A new study published online on March 25 in the International Society for Microbial Ecology Journal found that smoking significantly changes the microbiome in the mouth. Led by researchers from the NYU Langone Medical Centre and its Laura and Isaac Perlmutter Cancer Centre, the study found that 150 bacterial species out of 600 showed an increase in growth because of smoking while another 70 species showed a decrease in growth.

Previous studies have linked oral microbial population imbalance with gastrointestinal cancers and immune diseases like Crohn’s disease. However, the new study does not show that these microbiome changes can contribute to these diseases.

“Further experiments will be needed, however, to prove that these changes weaken the body’s defences against cancer-causing chemicals in tobacco smoke, or trigger other diseases in the mouth, lungs, or gut,” says senior investigator and epidemiologist Jiyoung Ahn, an associate professor at NYU Langone and associate director of population sciences at Laura and Isaac Perlmutter Cancer Centre.

Still, this is the first study and most comprehensive one to show that smoking can change the oral microbial population. This involved analysing mouthwash samples of 1,204 men and women in the US who are part of the National Institutes of Health and the American Cancer Society cancer risk studies.

Old woman smiling. Photo from Pixabay/jeltevanoostrum

Old woman smiling. Photo from Pixabay/jeltevanoostrum

The participants were 50 years and older. Of the participants, 112 are current smokers, 571 are former smokers and 521 have never smoked in their lives.

Based on their genetic tests and statistical analyses, the researchers found that smoking alters the oral microbiome. Smokers have fewer Proteobacteria, which helps break down the toxic chemicals from smoking, making up 4.6 percent of their total oral bacteria.

The same bacteria make up 11.7 percent of nonsmokers’ overall bacteria. Smokers also have 10 percent more species of Streptococcus, the bacteria that encourages tooth decay, than non-smokers.

Nevertheless, the oral microbiome of smokers returns back to normal after they quit smoking. The former smokers, 17 percent of who quit in the past 10 years, have the same oral microbiome like what was found in non-smokers.

Despite these results, a lot of questions remain unanswered so the team plans to conduct another study to determine how long it takes before a smoker’s oral microbiome goes back to normal after quitting. Moreover, they also plan to confirm in another research if alterations in one’s oral microbiome can actually cause cancer.