In the 1960s, a singer named Betty Everett belted, “If you wanna know if he loves you so, it’s in his kiss!”
Covered by Cher in the 1990s, the song neglects to mention what is also “in his kiss” – 80 million bacteria, according to a new study published in the journal Microbiome.
Before germaphobes swear off kissing forever, it should be noted that over 100 trillion microorganisms naturally live in our bodies. Called the microbiome, they are vital for digesting food, synthesizing nutrients and preventing disease.
The researchers – led by Remco Kort, of TNO (Netherlands Organisation for Applied Scientific Research) and adviser to the Micropia museum of microbes in the Netherlands – note that a number of different factors are important for shaping our individual microbiota, including genetic relatedness, diet and age.
But our surroundings – including the individuals with whom we interact – also affect our microbiota. The team notes that our mouths themselves contain over 700 varieties of bacteria, and these are also influenced by those we are closest to – particularly our romantic partners.
Kort says that as far as he and his colleagues know, “the exact effects of intimate kissing on the oral microbiota have never been studied. We wanted to find out the extent to which partners share their oral microbiota, and it turns out, the more a couple kiss, the more similar they are.”