Your Brain On... Cold Plunges

You've heard it on Joe Rogan, you've seen it on TikTok, it's been praised by CEOs, athletes, and biohackers. Cold plunges are everywhere, from morning routines in Montana to influencer spas in Malibu. And the way they're talked about, you'd think they're a miracle cure for your brain, for your body, and for your soul. But in this age of algorithm-fueled evangelism, when a ritual becomes this ubiquitous, this loud, we have to ask, how much of the buzz is backed by science and how much is just really good storytelling? From dopamine spikes to resilience myths, we're diving into the neuroscience of cold exposure, what's true, what's overstated, and why discomfort has become a billion-dollar industry. This is your Brain on Cold Plunges. I'm excited to speak about this topic. And I'll be honest, I took a lot of time to prepare for this topic because I have some bias against it. I absolutely loathe being cold. You know this. That's not good grounds for diving into. Is that the cold bias? The cold bias. That's a new logical fallacy. It might be. It might be. I wanted to learn about what this whole thing was about. and there's been so many podcasts and so many articles and so many individuals who are on social media and not on social media have spoken about this and have written about it. There have been books written about it and it's kind of this movement. And it's interesting that there's an anthropology human side to it and then there's the science part of it. And a whole lot of sociology. Talk to us about that. Yeah, I mean, when you see this kind of a movement this fast, you have to understand that it's not going to be massive new research that we've discovered. It's rare in science to have that kind of a breakthrough. In the age of social media, we've had multiple, basically, awareness revolutions that has just taken over social media with magical properties of certain things as far as health is concerned. Ketogenic diet was one of those, right? Right, that's true. And what was attributed to them was miraculous outcomes. And then when you go to literature, the hype, the volume of conversation about its positive effect is not often matched by the research. Or even if it is, I'm okay with that. But what intrigues me is what's behind these incredible fast movements. There's usually some intrinsic streams, intrinsic social streams. In some cases, it's a political stream. In some cases, it's a group of people that identify themselves in a certain way that want to kind of push a certain dialogue, a certain narrative. Ketogenic diet, without a question, was driven by a meat-centered bias. We still are exploring the utility of ketogenic diet in small measures here and there, and we should continue to do so. But the force behind it was the fact that people attributed or correlated ketogenic diet with meat. And even when they didn't know the science behind ketogenic diet, which was actually neurological for seizures and things of that nature, they just attributed to one category. So it was the movement of resistance to change or retaining a certain bit of capacities or needs that a group of people connected themselves to an outcome, which is scientific outcome. And it was powerful. I think the ketogenic diet at least had some science behind it for a group of population. I think the carnivore dietary movement is equivalent to what you're saying. It had a lot of the sociology, almost a cultish mentality, group-based thinking process without much research or any research. They all have some sociology. We are plant-based. And I'll tell you, the plant-based movement has a significant bias that's driving it. There's the animal rights. There's the environment. And then there's this group aspect. And that can become problematic when you become driven by the social connectivity and the language that connects you beyond the science becomes a bigger driver than the science. And we've seen that often. And how even in the plant-based movement, there are things that are pushed that are not science-based. I agree. This human species going through this journey of self-knowledge, self-knowing, self-identity, figuring out what's pulling him this way and that way. And especially at a time where we have to do that together. No camps, no groups, no silos, critical thinking and data. It's an unusual start, but I'm sorry. I'm going to start everything that way because it's important. I think this topic definitely requires that because it's such a complex area and it has so many different facets. If we don't look at it from that lens, that bigger lens, and if we just talk about the molecular aspects of it, I don't think we're going to get anywhere. because somebody else will come and will negate what we said about the science or about the anthropology part. All of it needs to be discussed. That said, we were so glad to have had the opportunity to speak with Scott Carney. Now, Scott Carney is an amazing investigative journalist, an author, and an anthropologist. He's written multiple books. He's actually worked with a lot of the primary influencers who propagated this idea, and we were very happy to sit down with him and talk about the anthropology and the sociology of cold plunges and cold exposure. Here's this conversation. I got into ice bathing because I wanted to break up a cult before it had fully exploded. I'd just written this book called The Enlightenment Trap about how intensive meditation can sometimes drive people crazy. And then I saw this picture of a dude on an iceberg. I know he was probably 55 years old and he was like in his underwear. He sort of exuded, at least in the photo, this picture of human resilience and health. And I was living in Los Angeles at the time, warm, perfect, 80 degree days all year round. And his name was Wim Hof. And he said that he could teach anyone to do his ice bathing method. Endure the cold and cure the war on bacteria. That's his line. And I was like, this is bullshit. And I'm going to go debunk him. And I got this assignment with Playboy because I was writing for Playboy at the time. Great magazine. and