How to Use Cold Exposure to Transform Your Health | Dr. Susanna Søberg

Welcome to the Dr. Gabrielle Lyon Show, where cutting-edge science meets innovation and practical application for everybody. Okay, in this episode, I sit down with Dr. Susanna Soberg. Why? Because I wanted to get to the... bottom of cold plunging and cold water therapy listen i go on instagram and i see some people are doing it for 30 minutes some people are doing it for 10 minutes some people are doing it in 30 degrees fahrenheit and people are doing it all over the place

In this episode you're going to know and learn exactly what to do, why to do it, and eliminate confusion both cold and hot. Please sit down with me in this conversation with Dr. Susanna Soberg. Dr. Susanna. So Berg, welcome to the show. Thank you so much for joining us. Thank you, Dr. Gabriella Leon. That's very nice of you. And thank you for having me. I have really been interested in cold exposure. Obviously, it's exploded onto the scene here in the US. And it seems as if it's been used in...

other countries, by other people for a long time. I would love for you to start by sharing a bit about your background and your experience with cold. With cold. My experience with colds started not that many years ago, but my story goes way back, all the way back actually to the hospital where I was working for.

not that many years but as a nurse and I was working as a nurse and trying to figure out that was my own like theory i wanted to figure out why people actually get sick and why they end up in the hospital in the first place and i was working in the vascular department surgery department and wanted to help people with vascular diseases. So typically they came because they had a blood clot somewhere in the body and needed operation for that. So amputation was quite often seen there, of course.

And the thing about that was that many of these people could actually have prevented much of this happening. And losing a leg is something that is debilitating, you must say. It was a hard job to have and I was very close with the patients as a nurse. You are there all the time and holding their hands and even when they cry in the night. And I think that actually motivated me to ask the questions.

What is keeping us healthy? Because many of these people, if they just have known how to do that, they would. maybe not have ended up in that situation. And asking these questions, I started to do research as a nurse and actually... help the PhD students and eventually only a few years later I ended up going back to university in 2013 and now well

Many study hours later, here I am still doing the same, but digging deeper and deeper. Yeah. It never ends. Education never ends. You know, I do. I do. I keep trying to turn away from the light, but it pulls me. back in. Now, you did your PhD in metabolism. Is that correct? Yes. Basic metabolic research and metabolism. Yes. And you became very interested in brown adipose tissue. Yes. Yes, go ahead. Sorry. Yeah, so Brown Oedipus tissue was...

some kind of a joker at that time because everybody knows about white fat, right? And when I was asked, do you know what brown fat is and do you want to research this mysterious kind of fat that we have in the body, which is healthy, I was first asking like,

do we even have brown fat? And I think that's the question most people ask today. It's like, do we have an organ in the body, which we haven't really heard that much about? So I wasn't triggered just by this mysterious organ, which we haven't really studied. that much in humans. But at around the millennium, we found out that the brown fat could actually also help preventing lifestyle diseases such as type 2 diabetes and obesity. So we could actually lose weight if we actually.

just activated it and it clears out the glucose from the bloodstream. And just that, hearing that, that just motivated me so much because what if we can just activate this in a natural way? not even needing any drugs for it, then we would increase our metabolism. And that hooked me. Hydration is key, especially in winter. And if you're anything like me, straight water can be a challenge.

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problem. You can give it away and get your money back. That's drinklmnt.com. You know, it's really fascinating having have been a nurse, right? So you were a nurse, you're on the floors. It sounds like you were in a vascular ward or you were taking care of individuals that, you know, suffer from vascular disease.

probably many of them had diabetes and things of that nature, metabolic diseases. Was there a moment in time where you said, you know what, I'm going to go back. I'm going to go back to school. I'm going to go. I'm going to stop working as a nurse. I'm going to go back and get my PhD. Absolutely. I don't think the goal at that time was to, oh, I want a PhD. It was just the questions. I had so many questions. I was always studying.

That actually led me to the next question and the next question. And then I knew at some point after being a nurse for a couple of years, I needed to go back to get some answers. And I couldn't find them in the literature. reading a lot of literature at that time already. So I knew a lot when I went back to the university and I wanted to figure out what is actually keeping us healthy. But that question was so big. So I dug into

mechanisms of it. I want to go into the cells and find out what is helping ourselves get healthy and what is causing the chronic stress, which I see the end result of at the hospital. So what can we do like exercise that is keeping our, our cells healthy.

Is there anything else we can do besides exercise? So at that point, I was interested in what kind of lifestyle, you can say, modalities can we incorporate to make a more wholesome... behavior that we can go out and tell people well this is actually also helping you but the mechanistic side of it i was so interested in so

what happens in the cells and what physiological effects does all these exposure have, whether it's exercise, whether it's cold or heat, whether it's breathing, all these things that we... do on a daily basis or some of the things we do on a daily basis, how does that impact our life? And when does it actually get too much when it becomes chronic stress? So I was interested in finding out what's the balance of this.

