The oral microbiome: very destabilized by smoking...but resilient

Smoking

Smoking severely disturbs the balance of the oral microbiome. Good news for those who are planning to quit smoking this year: 5 years from the last cigarette is enough for the oral microbiome to become similar to that of a non-smoker. This is the main result of a new European study.

About this article

Created 13 February 2024

Updated 14 May 2024

You might not know it, but the mouth is more than just a simple chewing machine. It offers room and board for a multitude of micro-organisms—the “oral microbiome”—which plays a significant beneficial role in our health.

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The bacteria of the oral microbiome do not like cigarettes

The problem: a study conducted in 2016 on Americans showed that smokers have a severely altered oral microbiome ¹, and this would not be without consequences for their health. Multiple studies have in fact shown that in cases of dysbiosis (sidenote: Dysbiosis Generally defined as an alteration in the composition and function of the microbiota caused by a combination of environmental and individual-specific factors. Levy M, Kolodziejczyk AA, Thaiss CA, et al. Dysbiosis and the immune system. Nat Rev Immunol. 2017;17(4):219-232. ) of the oral microbiome, the risk of cardiovascular problems and gum disease (inflammation and receding gums) increases.

Is the same public health problem found among Europeans? A team of researchers decided to explore the question and, for the first time, to determine whether quitting smoking would make it possible to fix the situation. ²

Would those who know what the oral microbiome is please raise their hands!

According to the International Microbiota Observatory, of 6,500 people surveyed in March and April 2023 (France, Spain, Portugal, Brazil, Mexico, China), only 17% knew exactly what the oral microbiome is.

Moreover, more than 1 in 3 Chinese people and Americans did not know that smoking could affect microbiota (gut, oral, etc.), in contrast to 1 in 4 French people and only 1 in 5 Brazilians.

They analyzed the salivary microbiomes of 1,601 Italians aged an average of 45 years, of whom 45% were smokers or former smokers. In particular, the scientists tried to determine whether the activity of bacteria transforming nitrates from food into nitrites, compounds beneficial for the blood vessels, was affected by smoking.

Return to equilibrium after quitting smoking

What did the results show? First of all, that Italian smokers had an oral microbiome that was much more altered than that of non-smokers. However—good news! —among ex-smokers, the more significant the number of years since quitting, the more the oral microbiome approached that of non-smokers.

Smoking: autopsy of a murderer

Heavy metals, toxic gases, tar, nicotine... Smoking is a veritable chemical factory and a formidable silent killer. According to the French national public health agency Santé Publique France ³, it is the cause of 1 in 3 cancers and constitutes a significant factor in myocardial infarctions, chronic obstructive bronchitis (COPD) and cerebrovascular accidents (CVA).

It is also an aggravating factor for gastric ulcers, diabetes, ENT and dental infections, gum disease, cataracts and age-related macular degeneration (AMD). It is responsible for 8 million deaths annually worldwide. ⁴ The cherry on top: there is no threshold below which cigarettes do not present a risk. And what if you considered quitting?

Among those who had quit smoking at least 5 years ago, populations of bacteria in the mouth presented nearly the same profile as those of non-smokers. The oral microbiome thus shows good resilience when it comes to smoking.

In addition, smokers were found to have decreased bacteria able to transform nitrates from food into nitrites. Why is this information of interest? Because nitrites are necessary for the production of nitric oxide (NO).

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Implication in cardiovascular risk

In cases of lowered NO, increased blood flow is observed in the gums, which leads to inflammation and receding gums. We also know that NO deficiency is a risk factor for developing cardiovascular disease. The oral microbiome would thus be implicated in the increased cardiovascular risk observed in smokers.

In spite of some limitations, this study is important, because it was conducted on a large number of people and precisely calculated the impact of the intensity of smoking.

Results to keep in mind when the time comes to make New Year’s resolutions!

Sources

^{1. Wu J, Peters BA, et al. Cigarette smoking and the oral microbiome in a large study of American adults. ISME J. 2016 Oct;10(10):2435-46.}

^{2. Antonello G, Blostein F, et al. Smoking and salivary microbiota: a cross-sectional analysis of an Italian alpine population. Sci Rep. 2023 Nov 2;13(1):18904.}

^{3. Santé Publique France}

^{4. WHO}