I flew out there with the idea of debunking him because I'd been debunking a lot of these false gurus and it turned out after I tried his method, which is basically some pretty simple breath work and hanging out in cold stuff for a long time, I could do the same things he could. I climbed up a mountain in a bathing suit. It was probably like five degrees out or something, pretty cold, bare chested. I was like, ah, this is amazing and you've probably seen photos of this stuff in your internet feeds by then. But in 2013, this felt unusual. This was weird. I wrote this story for Playboy where I had changed my mind about Wim Hof. Is he a cult leader? No, this stuff works. And that turned into a book. And Wim Hof got really famous from this article. This article led him on to Joe Rogan and to these other places. And he got huge. And then I wrote this book and it was a New York Times bestseller. It was huge. And all of a sudden, everyone in the world was doing ice baths. And I still do ice baths. Like there's something really magical here. But at the same time, I saw this group becoming a cult fueled by internet photos, big inspirational bathy events. And so recently I've sort of like switched my perspective on at least the movement of ice baths, not the ice baths themselves. Cause as you said, the thing in themselves has its own life. It's its own neural connections, the own things that happen and probably beneficial. Whereas the monetization of these personalities is pretty toxic. And about two years ago, I was like, look, we have to stop idolizing these ice bath evangelists. It's such an important concept that even within that culture, what happens is there are layers, the superficial physical layer. It attracts those people who are the superficial physical level. And then there's deeper and deeper levels, which is more cognitive, more intellectual, even beyond intellectual, more spiritual and all that, that is often not explored. Before we get into that side of the psychology, what makes a cult? You brought up the concept of a cult and there's a cultishness to this once you become that closed, that insular. There's a lot of definitions for cults but the one that's coming through my mind right now as we're talking is an adherence to unreality. Like the idea that an explanation for how the world, the universe works is different than what your repeatable science says and you'll see in the ice bath movement, right? You'll see in the ice bath movement that there's so many explanations for what is going on that are pseudoscientific. And I say pseudoscience, we throw this word around a lot. There is a fair amount of B plus level science on ice baths where people have studied it. They put people in different machines and looked at stuff and studied things. But none of it is like we know exactly what it is. And people glom onto ideas. One of these things that people talk about, for instance, is brown fat. And a few years ago, people were like, brown fat, it will burn your white fat away and get rid of your gut and do all these things for weight loss. And it's really good. and it's activated by cold. All of that is true, right? But then people made this leap that ice water will radically increase the amount of brown fat you have. And if you get this brown fat, you're going to be on your road to health. And I wrote about brown fat in What Doesn't Kill Us and other books because the research was interesting. It pointed to a good direction, but it wasn't conclusive. So a cult is this adherence to unreality and the blind faith, sometimes to an authority without the ability to contradict it and update. your terms. And one of the hallmarks of all cults that have a leader is that leader gets isolated. I'm seeing there's lots of people where somebody who's on the internet, very popular, they get isolated where they see the affirmation in those likes and those people saying you're awesome and you saved my life and all that stuff. They get that affirmation and they realize that they're always right and their gut instinct is always right and they start believing their own bullshit. Even people who start out good get twisted by that constant affirmation. You're absolutely right. It's a phenomenon that's repeated itself. And it's a sense of certainty, confidence that makes people feel good. One of the quotes I heard from one of my mentors was the civilizing influence of doubt. Science does not live in certainty. Science lives in directional uncertainty. As a society, and I think we're there. I think as much as people think we're in a dire state of misinformation and everything, no. Reason is incredibly sticky. What it's doing is lifting the floor of awareness and consciousness about concepts like logical fallacies and all of these things and not to extrapolate beyond the data and all of these concepts that are important for a civilized society to operate. Because without that, you're not a civilized society. Let's explore this ice bath concept. There is some benefit to it. That's a signal. That's not the end. That's the first step of an eight-step, nine-step arbitrary number, process of finding proximity to truth. Ice might be good, and there's an evolutionary perspective that tells you that they might be good. And you've explored that. What are your thoughts on that aspect of it? I think the most important thing about an ice bath is actually sensorial and the ways that you feel things. When you jump into an ice bath, usually we live in eternal comfort, right? Everything is climate-controlled and whatever. And when you jump into an ice bath it like intensely uncomfortable at first especially if you not prepared for it And it that movement in your the way you control your nervous system from going from oh my God this is terrible to I can handle it It okay And that ability to relax your nervous system response is frankly it magical It changes the way you feel about anxiety It makes your day better It has this huge psychological shift And also there an element of mind over matter because if the uncontrollable side of your body you are able to exhibit control over it's