And it's really interesting because I think most people will go to diet and exercise. We know those modalities. They're very common. We think about them. But you... went and turned your attention towards environmental exposures, so cold and heat exposures, was there something that made you say, this cold exposure, because you're known for the Soberg principle, which is, I know that we're going to talk all about that. Was there a moment in time, typically, you know, as we accumulate knowledge?

there becomes a moment where say, you know what, this is the thing. Was there something that had happened? Had it been maybe because you had been exposed to cold or open water swimming, any of those things that... It ended up being that cold was something that you ended up focusing on. Yeah, that's a good question. I think it's like you accumulate knowledge, right? And that leads to the next question.

And at some point I was asking myself about the behavior. So what kind of changes, what happens with the body when we expose ourselves to? to different things that could be exercise, right? It could be different diets. How does the body respond to these things? So anything that changes our biology. And cold and heat exposure came into the picture because

when I was asked, do you know about brown fat? Because you are so much into the behavioral science and what happens in the cells. I was told that Cold exposure is actually the most potent activator of the brown fat. So today we know that the brown fat is a temperature regulator in the body. And if cold is the most potent exposure...

Sorry, I'll say that again. If cold is the most potent activator of the brown fat, then we would know that any cold exposure might activate that, and then we can actually get a... clear our glucose and our fatty acids from the bloodstream. And I think that was very interesting. What if we can just do that in a small dose? Because the question was also how much.

How much should we expose ourselves to the cold to activate the brown fat? Is it like super much? Because then it's not really feasible for anybody. And that's why I asked the next question, how much is enough? I don't like the cold. At that point, I was very afraid of the cold, actually. I think I'm like most people, like very comfortable. I didn't want to get exposed to the cold because why should we?

question, why should we, was always asked, even here in Denmark, even though we are a winter swimming country, but many people don't want to expose themselves to the cold because why should we? helped me ask the questions, what can we use the brown fat for and how do we activate it? But I needed to figure out how much is enough.

And is that even feasible? So I got into it because I was asked about the brown fat and my hypothesis about behavioral changes could actually help us keep us healthy. That led me to the brown fat and that led me to the cold. And what do we know about brown fat? The most I know about brown fat is I think that as babies, we're born with a higher percentage of brown fat. We seem to lose it as we age.

From an evidence-based perspective, what can we say in humans brown fat does and how much do we have? For example, muscle mass. Do some people have more brown adipose tissue than others? Yes. So babies have a lot of brown fat. They're born with quite a lot, actually. And that's because they haven't developed the ability to shiver in their muscles yet. That develops around six months.

Before that, they could freeze to death because they cannot shiver. And the shivering is what increases our thermogenesis, meaning our temperature in the body. And we have kind of two tissues that can do that. We know about the muscles, right? They can shiver and generate this heat, but there's also the brown fat, which actually activates before the muscle starts to shiver.

That's why we don't run around and shiver all the time because we have... an inner regulator also which is the brown feather and it's centered around our central nervous system and we can get back to that why that is very convenient but babies have a lot of it because they will freeze pretty much together if they didn't have a lot of it. But as we get older, the baby grows.

brown fat gets smaller in size, so the mass shrinks a bit because then you have also the muscles which will help you keep that temperature up. So just because you have muscles that don't have to shiver to generate the heat, they also just basically keep your heat up in the body. But if you just get a little bit cold on the skin, if you go outside and you get a cold wind, then...

The temperature receptors in the skin will send a signal to the brain and the temperature regulating sensor has these sensors which can measure and tell your brain. Are you getting colder? Are you getting hotter? And if you're getting colder, it would send out. which will activate the brown fat. And depending on how intense the cold is, of course, and how cold you are and how many receptors has been activated, it will activate the brown fat accordingly.

So there's this inner regulator, which is the brown fat. It always regulates our temperature to keep our vital organs at the right temperature. That's why it's centered around our centered nervous system. It's absolutely fascinating. And is there a way to, I don't want to say exercise it. I'm assuming that you're going to say cold, but there's obviously utility.

in having this brown fat. When you think about cold exposure, how do you think about that in terms of brown fat in terms of I think that the overall outcome is health? How are we going to leverage the cold to activate brown fat? And you've got very specific protocols for overall health and wellness. Yeah. So what we.

then studied in my research is to figure out what is the, you can say the minimal dose, because I was not a winter swimmer myself and I was interested in figuring out how can we activate this healthy brown fat. and get the outcomes that we have seen in the literature without like overexposing ourselves. And what we would see here is, or what we lean on is...

that there is something called hormetic stress and that's the healthy kind of stress that we want. And if we activate our healthy stress we will have a healthy kind of activation of the brown fat. It's a small dose. And according to Hans Seeley, who actually figured this out, that there was these different stages of hormetic stress, you would have an acute phase where you activate it if, for example, you go out in the cold or into cold water.

