Show Notes

Cold water immersion may be one of the most powerful yet underutilized therapeutic interventions available today.

In this episode of The Dr Kumar Discovery, Dr. Ravi Kumar sits down with Dr. Mark Harper, a consultant anesthesiologist who has spent years researching cold water physiology. Together they explore how controlled cold exposure transforms brain and body function at the neurobiological level, and why this simple, accessible intervention is showing remarkable results for depression, PTSD, burnout, and chronic pain.

In this episode, you will discover:

• How cold water immersion activates the mammalian dive reflex and what that means for your nervous system
• The role of the trigeminal nerve and vagal tone in the body’s response to cold exposure
• Why cold water exposure has produced 60 to 80% remission rates in depression, compared to typical SSRI response rates of approximately 40%
• How hormesis and stress inoculation principles explain why controlled stress can build resilience
• Applications of cold exposure for PTSD, burnout, and chronic pain
• Clinical safety protocols for cold water exposure
• Practical frameworks comparing cold showers, immersion baths, and sea swimming
• How Dr. Harper developed outdoor swimming as a clinical intervention
• Dr. Harper’s collaboration with the Extreme Environments group at the University of Portsmouth

Key Takeaways

• Cold water immersion triggers a powerful neurobiological response through the mammalian dive reflex, activating the trigeminal nerve and increasing vagal tone
• Depression remission rates with cold water exposure (60 to 80%) significantly exceed typical SSRI response rates (approximately 40%)
• The principle of hormesis explains why controlled, manageable stress can strengthen the body’s adaptive systems
• Cold exposure is not one-size-fits-all: cold showers, immersion baths, and open water swimming each offer different levels of intensity and benefit
• Safety protocols matter, and gradual, supervised exposure is key to getting the benefits without the risks
• This is an accessible, low-cost intervention that could complement existing treatments for depression and other conditions

Guest

Dr. Mark Harper is a consultant anesthetist specializing in cold water physiology. He has developed outdoor swimming as a clinical intervention and collaborates with the Extreme Environments group at the University of Portsmouth.

Resources

• Dr. Mark Harper’s Website: drmarkharper.com
• Dr. Mark Harper on LinkedIn: LinkedIn
• Dr. Mark Harper on Instagram: @thewildswimdoctor

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Transcript

[00:00 –> 02:21] Dr. Ravi Kumar: Welcome to the Doctor. Kumar Discovery. My name is Doctor. Ravi Kumar. I’m a board certified neurosurgeon and assistant professor at UNC. Today, we’re talking about cold water immersion. If you’ve ever taken a cold shower or stepped into a cold plunge, you know the feeling I’m talking about. You get out, and it’s immediate. Your body feels different. Your brain feels different. Honestly, I would call it almost euphoric. But in addition to the immediate mental benefits, there’s a complex physiological response with cold water immersion that leads to significant benefits in your overall health and resilience. My guest today is doctor Mark Harper. He’s an anesthesiologist in The UK, author of the book, Chill, the Cold Water Swim Cure, and one of the world’s leading experts on the clinical applications of cold water. In this episode, we’ll get into the physiology of cold water immersion, stress adaptation, inflammation, mood, and talk about the groundbreaking research that doctor Harper is currently conducting on depression and cold water swimming. If you’ve ever wondered why cold water does what it does to your body, this is the episode you wanna listen to. At the end, doctor Harper will outline how you can safely and effectively improve your life with cold water. This show is a real gem, folks, so I hope you enjoy it. And before we get started, it’s important to note that this show is for informational purposes only. It’s not intended to diagnose or treat any medical condition. Both doctor Harper and I are physicians, but we’re not your doctors. I want this show to empower you with knowledge that will help you make better decisions about your own health. Also, this show is separate from my role as assistant professor at UNC. Okay. Let’s get into it. My name is doctor Ravi Kumar. I’m a neurosurgeon in search of the causes of human illness and the solutions that help us heal and thrive. I want you to join me on a journey of discovery as I turn over every stone in search of the roots of disease and the mysteries of our resilience. The human body is a mysterious and miraculous machine with an amazing ability to self heal. Let us question everything and discover our true potentials. Welcome to the doctor Kumar discovery. Doctor Harper, thanks so much for coming on the show today.

[02:21 –> 02:22] Mark Harper: Yeah. Thanks for inviting me.

[02:22 –> 03:12] Dr. Ravi Kumar: I’ve been super excited about having you on the show because you’re one of the world’s experts in cold water immersion and its effect on the human body, and this is something that everyone’s interested in right now. One thing about cold water immersion, unlike vitamins or any other thing you can do for your health is after you get out of the cold water, you feel an immediate effect. It’s like immediate. You know something happened. Something good happened. It’s been something that has been very helpful for me. I wanna learn from you, and my audience is gonna love hearing from you all about this whole thing of cold water immersion, how it affects the body, how it can help us with disease states. So I thought maybe you could start off with just telling us how you got into this because you were doing it before it was cool, you know? And so what’s here? How how did you get the crazy idea of just getting in cold freezing water?

[03:12 –> 07:35] Mark Harper: Well, I’ve come to kind of from two directions. First is my first line of research, my PhD, that’s all about perioperative hypertherapy, which means what we want to do is you get more complications if you become cold during surgery. And so it was looking at keeping people warm. So I had a kind of background in cold stuff, really. But then to actually come about researching cold water swimming, that came because I I while I’d always been a swimmer, I used to lifeguard on the beach in my summers as a student and but it never went into the water if I could possibly avoid it. But when I sort of took up my consultant job in Brighton, you know, because I was attending, I think, is, uh, what it would be in The US. Joined back up with my local swimming club, but it was shut January. So middle of summer, shut January for two weeks during the holidays. And I was complaining about this to an old friend of mine. He said, uh, just go and go, uh, go swim in the sea. Well, I didn’t even know the club had a sea swimming section. And when he told me they swam all year round, I was as amazed and shocked as everyone else. But, anyway, I started doing it for you know, the plan was just do it for two weeks when the pool was shut. Went down, and and my swim probably twenty, thirty minutes in the sea. And this is when it it’s at its warmest. In The UK, it’s about 20 degrees centigrade, 68 Fahrenheit. And as I came out from that swim, I was walking back up the beach to the the hut where we all change, and I just felt so good. I thought, this is funny. I really hadn’t expected that. And it was that feeling of, you know, feeling so good after I got out of the water, even when it was a relatively warm 20 degrees, That kept me doing it. And so, like, nearly twenty five years later and, uh, you know, research, a book, everything like that, it’s, uh, I’m I’m still doing it. And that’s that’s the reason. But I kept coming across articles actually more in relation to my surgical anesthetic research about how cold adaptation, which is generally done through getting in cold water, affects the body and how, over time, it changes the body’s response to stress. And one of the things we do as anesthesiologists is to try and reduce that stress response. Everything it was doing so you you had you know, getting cold water is a stress response as surgery is, and this stress response is attenuated over time. And the attenuation goes in exactly the same way as we would want it for our surgical patients. Now the first paper I wrote was about how we could maybe use cold water swimming as a program to reduce complications for surgery. That was written in medical hypotheses, and it remains a hypothesis, although I am convinced that it would have a good effect. However, a bit later, I read, uh, an ask in the newspaper which linked depression to inflammation. And that got me thinking, well, I know now from the physiology that regular cold water swimming reduces inflammation. I, not depressed, feel so good after I come out of the water, maybe we could use cold water swimming to treat depression. So a few months later, by chance, I met this guy called Mike Tipton, professor Mike Tipton. He’s the world’s leading expert on the physiology of cold water. And most of these studies had been done by him, the ones that I was reading and showing all these effects of adaptation. And I gave my theory to him, and he said, oh, that sounds interesting. You know? It’d be really good to find a clinical application for it. And a few weeks after that, he was contacted by the TV doctor, Chris Van Tueken, who said, I’m doing a program called the doctor who gave up drugs. Is there something we can use cold water swimming for? And Mike said, well, I happen to have met this guy who has this theory. What about that? And so with the might of the BBC, we found a young lady who was prepared to take part. And so that’s where the research started, basically.

