How does the gut-brain connection work?

[MUSIC PLAYING] FLORA LICHTMAN: Hey, it’s Flora Lichtman, and you are listening to Science Friday. We are coming to you today from Aspen Ideas Health with two leaders of a field that, in my opinion, is among the most exciting frontiers in medicine and biology. We are talking about the gut-brain connection.

And look, we have a lot of language about trusting our gut– gut feelings, gut checks, spilling your guts, getting butterflies. And they describe feelings that are familiar to us. I mean, let me just do a poll. Who here has gone with your gut in real life?

The 10% of people who didn’t raise their hand, I want to talk to you.

[LAUGHTER]

But how well do we understand this connection on the biomolecular level, the connection between our brains and our bowels? Which of those organs is actually in the driver’s seat. And what does it mean for how we understand diseases like Parkinson’s or depression? Those are just some of the questions that we’re going to churn through with my guests. Let me introduce them.

Dr. Emeran Mayer is the director of UCLA’s Center for Neurobiology of Stress. He spent four decades studying this. Is it fair to call you a gut-brain OG?

[LAUGHS]

I’m going to take that as a yes. And Dr. Trisha Pasricha is a neuro-gastroenterologist at Harvard Medical School, and she is also a poop influencer, which I hope we can get to later. Thank you both for being here.

TRISHA PASRICHA: Our pleasure.

FLORA LICHTMAN: What is a gut?

EMERAN MAYER: What is the gut?

FLORA LICHTMAN: What’s the gut?

EMERAN MAYER: Well, the gut is a simplistic term for the digestive system. I think the way it’s being used, it would include all the parts of the digestive system from the esophagus all the way down to the end of your large intestine. In more scientific or gastroenterological terminology, it would be primarily the small and large intestine.

FLORA LICHTMAN: Not my stomach?

EMERAN MAYER: Well, that depends. I think in the whole fascination now with gut health, I think people include the stomach as well.

FLORA LICHTMAN: This is a controversy? This is so spicy.

TRISHA PASRICHA: I know. We’re going to have such a hot debate. But I think the gut does mean the gastrointestinal tract and we shorten that to the gut. So I think in just common parlance, I’m with you. I think when we, as doctors, are like the gut, we are really thinking about the bowels. But I do think if we’re being a little more technical, I think what people think about, it’s everything from the esophagus all the way to the exit hatch.

FLORA LICHTMAN: Does it seem weird that we don’t have an agreed upon definition?

TRISHA PASRICHA: Totally. It’s a big problem for us.

FLORA LICHTMAN: Is it? If you’re a gastroenterologist it’s a big problem?

EMERAN MAYER: I think gastroenterology, the specialty, has been taken by surprise how all of a sudden their organ of interest is–

FLORA LICHTMAN: Is everywhere?

TRISHA PASRICHA: Yeah, we’re are the cool ones now. Take that, Neurology.

[LAUGHTER]

FLORA LICHTMAN: Well, why do you think social media has glommed onto the gut?

TRISHA PASRICHA: Yeah, I mean, Dr. Mayer is totally right. 10 years ago, when I was in med school, no card carrying gastroenterologist would use gut health. They wouldn’t talk about #GutHealth. And now it’s everywhere. Now I think we’re actually realizing we have to use that word, the American Gastroenterological Association, which we’re both members of, we’r3e forming an advisory group to talk about how we need to own this space. Why haven’t we owned this space before? Well, we’re going to try to figure it out.

And part of that is defining what that is. Because most of GI, we think about curing disease. But maybe what gut health really is, is the absence of disease and preventing said disease. And that’s obviously not been the focus for a lot of that 15-minute visit that you get when you already have a problem with your doctor.

And I spend a lot of time, for better or for worse, on Gut Health TikTok on #GutTalk. And I spend a lot of time in social media talking about gut health. And so I think about this a lot. But my suspicion for why this has really blossomed is twofold. One is a good thing.

I think Gen Z is so much less ashamed of their bodies than we were as millennials and everyone older than us. And they are destigmatizing mental health. They’re destigmatizing gut health. And I love that. So I think that it’s wonderful that they are bringing this and leading the charge there.