And the second stage is where you get adapted. So you can optimize the body for these future exposures. process of hormesis and that is the healthy stress. And because of that, we figured out, well, we have to study winter swimmers because winter swimmers are exposing themselves to the cold all the time. And why we chose them, we can get back to that. But I think that is interesting to look at why or how much do the winter swimmers expose themselves and how much brown fat do they actually have?

Because if we look into the literature, we could see that there are studies where they have found that people who sleep in the cold at 19 degrees Celsius, and they do that for a month, they have increased their amount of brown fat and the efficiency of it, meaning they could increase it faster and more. So they will clear out more glucose and...

Actually, their insulin sensitivity was improved in that month. That means that you don't really have to do anything extreme and just a small amount of... cold could actually have a huge impact on your metabolism. And these people were diabetics. So I think that's very interesting that you actually with a metabolic disease could move that. almost over to helping them with that disease so they will get healthier. And what they did the next month was then ask them to sleep in a warm room again.

24 and 27 degrees. And then they could see that this brown fat tissue then got smaller again. So it really means, like you said, that you can exercise your brown fat. So I always say you should. use it or lose it it's just like the muscles and if you look in the microscope it actually in color looks a bit like the color of the muscle and it has many mitochondria just like a muscle so you can train it you can train

how much brown fat you have, how efficient it is, and also how well it clears out the glucose and fat from the bloodstream. And we wanted to test that in winter swimmers to see, can we go out and... and do some applied research and give a protocol to people so they can go out and help themselves with their metabolism, not taking exercise out, but adding it to their already exercise protocol.

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Would winter swimming, and then you should definitely highlight to us how cold and how long someone has to do winter swimming. Is it the activity of swimming versus the cold exposure? that is potentially improving the removal of glucose from the bloodstream or insulin sensitivity. Yes, that's a very good question. I think that if we did a study where we looked at people who were sitting in the cold water compared to people who were swimming.

I'm pretty sure I could tell that the outcome would be that those who are moving in the cold water would increase their metabolism even more. For many reasons, they break the... you can say the cold barrier even more, the thermal barrier, and also they are moving their muscles, but the muscles also help keeping them warm, which means that winter swimmers who actually swim.

they would increase their metabolism more, but it could also be that they are swimming way too long. So that might also exhaust the cells a bit. So it's this balance, finding that balance. The winter swimmers that I studied was not swimming in the water. They were sitting in the water. So plunging, it's more like a cold plunge and then they go up again. Sometimes winter swimmers in Denmark take a small swim.

out in the water and then back again, but it's not more than a couple of minutes. What is the standard practice? Can you define winter swimming? And I looked this up and it looked like people were swimming in lakes with ice. Yeah. So we don't always have ice. That sounds like it is cool. But I mean, cold water is defined by 15 degrees Celsius and below.

If the water is 19 degrees, that's also cold enough for the body to actually get that increase in activation in brown fat and also increase the metabolism. So I always say that. Do it all year because it doesn't have to be only in the winter month. Doing it all year round also activates the brown fat because of the hydrostatic pressure, the temperature differences also from... from being dry to getting wet to the wind. Everything helps your temperature.

regulation and that activates the brown fat as well so i think that it's an all-year thing and winter swimmers that's just a concept that's we call it winter swimming in denmark but most winter swimmers here, we actually just cold plunge and we do it all year round. So even in the summers, and it's pretty cold here anyways. And for the audience, you said 19 degrees Celsius, right?

19 degrees Celsius is cold enough to activate the brown fat. Which everybody, sorry to interrupt, but everybody is like, this is amazing. That's 66 degrees Fahrenheit. Yeah. That's not too cold. It's not so cold, not at all. I think it's a good place to start if you are like me, one who is not really a fan of the cold. I wasn't, but today I'm fine with the cold water and I'm actually warmer today because of it.

And we can get back to that also, but 19 degrees and below is fine. You can start there, but definition of cold water as per activating your cold shock is 15 degrees Celsius and below. So this is studied already in the research. When do we activate our cold shock response? And that is 15 degrees and low. So per definition, that is cold water. If you were going to tell the audience, one should implement cold plunging, what would that look like in terms of a degree range and amount? And also...

For what outcome? Would we say that the outcome would be to improve metabolism? Is the outcome to improve mood? How do you begin to think about health outcomes? Yeah, so I think that we can divide it a bit. what we can talk about is how much should you do to get some metabolic benefits. And I'm a metabolic researcher, so of course I always lean on that. And that's also what we studied in my research. So we found that...

