 1 week, the oral microflora is suppressed to such an extent that the conversion of nitrate to nitrite in the oral cavity is strongly reduced. As a consequence the nitrite-dependent blood pressure lowering and gastroprotective effects of nitrate are abolished. This study suggests that symbiotic oral bacteria play an active role in the regulation of physiological functions in the gastrointestinal tract and in the cardiovascular system.”

Can Mouthwash Increase Blood Pressure in Humans?

A study conducted in humans suggests that rats aren’t the only creatures affected by mouthwash. Investigators in the UK and Sweden reported that (Free Radical Biology and Medicine, Feb. 2013): 

“We have shown that twice-daily use of an antiseptic mouthwash for 1 week nearly abolished oral conversion of nitrate to nitrite. More importantly, this was accompanied by a decrease in plasma nitrite concentration (about 25%) and a concomitant increase in BP… Our data demonstrating a robust correlation between changes in plasma nitrite levels and changes in BP support our contention that prevention of the conversion of nitrate to nitrite by antiseptic mouthwash underlies the increases in BP.”

Exercise, Blood Pressure and Mouthwash:

Experts acknowledge that an episode of brisk exercise usually lowers blood pressure. During physical activity, blood vessels dilate due to production of nitric oxide. This important compound degrades into nitrate. New research shows that oral bacteria are able to convert nitrate back into nitrite and from there to nitric oxide. (Free Radical Biology and Medicine, online, July 29, 2019). 

People who used antibacterial mouthwash after running on a treadmill had significantly less blood pressure reduction than those who swished with mint-flavored water. The researchers suggest that oral bacteria are like the “key” to opening blood vessels and lowering blood pressure.

The People’s Pharmacy Perspective:

We are learning that the microbiome can be our friend. In fact, the bacteria in our mouth and digestive tract are impotant for our good health. For one thing, nitric oxide is essential for blood vessel flexibility and vasodilation. That means it can help lower blood pressure. NO also helps protect our stomach lining. We might want to be thoughtful about using antibacterial chemicals in our mouth. Can germ-killing mouthwash increase blood pressure? It is beginning to look like a possibility. We call this the law of unanticipated consequences. 

Share your thoughts in the comment section at the bottom of the page. 

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
  • Ashworth, A., et al, “Dietary intake of inorganic nitrate in vegetarians and omnivores and its impact on blood pressure, resting metabolic rate and the oral microbiome,” Free Radical Biology and Medicine, July, 2019, https://doi.org/10.1016/j.freeradbiomed.2019.05.010
  • Petersson, J., et al, “Gastroprotective and blood pressure lowering effects of dietary nitrate are abolished by an antiseptic mouthwash,” Free Radical Biology and Medicine, April 15, 2009, doi:10.1016/j.freeradbiomed.2009.01.011
  • Cutler, C., et al, “Post-exercise hypotension and skeletal muscle oxygenation is regulated by nitrate-reducing activity of oral bacteria,” Free Radical Biology and Medicine, online, July. 29, 2019, https://doi.org/10.1016/j.freeradbiomed.2019.07.035
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