ALICE: I’m continually fascinated with the world of microbes, and how the trillion microbes that live on and within us shape what makes us human. Our guest Dr. Susan Erdman and her research team at MIT have discovered amazing links between a single microbe that can influence our sense of bonding, identity, purpose... and love.
DR. SUSAN ERDMAN: I've always been a person who's interested in how the world works, and the bigger picture of things. Even as a child, I remember being curious about even things like how we know everybody is seeing the same color when they hear the word "green." And with the-always with the idea of understanding our environment and ourselves, in a way that we could create a more balanced whole.
ALICE: Dr. Susan Erdman is a Principal Research Scientist, and Assistant Director, in the Division of Comparative Medicine at MIT. Her research is funded by DoD and NIH grants. She is Board Certified in Comparative Medicine (A.C.L.A.M.), and studies how bacteria and inflammation contribute to systemic health and diseases... and how bacteria affect our hormones.
DR. SUSAN ERDMAN: A single microbe can be very powerful. This is not an intent to have one single microbe answer all questions, but rather, give us a direction, give us motivation to continue unraveling the mysteries of how microbes interact with our bodies as a whole-particularly with these players of our best friends, the immune system. And then optimizing how our brain-our master control for interfacing with the environment keeps us in a healthy frame of mind, keeps us focused on positive things-even extending to positive social relationships and the benefits of caring for others, in the same ways that ultimately mimic how a mother is intensely interested in taking care of her baby, and making a healthy world for that baby.
That same concept, we hypothesize, can be extrapolated to a society as a whole, and that more of these microbes that boost these hormones that make us care about others-want to take care of others-don't do it at the expense of taking care of ourselves. We still take care of ourselves. We have the capacity to reach outside of ourselves and take care of others, and try and make this a better world for all of us.
ALICE: Why do you suspect microbes may improve our relationship with ourselves, and others? And what was your ‘aha’ moment?
DR. SUSAN ERDMAN: This question about our identities, our sense of purpose, our desire to care about more than ourselves for the greater good is probably one of the most riveting questions of human existence. And we set out to try and understand some of the scientific underpinnings of that exact question. When we started to investigate organisms that we thought would have the potential to help us really understand who we are and how we can stay healthy, we zeroed in on a human breast milk microbe, with the reasoning that these are the tools that a mother passes onto her infant. This is a survival kit for the future.
And what this survival kit does is it also helps Mom. It helps Mom because she's carrying these microbes. And because her hormonal environment is one that supports this passing along the survival kit to her developing infant, she also is connected, in a very deep kind of way, to this microbial connection. We decided to scientifically mine-to dig deeply into the scientific underpinnings of this connection-to help us understand how this survival kit might be a clue as to what mammals have the potential to become.
ALICE: Dr. Erdman’s research looked deeper at the connections this microbe makes, and found it is a powerful player in the role of bonding.
DR. SUSAN ERDMAN: Most powerful among those things in the mother-infant bond is a social bonding hormone called oxytocin.
Oxytocin causes muscle contractions in the uterus that introduce the infant to the world. The infant is bathed in a sea of oxytocin at the time of birth, and begins to develop neurological connections, and also gut microbial connections based on relationships with this hormone, oxytocin. But one of the most powerful things, which is well-substantiated by animal models systems, is that oxytocin is really important in a mother having a desire to take care of her infant. And this, in the most simplistic way, is kind of earth-shattering. So earlier, Alice asked, did you have an aha moment? This is about as close to an aha moment as what we've had in our entire scientific journey. Because realizing that this microbe fills this niche with this mother-infant bond was what led us to explore the possibility that this microbe might actually be interfacing with this hormone oxytocin.
ALICE: Wow. So, a single microbe within us may be what induces our love hormone oxytocin? And it starts at birth?
DR. SUSAN ERDMAN: In mouse models, and in other animal model systems, it becomes very obvious that not only is the oxytocin important in actually the contractions of giving birth and the contractions of supplying that breast milk-which are key to a mammal being able to interface with the environment and get their offspring started on this trajectory of life-these life-giving events, the very essence of the mother caring for her infant, also requires oxytocin.