actually a skill that we don't generally have. Like I'm moving my hand right now, right? And this is mind over matter. My mind is saying hand moves and that's your somatic system. But now we're doing it to this, this part of your nervous system, which is autonomic, which happens automatically and you're able to express will over that, it shows that we have some little bit of control over these things that we think are uncontrollable. And here's where the problem comes in is that people will then extrapolate that to say it cures everything. I think there's this interaction between consciousness and the stuff you do, which does have an effect, which leads us into this gray area, which then gets exploited by people who are able to profit off of it. Yeah, absolutely. Placebo effect is a big part of medicine. And explaining off placebo effect is complex because placebo effect often has to do with stress management. Stress has an effect on every aspect of the body, short-term, long-term. It has an effect through sympathetic system, the autonomic parasympathetic system. It has an effect through the hypothalamus, the limbic pathway. And so it can have a short-term effect or a long-term effect. Cortisol, short-term, long-term, and completely restructuring. So whatever affects your stress is going to affect the body in that way. But it varies. So that's why we don't take placebo effect that serious as a mechanism. Because if it's stress, your stress and your relationship to that thing that reduced your stress and your history of your relationship with stress, they're so complex that you can't make it into a codified thing for everybody, right? So everybody's going to respond to stress reduction of some sorts. And I'm even simplifying it. If I believe in acupuncture, I'm going to respond more. My stress is going to be reduced much more. So my body's going to... But if I don't, it's different. That's a phenomenon that has to be thought out that, okay, placebo is good. But can I use that as a phenomenon of intervention? No, because in this case, like ice bath, the effect is really amazing to a lot of people. And everybody jumps on dopamine. And I hate that, but I'll go into it. Your dopamine is the anticipation neurotransmitter. It was created for you to move where a being didn't want to move so that it would create greater probabilities and greater survival. And anything that creates attention, anticipation, and if it's released without killing you, it creates great relief, great sensation. In your book, The Wedge, you explore the gap between stimulus and response. How do you define that wedge? And how might it apply to everyday stress? Not just cold or altitude or things of that nature. So when you feel something, anything, whether it's an emotion or a stimulus like an ice bath or heat or anything, your sensory system detects it through your peripheral nervous system. It comes in through your nerves, goes up to your brain, goes to the bottom of the brain and then to the top of the brain. Consciousness, and there's a huge debate on where consciousness is, but we know that it is. We think, therefore, we are. And we can, when we feel something, signify what that sensation means. In an ice bath, it's very obvious because that's a very strong sensation. Think about the volume button. It's all the way up in an ice bath. It's the sensation of death because your body goes immediately into fight or flight. You can get into that ice bath and think to yourself, this is the worst thing in the whole freaking world and lean in to that death feeling and you will have the worst experience because you will have signified that raw data coming in from the nervous system into your brain goes from feeling to your cognition of that feeling and you will change that to a horrible experience. You will send these cascading neurotransmitter storms through your whole body saying horror and your whole body experiences horror. Or you can get into that exact same stimulus, the ice water and think this is just sensation in my skin and it feels awesome. And you can will yourself to feeling this is awesome. And then that raw sensation gets your brain. And instead of sending that cascade of horror through your body, you can send an element of awesome through your body and you get out and you feel great. That is a hugely powerful thing. And it does show that you have some aspect of control over literally those neurotransmitters that come through you, but the hormones cascades, every cell in your body that gets affected by that stuff has a different view on that external environment, which I believe is good for you. How it's good for you is the mechanisms for how that's good for you. We can't study. We can point to some ideas, but we can't like know exactly what it is. But there is a mind over matter element of that. And you can do that with everything. And there's more to this. Like when I talk about the concept of the wedge, it's putting your anticipation and your perception in between the sensation and your response. That's the wedge. This entire book, The Wedge, is me going through 10 different strong sensations, right? And then using those strong sensations to create generally positive outcomes. And there are things that we know about, like psychedelics. That's a huge sensation, right? You take a huge sensation and then you redefine it for how it means. Maybe you can use it for mental health stuff. There's meditation. I did stuff with fear, with eating and with taste and any sensation, you have this ability to insert a wedge. So this book is sort of like how I conceived of giving you the tools to use literally anything to interact with your nervous system. And the problem is that we don't know exactly what you're doing, right? This is still experimenting. We don't know exactly what it is, but we do know that we can re-signify things. It seems pretty useful for things like PTSD, pretty useful for anxiety. Sensory deprivation has some really cool anti-anxiety effects that rate next to placebo, interestingly enough. Yeah, yeah. You've done an amazing job, and your books have actually, directly