Dr. Perlmutter and the Science of the Kiss

January 25, 2016 by David Perlmutter WellnessEnglish

“Intimate kissing involving full tongue contact and saliva exchange appears to be an adaptive courtship behavior unique to humankind and is common in over 90% of known cultures…” report researchers in Amsterdam.

So have you ever wondered what may be going on from a germ perspective during intimate kissing?

To answer this question, the researchers recruited 21 couples between the ages of 17 and 45 years and asked them a number of questions about their frequency of kissing, most frequent kiss, most frequent meal and meal composition. But then the science began. The researchers sampled the front of the tongue of each participant before and after an intimate kiss and took samples of saliva as well.

The samples were processed to identify the types of bacteria present by analyzing the bacterial DNA. Then, the researchers had one of the partners consume a probiotic yogurt drink. The tongue and saliva were sampled after 10 seconds and then the person was asked to kiss his or her partner for 10 seconds. At that point, the partner’s mouth was sampled specifically for the strains of bacteria in the yogurt drink.

The findings of the study were fascinating. As expected, those couples who kissed more frequently shared more similar mouth microbes. Even more intriguing was the finding that males strongly over reported the number of times they thought they kissed their partner each day, by a factor of 2 to 1. But perhaps the most compelling finding, based on the probiotic yogurt part of the study, was that the calculated number of bacteria transferred from one partner to the next during a 10 second kiss was 80 million! 

So why do we do it? And it’s not just us. Mouth to mouth contact is seen across the animal kingdom from fish to birds and of course to primates like us. A scientific answer, at least according to the researchers in this study, explores how the first kiss, at least in human mating situations,“… serves as a useful mate-assessment function and the following for mediation of feelings of attachment in long term relationships, rather than the facilitation of sexual arousal. Kissing may contribute in mate assessment and bonding via sampling of chemical taste cues in the saliva, including those resulting from the metabolic activity of the bacterial community on the surface of the tongue.”

Sounds like a lot of science-speak. But basically, it looks like intimate kissing plays a role not only in influencing how we select our mates, but also how we decide on long term relationships. And what’s really something to think about is the fact that once again, this is a great example of bacteria, in this case in the mouth, are directing our decision making process!

Dr. David Perlmutter M.D.

About Dr. Perlmutter: David Perlmutter, M.D., is an expert in the human microbiome, a board-certified neurologist, Fellow of the American College of Nutrition, America’s brain-health expert and #1 New York Times best-selling author.

This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.


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