So, animal model systems that are completely missing oxytocin are capable of producing milk. They're sometimes capable of giving birth, although not very efficiently, because they don't have the hormone to give birth. The mothers have zero interest in actually taking care of their babies in the absence of this hormone oxytocin. That's how important it is for everything about the mother-infant bond. In the absence of this hormone, there are other hormones that might step in to help kind of try and patch things together, as part of feedback loops. But oxytocin is the master controller when it comes to a mother's interest in taking care of her infant.
So, this is the lightbulb moment. This is flash, flash, flash. If a mom is going to take care of her baby, she has to have this hormone. If this microbe is facilitating the production of this hormone, we have discovered something incredibly fundamental about what it takes for life-what it takes to build a life, to keep a life, and then to create a very interesting, selfish microbe who actually is invested in the social existence of mammals.
ALICE: It turns out that our microbial passengers are invested in our survival, and perhaps, making us social. Could the future be bioengineering love microbes?
DR. SUSAN ERDMAN: Are they actually helping us be a social being? Are they actually helping us want to take care of our-the next generation? This was the question that we went after. And we were completely shocked when we hit the jackpot, and found out that this microbe, when it's separated from that system and given to an adult animal, is actually capable of boosting the levels of the hormone oxytocin within the brain, and within all of the tissues of the body of the lucky individuals that are carrying this organism.
This particular concept, this idea that you could separate this microbe out and you could cause oxytocin to increase gives us clues to social networks that are previously uncharted. So, what do we have? We have a microbe that boosts a hormone that isn't just important in how a mother takes care of her infant, her interest in nurturing that infant.
Basic scientific studies looking at how important family nurturing of offspring is, in order for that individual to be a good, contributing, healthy, happy member of society in the future-whether it's an animal model system, or it's a person-that psychology science is very well-established.
But just as amazing is the potential you could take that microbe out of that system and separate it, and put it into an adult, and change that adult's interest in taking care of others.
ALICE: Could manipulating this microbe change the axis of caring in an individual? In a society? Could a single microbe be the key to survival of the kindest?
DR. SUSAN ERDMAN: So, let's play with that concept for a moment and say this is a hormone that, in human subjects, has been connected with expressions of empathy, expressions of altruism, and expressions of enjoyment of spirituality-the concept of belonging to a greater whole. That doesn't mean traditional religions, necessarily. It means the common threads of humans having a meaningful, spiritual experience that makes us belong to something, that makes us part of a larger whole, and makes us care about that larger whole to the same extent that we care about ourselves, maybe even more than we care about ourselves as an individual.
And that concept, that sort of thing that humans have searched for, that idea of what would make us care about-what would make us altruistic? What would make us care about some individual that's not even clearly related to us? Why would we possibly care about their survival? We care about their survival because these microbes are manipulating an axis within our brains that is giving us the capacity to return back to a primal, larger whole-that the survival of that whole is ultimately what drives the ultimate benefit of the survival of each of us as individuals. And these holistic relationships-this holobiont, these microbes that we carry with us-sometimes the microbes that we've dismissed over time, because our practices are not so natural as they used to be, our diets are not so natural, our birthing processes are not so natural, we use antibiotics to counteract bad microbes-this ends up changing elements of those microbial underpinnings, these very fundamental relationships that drive our potential with human existence. We have the opportunity, by understanding this process, to get the benefits of how antibiotics might help us counteract bad bacteria, how giving birth within a hospital and under certain conditions might help us eliminate deadly diseases-we can still get the benefits of all of those things, and still have the potential to understand how to make us the best human beings and human experience that we can possibly have, in the larger picture of things. And we see those connections in a very fundamental way, with scientific underpinnings between microbes, how the immune system works, and hormones that have far-reaching potential. And oxytocin is not the only hormone that's modulated by this microbe, but in ways that has the potential to change who we can become as a society, how much we care about others, and our interest in caring for others to the same extent that we care for ourselves-that potential exists with a key, through a hormone like oxytocin.
ALICE: Thank you, Dr. Susan Erdman, for explaining the amazing connection of microbes and the love hormone oxytocin and its role in bonding, empathy, altruism and yes, survival of the kindest. Imagine when we can bottle that microbe! Are you thinking, like me, love-biotics? Sign me up!
That’s it for this mad tea party. Stay tuned for more microbial wonders with Dr. Erdman. Check out our weekly newsletter Alice in Futureland on Substack, and our book “Thriving with Microbes.” And until next time... keep wondering.
EP022 Microbes & The Love Hormone: Dr. Susan Erdman