or indirectly, that's why I was attracted to your work, have addressed this complexity, this weirdness of data, partial data, placebo, all these things. and you're bringing in service. And at the same time, also giving space to things that are not explainable yet, but I feel something there. You even actually put yourself under the microscope. I follow this man. I invested. I double invested. And yet when I found it was false, this is how I did. And that's valuable. And that's the most important thing is that if we try to look for somebody who is honest, like what is honesty? Honesty is a very important character for people. And it is being able to issue a correction which is personally hard, which personally undercuts something that you have built up in yourself. If we look around at major influencers, how often do they issue corrections? You can probably even do a scientific study on the number of corrections issued corresponding to the credibility of that person. And especially not just minor corrections. Oh, I messed up a person's name and doing a false apology, but actually saying, look, I really messed this up. I doubled down on something and I was wrong. and I'm sorry and people get things wrong. That should be a forgivable state for an audience. It usually isn't. Usually people respond in an audience being like, you're right and you're also wrong. So you're right as in the value you're expressing is absolutely right. If I see someone giving a correction, I know that that person is somebody that I should double pay attention to. However, I would say that on the internet, the currency of the social economy is that if you admit a failing or a weakness on the internet, you expose yourself for people like, well, that person was wrong once and I should never trust them again. And you actually get currency by doubling and tripling down on lies. This is a problem with either the way humans interact or maybe how algorithms feed. I don't really know which, but we as an audience, as a society, we punish people who make mistakes and admit their errors. And that is really a problem. I've done all these videos about these mainstream health influencers who have real moral problems and all of the corruption with them. But I wonder to myself, I think about this often, what does that person need to do to reverse direction? Because I think that everyone ultimately can. We need to offer paths to people who are these ultimate grifters to be able to shift and to be able to come back to reality. Otherwise, we are enabling that bad behavior. Yeah. I don't think that if there's a lot of loss, financial or otherwise, it's not going to change. But what will, I think, change our entire understanding as human beings of how to approach this, as I said at the beginning, I think reason and logic is powerful. Certain complex logical sequences have not become the fabric of humanity and definitely not the social media crowd, which is immediate, right? But there's no question that there's truth in the fact that if somebody in a genuine way changes their mind, that's an incredible strength. The more they see this, the more they see people doing it, people become aware more and more of that as being a strength. Your work has spoken to that. Scott, your work is amazing. It's important. It uses health as a tool, but it speaks to human experience and human evolution with information. So I really appreciate your work and would love to have many other conversations with you. Well, anytime, this has been a lot of fun and keep doing what you're doing because we need good, rational, humble information in the world and we need to correct our mistakes. And if you keep doing that, you're on the right path. That was a great conversation with Scott. I love the human story aspect of it as well. And it was both interesting and kind of scary. It was. And he's gone through his journey. It's interesting that he was open enough to go through the entire journey from a devout believer and all that to a skeptic as a reporter coming out the other side with somebody who is looking at it from both sides now. Absolutely. Let's go ahead and zoom back in and ask a simpler question, which is essentially, what does the science actually support and you know where does it stop? I think a good place to start would be and I have my notes here with me is to look at the physiological responses of what happens when we do a cold plunge and this is pretty solid. There's a lot of data that supports it. Generally speaking when we're exposed to cold it triggers our sympathetic nervous system. What happens when you are activating your sympathetic nervous system? Your heart rate goes up, your blood pressure goes up, your peripheral arteries vasoconstrict, which means they kind of shrink and they get smaller to preserve heat. And you also have an increased respiratory drive. So you start breathing really harder as well. And then neurochemically, there are a couple of things that happen as well. There's a short term increase in norepinephrine and there's a short term increase in adrenaline. And it's really important to know that it's short term, it's not long term, it's a survival response. It's as if you just faced a tiger. It's the same proverbial tiger I bring up every time. Fight or flight, you have to survive. And what happens is when you do survive, when you get past that hill and you realize that you're not dying, it's an incredible response. And that's actually secondary response. But the initial response is massive enough. Your body had just went through a massive shock and it responded to it. It responded to it with every part of your body, from your heart, from your lung, from your cells, from your skin, from the vasculature, to the nervous system, to the frontal lobe closing because you just have to survive. It's your limbic system on fire. Your reproductive system, forget about that. Yeah, yeah. They're frozen. Yeah, I'm frozen. Keep me at bay, forget it. And then immune system even immediately and of course long-term is responsive to that. So every part of your body. So it's a major attack on the body, but