You guys think fiber maxing is cool. Wait till you hear about poop maxing. That’s trending. So this is great. But I think there’s a darker side to this, which we know so well. But one of the most common diseases in GI, I’ll give you this example, is Irritable Bowel Syndrome. 15% or thereabouts of Americans have IBS.

This is one of the most misunderstood diseases in all of medicine, not just misunderstood by patients, but misunderstood by doctors. And yet it is so incredibly– we all know somebody with IBS. Maybe we’ve had it. Maybe we got COVID and we never pooped correctly the same. This happens to all of us at some point.

And I think when there’s such a big void about that information, not that the science doesn’t exist, it exists. I think we just haven’t communicated it well. But when that void exists, I think then the influencers online, you enter this wonderful space as a patient where you go online. First of all, you can’t get an appointment with your gastroenterologist for the next six months. This is a big problem.

Now you’re scrolling and you see some really attractive influencer saying, hey, do you have bloating? Do you have brain fog? Does your doctor not take you seriously? It’s leaky gut, and/or fill in the blank. And they’ll tell you all about their journey and all about the supplements that worked for them. And there’s a million videos like this. And for the first time, you’re somebody who’s been suffering, and you feel heard. You feel seen. You feel like you’re connected to a person.

And that is, I think, almost 80% of the gut health space right now, it’s coming from people who are not physicians or the scientists, but it’s coming from people who are helping connect with somebody who has been a little bit dismissed or greatly dismissed by the health system. And I think that is the darker side of why this has become so popular.

EMERAN MAYER: Yeah, and I mean, being a gastroenterologist myself, and so I went through the first, I would say, 25 years of my career, battling the dogma in gastroenterology that it’s the gut. Many comments when I give a talk, people get up and say, doctor don’t forget, it’s the gut. When I talk about the brain-gut connection.

FLORA LICHTMAN: What do you mean. They were saying, it’s the gut? They were the brain is not involved?

EMERAN MAYER: The brain is not involved. And just based on that experience, this negative experience and what’s happening now that this has sort of been taking the discussions, been taking away from gastroenterologists to functional medicine and to influencers, and the topic is widened to stuff and entities that as a gastroenterologist, you’re not trained in. You’re not trained in what brain fog is or all these symptoms that are now blamed on the gut in some ways, or gut dysfunction.

But I’m not too optimistic that this new awareness will come in gastroenterologists and patients, there’s a tremendous growth of functional medicine, for example, because even though they don’t have all the science, they have managed to incorporate this holistic concept that includes the brain and the rest of the body in their conceptualization of gut health. I mean, it may be wrong, but what I’ve seen so far, the interest has definitely shifted away from gastroenterology, which is a specialty trained in identifying diseases of the gut, not of the brain, and has developed together with the pharmaceutical industry and with endoscopic procedures, a very effective way of dealing with the gut, but not with these brain-gut problems.

FLORA LICHTMAN: OK, Trisha, I’ve heard you say that our gut is a brain. I think of my gut as plumbing.

TRISHA PASRICHA: Yeah.

FLORA LICHTMAN: Help me reframe.

TRISHA PASRICHA: Please reframe. We all grow up thinking about our gut as plumbing. That’s very common. That’s not how I grew up. I’m the daughter of a gastroenterologist. I’m the daughter of a neuro gastroenterologist, like Dr. Meyer. And we have known for centuries that your gut is a brain. It contains 500 million nerve cells. That is more nerve cells than are in your spinal cord.

And that brain, for some animals, it’s the only brain they got. We call it the enteric nervous system. We humans have evolved to have a second brain in our head. Some people call the one in our gut the second brain. That’s not what I’d call it. And they are evolutionarily very closely intertwined.

And one of the ways that they communicate is the vagus nerve. And we’ll talk a lot about that, but remember that your gut does a lot more than just transport and magically transform food into waste. It is constantly producing neurotransmitters, the same neurotransmitters that the brain in your head produces, like dopamine, which is what I study in my lab, serotonin.

