Love: It’s in your bowels

Let’s talk some more about our favorite microbe, Lactobacillus reuteri, and its effects on humans:

• L. reuteri, when present in the human gastrointestinal (GI) tract, takes up residence in both the colon and upper GI tract, unlike most other probiotic species that only colonize the colon. (I therefore believe that L. reuteri provides advantage in preventing upper GI colonization by unhealthy microbes, i.e., SIBO.)
• L. reuteri provokes the hypothalamic/pituitary release of the hormone oxytocin (an effect mediated via specific T-cells and the vagus nerve).
• Oxytocin is associated with feelings of affection, love, connection, desire for human companionship, love for a child, love for a pet, belonging to a group.
• Oxytocin is also associated with causing increased dermal collagen, thicker moister skin, acceleration of healing and hair growth, restoration of youthful muscle and strength, reduction of appetite, increased libido, deeper sleep, preservation of bone density.

The German microbiologist, Dr. Gerhard Reuter, discovered this microbe in the 1960s, labeling it Lactobacillus fermentum. Subsequent analyses uncovered important differences in this species and it was renamed L. reuteri after its discoverer.

The early and extensive work by Dr. Reuter detailed how he recovered L. reuteri from the upper GI tract and how it was present in the majority of intestinal specimens he studied. Likewise, L. reuteri has been recovered from the microbiomes of primitive people such as those from Papua, New Guinea, with every individual carrying the species. More recent analyses suggest that most people in Western society, however, have lost L. reuteri, likely a consequence of exposures to such things as emulsifying agents, synthetic sweeteners, antibiotics, glyphosate, chlorpyrifos, heavy metals, etc., i.e., the many factors in modern life that have reshaped the composition of the human microbiome. (L. reuteri is not alone; there are probably dozens, perhaps hundreds, of other species that modern people have lost. Bifidobacteria infantis, for instance, is another.) It is now rare to find L. reuteri in a modern individual’s microbiome.

We can therefore extrapolate that loss of L. reuteri may be associated with a reduction in oxytocin levels in most people. Unfortunately, methods to measure oxytocin are, even today, of questionable reliability, given the antibodies used to measure it and the recent recognition that most oxytocin is bound to other molecules and was therefore inaccurately measured in earlier studies. So we cannot look back to see if oxytocin levels have dropped over the years. Contemplate what this could mean, however: If most modern people have lost L. reuteri and thereby its oxytocin-boosting capacity, while we as a society are suffering record-setting levels of social isolation (even before the pandemic restrictions), suicide, and divorce, could these phenomena be related?

Tough to prove. But I will tell you that more and more people who consume the L. reuteri yogurt that yields more than 200 billion CFUs per 1/2-cup serving (via our flow cytometry assays; the most recent count yielded 262 billion)–i.e., far more than the millions provided by the bacterial probiotic source–are reporting increased feelings of empathy for other people, closeness to their partners and families, less social anxiety. A number of people tell me that they feel compelled to introduce themselves to strangers.

L. reuteri, with bacterial counts boosted via our yogurt-making efforts, provides a wonderful example of the emerging world of psychobiotics, i.e., bacterial species/strains that have important effects on the human mind.