at the same time it exhilarating What is exhilaration exhilaration is that moment where you realize I not gonna die you know my body not going to implode or explode I just went through this valley of death and I'm coming across the other side. So almost everything now is flushing through. So that's the response. And we mistake that for long term. What's the purpose of your attention? There's a billion things you can pay attention to at any one point. There's degrees to attention. There's an alternative state where the attention becomes so focused as if there's nothing else is important but the thing in front of you right so there are degrees of attention guess what this is this is that when there's a tiger in front of you i better change another animal dragon i know you yeah dragon well yeah mythical okay fine yeah why not it's our it's our podcast cockroach no no no no i can't i can't handle that that's my biggest fear but um let's say it's a drag in front of you right does anything else matter? Does the texture of the seat you're sitting on matter? Does the temperature of the room matter? Does the fact that your two-thirds matter? This is that. So the cold plunge brings you in front of the dragon because it's that degree of intensity that brings all of the focus. So the sharpness that people are experiencing, short term, we're talking about minutes and even hours afterwards, people are sharper. And what that is, that's the brain actually now quiets down all the other limbic distractors. The limbic distractors are quiescent. The brain is not thinking about, you know, the quantum theory. It's about the dragon. There's something about anecdotes as well, you know, when so many people say the same thing, that's a powerful experience. I actually watched another video of a group of men somewhere in Europe getting together and they all bonded, just seeing human beings get together and talk about their oneness brings up this primal memories of brotherhood and being together. And then they all did some cold plunging. That was powerful. The relationship with this behavior is extremely physical and extremely visceral. And even, you know, primal. It's cold. It's heat. It's pain. There's incredible power to it. And then you add ritual to it. Then it takes another level. So let's move through the science real quickly, because I have so many questions for you at the end of it. One of the statements that you keep on hearing in the ether is that dopamine increases when people do cold plunges. And there is actually some science to it. Some studies have suggested that dopamine can increase up to two and a half times the baseline. But again, when you look at the studies, they're basically just these short acute responses. It's context dependent, and there's really no long-term follow-up. It's almost the same thing that happens when people are under acute stress. Dopamine fluctuates all the time. It doesn't really equal to treatment of mood disorders or brain diseases for that matter. It's just this blip that we see, an acute response, and then it goes away. Dopamine responds to chocolate. Dopamine responds to a funny movie. Dopamine responds to a smile. It doesn't mean that that response has any meaningful short or long-term connotation. So it's important that we actually take control of this dopamine beast that has taken over our culture. The fluctuations in dopamine, the same way that another beast has taken over our culture, like the fluctuations in glucose, are all context dependent. Let's not make things out of any number that you see go up and down. They have meaning, they have context. And then on top of that, you have to see if it has long-term connotation. And that's never looked at often. So the dopamine story is true, probably. Everything affects dopamine, but does that have meaning. Right. So feeling better is not equal to becoming better. Correct. Oh, that's great. When it doesn't change you, you know, it's just feeling better. Let's talk about this arousal that people actually feel after cold plunges, this acute alertness that you were talking about. There's actually no study whatsoever out there. We don't have any objective evidence that this acute alertness is equal to things like neuroplasticity, where the brain cells makes connections. There's no evidence that it improves cognition or it lowers the risk of neurodegenerative diseases like Alzheimer's disease and vascular dementia in the future. Definitely there's no evidence of it treating anxiety or depression. There are some studies and they're basically anecdotal and observational, but they're not using any validated measures of anxiety or depression to show any meaningful change later on. So I actually couldn't find any convincing evidence for cold sources for mental health or brain health. I mean, in PubMed, which is where we actually find data, you can find a paper on anything nowadays. So to not find anything meaningful is surprising. And then the disproportionate noise and volume you hear about it out there and not finding data. Yeah, it was humbling. And so this striking lack of data on human data and human trials, it actually kind of makes us confident to say that right now it shouldn't be used as a tool. You know, you can't really say, oh, do cold plunges for your mental or brain health. We can't say that confidently. Positive side, it actually opens up this curiosity for scientists to say, okay, let's study it. This doesn't mean that we shouldn't do it. It's really important for us to separate the question of whether this should be used as a therapeutic, that this is a method of improving mood or improving health or diminishing cognitive decline. No, we don't have that data there. But you know, if people want to do things just because they feel good and they want to challenge themselves, all that? Absolutely. That's completely legitimate. And then I love the fact that you said that it doesn't mean that the research shouldn't continue. Whenever we are countering something, we're never completely negating it. Because as a scientist, you just say what's available right now. You can't