Susan E. Erdman, DVM, MPH, on Microbes’ Influence on Oxytocin Regulation and Production

The microbiome is increasingly playing a part in neurological disease. And as researchers work to further understand this connection, it has become clear that microbes play a role in regulating multigenerational health.

In a session at the 144th Annual Meeting of the American Neurological Association (ANA) in October 2019, Susan Erdman, DVM, MPH, will be speaking about “Microbes Modulate Host Oxytocin and Multigenerational Health.”1 Neurology Consultant spoke with Dr Erdman to get a preview of her session and an inside look at her research.

Susan E. Erdman, DVM, MPH, is a principal research scientist and assistant director in the Division of Comparative Medicine at the Massachusetts Institute of Technology.

NEUROLOGY CONSULTANT: Can you give us an overview of your session?

Susan Erdman: This presentation involves the microbiome and neuropeptide hormone oxytocin (sometimes referred to as the “love hormone”), which has roles in reproduction, social bonding, energy metabolism, and wound repair—all contributing to overall good health. Our underlying research investigates microbes that have been inherited, much like genes for most of human history, but that many people have since lost due to modern living practices like refined diets, antibiotics, Cesarean-section births, and bottled-milk formulas. These “lost heirlooms” imply that targeted microbial reintroductions have the potential to revitalize individuals and societies.

It was previously shown that feeding a probiotic human microbe, Lactobacillus reuteri, originally isolated from breast milk, is sufficient to increase endogenous oxytocin levels in animals. This raises important questions about the influence of these bacteria, especially around the time of birth. Interestingly, we found that feeding L reuteri to pregnant mice improves their infants’ survival and ability to thrive. We found that passing live microbes from mom to infant imparts many potential health benefits and that supplying mouse moms with a sterile killed form of L reuteri also increases systemic oxytocin levels and conveys lowered risk for cancers and obesity in their offspring. More research is needed to determine which specific bacterial factors may modulate host oxytocin secretion for potential public or personalized health goals.

NEURO CON: How do microbes influence oxytocin production?

SE: This is a great question. From studies in animals, we know that some microbes naturally increase levels of oxytocin within the mammalian brain, but it isn’t entirely clear how. Studies in mouse models implicate the vagus nerve and anti-inflammatory immune cells in the mechanism of action, but there are many possibilities linking microbes with a gut-immune-brain axis. 

NEURO CON: How does this process affect health throughout a person’s life? 
The increase in oxytocin expression caused by consumption of L reuteri is accompanied by lower blood levels of the stress hormone corticosterone in mice, potentially linking microbes with reduced stress responses in the body. Consumption of L reuteri has been shown to improve skin wound healing capacity and boost oxytocin levels in humans, too, though the mechanisms of action need further study. It has been shown in animal models that early life effects of the microbiome and oxytocin do influence things important to humans, such as sociability, physical health, and reproductive fitness later in life.

Indeed, increased nurturing during infancy has been linked with many health and performance benefits later in human life. Studies using refined high fat/low fiber diets in mice reveal that a grandma’s dietary indiscretions and consequent microbiome changes may be more than lifelong and actually span several generations. Interestingly, a probiotic remedy reduces diet and microbiome-associated risks for diseases such as cancer and obesity. Possible lifetime and generational effects remain to be tested in human subjects.

NEURO CON: Is there any way to ameliorate these health affects?

SE: Preclinical trials using fast-food chow in mouse models demonstrate that microbiome alterations may influence disease risks that span several generations. In those studies, a probiotic microbe remedy reduced risks for some types of cancer and obesity.

NEURO CON: What are the clinical implications of microbe modulation of host oxytocin?

SE: Data from animals and humans show that a microbe-mediated boost in oxytocin may modulate sociability, impulse control, and behaviors such as empathy and altruism. Indeed, findings in mouse models suggest L reuteri and oxytocin as a potential remedy for autism spectrum disorder. L reuteri-treated mouse moms also take better care of their babies. Further, oxytocin reduces stress hormones that otherwise contribute to many chronic disease processes. In mouse models, there is not only better wound repair but also improved muscle mass. All of these things are possibilities that remain to be tested in human subjects.

 NEURO CON: What else do neurologists need to know about microbe modulation of host oxytocin?

SE: Findings in animal models suggest that some types of bacteria may naturally boost levels of oxytocin in the brain, with many downstream benefits in physiology and behaviors. It is unknown whether these many probiotic-induced benefits extend to human subjects.

NEURO CON: What is the key take-home message from your session?

SE: A probiotic microbe originating from human breast milk was found to naturally raise levels of a neuropeptide hormone oxytocin involved in reproduction, nurturing, and social bonding.

This oxytocin-boosting organism, L reuteri, is believed to be less common with modernized living due to refined diets, antibiotics, Cesarean-section births, and bottled formulas rather than breast milk. Strategies to replace beneficial microbes may have a vast impact on health and well-being of individuals and societies.

For more information about the ANA’s Annual Meeting or to read more about Dr Erdman’s session, visit the ANA’s website:



  1. Erdman S. Microbes modulate host oxytocin and multigenerational health. Talk will be presented at: ANA 2019; October 13-15, 2019: St. Louis, MO.