[07:35 –> 08:35] Dr. Ravi Kumar: We’ll talk more about that later, but you basically found a young woman who was depressed. You had her cold water swim and saw significant clinical benefits, and then you followed that up with a clinical study. So just so the audience knows, we’re gonna get into that and we’re gonna talk about that because it’s pretty fascinating, honestly. And if you ever get in cold water, even a cold shower, afterwards, I mean, the feeling is awesome. I mean, you feel euphoric, you know? And maybe you could talk a little bit about that. What is happening to our bodies when we get exposed to cold water? Hey, guys. I need a quick favor. If you’re getting value from this show, would you please take thirty seconds to rate and review us on Apple Podcasts? I know it seems like nothing, but it genuinely changes how many people the algorithm puts this show in front of. And if an episode hits home for you, send it to someone who you think needs to hear it. I’m doing this to cut through the noise and bring you clear, honest information on health topics that actually matter to all of us. So please help me get the show to more people who need it. Cheers.

[08:35 –> 10:05] Mark Harper: So a number of things happen. I think the the main mechanism that happens is it is it triggers a stress response. And that that stress response involves the release of adrenaline, noradrenaline, of, uh, all kinds of other, uh, things, dopamine, uh, as well. But the the main physiological responses are seen in response to the adrenaline noradrenaline. Because what happens is your body wants to keep the core warm. We want our organs to function at their optimum temperature. So the effect of those hormones is to close-up all the blood vessels to the skin and create a barrier between the cold and the warm your organs your warm core. And that has the effect of raising blood pressure, raising heart rate. You also also has a a variety of other effects which are not necessarily related to the high that you get out of it because it has things like it causes, uh, you to pee. So anyone who’s been cold water knows that half an hour, hour after, they wanna pee. And that’s because it stimulates the kidneys to secrete more war more salt, and the more sodium goes out of the body. And so the water follows it. And this is a good thing. This is kind of a a good side effect because we want to reduce sodium levels, chloride levels in the body, and so you’re having a good side effect from from that as well.

[10:05 –> 10:07] Dr. Ravi Kumar: So it’s essentially a diuretic, like a pill that you would take?

[10:07 –> 10:21] Mark Harper: Basically, it is. It’s a it’s a diuretic, but the way it works is through excreting salt, which may which is a good way. So you reduce salt levels in the body, which is a a good thing for all other kinds of reasons.

[10:21 –> 10:57] Dr. Ravi Kumar: So and there’s something called the mammalian dive reflux. I did my undergraduate in marine biology, and I thought it was this was a fascinating reflex that marine mammals have. Walruses, seals, when they dive deep, their physiology changes in response to this cold water hitting the trigeminal nerve, which innervates the skin of the face. And when I became a doctor, you know, we started talking about this with arrhythmias and all sorts of things because humans have this reflex still. Can you kinda talk a little bit about what that is and what role that plays? I mean, what does it do into your heart and to your your physiology in general?

[10:57 –> 12:51] Mark Harper: We can maybe talk about how the body adapts to cold water, which is what basically, a sympathetic response is what you get, which is the fight flight response is what you get when you put your body in cold water. But as you say, we have a parasympathetic rest digest response when we put our face in the cold water. And this has a number of implications. What happens is it’s very strong in children, particularly in babies, and it becomes weakened over time as we grow older, but it’s definitely still there. The importance is, uh, stimulates the parasympathetic nervous system, and this has a direct anti inflammatory effect. So this is an immediate effect or an immediate benefit if you’ve got high levels of inflammation. It’s getting your face in the water. And it’s a separate thing, completely separate to the sympathetic response, the stress response you get from putting your body in the water. So, obviously, first implication is it reduces inflammation, you know, on the short term, which is great. The other thing that is the it’s one of the kind of a safety thing because once you’re used to cold water, once you’ve adapted, it’s fine. But when you’re starting out, it’s really important to get the body in first, get past that stress reaction before you put your face in because that has the opposite effect. And if you put them both in at the same time in very, very rare cases, but it has been shown, is that you get something called autonomic conflict. And so, basically, the heart doesn’t know whether to speed up or to slow down, and you can go into very dangerous arrhythmias. You know? The the heart electricity can, uh, become, you know, pretty bad and even even lead to death. So it’s very important to do this carefully and take into account this kind of thing when you get into the water. But, as I say, once you’ve adapted, it’s it’s fine. And it happens very, very rarely.

[12:51 –> 12:56] Dr. Ravi Kumar: Yeah. So that okay. That that that’s not common, getting this autonomic conflict that leads to an arrhythmia.

[12:56 –> 13:06] Mark Harper: Yeah. I mean, um, you know, incredibly rare. But, you know, this thing is to get your body in first and then wait and have your face in afterwards.

[13:06 –> 13:30] Dr. Ravi Kumar: Okay. So when your body the cold water hits your body, you get this sympathetic response, which is this fire flight reaction. Your heart rate speeds up. Your blood vessels clench down. And then when that water hits your face, then you get this parasympathetic response, which kind of relaxes you. It slows your heart down. And, essentially, its goal is to allow you to hold your breath longer. I I assume that’s why that Yeah.

[13:30 –> 14:14] Mark Harper: Exactly. It’s to survive without holding your breath. And it’s really interesting. I did, uh, I’ve done some courses. I actually even published a trial on on the outcomes of this with, um, with kids, with teenagers. And one of the things I do as a half day thing, I try and make it a bit fun. We do some experiments in the process as well as, obviously, going for a cold water swim. And I have a pulse oximeter measuring their pulse. So we know what their their heart rate is. They put their hand in a bucket of ice cold water. And what you see is that the heart rate goes up. It’s painful. It’s a stress response. Then I get them to put their face in the bucket of cold water. And, you know, that’s pretty painful, pretty unpleasant, but you see their heart rate go down. So you can see this in action.

