Kissing may be dirtier than we thought; new research suggests about 80 million bacteria are swapped during a 10-second French kiss.
The recent kissing study also found partners who kissed each other at least nine times per day shared similar communities of oral bacteria, BioMed Central reported.
The microbiome (communities of microorganisms that live in the body) aids in the digestion of food, systemization of nutrients, and disease prevention. This microbiome can be affected by factors such as our genetics and age, but also our environments and whom we interact with.
To make their findings researchers asked 21 couples to fill out questionnaires on their intimacy habits, such as how often they kissed. They also took swab samples to investigate the populations of microorganisms living in their mouths and in their saliva. The results showed couples who kissed frequently shared a great deal of their microbiota.
"Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90 [percent] of known cultures. Interestingly, the current explanations for the function of intimate kissing in humans include an important role for the microbiota present in the oral cavity, although to our knowledge, 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," said lead author Remco Kort of TNO's Microbiology and Systems Biology department.
In a second experiment, one member of each of the couples drank a probiotic drink containing specific bacteria such as Lactobacillus and Bifidobacteria. The couples then shared an intimate kiss, and samples revealed this increased the probiotic bacteria in the receiver's mouth three-fold. The team also calculated a 10-second kiss would facilitate the transfer of about 80 million bacteria. In order to calculate the findings the researchers employed average transfer values and a number of assumptions related to the observed bacteria transfer, saliva volume, and kiss contact surface.
The researchers noted 74 percent of men reported higher intimate kiss frequencies than their female partners.
The findings were published in recent edition of the journal Microbiome.