And it sends these signals up through the vagus nerve to the brain, and it’s in the background. But it is constantly influencing our mood, our hormones, and probably most diseases in all of our body, our heart, our lungs, our brain, you can trace the origin to some extent to the gut.

FLORA LICHTMAN: Emeran would you call it an axis, a gut-brain axis? I’ve heard that used.

EMERAN MAYER: Yeah, no, I’ve been trying the last few years to change people’s use of these terms. It’s really much more common. It’s not an axis. It’s not a linear system that we can understand with our reductionistic scientific approaches. If we look at it with systems biology, which basically postulates that everything is interconnected, it’s a brain-gut microbiome system. And these elements interact in bidirectional fashion, not just amongst each other, but they also are the main system in the body that regulates our homeostasis.

So the basic balance within our bodies is dependent on this system. And it goes back in evolution, as Trisha mentioned. So the first marine animals, they had an enteric nervous system, look-alike structure surrounding basically just a tube that was moving and digesting everything together. With the development of a head in evolution, all the functions that were important for the overall body and survival were moved to the brain using the same neurotransmitters and the same cells, which just shifted up there.

With the enteric nervous system, its main function became to run the intestinal function of secretion, motility, permeability. Anything that has to do with the GI tract is run by the enteric nervous system fairly autonomically.

FLORA LICHTMAN: It’s independent.

EMERAN MAYER: Yeah. Only if we get into a situation that threatens the whole organism, which triggers the fight-and-flight response, then the brain basically gets involved in regulating the gut as well, but not in the normal homeostatic situation, in balance.

TRISHA PASRICHA: And there’s an uncomfortable truth there too, which is that we can survive despite being brain dead. Why? How? Well, it’s because we have a functioning enteric nervous system. As long as that is functioning and you still have some brain stem input with a breathing tube, you will survive because your enteric nervous system is still nourishing and feeding all of the other cells in your body. That’s how important it is.

FLORA LICHTMAN: When we talk about the gut and the brain talking to each other, how are they talking? What is the mode of communication, Trisha?

TRISHA PASRICHA: Yeah, there’s two main ways. Well, most of how we’ve thought about the gut-brain connection, I think, has been in terms of how the brain communicates with the gut. We live that experience every day. When you’re going on a date, you get butterflies in your stomach, like Flora mentioned. Or if you’re nervous, suddenly you have to use the bathroom and it’s your turn at karaoke and there’s no bathroom in sight. Why? And then when you sing your song, suddenly you don’t have to go anymore.

And some of the ways those types of communications happen, some of it is hormone signaling. Some of that can happen through the bloodstream from the brain down to the gut. A lot of it happens through the vagus nerve. The vagus nerve is this long cranial nerve. It extends down from the brain to almost every internal organ. But it has a very close relationship with the gut.

Now the gut, to communicate back up to the brain, it can’t quite use the bloodstream the same way, because the brain has enacted this really rugged barrier called the blood-brain barrier. And so it doesn’t let a lot of things cross through, although some does. Most of how the gut communicates with the brain is through the vagus nerve.

And the cool thing that we’ve learned is just how much of that communication in the vagus nerve is not top down. Most of it, 80% of it, is from the gut upwards. So the gut is talking all the time. We don’t perceive consciously most of that communication. Our conscious brains perceive what comes to us from our five senses– our eyesight, what we hear, what we feel, what we smell. But there’s this whole realm called interoception, which is all the information from inside your body that is reaching your brain at the same time every second.

Your brain has to grapple with that while also dealing with that outside information. That internal set of signals is called interoception. And your gut, all of that communication for the most part, is happening without you consciously realizing it. And I think that’s why it’s been neglected for so long. But it’s been happening under the radar nonetheless.

EMERAN MAYER: Yeah, it’s just a comment to just any emotion that we have, negative or positive, so just like we see it in the facial expression, the muscles within your face express that emotion if you want or not. The same thing happens at the gut level. The gut changes with every emotion, and there’s emotion-specific motility patterns and secretion patterns in the gut.