[14:14 –> 15:02] Dr. Ravi Kumar: That’s very cool. That’s very cool. So let’s talk about this cross adaptation that you’re you’ve talked about with cold water. Because going back to the surgery thing, your your thought was that, and you published your hypothesis paper on this, that if someone cold water swims or cold water immerses for a period of time before they undergo the stress of surgery, which, you know, with stress, we’re talking about physiological stress. It could be mentally stressful, but when you go under surgery, even though you’re asleep, your body’s under a lot of stress because it’s being injured, essentially, to try to create some kind of healing effect. But that if you cold water immerse for a period of time before surgery, you’ll be able to basically tolerate that stress much more effectively and have a much better surgical outcome because, essentially, you’re more resilient. Is that the hypothesis?

[15:02 –> 17:08] Mark Harper: There are two parts to this, actually. So that is one of the things. Yeah. So you’re more resilient, but how do you become more resilient? And that’s because you you’re adapting to stress. So the issue is with surgery is it’s what you get from that. I mean, it’s as if you’re being attacked by a knife. And although you have a your anesthesiologist is there keeping you asleep, you remember nothing, you feel nothing, your body is still reacting pretty much as if you were being attacked when you were awake with a knife. And this sets off a massive stress response. And what we want, we can have too much of a good thing. So we need the stress response. Yeah. It’s an evolutionary mechanism to keep us alive. However, we don’t want too much of it. And so what we’re trying to do, what I think we’re getting a lot of the time with cold water swimming in, particularly in this context, is that it attenuates that stress response. So your peak stress response so so you get the pathological red zone, the bad, bad stress response, and then a bit lower is the good stress response. That’s what we want. So we wanna keep it in the good zone. And what’s happening with adaptation to cold water or any stress, really, you can do it with thermal stress. So you can do it with a sauna, for example, is that it brings that stress response down. And so you spend less time in the bad zone. You go less high into the bad zone, and you spend more time in the good zone. So you are getting the benefit to the stress response without the side effects of too much stress response. But there is you know, you talk about cross adaptation and resilience. So there is one study which looked at a static bike exercise in a hypoxing environment. I think it’s, like, 14% oxygen. So everyone did the exercise, and then half of them underwent a cold water adaptation program, and half of them didn’t. At the end of it, the ones who’d had the cold adaptation program performed better, whereas there was no change in those who hadn’t undergone it. So there is an adaptation from that. Cold stress seems to mean that you have adaptation. You improve in other stressful situations.

[17:08 –> 17:25] Dr. Ravi Kumar: Yeah. So any stressful situation, it’s maybe it’s work stress, maybe it’s relationship stress, maybe it’s, um, I don’t know, viral illness or any kind of or heavy exercise. Is going into the cold water regularly just gonna make you more resilient in life in general with all these things that we have to deal with?

[17:25 –> 18:25] Mark Harper: That’s certainly the theory. Yeah. Because, I mean, as you’re well aware, you know, our issue is, a lot of the time, is chronic stress rather than acute stress. And, you know, and that’s just bubbling bubbling along all the time. If you’ve adapted to cold water, and this means that blood pressure increases less, You get, um, your insulin resistance improves, for example. So your your levels of inflammation go down. And this is a long term effect, which you get from adapting to this stressful situation. So you’re in the good zone much longer this way, and that works for everything. Because the body, while complex, is very simple. You’re not gonna have more than one stress response. You’re not gonna have a different stress response when you’re late for the bus or the train or whatever than you are if if you’re being chased by a lion. It’s gonna be broadly speaking the same. So if you attenuate one stress response, actually, that’s your only stress response, and you’re gonna be attenuating all your stress responses.

[18:25 –> 18:53] Dr. Ravi Kumar: So this is essentially hormesis, where you’re challenging your body. Yeah. You’re challenging your body, and it makes it more resilient to the challenges that you normally see. Now, I think one thing that comes to my mind is being in the cold water or cold, I guess, any cold situation for long periods of time ends up being harmful. Correct? It’s not it has to be like an in, you get the the response, and then you’re out of that stressful environment, and your body can build up its defenses. Is that correct?

[18:53 –> 20:58] Mark Harper: Absolutely. Hypothermia is always bad for you. And, yeah, and this is why you have more complications when you become hypothermic during an operation is because it’s bad for you. Yeah. And you never want to become hypothermic. I think there are a couple of really important points to bring out here. One is the cold isn’t actually that cold. So at 20 degrees centigrade, so 68 Fahrenheit, you go into water at that level, you get maximum vasoconstriction. So you see a what I mean by that is your blood vessels clench up, and they clench up to the maximum level. They can’t clench anymore. And so what that shows is even at relatively warm temperatures, you are getting a really, really strong physiological response. And the studies we’ve done have been English summertime, and we’re basically looking at temperatures between fifteen and twenty degrees centigrade. So it doesn’t have to be that cold to have the effect. And the other is if you stay in too long, yes, you’re more like you know, certainly at lower temperatures, if you stay in too long, you’re likely to become hypothermic, and then you start undoing all the good. As you say, what you need to go do is just go in long enough that you feel that stress response and you yeah. I mean, still after twenty five years of doing it, I get in and it’s like, you know, I feel that, uh, that thing. But then a minute, two minutes, if that later, you know, I I go past that, and I can look around, look at the sky, enjoy enjoy the experience. When you’ve done that, you’ve done enough. When your breathing is under control and and you can concentrate on things around you rather than the the shock of the cold, then that’s enough. You can get out there, and you’ve done done the good. Of course, if you wanna do some exercise, if it’s warmer, fantastic. You’re getting exercise as well. Another great, uh, great thing for the body. But the key thing is you’re not gonna get any clinically significant further benefit once you’ve gone past that initial shock.

[20:58 –> 21:11] Dr. Ravi Kumar: Okay. So you go in and, like you said, you start hyperventilating. Right? That’s a sympathetic response to the cold water hitting your body. And when that slows down, then you put your face under the water at that point?

[21:11 –> 22:19] Mark Harper: Yeah. So that’s what I would do. So, yeah, once once that slows down, once your breath is under control, then, yes, then you’re fine to put your face in the water. And then you’re getting the extra benefits of the anti inflammatory effects of that. I think talking about the breathing, I think it’s another really important point to bring out. So what kills people in very simple terms actually isn’t the heart. You know, I’ve no. I’ve mentioned that. But the the effects on the heart are actually pretty, uh, or the body can cope with them, then they’re not that significant. The big issue, particularly when the water’s cold, is you adapted, you’re fine. Before you’ve adapted, you start hyperventilating, and you can’t control it. Yeah. I still hyperventilate when I get in the water a bit, but I can control it now. The the initial breath is as massive breath. You know, uh, one half, two liters. You know, it’s enough pretty much to fill your lungs. You can’t help it. And if a wave comes over you, if you go straight under the water, you’ve got a lung full of water, And that’s a really bad thing. And that’s what motley kills people.

