Smoking linked to 'profound' changes in mouth bacteria

An investigation into the impact of smoking on microorganisms found in the mouth has shown that it causes profound changes to the oral microbiome.

The microbiome is all the genetic material of all the microorganisms (e.g. bacteria, viruses or fungi) located in one site, for example the mouth or the gut, which are collectively known as microbiota. More loosely, the term is increasingly used to describe the entire microbiota in one area, not just the genetic matter.

Examining the oral microbiome of 1204 people, scientists at the New York School of the University of Medicine found that more than 150 bacterial species showed significantly increased growth in the mouths of smokers, while another 70 showed sharp decreases in growth. Around 600 species of bacteria live in the human mouth.

Around 75% of oral cancers are thought to be linked to changes in the mouth microbiome - whether these changes increase smokers’ susceptibility to cancers has yet to be demonstrated.

"Our study is the first to suggest that smoking has a profound impact on the oral microbiome," says study senior investigator and epidemiologist Jiyoung Ahn, PhD.

"Further experiments will be needed, however, to prove that these changes weaken the body's defenses against cancer-causing chemicals in tobacco smoke, or trigger other diseases in the mouth, lungs, or gut" says Ahn.

The study also suggests the oral microbiome of ex-smokers does not differ from that of people who had never smoked – in other words, giving up smoking reverses these alterations.

Published online at nature.com