And it goes all the way down to the microbes. So the microbes know when you are angry or when you’re stressed because the sympathetic nervous system, part of this signaling pathway, secretes molecules that acts on receptors on microbes, changes the gene expression of these microbes and their behavior. So there’s a lot of studies on the effect on virulence of microorganisms and of pathogens. So when you’re angry or stressed, you’re more likely to get a more severe gastroenteric infection or more long-lasting symptoms, as if you’re relaxed and your microbes don’t get this warning signal from the top down.

So there are many fascinating dimensions to this story that most people don’t think about when they talk about gut health. But as you said in the beginning, this is really the potential for us to really reconceive the whole organization of our bodies and our brain.

FLORA LICHTMAN: That’s very exciting. And I want to talk about some specific examples. Trisha, I know you work on Parkinson’s. We know that’s a disease where you have misfolded proteins in your brain. What’s the connection to the gut?

TRISHA PASRICHA: Yeah. We have had hints that there may be more to Parkinson’s than just the brain for a long time. If you go back to James Parkinson’s early writing and his first case description of these patients, he did notice that they tended to have just incredibly severe constipation. He wasn’t sure why.

And when I started my GI fellowship, by chance, I started seeing a lot of patients with Parkinson’s disease, people with Parkinson’s disease, and they would just tell me I have had constipation. It started 10 years, 20 years before these motor symptoms. And when you go look in the literature, it turns out that’s been well described. We showed this. We replicated it in my lab.

But people tend to get nausea. Sometimes we call it gastroparesis when it causes a delay of movement of the stomach, constipation, and all kinds of GI symptoms, years if not decades, before the motor symptoms that we often think about as being Parkinson’s related, like the tremors. And we think that for at least a subset of patients now, we know this, that the disease itself begins in the gut.

And as you mentioned, Flora, Parkinson’s is characterized by misfolded alpha synuclein protein. It’s this protein. When it misfolds, it causes the death of the dopamine neurons in a certain part of the brain. Well, they’ve done these studies that started in mice, and now we have human data that found that in some people, there’s some trigger that happens. It’s probably a different trigger for lots of people.

There have been a lot of research and interest in pesticides, for example, paraquat. We’ve talked a lot about that in our field. Ultra-processed foods is potentially implicated. Maybe it’s an infection. There’s lots of different things that enter our body through the gut and potentially trigger that misfolding or even other changes that we haven’t yet quite understood that are related to it. But that misfolded protein starts to misfold in the stomach, for example, and then it propagates like a prion, which is a kind of disease that basically induces the next cell to start misfolding. And then that one causes the next one, the next one, and it goes up the vagus nerve to the brain.

And it turns out in humans back in the ’70s and beforehand, we were doing this procedure called a vagotomy pretty often, where we would cut the vagus nerve for certain conditions, really bad ulcers or severe reflux. Well, if you look at the natural history of what happened to people during that time period, and obviously we don’t do this that often anymore. It’s not necessarily– we shouldn’t all be getting vagotomies.

But if you look at that natural history, people who had that procedure, their risk of Parkinson’s disease got slashed by almost half. And it tells us that that link is probably real. And we’re looking into some of this in my lab today to try to figure out what are the triggers. Why does it happen in some people? Obviously, and probably not all, though. There are some people where I think it does start in the brain. What makes these two things different?

FLORA LICHTMAN: Does understanding this role of the gut lead to– are there new opportunities for earlier interventions or diagnostics? What is the meaning for patients?

TRISHA PASRICHA: Yeah, I mean, I think that is the hope of our whole field is that if you think about it, in a way, it feels scary to hear that Parkinson’s is starting in my gut. And maybe this is happening well before I would even know that it’s there. But the other way of looking that at that is to say, well, what an enormous opportunity we have. This means that maybe there is years of time, maybe even longer, where there’s a window before the disease reaches our brain. And that’s exactly what a lot of us in the field are trying to figure out is, can we identify a biomarker in the gut that will herald what may happen years down if we don’t intervene?

And of course, what we need to do is also come up with a way to intervene. And there’s a lot of work being done on both of those fronts right now. So it’s actually, I mean, we’re incredibly biased in that, but it’s a really exciting area of research, I think, in all of medicine right now.