extrapolate and go full ahead of yourself and say, oh, it's not going to work for anything. There is some evidence that cold plunges can temporarily improve certain aspects of our life. There's been some data that shows that stress is reduced after cold plunges and that it may improve sleep as well. The mechanism that was suggested is essentially related to reappraisal of one's stress levels. It also offers the availability of a ritualistic system where you do something and then you follow certain things. Human beings rely on rituals to take care of their life and to take control of some of the chaotic things that are around us. And this ritual is powerful. Let's be honest. You're doing something regularly. I mean, that's the idea. And you're doing it at a sacrifice, which means that you at least tell yourself that I have discipline. And that can be empowering. That can actually expand into other behaviors, because if you have confidence that I'm doing something this difficult, then it might give you confidence to do other positive things. Remember that one of the things we tell people who have anxiety, of course, besides therapy, seeing a psychologist, and some of them may need medication, but be it anxiety, be it attention deficit or others, as an adjunct, not as an end-all be-all, is a morning exercise routine. So the routine gives you control. Control affects anxiety, control affects attention. And on top of that, the physical component of it and repeatability of it and the sacrifice of it gives you something to build on. All right. So what about the autonomic nervous system and the heart rate variability claims? There've been some claims that show cold plunges can change our parasympathetic markers as well. And one of them that can be measured appropriately is HRV, which is heart rate variability. Heart rate variability is measured in milliseconds, and it essentially is very, very sensitive to so many things that we do. That is one of the limitations of measuring HRV and associating those changes to just cold plunges. For example, your heart rate variability can change depending on what time of the day it is measured at. It changes when your breathing pattern changes. So you breathe hard, your HRV changes. If you breathe slow, it changes. What position you're on, lying down, sitting, standing, upside down, changes your heart rate variability. And other measurement conditions like temperature, your mental state can impact it too. So for something so variable, for us to kind of couch that as a marker of parasympathetic system for cold plunges, I think is not appropriate. Confounders. All these other things that could affect it from this one thing, which is cold plunges. So I think that to ascribe some effect on HRV from cold plunges is going to be very difficult to cleanly separate, cleanly describe. Right, right. So our bottom line thought is HRV is a physiological signal, but it's really not a clinical endpoint, and it can't be used as a clinical endpoint because of the very things that we just suggested. Another important point that we have to talk about during this podcast is the impact of cold plunges on our heart health and cardiovascular system. When people are exposed to cold shock, it can increase their heart work. So cardiac output is increased, which basically means that the heart is pumping faster, blood pressure goes up, it can actually increase the demand of oxygen in the heart muscles. And that could potentially cause some problems for people who have, you know, myocardial infarction, or they have narrowed heart arteries, or some sort of a cardiovascular disease, because it could provoke arrhythmias, it could provoke a heart attack, it could provoke even vasoconstriction peripherally putting a lot of load on the heart. So that is usually never talked about. No, no, I haven't heard it, but there are cases. It's a stress test. And those that are not ready for the stress test, a lot of people that might have significant risk at the precipice of a heart attack or not even at the precipice, maybe they're at risk and they put themselves through this, they're going to be stressed. And then let's say that they have a heart attack in that situation, then they're not prepared and they might not get to a place or situation where they can remedy. There are actually some really good review papers that talk about this. There was one that was published in 2017 by MJ Tipton in the Journal of Physiology. And what that paper showed is that cold shock causes rapid blood pressure spikes, increased cardiac workload, and arrhythmia risk in susceptible individuals. So cold plunges are not just benign. People actually have to understand that if they have cardiovascular risk factors, the stress on cardiovascular system is real. And especially for people who have an underlying heart disease or cardiovascular risk factors, they have to be really careful. Another condition is asthma. Right. So some people who have asthma have reaction to cold, even just regular cold. They can actually have a really massive response that might injure them significantly. Absolutely. I actually read this from a cardiologist that has published heavily on the subject and also is a cardiologist and a primary doctor. And he said that people who have atrial fibrillation or rhythm disorders, people who have coronary artery disease, if they have peripheral artery disease, Raynaud's syndrome, pulmonary issues, it's very important for them to stay away from cold plunges. And those are not rare conditions, very common conditions. Right, right. Let's talk about muscle recovery and muscle growth. Now, this is one area that has been studied recently. We know that a lot of athletes, whenever they do heavy lifting, resistance training, or some sort of an aerobic exercise, it's quite common for them to kind of go into a bucket of ice. I actually have seen it in a lot of movies where guys in the locker room are like hanging out in ice buckets. And there's actually data that that might not be a good thing. It does get rid of soreness but specifically when it comes to building muscle there been