[22:19 –> 22:28] Dr. Ravi Kumar: So it’s a forced inspiration, essentially. It’s a forced inspiration, and you don’t wanna have your face underwater when you get that forced inspiration, essentially.

[22:28 –> 22:29] Mark Harper: Yeah. Basically.

[22:29 –> 23:09] Dr. Ravi Kumar: Okay. So and that’s good to know. I mean, a lot of people are just getting in cold showers or sitting in a cold tub, at least in The US. But if you’re going in the ocean, you’re going in the lake, uh, pond, or whatnot, Wading in sounds like the way to go, getting over the initial cold shock and before you put your face under water. Okay. So say we’ve done all that. We’ve gotten past this initial sympathetic response where we’re hyperventilating. We’ve gone under the water now. We’ve activated our parasympathetic response to the trigeminal nerve. Is the benefit over at that point? I mean, do we have the benefit we need from the cold water immersion? Because I know you go in and you swim around piers, and you do and swim around islands with your your son. And like, I mean, you’re staying in the water quite a while.

[23:09 –> 24:58] Mark Harper: Yeah. Well, I’m staying in the water quite a while when I know it’s warm enough and that I know I’d not gonna become cold. I do everything to avoid getting cold. You essentially, you’ve got enough benefit then. You will get more. As I said, I think, you know, exercise is good for you. So that’s great. Being out, I mean, light, so important for you. You know, it’s you’ve done episodes on vitamin d. You know, there’s I understand there’s a lot of evidence it’s the sunlight. The vitamin d is more a marker for sunlight exposure than it is for actually vitamin d levels, if you see what I mean. And you’re getting light, so that’s great. Just being out in nature, we know that green therapy is good. We know that blue therapy, a view of the sea is good. So you’ll gain all of these things as well. You will have the main benefit from just having gone in the water, but you can expand that benefit. I think the other really important thing is that’s what makes it so much fun. That’s what makes it so nice. It’s being out in nature. It’s all these things. And it’s like the diet that works. The diet that works, they all work if you do them properly. But the one that really works is the one that you can persist with and the one that, you know, you can keep doing. And so because you get all these extra things and that is part of staying in the water a bit longer when it’s a bit warmer, then that’s what keeps you coming back. And also, which we haven’t touched on yet, but the the social aspect of it, because it’s much safer to do it with other people, and it’s also a lot more fun to do it with other people. And so you get this social effect, and that brings people into your circle, and you feel a bit of responsibility. In fact, there was a study recently published in the last couple of months or so, which was it’s called friends with health benefits. And it’s the fact that people who exercise together, uh, do better than those who who don’t, essentially.

[24:58 –> 25:51] Dr. Ravi Kumar: Right. So, yeah. And that’s a big big one because when a lot of people think about cold water immersion, they’re just thinking about taking a cold shower or getting in an ice bath, which does work, does give you the effects. But there’s a whole social aspect to what you’ve talked about in your book, Chill, where there’s a lot of benefit there. If you know about mental health, social isolation is one of the worst things for your mental health. Getting together, doing something that’s difficult, because getting in cold water is difficult, doing it something that you’re sharing in this experience is, I I think, a large part of what you’re talking about. And, um, that’s not something we do a lot in The United States. I know there are groups that cold water immerse together, you know, polar bear club and things like that. But, I mean, I think we were possibly missing a big component of this. You know? It’s not just cold water. It’s the togetherness in doing something kind of extraordinary in your day.

[25:51 –> 26:31] Mark Harper: Totally. Yeah. So it is. It’s doing that together. It’s doing the challenge and having a challenge together. I was interested in my, uh, my sister-in-law isn’t a cold water swimmer at all, but she does do ultra marathons. She, uh, her observation was that when people say, uh, you know, she said tells me she does it, and and they say, oh, you’re you’re mad. Yeah. What on earth? I could never do that. You know, that brings them as a group together. And so if you do something as a group, which is challenging, and although it’s sort of cobalt or something, it’s got a bit mainstream, it’s still without a doubt challenging, then, you know, that brings you closer together. And it sort of reinforces those really important social bonds.

[26:31 –> 27:57] Dr. Ravi Kumar: Yeah. Absolutely. Hey, guys. There are currently 8,000,000,000 people on Earth. And somewhere out there, someone has already solved the health problem that you’re struggling with. Maybe it took them years of trial and error, or maybe they stumbled on it by accident, but they did figure it out. The problem is there’s no way for their discovery to reach you. Doctors don’t have time for deep investigation. Research moves slowly, and that solution, the one that could change your life, stays lost in the milieu. I’m building something to fix that. It’s called sharemytrial.com. It’s a platform where people share what worked for them, and the community validates and rates those solutions so the best ones rise to the top. Right now, I need beta testers. If you’re interested, go to sharemytrial.com and sign up. Help me build a place where real health solutions find people who need them. So let’s, uh, transition in this part of the show to talk about these different diseases. Because so far we’ve talked about wellness. And cold water on your body, on your face daily feels really good. It makes you feel good. It makes your day feel good. You feel more energetic. You feel better mentally. But what about specific diseases? And I know you mention a lot of these in your book. Maybe we could start with PTSD because you mentioned a couple people who had PTSD who saw benefit from cold water immersion. I know they’re doing clinical trials on this right now. Talk to me a little bit about that.

[27:57 –> 29:54] Mark Harper: This is interesting. So PTSD, you have these loops, and, uh, you talk about was it the full mode network? You’re sent to this these loops, and it’s really difficult to get out of. And I think we don’t have evidence for this. Yeah. I haven’t got I I couldn’t tell you, but I think this is one of the big advantages of actually doing the therapy myself and having done it for so long. When you get into cold water, it just clears everything. It’s just as if it resets the default mode network. And I think that’s why people with PTSD find it helpful. Um, there’s also her name escapes me at the moment. Jill Bolte Taylor, the neuroscientist who had a stroke, knew she was having a stroke, but didn’t care. The whole world felt wonderful. And the reason was she was having a stroke on the left hand side of the brain. I know I don’t need to tell you this. Uh, yeah. It was a bleed on the left hand side of the brain. Left hand side of the brain, that’s the to do list. That’s tomorrow. That’s there’s all those worries. The right hand side of the brain, that community, that empathy, that’s all the all the nice things. And so, basically, she was shutting down that left hand side of the brain and just working from the right hand side of the brain. And when she came through this, it took a long time. One of the big motivations was to say, god. What we gotta do is take a step to the right. And, you know, and that’s kinda what I find. When I go for a swim, you know, I can be there. I can you know, maybe I’ve cycled. Yeah. One of the place I swim, I cycle about 15 miles to. I go go to work straight afterwards. I get there. I’m hot, sweaty. My brain is all going. I get in the water. I come out, and it’s yeah. The the whole world is a is a wonderful place. And so I think, you know, we’re taking a step to the right. And I wonder if that’s, you know, resetting the default mode network, whatever it is. It just stops those loops. And I think that’s probably what is happening with PTSD.