FLORA LICHTMAN: I hope you’re enjoying this conversation from Aspen Ideas. We have to take a break. But when we come back, do probiotics actually work? We will get into it.

[MUSIC PLAYING]

I want to talk a little bit about GLP-1 drugs, because they feel like an interesting case study in this gut-brain system world. As I’m talking about Ozempic or Wegovy, we know that they slow digestion, but they also seem to have effects on the brain. And we’ve seen evidence of this in early trials for GLPs and addiction, for example. What are they telling us about the gut-brain system.

EMERAN MAYER: Yeah, this is a particularly fascinating story. GLP, glucagon-like peptide, is a hormone that’s stored in cells that are in the gut and lining the gut. There’s about 40 different types of cells like this in the gut, in the endocrine cell system, because hormonal system in our body is actually in our gut. Now, you may have heard about the latest version of the GLP-1 drugs, which has now three of these peptides combined, and it’s even more effective.

And all three peptides come from the gut. So basically what industry has done is found out that so you take these signaling molecules that are in our gut that have for hundreds or thousands of million years, worked perfectly well to signal satiety, generate all these signals to our brain that it knows what goes on in the body.

But I think somehow our lifestyle, the changes in the last 100 years, have overwhelmed the system. It’s no longer working. So what industry and science has done, so you take these same messengers that nature has developed and give them in much, much higher doses. And they seem to be working and we don’t what the long-term consequences of that attack is, because right now, it seems to be the only solution to the obesity epidemic and with all its associated comorbidities, the whole list of these chronic disease, these chronic diseases that have appeared.

They seem to be all interconnected. I call it the chronic non-contagious disease epidemic that affects everything from colon cancer to Parkinson’s to Alzheimer’s. So somehow with this system being compromised and now we have a potential pharmaceutical solution to fix it, at least as long as you take these medications, I think this will dominate the discussion and the clinical practice for some time.

FLORA LICHTMAN: Do you think that’s a good thing?

EMERAN MAYER: OK, so if I put on my scientific hat and clinical hat, I would say, yeah, it’s a great thing. We can help so many people, save a phenomenal amount of money because a lot of the interventions that medicine has come up with from bypass surgeries to expensive drugs, all these costs will obviously go down.

On the other hand, when you think about it, is it a good thing, so now we’re really– humans at a certain age are really dependent on the statins and on antihypertensive medications. So now we add the GLP-1s. Is this the way we want to deal with our world that’s gone out of balance, or do we actually want to work more on the root causes that are causing all of this? So we can right now we have pretty good tools now that we can prevent people dying from this, as long as they stay on these drugs. Obviously, a dream for the pharmaceutical industry.

[LAUGHTER]

FLORA LICHTMAN: Trisha, what’s your take on this, anything to add?

TRISHA PASRICHA: Yeah, I’m in agreement on most fronts here. I mean, I think what we’ve found so fascinating in GI is a lot of people are hesitant about GLP-1s because they’re worried about the GI side effects. And GLP-1s is something that we study in my lab to and we’re finding more and more that there are these effects that GLP-1s have that seemingly don’t have much to do with weight loss. And I think that those other effects, for example, in my lab, we found that taking a GLP-1 medication, it’s associated with a decreased risk of getting ulcers, of having damage to the mucosal lining of your stomach.

It doesn’t have anything to do really with weight loss. And these big studies have come out about how GLP-1 medications are associated with a decreased risk of 13 different cancers not related to weight loss, per se. And as exciting and I keep saying that word “associated with,” and these studies are very exciting. We don’t know the mechanism quite yet, and we haven’t nailed some of that down. So I’m incredibly optimistic about them.

I’m a realist that we’d like to help people in ways that don’t involve medication. I am so on board with this medication because it will help so many people, though. And I think, though, that my pause is just– and we’re working on this. Is we need to understand in a lot more detail than we have right now what it’s doing exactly molecularly, and why some of these benefits happen.

I think GLP-1s, just a lot of for example neurotransmitters and the history of medicine, dopamine is a great example. What we know they do in the brain is not what they do in the gut, and they act very differently. Estrogen, all of these things, behave very differently in different organs, in different types of environment. And so it’s a lot to unpack.

