The bacterial species Lactobacillus reuteri is a star in the world of intestinal microbes, one that yields spectacular effects for its human host. Up until the mid-twentieth century, most people in the Western world enjoyed the benefits of this bacterial species dwelling in their GI tracts, which they had acquired from their mothers as infants by passage through the birth canal and breastfeeding. Indigenous people living in jungles and mountains, as well as chickens, pigs, and other creatures, carry this microorganism, suggesting that it plays an essential role in survival.
But modern life has eradicated this species from 96 percent of people in the Western world. Today, only 4 percent—fewer than one in twenty people—continue to enjoy the presence of this marvelous species.[16,17] Among the many benefits of L. reuteri is its unique capacity to trigger the release of the hormone oxytocin from the human brain, which has been demonstrated through an elegant series of experiments conducted at the Massachusetts Institute of Technology (MIT). Think about that: a microbe living in your GI tract determines an important aspect of your brain’s functioning.[18]
Oxytocin is the hormone of empathy and connectedness. It is the hormone that surges when you are in love or feel closely connected to another person or pet your dog. Oxytocin helps you see the other side of an argument, cultivates sympathy for the plight of other people, and reduces social anxiety.
Loss of L. reuteri and its oxytocin-provoking effects means that modern people have lower oxytocin levels than people of fifty years ago. We live in a time plagued by increased social isolation, record-setting rates of suicide, skyrocketing divorce. Could the loss of the oxytocin-boosting L. reuteri be at least one cause behind these disturbing social trends? Surely, these are complex issues with many potential causes, but could the modern devastation of the helpful organisms in the thirty feet of GI tract, including the disappearance of L. reuteri and the accompanying loss of empathy and desire for human connection, be at least part of the explanation? I believe it is.
Restore this lost bacterial species, and many experience a flood of empathy and desire for human connection. People report liking their families and coworkers better, a renewed desire to converse with strangers in line for coffee at Starbucks and gather with friends, and a tendency to cry more at movies. They also report being better able to understand the views and opinions of others.
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Molin G, Jeppsson B, Johansson ML, et al. Numerical taxonomy of Lactobacillus spp. associated with healthy and diseased mucosa of the human intestines. J App Bacteriol. 1993;74(3):314–323.
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Walter J, Britton RA, Roos S. Host-microbial symbiosis in the vertebrate gastrointestinal tract and the Lactobacillus reuteri paradigm. Proc Nat Acad Sci. 2001;108(suppl 1):4645–4652.
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Erdman SE, Poutahidis T. Microbes and oxytocin: benefits for host physiology and behavior. Int Rev Neurobiol. 2016;131:91–126.
Davis, William. Super Gut: A Four-Week Plan to Reprogram Your Microbiome, Restore Health, and Lose Weight (pp. 25-28). (Function). Kindle Edition.