[29:54 –> 30:36] Dr. Ravi Kumar: Yeah. And so for the audience, the default mode network is this background rumination that you can get stuck in, especially in depressive states. And, um, you know, psychedelics quiet the default mode network. There’s a lot of things that you can do. Meditation quiets it. And when you quiet this, like, hey, what do I have to do today? My gosh, am I gonna lose, you know, this money? Am I gonna do I have to pay these taxes? What did they say about me? When you can quiet that loop, life generally gets better. And that’s something you can learn to do, but it’s I I think doctor Harper’s right, because when I get in cold water, that quiets down. It is an almost like an automatic response. It’s almost like cold water’s a a form of meditation, honestly.

[30:36 –> 31:06] Mark Harper: Yeah. That that’s it. I I think of it as my form of meditation, really, because, uh, it does. It just quads the brain and then, you know, and that’s when you have a bit more time. You can, you know, sit around and, you know, appreciate your surroundings. And that’s kind of a meditation. That’s one one form of meditation is sort of Yeah. Feeling the sensations, looking around, seeing the world, and doing that without these loops of the to do list and,

[31:06 –> 31:06] Dr. Ravi Kumar: you

[31:06 –> 31:09] Mark Harper: know, all our our daily worries interfering.

[31:09 –> 31:40] Dr. Ravi Kumar: Or something more wicked if you got PTSD, you know, these these horrible ruminating thoughts that torment these folks. So, you know, I know there are ongoing clinical trials of cold water swimming, cold water immersion for PTSD, but right now, the evidence is still pending. Why not give it a try? If you’re if you’re suffering with something and, you know, medication and and counseling are not working for you, why not try the cold water? I I think it’s definitely worth a try. You’ve outlined some people who have had great benefit with it. You know? That’s impaired data, but it it it is there.

[31:40 –> 32:55] Mark Harper: Yeah. And, uh, it’s still just noise as it were, but the noise is all positive. Yeah. And, you know, people contact me spontaneously to tell me about how good it’s been. So as you say, there’s nothing to lose. I mean, what are the side effects of getting in a getting in a bit of cold water? Well, a bit of exercise. I mean, that’s a positive thing. Yeah. So it’s definitely worth it. I I would say, maybe at this point, what you need to do is not actually very much. You adapt over a period of about six immersions. That’s always. Six immersions under 20 degrees centigrade. So you don’t really have to do it for that long even to see if you’re having an effect. I think you definitely need to do it. You you need definitely need to plan to do it at least three times because the second time is always the worst. Because you’ve done it the first time, and you’re all set up for it and say, oh, yeah. I survived. The second time, your body hasn’t started adapting yet. But you think, oh, it was alright last time. And so that’s the worst. And then from the third time, you begin to adapt. So at that point, it becomes easier and easier. So so don’t give up after two. You have to sort of set yourself a target of, uh, of a few times. And they could be once a week is fine. You know, all our studies have been just going into the water once a week.

[32:55 –> 32:55] Dr. Ravi Kumar: Once a week.

[32:55 –> 33:12] Mark Harper: I think you can do it more. You can if you if you want, you can do it in a day as long as you warm up in between. But, you know, it’s, uh, you know, once a week, not less than that, more if you if you fancy it. But it it shouldn’t be too challenging.

[33:12 –> 33:36] Dr. Ravi Kumar: Right. Okay. So you’re you’re recommending trying it at least six times to see if you have a clinical effect. The first time you have an anticipatory drive that kinda gets you through this. The second time you’re like, I know how bad that was, and I’m not all hyped up anymore. So the second time’s the hardest. You talked about that in your book. But once you hit three, you’re kinda coasting. I feel like that’s pretty spot on from what I’ve I’ve experienced.

[33:36 –> 33:42] Mark Harper: Yeah. And, uh, yeah, and, yeah, people say that to me as well. So I I I tell this to people, and they say, yeah. You were right. Yeah.

[33:42 –> 33:58] Dr. Ravi Kumar: Okay. Let’s talk about depression because this is one you’ve actually published on, you know, one case study and one, uh, clinical trial, maybe more if you you can tell me about them. But tell me about depression and cold water, and what have you observed, and what kind of results have you seen?

[33:58 –> 35:25] Mark Harper: So yes. So in fact, we have three three publications now with it. The first was the case report I, uh, referred to earlier, and that was Sarah. She was 24, single mom. Dad had, uh, killed himself. Brother had died of a drug overdose, you know. And she was really motivated by the fact she didn’t want her daughter baby daughter growing up seeing her mom just pop pills for depression. It was like, yeah, as I know you advocate, it’s looking at other ways to do this. And so, yeah, she joined us. And one day, we took her down to Mike’s lab and you know, so this is the adaptation over a day. She I think she swam three or four times. She had another one in the morning afterwards, and then we went out and swam in the lake. And, you know, I saw the just in those two days, I saw how much she changed. It was extraordinary. And as you talk about the challenge, when we got out of the water, out of the lake, so it was the long swim. She said, I think that was the hardest thing I’ve ever done, but she was so pleased with herself. Anyway, over time, Chris followed her up, and she got off the tablets, you know, and getting off antidepressants or, you know, uh, SSRIs can be really difficult. I mean, it yeah. It can be really difficult. And she got off them over a course of a few months. And, you know, ten years later, she was still pill free and saying, you know, that cold water swimming has done for me more for me than the pills and doctors ever have.

[35:25 –> 35:27] Dr. Ravi Kumar: That was a complete remission for her?

