Some oral bacteria can cause periodontal disease and other issues, while other oral bacteria convert dietary nitrate into nitric oxide (NO), which helps maintain normal blood pressure. Now, a multi-institutional team of researchers has found that chlorhexidine in mouthwash may kill these good bacteria and raise systolic blood pressure.
“Nitric oxide is one of the most important signaling molecules produced in the human body. As NO is a ubiquitous signaling module, the systemic effects of orally produced bacteria may have other significant effects on human health beyond maintenance of blood pressure,” said Nathan S. Bryan, PhD, adjunct assistant professor at the Baylor College of Medicine.
Using 16S rRNA gene sequencing and analysis, the researchers examined whether the introduction of chlorhexidine antiseptic mouthwash for one week was associated with changes in tongue bacterial communities and resting systolic blood pressure in healthy normotensive individuals with documented oral hygiene behaviors and free or oral disease.
According to the researchers, the frequency of tongue cleaning was a predictor of changes induced by chlorhexidine in systolic blood pressure and in the composition of the tongue microbiome. When chlorhexidine was used twice a day, there was a significant increase in systolic blood pressure after one week of use.
Recovery from use resulted in an enrichment in nitrate-reducing bacteria on the tongue. Subjects with relatively high levels of bacterial nitrate reductases had lower resting systolic blood pressure. Overall, the researchers said, these results reinforce how the oral microbiome contributes to human health via the enterosalivary-nitrite-NO pathway.
The researchers concluded that management of the tongue microbiome via regular cleaning, along with adequate dietary intake of nitrate, provide an opportunity to improve resting systolic blood pressure.
“We know that one cannot be well without an adequate amount of NO circulating throughout the body. Yet the very first thing over 200 million Americans do each day is use an antiseptic mouthwash, which destroys the good bacteria that helps to create the NO. These once thought good habits may be doing more harm than good,” Bryan said.
“The demonstration that the presence of NO producing bacteria in the oral cavity can help maintain normal blood pressure gives us another target to help the more than 100 million Americans living with high blood pressure. Manipulation of the human microbiome as a therapeutic target for disease management is on the near horizon,” Bryan said.
“Screening the oral microbiome of resistant hypertensive patients may provide new insights into the etiology of their hypertension. Two out of three patients prescribed high blood pressure medication do not have their blood pressure adequately managed. This may provide an explanation as to why. None of the currently FDA-approved drugs for management of hypertension are targeted towards these NO-producing bacteria,” Bryan said.
“The oral cavity is an attractive target for probiotic and/or prebiotic therapy because of the ease of access. The potential to restore the oral flora to provide NO production is a completely new paradigm because of the ease of access. The potential to restore the oral flora to provide NO production is a completely new paradigm for NO biochemistry and physiology as well as to cardiovascular medicine and dentistry,” said Bryan.
“These studies provide new insights into the host-oral microbiome symbiotic relationship. If we are going to make a leap forward in health, we need to take another look at boosting oral health as it related to NO production and the role it plays in disease or find safe and effective therapeutic strategies to recapitulate NO production in the oral cavity,” Bryan said.
According to the researchers, this is the first longitudinal next-generation sequencing study demonstrating the impact of oral hygiene on the composition of the tongue microbiome. While the ADA recommends regular tongue cleaning based on evidence that it can reduce the severity of halitosis, the researchers say there is no epidemiological data on tongue-cleaning practices or frequency in the United States population.
The study, “Frequency of Tongue Cleaning Impacts the Human Tongue Microbiome Composition and Enterosalivary Circulation of Nitrate,” was published by Frontiers in Cellular and Infection Microbiology.
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