FLORA LICHTMAN: We have to talk about the microbiome, because I feel like that’s a huge part of this. And we haven’t really dug in there. Do we know what a healthy microbiome looks like? We know more diversity is better. I feel like I’ve heard that before. But do we know specifically what we’re aiming for with a gut microbiome?

EMERAN MAYER: I think this definition has developed a general consensus, and the concepts have been taken from ecology. So diversity and resilience are all the terms that we know from other ecological systems, from nature, that have been applied to a healthy microbiome, is resilient to perturbations. It has a high diversity, has a high richness. So it’s not just having 100 different types of bacteria, but each bacteria is just 5 or 10 members, but it’s hundreds of thousands.

There have been some attempts that based on the function, so the microbiome field, has moved from asking who is there, which microbes are there, shifting pretty rapidly now to what are these microbes doing and what is their capacity, their genetic capacity. So in a few years, we won’t have any microbiome tests that just look at who is there, but basically what they’re doing.

And one good thing that there’s general agreement on is if they produce molecules, so-called metabolites that they generate from breaking down complex carbohydrates or fiber, it’s a group of molecules called short chain fatty acids. Probably some of you may have heard this word butyrate, which have a lot of beneficial effects on not just the gut, but also in the brain, every system in our body.

One of the most important ones is probably this anti-inflammatory. So we have built into our body a production site for aspirin, that anytime we have an insult to counterbalance, so that’s why a healthy diet, whole food diet is so beneficial, because it nurtures the healthy gut microbiome function, which are to a large degree not exclusively, but anti-inflammatory.

So I would say these definitions, getting it down to which microbes need to be there in a healthy microbiome, there’s also a large-scale studies that have identified, a handful of microbial species and strains that have been associated with the absence of diabetes or metabolic syndrome. But I think going with the concepts of these anti-inflammatory effects and microbes that have the genes to produce these molecules, in my opinion, right now is probably the best definition.

FLORA LICHTMAN: What would you add to that?

TRISHA PASRICHA: Yeah, I agree. I mean, I think something that I find so frustrating right now in the world we live in is that I think that what we think about the microbiome is very tempered, and we understand a lot about certain associations with diseases and maybe the upregulation of certain microbes. But when you as a consumer, as a patient, hear about this, see it on social media, it feels very black and white. It feels like, let’s check your microbiome. If you have too much of this bacteria, we’re going to cut it out. If you don’t have enough of this bacteria, that’s bad. Let’s give you a supplement and we’ll fix it.

And the science is just not there yet. But we’ve started monopolizing on this and profiting off of it a little bit too early. And the way I think about the microbiome, just in simplistic terms here, is it’s like a garden. And if you have this garden and you imagine what I want are a bunch of flowers and you start seeing weeds growing, you might just pluck out all those weeds because we don’t want them. And let me sprinkle some beautiful rose seeds that I do want, and it’s not going to be that simple.

What if those roses aren’t growing, not because the seeds weren’t there, but because the soil pH was wrong. Because you’re not getting enough sunlight. And I think sometimes when we think about #GutHealth, or just the gut in general, lately all we talk about is the microbiome and we just really focus on that. But remember the microbiome, these trillions of organisms, they exist in this ecosystem that is part of us. We have to think about how these microbes are interacting with our individual immune systems, with our nerves.

One species, for example, of some microbe, can behave very differently in me than it will in you because the milieu is very different. And we’re seeing all of this play out in studies. So I find it frustrating when patients come to me and they’re like, I have spent hundreds of dollars on this testing kit, the supplement, it’s gotten me nowhere. Look at the results of my microbiome. Tell me what I should do next.

I wish I could. I mean, what I can tell you, and what I do tell my patients is that here are the principles about healthy or healthful eating, that these are the types of foods that support the microbiome. But at this stage, we don’t have targeted microbiome directed individualized therapy just yet.

