It Takes 5 Years for the Oral Microbiome to Return to Normal After Quitting Smoking

The microorganisms in the mouth, known as the oral microbiome, refer to the diverse community of bacteria, viruses, fungi, and other microbes that live in the mouth. These microorganisms play a crucial role in maintaining oral health by helping with digestion, protecting against harmful bacteria, and supporting the immune system. They contribute to various functions like breaking down food particles, defending against infections, and supporting overall oral health. An imbalance in the oral microbiome can lead to issues such as tooth decay, gum disease, and bad breath.

Woman Smoking

Woman Smoking

Smoking, on the other hand, is a major risk factor for numerous severe health conditions. It significantly increases the risk of various diseases, including lung cancer, heart disease, stroke, respiratory issues like chronic bronchitis and emphysema, as well as other cancers like throat, mouth, bladder, and pancreatic cancer. It damages nearly every organ in the body, weakening the immune system and causing long-term health problems.

What do scientists have to say?

Research conducted in Bolzano, Italy analyzed saliva samples of 1601 people, aiming to find out two things majorly; what exactly happens to the oral microbiome when one smokes and the effect of quitting, on the oral microbiome.

The participants were split into groups based on whether they were current smokers how many cigarettes they smoked each day and also if they had quit smoking, when they did, and if they had never started.

The results of the study revealed that the number of aerobic microorganisms decreased with each day of smoking, in smokers, and increased with each year of cessation in former smokers. Also, former smokers who had quit for longer than 5 years had a microorganism abundance similar to that of non-smokers.

What are aerobic microorganisms?

Aerobic microorganisms are organisms that require oxygen to survive and grow. These microorganisms utilize oxygen for their metabolic processes, including the breakdown of nutrients to obtain energy. In their absence, anaerobic organisms that do not exactly need oxygen can thrive.

Clinical significance

Some of the aerobic bacteria play a role in the nitrate reduction pathway. In this process, they convert nitrates, found in foods like vegetables, into nitrites.

These nitrites can be further metabolized in the body to produce nitric oxide (NO), a molecule important for various physiological functions such as regulating blood pressure and immune response. Nitric oxide acts as a vasodilator, widening blood vessels and improving blood flow. Insufficient blood flow predisposes the mouth and gums to various infections as decreased blood flow leads to a decreased availability of leucocytes which are the body’s defenders. This in turn will lead to increased risks of various heart conditions such as infective endocarditis.


Recent findings have assured us of how important it is to have a healthy oral microbiome. An imbalanced oral microbiome, such as one created by smoking, could in the long run lead to serious cardiovascular diseases. The good news, however, is that the risk is reversible. People who quit smoking for over five years have oral microbiomes that are close to indistinguishable from those of non-smokers.


Antonello, G., Blostein, F., Bhaumik, D., Davis, E., Gögele, M., Melotti, R., Pramstaller, P., Pattaro, C., Segata, N., Foxman, B., & Fuchsberger, C. (2023). Smoking and salivary microbiota: a cross-sectional analysis of an Italian alpine population. Scientific reports, 13(1), 18904.



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