[35:27 –> 37:52] Mark Harper: Yes. Basically. Yeah. I mean, that seems pretty good. But that’s just one person. And, you know, it’s quite funny. When we’re going to the lake driving to the lake, I said to Chris, yeah, what happens if this doesn’t work? You know, my whole theory is blown apart. He said, don’t worry. Always works on TV. So, uh, so, anyway, so it did. But you you have to take it out into the real world. So the next stage was to just see if people would even do it. So a a guy, Mike Morris, in Southern England, Coast Of England, he got in contact and said, yeah, I’d really like to help and put together a program, which was a session a week for eight weeks. He did the teaching or the guiding really because it’s, uh, not about it’s very much about just getting confident in the water and having a bit of fun rather than learning technique or anything like that. And we did the study, and we took the statistics. So what we found was in the ME, people did turn up, and it did keep coming back, which was the first thing. And that’s what we really wanted to know. And then although it’s a small study about sixty p we saw something like depending on how you measure between sixty and eighty percent remission rate. And as I said to him at the time, if if this was a drug, they wouldn’t believe you. No. And, uh, and, you know, it really was that good. And even better was, like, three months afterwards. Most of them were still doing it, and most still were better. And so this backs up my theory. It’s the thing that you can stick with, and people do tend to stick with cold water swimming. So that was good. And then the next phase, obviously, what we wanna do is a randomized control trial. So the next phase was to do a pilot study for that or pilot randomized control trial, which we did. We recruited effectively. And although it’s a pilot trial, so we can’t really say there’s a definitive effect, we did see similar numbers. So, again, I talk about the noise. The noise is still the same, and the noise is still positive. Last year, we finished completed a two year trial where we recruited over 500 participants for which is totally randomized controlled trial, outdoor swimming or standard treatment for depression. And so this, we should be able to report later this year. So we’ve had three publications to date, and the fourth and definitive trial should be available later this year.

[37:52 –> 37:56] Dr. Ravi Kumar: And have you got the results from that trial yet? Are you analyzing them now?

[37:56 –> 37:58] Mark Harper: We’re in the follow-up interview phase now.

[37:58 –> 38:06] Dr. Ravi Kumar: That’s really interesting because you said 60 to eighty percent improvements in your pilot trial in the in the, uh, case series. Correct?

[38:06 –> 38:06] Mark Harper: Yes.

[38:06 –> 39:28] Dr. Ravi Kumar: Yeah. So if you think about that, uh, antidepressants like SSRIs have about a forty per around a forty percent effectiveness rate for improving depression. Placebo is around thirty percent. So the drug effect is about ten percent there. And there’s all sorts of side effects with SSRIs. And I’m not against SSRIs. I think they are a valuable part of depression treatment, and they should be used, when appropriate, by a doctor. But side effects. I mean, men can develop erectile dysfunction and and lose their libido. Women can lose their libido. You can gain weight. You can have all sorts of neurological disturbances that are part of modifying your nervous system with a chemical. That’s just what drugs do. They go in there and they chemically change things. Cold water swimming, you’re getting 60 to 80% benefit and no side effects essentially, and overall well-being is improving. I mean, these are the kind of things that people just don’t know. You can go to your doctor. Say, I feel sad they give you an SSRI, but they don’t say go try some cold water swimming. I think that if you’re not in danger, why not try the things that make you better and have potentially a much better outcome? And it’s because people don’t know about it, and doctors don’t know about it, honestly. In The UK, I’m not sure it’s maybe more popular. But here in The US, you go to your primary care doctor, they’re not gonna prescribe you cold water swimming.

[39:28 –> 41:26] Mark Harper: No. It’s it’s getting there. But I said, another story is I was, uh, a friend of mine, uh, emailed me to say or one of my colleagues at work had been teaching medical students. And they were saying, you know, what are they talking about pain pain relief and things like that, and, you know, how do you deal with chronic pain and stuff like that? And then one of them, uh, answered, yeah, what, yeah, what can you do? He said, oh, cold water swimming. So it’s getting out there. Yeah. I mean, that’s pain that yeah. It’s getting out there now. It’s not not there yet. It’s it’s improving. Yeah. But I think people are also very wary of prescribing something that, you know, doesn’t have a strong statistical basis to it, you know, and proper clinical trials. And, hopefully I mean, who knows? We maybe it will turn out to be it was complete rubbish after all. But, yeah, hopefully, when the the results of this come out, you know, there will be something some good evidence. And I think that’s what we will be getting you know, and that that’s what we need at this point. Another thing we’ve been very careful to do is one of you know, statistics alter policy. And so that we need those statistics. But I think stories change minds. So stories affect people. And so there’s a strong qualitative element to our study as well. And that’s been a really important thing. And I think, you know, for writing the book, the best part for me was getting these stories. Even people I knew really well, I knew that they’d used cold water swimming. I didn’t realize the extent of how bad they’d been and what profound effect it had on them. And they all wrote so beautifully. Yeah. When I spoke to them, yeah, I got these amazing stories from people, which, uh, are so beautifully presented. And that’s that’s really important, I think. And so we’ll have a there’ll be a separate qualitative paper, you know, telling people stories, dissecting in a way how the different ways in which this has a positive effect on people. Yeah.

[41:26 –> 41:58] Dr. Ravi Kumar: That’s really cool. Because that’s one thing I really believe in is that storytelling is one of the best ways to teach. I use it in my podcast a lot. Your book was just like that. There was tons of storytelling. It’s just not a book about science, you know. You’re talking about human health and how cold water affects it, but you’re telling stories the whole time. That’s why I enjoyed it so much. Okay. You mentioned pain and chronic pain, and that’s something you talked about in the book too. Can you talk about the biological basis for that? Why is cold water helping with pain? And and what have you seen with these people who have written into you and told you their stories?

[41:58 –> 44:17] Mark Harper: Well, I think the the interesting one for that was a a guy called, uh, Grant who came along to the course. Yeah. This that was the one we did in, uh, Southwest England. And he came because he was depressed, you know, and he was thinking he’d had chronic pain. So he was a fit guy. He wasn’t someone who just wanted to lie around on the couch. He was a almost professional cyclist in his youth. He loved surfing and had but had multiple back problems, you know, disc after disc popping out. And, you know, it’s really restricted him. So he was thinking of getting a referral into, you know, the chronic pain clinic. He’d finally given up. And then he saw, uh, article about this study this course and this study that we were doing. And so I thought, oh, go along and give that a go just because he was depressed. It, you know, it was only advertised as that. And so, well, at least I can, you know, sort my sort my mind out. What he found was that he suddenly he could you know, he found that his back pain was getting better, and he had less chronic pain. He was able to do so it doesn’t go away. And I think this is what so I know the book’s called the, uh, Coldwater Swimming Cure. Probably not a cure. But what it is, it gets people from nonfunctional to functional. So it it has a clinically significant benefit. And so he found he got much better and yeah. So his pain had gone. He became much more functional. He was able to go out. And at the same time, the depression, his mood improved. Now it comes back to those loops. Pain is in the brain. Pain is not in your body. Pain is a response to signals from the body, and pain is very real. I’m not saying it’s not real, but all pain is is in the brain. And I think this comes back to the same kind of thing that with PTSD. What you’re doing is you’re resetting those neural networks because, uh, I don’t know what’s going on functionally, but that is my impression of what is happening when you go into the cold water. I guess, also, you’re getting the anti inflammatory effect and you get a loop not only in your brain, but you get a loop of inflammation around areas of chronic pain. And so that can be reduced as well. So there’s probably some kind of physical effect as well.