some studies that show that it could blunt the inflammatory signaling that is really important for muscle growth There was a very important randomized control trial published in 2015 by L.A. Roberts. The title of the paper is Post-Exercise Cold Water Immersion Attenuates Acute Anabolic Signaling and Long-Term Adaptation in Muscle. And it was a two complementary human studies. They did 12-week strength training studies in 21 men. And then they did an acute mechanistic study with muscle biopsies in nine men. And they compared cold water immersion with just regular active recovery. Both of these groups trained equally. But they found out that the active recovery group, not the cold water immersion group, the active recovery group actually gained more muscle strength and more muscle mass. And there were some specific differences, and I don't want to geek out right now, but they looked at their isokinetic strength, the type 2 muscle fiber size, the myonuclei per muscle fiber, how it actually went up by 26% with active recovery. And these were not seen in the cold immersion group. So the takeaway was regular post-exercise cold immersion, blunted strength, and hypertrophy gains. There have been other studies that have come out since then as well that kind of refined on that. They actually found that strength gain is not that affected. But still, it is our understanding right now that when people do cold water immersions right after exercise, that really blunts muscle growth. That's remarkable. That's a piece of information that's often not shared. And it's important because most people, most of the athletes and young men that do this, do it because they think that they're gaining something out of this, especially recovery. What about its effect on inflammation, joint inflammation? So the big story here is that therapy like this or ice baths actually reduce inflammation around the joints, especially in athletes. What's the data on that? When it comes to data regarding inflammation and changes in inflammatory markers after cold plunges, the data is kind of all over the place. There are some studies that show that cold plunges lower inflammation. It definitely lowers perceived pain. athletes actually feel less pain. But objectively speaking, some studies show lower inflammation, some studies even show high inflammation, and then others show a wash. So we really don't have good evidence to say it with great degree of confidence that yes, you know, this is something good. And you know, just talking about inflammation, you and I were chatting about it earlier today, inflammation has two phases, too much of it can result in dysfunction of the body, and too little of it can actually impair healing and our adaptation, muscle growth and tissue reorganization for better health outcomes. And so inflammation is not always bad. Maybe cold plunges is kind of highlighting that. Correct. I mean, in the muscle growth component, you actually spoke about the fact that the kind of inflammation needed for muscles to grow. Remember, the muscle growth is an injury process. The actin and myosins are injured so that there are more cells produced. There's an inflammatory response. That inflammatory response actually is involved in growth of the muscles. So the term inflammation is not always negative. There's so much to it as far as chronicity, the extent of it, and the localization of it. So we can't look at it that way. And then the data itself is all over the place anyway. Right. So bottom line, a cold water immersion can reduce pain and soreness after intense exercises. But the evidence that it meaningfully improves, say, joint health or bone health is very weak. And a regular use of cold water plunges can actually interfere with the body's normal repair processes. So athletes need to be very careful about that. At least aware of it. So one thing that you always tend to hear whenever there's a podcast about cold plunges is brown fat. Have you heard of it? Yes, yes. I mean, I've heard about brown fat so much that, you know, it really intrigued me and I've been reading about it a lot lately. One of the most amazing things is confidence that some of the people that for the first time they hear a term and then they get stuck on that. And so I had a debate with one of my cousins who was a finance background. And he was all over brown fat. You would think that he was dealing in brown fat. And no matter what I would do, I couldn't shake him off of that topic. To his credit, to be honest with you, there was a time, I think maybe a few years ago, where it was the discovery. You know, it was the topic that everybody wanted to talk about. And they're still talking about it, but I'm glad that we're having more information about it. So let's kind of just jump in. Why is it called brown fat why is there a white fat a beige fat and then a brown fat there's a beige fat there's a beige fat too amazing so it's called brown fat because they look brown under a microscope and the reason they look brown is because they have a lot of mitochondria i would have never guessed that yeah they have a lot of mitochondria they look brown yeah you look like you're about to say a joke there dad joke coming out i don't have dad jokes i have you do really sophisticated sophisticated dad joke which we all love very much in any case so these mitochondria carry a lot of iron and so iron gives them that kind of brownish color right i think for the purpose of this conversation we're just going to refer to it as brown fat but in scientific terminologies it's usually called brown adipose tissue or bat okay it basically burns energy to generate heat thermogenesis is its thing correct it's made for thermogenesis that's why babies have a lot of brown fat and it uses a protein called ucp1 right so that's one of the proteins that it uses and it sounds really compelling like imagine having some blobs of fat in your body that burns fat correct that's amazing you mean i have fat that can burn fat and calories that's awesome right and there have been some studies but most of them have been in animals i looked for some human