About 80 million bacteria are transferred during a single 10-second kiss, says a group of researchers from the Netherlands.
Partners who kiss each other at least nine times a day share similar communities of oral bacteria, the team says. Image credit: Skyggefotografen / CC BY 2.0.
Dr Remco Kort of the TNO Microbiology and Systems Biology in Zeist and his colleagues from Micropia Museum and the VU University Amsterdam investigated the effects of intimate kissing on the oral microbiota of 21 couples by self-administered questionnaires about their past kissing behavior and by the evaluation of tongue and salivary microbiota samples in a controlled kissing experiment.
The results showed that when couples intimately kiss at relatively high frequencies their salivary microbiota become similar.
On average it was found that at least 9 intimate kisses per day led to couples having significantly shared salivary 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,” said Dr Kort, who is the lead author of the paper published in the journal Microbiome.
“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.”
In a controlled kissing experiment, a member of each of the couples had a probiotic drink containing specific varieties of bacteria including Lactobacillus and Bifidobacteria.
After a 10-second intimate kiss, the team found that the quantity of probiotic bacteria in the receiver’s saliva rose threefold, and calculated that in total 80 million bacteria would have been transferred during a kiss.
The study also suggests an important role for other mechanisms that select oral microbiota, resulting from a shared lifestyle, dietary and personal care habits, and this is especially the case for microbiota on the tongue.
The researchers found that while tongue microbiota were more similar among partners than unrelated individuals, their similarity did not change with more frequent kissing, in contrast to the findings on the saliva microbiota.
“An interesting but separate finding was that 74 percent of the men reported higher intimate kiss frequencies than the women of the same couple,” the scientists said.
“This resulted in a reported average of 10 kisses per day from the males, twice that of the female reported average of five per day.”
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Remco Kort et al. Shaping the oral microbiota through intimate kissing. Microbiome 2014, 2:41; doi: 10.1186/2049-2618-2-41