[44:17 –> 45:32] Dr. Ravi Kumar: Yeah. And the the research supports that. I mean, there’s a reason that, you know, all physical trainers have ice baths in their locker rooms. You know, these players come in from a hard game. They go in an ice bath. It gets rid of the pain. It helps calm down the overactive inflammatory cycle of chronic injuries that these players are having. So, yeah, I mean, cold has real physiological effects on the body, inflammation and healing. There is some research that says after a workout, cold water immersion might cut your gains, you know, because building muscle is actually an inflammatory response. You know, one thing that people have to understand that inflammation is not bad. Inflammation is a normal part of our body’s homeostatic mechanisms for building and repairing. And you mentioned this earlier. You just don’t want to go into the red zone. You don’t want to be and we a lot of us are. I mean, even if we’re not playing in the NFL or in the football league, you know, we’re we’re in this bread zone of inflammation from diet, lifestyle, whatever, you know, smoking, and the number of things that we do, uh, metabolic disease, the number of things that we do that create inflammation in our body. So, cold water can kinda bring you back into that that normal zone, I suppose. And and that’s one of the reasons why I think you’re seeing this benefit with chronic pain.

[45:32 –> 46:12] Mark Harper: Yeah. Absolutely. And is it I see what you say about the not getting the muscular gains after if you go straight after. So it’s great during a tournament where you want fast recovery or during the season when you want fast recovery. But if you’re doing the build up thing, you don’t wanna do it too soon after a workout because, you know, it’s those micro tears. It’s that inflammation as you said. And, uh, I quite like the analogy to go back to, you know, how to do it safely. You don’t wanna pull a muscle. That’s bad for you. These micro tears, they’re good. That’s what builds your butt your muscles up. Again, going into the cold water, getting in, having that hit of the cold, that’s the micro tears. Hypothermia, that’s the injury.

[46:12 –> 47:23] Dr. Ravi Kumar: Yeah. Exactly. Yeah. So, I mean, you know, the muscle injury during a workout is essentially hormesis just like the cold water immersion or sauna therapy or whatever you’re doing that gives you a little bit of stress, small amounts of injury so that you build back stronger. But as soon as you start tearing yourself down with overzealous stress, you know, cold injury, whatever it is, you end up in a hole. And so that’s, you know, people tend to take things to extremes, especially people who are interested in health and wellness. So, that’s something to keep in mind, that you don’t want to go jump in the cold water for over an hour, lower your body temperature to the point of hypothermia. You don’t want to sit in the sauna for over an hour. I mean, people will do this, and that is stressful. But that’s stressful to the point where you’re past that hormetic curve of benefit. And so that’s something really important I think people should keep in mind. Let’s I know you’ve mentioned this already, and we’ve talked a little bit about it. Let’s jump into the practical side of cold water immersion, cold water swimming. You know, let’s say that you’re talking to many of the people in my audience who haven’t done this before. How can they start off? How can they do it safely? What is your recommendation for them if they wanna start with cold water swimming or just cold water immersion?

[47:23 –> 50:02] Mark Harper: I think the key message is it’s very simple. You don’t have to go down the route of getting a complex ice bath or paying hundreds of dollars and getting down to far four, five degrees, you know, get with ice on the top. You know, this is very simple. The way to do it safely is is basically to keep warm in a way. So what you wanna do is you need to check out your spot. You need to find somewhere where other people do it so you know you can get in and out safely. There’s this great law. It’s called Agnes Allen’s Law, which is that almost anything in the world is easier to get into than out of. Plies for everything, applies to cold water swimming. And so, yeah, make sure you can get out. Do it with someone else because they will help you get out if if there’s a problem because it is a a stress, particularly those first six times. Make sure you’re warm before you get in. As I said, the effect is from the stress of the cold. It’s not about getting cold at all. Your body can contain a certain amount of heat, and if it’s maxed up and this is why it’s quite good to go in a sauna first. It’s maxed up. You’ve got longer in the water before you’re likely to become hypothermic. So go in warm. And then when you come out, warm up again quickly. You do feel when you get out, you feel actually quite warm. It actually feels really nice. And the the number of times I sort of gone in walking down the beach, middle of winter, into the sea, thinking, oh, this is why am I do uh, and then I come out and the yeah. The world’s a wonderful place. Yeah. I’ve got the rain on me still, but it just feels nice. And but that’s kind of also a a danger that you ought to look out for because you don’t feel the cold immediately, but you are cooling down. So you need to get dry really quickly and particularly get out of the wind. Okay. So you keep warm. You might know if you’ve done it, uh, well, you probably don’t need any form of active warming afterwards. And the best form of warming I mean, yes, if you get saunas, great. But the best form of warming otherwise is exercise. It’s warming from the inside out. So cycle down to beach. I mean, I noticed the difference if I occasionally have to drive to where I swim. And, you know, I notice it. I’m not as warm as those times I cycle. And I only cycle in a couple of miles. It’s not far at all. So it’s important to yeah. If you need to warm up, exercise is the best way of doing it. And, yeah, do it with yeah. Do it with friends. Do it as a social thing. Make sure you have a a regular date set up, you know, for to do it several times.

[50:02 –> 50:28] Dr. Ravi Kumar: Okay. Okay. So first step is make sure it’s safe. Make sure you have a way out. I surf, so I know this. You can get into the ocean, no problems. Getting out’s gonna be a challenge. So make sure you can get out. Back to what you had mentioned earlier, get your body in first and get past that initial hyperventilatory response. And go underwater, get your face wet if you want. That that’s not necessarily a requirement, though, right, to getting what you No.

[50:28 –> 50:38] Mark Harper: You still get a good benefit. And it is just the face. Yeah. It’s just the face. It is just the face, not the whole head. I always or almost always wear a wear a hat, a proper swimming hat.

[50:38 –> 50:38] Dr. Ravi Kumar: Okay.

[50:38 –> 51:07] Mark Harper: You can wear a a bobbly hat or whatever you want. And then with the face thing as well, it’s straight in and out does not have the effect. But it’s like when you get into the water, you put your face in after two or three seconds, then the effect you know, that pain’s passed, take it out. So it really doesn’t have to be for very long at all. And, you know, you are getting the benefits, whatever, just getting in the cold and exposing your body to it, but you will probably get more benefits if you put your face in as well.

[51:07 –> 51:30] Dr. Ravi Kumar: Okay. And once you get that, you can exercise and swimming is great. But, uh, once you’ve had that initial response, you’ve pretty much got the hormetic effect. Right? Spending a little bit more time can offer some mental benefit from just the enjoyment of being in the water with friends. Mhmm. And when you get out, you wanna warm up. Best way is exercise, getting dry, getting out of the wind. And, uh, you also mentioned in your book, Hot Drinks.

[51:30 –> 51:32] Mark Harper: Yeah. Hot drinks. I mean

[51:32 –> 51:33] Dr. Ravi Kumar: That just for the pleasure?