EMERAN MAYER: And there’s obviously a lot of– I mean, I shouldn’t call it abuse, but commercial exploitation of that uncertainty is it’s an unfortunate phenomenon. I mean, not for the companies. It’s a billion-dollar industry, the probiotics and prebiotics and postbiotics and synbiotics industry comes up with, always new expressions to justify a new supplement. But if you look at the evidence that these interventions make actually a significant difference, it’s very weak.

So you would not get an FDA approval for any medication with the weak evidence that exists for any of those biotics. And that’s unfortunate because I think I’m optimistic. I think we’re in the second generation of probiotics right now. The next generation will have amazing things for people. It’s already an active area of research where people manipulate the genes of certain microbes to do specific things.

I mean, I’m sure there’s quite a few people here in this room that take probiotics.

FLORA LICHTMAN: Who takes probiotics?

EMERAN MAYER: Yeah.

FLORA LICHTMAN: It’s a safe space.

TRISHA PASRICHA: We’re not here to judge by any means.

FLORA LICHTMAN: But Emeran, at the same time, and Trisha, I to hear your thoughts on this, too. I mean, I have about doctors prescribing diet for mental illness, and other diseases. What do you think about that?

EMERAN MAYER: Well, that’s a different story. I mean, diet is probably one of the most complex vehicles to deliver tens of thousands of molecules, phytonutrients. And when you eat something, a fiber-rich meal, it’s not you’re just eating one fiber like inulin. You ingest thousands of these different fiber molecules. They all do different things to your microbes. So you can’t really compare when people have created this term psychobiotics. You take this one organism and they think it’s going to change your depression, or your anxiety, or ADHD. I mean, it’s ridiculous to think that way.

But diet, there are emerging studies that have shown certain– and the evidence is best for as usual right now, the traditional Mediterranean diet, but also for certain situations like advanced Alzheimer’s disease, a ketogenic diet, or for refractory epilepsy in children, also ketogenic diet. But that’s the exception.

So in general, I think what this traditional Mediterranean diet concept is, it gives you thousands of these molecules that you can put into a capsule and think that this one molecule will actually be of great benefit to you. So that’s my view. I don’t how you think about it.

TRISHA PASRICHA: Yeah, I totally agree. I mean I think actually this is why these alternative medicine and holistic providers do really well is they give this holistic picture. They will advise you a lot more on lifestyle and diet when you’re dealing with something that doesn’t necessarily feel that connected, like depression or anxiety. I mean, as Dr. Mayer said, the Mediterranean diet has been pretty consistently, reliably shown to be associated with reduced rates of depression, of mental health disease, and of course, neurodegenerative disorders.

But that’s not often part of the conversation that you have when you go to see a primary care doctor. It might happen briefly, but we don’t dwell on it in I think in the way that we should. But I think the other thing I want to just point out about that is, when we’re talking about something like depression and anxiety, to use that as an example, I think about that as being part of this gut-brain connection. I don’t think of it as being purely in the head, just as I think of a lot of diseases not being purely in the gut.

And so I think it’s wrong to go completely in the other direction and say, let’s just focus on diet when we’re thinking about depression. I think we all have to think about looking at that connection, which often forms less of a connection, more of a vicious loop. How are we going to treat the brain in our heads and the brain in our guts? I start people on anti-depression medications all the time for their GI symptoms, and vice versa.

And at the same time, we need to also be thinking about diet. But I think there’s often there’s one side of maybe more traditional medicine or these quick visits where you say, all I’ve been told is to take a medicine, then maybe you go to a more holistic practitioner and all you get is sometimes supplements or lifestyle. We have to find that medium that is still very rigorously science-based, and that exists, but it just our model isn’t always set up to have those longer conversations.

FLORA LICHTMAN: There’s so much to talk about, obviously. We are out of time. I am so grateful to my guests, Dr. Trisha Pasricha and Dr. Emeran Mayer. Thank you so much for joining us today.

EMERAN MAYER: Thank you.

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FLORA LICHTMAN: That is it for today’s show. This episode was produced by Kathleen Davis. Special thanks to Tonya Bauer, Libby Franklin, and Ryan Zynger from Aspen Ideas Health for having us and for making this go. And thank you for listening. I’m Flora Lichtman.

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