studies and we've actually found out that cold exposure does activate this brown fat. There was a paper that was published in the New England Journal of Medicine in 2009 by Dr. Lichtenbelt and team. Cold activated brown adipose tissue in healthy men. They used PET scans, the imaging, in healthy adult men and they found out that cold exposure activated existing brown fat and this brown fat increased glucose uptake during cold exposure. There was another study in the same year by Vertanin And they confirmed that adults do have metabolically active brown adipose tissue and that activity increased when they were exposed to cold. It's there. It happens. Yeah, exactly. So the statements like cold exposure activates brown fat is factually correct and it's been supported in humans. And so where the evidence kind of starts to thin out is the extrapolation beyond that, right? So when you look at the volume of brown fat in human adults, it's really, really small. It's not significant at all. It's mostly, you know, around the neck, around the shoulders. And it's very variable. Some people have a lot of it. Some people have a little of it. It's much lower than what we find in infants and in rodents. And its activity is seen mostly in younger individuals and in leaner individuals. So people who are metabolically healthy. The key implication is that even when brown adipose tissue or brown fat is activated, there simply isn't much of it to work with in most adults, right? Correct. If there's a time when we can actually maybe inject brown fat in human beings, if technology allows for that, that's going to be cool. So let's dive deeper into the calorie burn aspect of it. I think this is the biggest misunderstanding. Activation of brown fat doesn't necessarily mean any meaningful energy expenditure. There have been some studies that have actually looked at it. There was one review that was published in the Journal of Diabetes by Dr. Betts and colleagues, and they basically reviewed all the available human data on brown fat, and they concluded that brown fat activation increases energy expenditure only modestly, and the additional caloric burn is very small, and it is often comparable to a short walk, mild physical activity, and not enough to meaningfully affect weight loss, body composition, and cardiometabolic risk. That's remarkable. As much as we hear about it, and then the data doesn't even come close to the outcomes that are often spoken about. Yeah, I think 20 minutes of dancing the macarena can actually burn more fat than, you know, plunging into the macarena burns a lot of calories. So I think the core correction that our lovely audience need to understand is that brown fat activation does not equal to significant calorie burn. So those are the studies that we phone. Now, let me tell you about what I didn't find. I actually didn't find any meaningful studies that looked at mental health measures and cold plunges. So no depression and cold plunges, no anxiety and cold plunges. No strong human studies. There are some anecdotal studies and there's some observational studies, but there's really nothing that looked at validated measurement tools and clinical outcomes. That could be because one, it's something new. Not a lot of people, have tried it for a long period of time? Well, I'll tell you, I mean, it is difficult for long-term outcome studies like dementia, because dementia starts years earlier, and to correlate that, it's going to be difficult. But even then, if you catch some group of individuals at MCI stage, you could see how many of them develop dementia later on, and that's not a hard study to design. And for anxiety and depression, it's a lot easier. You can actually identify individuals with those symptoms and then have a control group and see over six months what's the outcome. Those are meaningful results that one can rely on. Yeah, but there's a lot of studies on mice and rodents, and we know that rodent studies don't really translate well. Mechanistically speaking, you know, mice are not men or women. So how would you frame cold plunges from a public health perspective? So they should be used optionally in individuals that are healthy, and they should not be framed as a treatment or as a therapy. They should not be marketed to people as a cure for any of the diseases. And we should all be aware of the fact that the data does not even come close to what is purported out there in the public. And on top of that, people should recognize the fact that it's not without potential harm. The number of individuals who are at risk of vasoconstriction, of vascular disease, of asthma, especially reactive airway disease, these are large numbers. So people who are just trying it because they think there's nothing to lose, there is a possibility of loss because of those consequences. All in all, at this point, I don't think it's a public health recommendation. At this point, it's something to be observed for us to do more studies on. And more importantly, be cautious because we want to make sure that we don't push this concept so aggressively in populations that are susceptible. Absolutely. And I just wanted to add that it should not be used to replace evidence-based care. If there is something that there is a medicine for or if there's a therapy for that has been studied for a long time and it's being offered by a health care provider, cold water plunges is not a replacement for that. And I'm saying this with a lot of love and affection for our audience. But I have actually seen people deny getting mental health therapy and opting for many things, cold plunges being one of them as, you know, something that could potentially help them. And that's not how it works. you definitely need therapy. So it should not be replaced by this. Absolutely. Thank you so much for listening. We hope you enjoyed this episode as much as we did. And we hope that you found it useful. The references and the citations of the research that we spoke about during this conversation will be listed in the show notes. And we hope to connect with you again very soon. Thank you for listening.