[51:33 –> 52:26] Mark Harper: It just feels good, doesn’t it? Yeah. Yeah. Yeah. The the amount of warmth you have in a hot drink is negligible, really, and how much is gonna transfer to the body in a purely physics Yeah. Uh, way. But it does feel good. It’s a nice way of doing it. And it’s a nice way of being, uh, being social afterwards. And we know caffeine. Caffeine’s generally the thought of as healthy these days as well, which is quite quite nice. I think one other thing I would point out is not about doing it safely, but is it, uh, keeping the enjoyment is is wearing gloves and boots. Below 10 degrees, I always wear gloves and shoes. And it’s not, you know, it’s not dangerous if you wanna go in without, but it’s so much more pleasant if you do. Yeah. Because the I, uh, for me, I get real pain in my hands and feet. You’re losing none of the benefits, but it makes the whole experience so much better if you wear gloves and shoes.

[52:26 –> 52:50] Dr. Ravi Kumar: Okay. Yeah. And then let’s say so there’s a lot of people on the coastline of The United States. You know, this time of year on the East Coast water’s pretty cold. The Pacific Coast of The United States is cold all the time. So it that’s perfect. What about people who don’t live on the coast, don’t have access to cold water bodies, like a lake or a pond that’s swimmable? Can they get the same benefit from getting in a cold shower or filling up the bathtub with cold water?

[52:50 –> 53:46] Mark Harper: So there are two things that affect the response to cold. There are two factors. One is the rate cooling, and one is the absolute temperature of the water. So, yeah, for the same temperature, getting into immersing yourself in cold water is going to be more effective than a shower which doesn’t cool you down as as quickly. However, we do know that, uh, there is a study that has shown that showers do have an effect. And what they did was they had, uh, an office, and half of people took cold showers every day for the study period, half of people didn’t. Those who took the cold showers have fewer sick days. So we can see a measurable effect. It won’t be as much. You know, cold bath at the same temperature will be more effective than a cold shower. And I hate cold showers. Getting water below freezing, and that’s fine. Cold shower. I hate it.

[53:46 –> 53:50] Dr. Ravi Kumar: That’s surprising. So you prefer to get in the cold ocean around England than

[53:50 –> 53:53] Mark Harper: Yeah. Or Norway. I’ve been I’m in Norway half a year. Yeah.

[53:53 –> 53:54] Dr. Ravi Kumar: Oh, you’re in Norway. That’s right. Yeah.

[53:54 –> 54:00] Mark Harper: Yeah. Yeah. So, uh, I’ve been yeah. When there’s there’s ice on the, uh, surface of the ocean. Okay.

[54:00 –> 54:02] Dr. Ravi Kumar: Prefer that to a cold shower.

[54:02 –> 54:35] Mark Harper: I prefer that to a cold shower. Well, that’s that’s personal, uh, personal preference. But, yes, a cold shower will have an effect, and a cold bath will have an effect and probably a better effect than than a cold shower. But then a cold shower, I mean, isn’t that so easy? Part of this is about making it accessible, filling up a cold bath and getting into that. Not much fun. But, yeah, you can, um, if you’ve got a a garden, yeah, you get a old bathtub, put the plug in it, fill up with rainwater, you know, and then you’ve got, uh, got all the benefits.

[54:35 –> 54:40] Dr. Ravi Kumar: Right. Yeah. And you’re outside too. Right? Because, I mean, get that green therapy that you talk about in your book.

[54:40 –> 54:41] Mark Harper: Yeah.

[54:41 –> 54:54] Dr. Ravi Kumar: So okay. Well, fantastic. Doctor Harper, this was an awesome conversation. I learned a ton. Where if people wanna learn more about you, read your book, Chill, the Coldwater Swim Cure, how can they get a hold of you? Where can they get your book?

[54:54 –> 55:26] Mark Harper: So, uh, the book is widely available. Also available with, uh, me narrating it as a audiobook, you know, on Audible, on wherever you get your audiobooks. I have a website which is very regularly updated, but you can contact me through that, which is doctormarkharper.com. And I do post stuff. When I come across, uh, interesting fun stuff, yeah, fun stuff, fun studies, or interesting studies that come out, I do post occasionally on Instagram, which is at the world swim doctor. So do come and say hello.

[55:26 –> 55:46] Dr. Ravi Kumar: Okay. Yeah. I’ll put all those links in the show notes. Thanks so much for being here. This was fantastic. And, uh, if you haven’t read doctor Harper’s book, I definitely recommend it. I listened to it on audiobook, on Audible, and it was just so many great stories. It’s just an enjoyable read. So go check it out. Cheers, and thanks for being here, doctor Harper.

[55:46 –> 55:50] Mark Harper: Yeah. Thank you very much. Thanks for inviting me. It was a a total pleasure.

[55:50 –> 55:50] Dr. Ravi Kumar: Okay. So I hope you enjoyed that. This was really an enjoyable episode for me because doctor Harper is genuinely a good guy. He’s calm. He’s thoughtful. And he’s one of those people who can explain complicated physiology in a way that’s very understanding and compelling. And honestly, the benefits of cold water are hard to ignore. A lot of health trends are subtle, or they take weeks before you can tell if anything is happening. Cold water exposure is different. You feel it right away. That doesn’t automatically mean it’s magic, but it does mean something real is going on inside your body. And the science around stress adaptation, inflammation, and nervous system signaling is starting to catch up to what people have been experiencing for a long time. And this is where I wanna zoom out for a second. We live in a world where medicine is heavily pharmaceutical, and I’m not anti drug at all. I’m a neurosurgeon. I use medications every day in my practice, and drugs save lives. They reduce suffering. They’re essential to what I do in medicine and what many doctors do in medicine. But I also think we make a mistake when we act like pharmaceuticals are the only levers that matter. Because when you ignore basic physiology, the way the human body adapts to controlled stress, the way nature changes your nervous system, the way your brain responds to temperature, breath, and environment, you end up cutting out some of the lowest risk, highest upside inputs that we have. Things that are basically free. Things that stack benefits. Things that make you healthier in a way that doesn’t come with a laundry list of side effects. That’s why I love seeing physicians like doctor Harper take topics like this seriously and bring them back into the mainstream medicine with real research and real humility. He’s not overpromising. He’s not making it sound like a cure all. He’s just saying, look, there’s something here, and we should study it because it might help a lot of people. So, no, you probably won’t get a prescription for cold water immersion from your primary care doctor, at least not yet, but you can still use this as a very powerful tool. You can do it safely. You can start small. You can build the habit. And for a lot of people, it can be one of the most reliable ways to feel better in your body and in your mind. If you enjoyed this episode, make sure to check out doctor Harper’s book, Chill, the Cold Water Swim Cure. I put all his links in the show notes, including his website and his Instagram. And if you try cold water immersion or cold water swimming after listening to this, let me know how it goes. I always love hearing your experiences. Alright. Thanks for being here, and remember, stay curious, stay skeptical, and stay healthy. Cheers.