If you do 11 minutes of cold plunging or cold water exposure, 11 minutes per week is enough to see an activation of the brown fat. And it's enough to see. glucose clearance and increased insulin sensitivity. Systemically? Across the board? The whole body, right? The whole body. Yes. So you have to submerge up to your shoulders or up to your neck what you prefer. And if you even can do that with...

contrasting that with heat exposure as a sauna. And you do that 57 minutes a week and everything here is divided on different days. So it's two to three days and divided out on. two dips per day and, sorry, divided on three dips per day and two sauna visits. So to sum that up again, so if you do a contrast therapy, that's what we studied.

The 11 minutes in cold water divided on two to three days, two dips per day. And you also do the sauna, which is also two to three days per week, but 57 minutes in total. So you shouldn't do 11 minutes in total or 57 minutes in the heat in total. You have to divide it on different days. So if you then divide that into minutes.

It corresponds to like one to two minutes in the cold water at a time. And in the sauna, you only have to do 10, 15 minutes. And it's really feasible, I would say, but that's what we found. Yes, and that's the minimum effective dose to begin to activate brown fat. Could one go longer? It's a good question. Could one go longer? I think we need more studies on...

How does longer exposure activate the brown fat? And when do we get, you can say, you always have to think about when does the cardiovascular system get to. too activated or when does it get exhausted? And you have inner organs which you need to take care of. And if you do a lot of cold exposure, sit very long, you also activate

Sorry, you don't activate. Please cut that out. If you sit too long in the cold water, there are some certain risks that you have to think about. So we can talk about long exposure. acutely when you do one plunge or one sauna, but you could also talk about what happens in years if you keep doing that protocol of very long exposures in the cold water or in the sauna. I think there is some safety here we need to also.

debate at least. So even though we don't have that longitudinal study on longer exposure, we could... think about what actually keeps our cells healthy. And again, going back to hormetic stress, I think we can say that if we do longer exposure, you are cooling your deeper tissues. And there are studies showing that if you just want health outcomes on metabolism, on mental health, then you don't need to cool your deeper tissues because there are no receptors really.

needed to activate inside your body. You don't need to cool your heart or your lungs, your kidneys, in order for you to get the health benefits. everything is on the surface. So it's on your skin and it's just beneath that surface. So it's not needed to sit in cold water for 20 minutes or 30 minutes, which I've seen and heard. And people cannot get up because the nerve endings are just numbed. So they cannot even stand up. So these are the things that could happen. And I also see that.

when people do this, showing it online, which is not that good because the longer exposure. really is not helping anyone and you are in risk of hypothermia. So acutely long exposure, I wouldn't recommend that. There is no health outcomes showing that that is necessary. There are no... receptors that deep in your tissue you need to activate to get health benefits on the physiology or any on your mental health.

The mental health part is actually within a few minutes because that's where you activate the dopamine. You activate the sympathetic nervous system, which... increases the dopamine and up to 2.5 fold actually within just a few minutes and no adrenaline the same and also within a few minutes. So that mental health.

aspect of it, the outcomes that is in the beginning. It's not really necessary for the long exposure, but some do it very long. And we can also debate why is that? And I think that's kind of like a new kind of. another kind of, I don't know, goal. Maybe it's pushing your mindset or pushing your, I don't know, it's just to get tougher, but it doesn't really have anything to do with health outcomes.

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What you're discussing is this brown adipose tissue, which is fat tissue that has mitochondria that can help increase resting metabolic rate that seems to require various exposures like cold. I have some data here. It says that cold exposure can increase resting metabolic rate up from 5% to 30%, which 30% definitely seems high, but depending on the temperature and duration.

That is really fascinating. This was an article in the New England Journal of Medicine. What I'm hearing you say is that... what you're looking for when you are going for health outcomes is really about the skin receptors to generate shivering. Is that correct? To generate shiverings? It is a temperature regulation. It helps with temperature regulation. It sends messages to your central nervous system. You release adrenaline, noradrenaline. And that is...

And you'd mentioned cold shock proteins. I don't know much about that. I'd love to hear. But those are the domains that the evidence would support are beneficial. Is that correct in saying? Yes, you can say that. I would add to that that maybe you don't have to wait for the shivering. I think that's... a concept that it can be a little bit rigid in thinking about it that way, because when you adapt to the cold and as you adapt to it, your shivering will become less.

because you adapt and the shivering is is maybe not that you can say visual. So in time you would increase your mitochondria, not only in the brown fat, which means you will activate your, you will increase your temperature very fast, but the muscle will also help. So the brown fat and muscles are.

working together and actually talking together. So this is called organ cross talk. So the brown fat and the muscles are signaling molecules to each other, telling it to help keeping the temperature up in the body. But as you adapt. and you optimize the body with cold exposure or with heat exposure, you would, when we're talking about shivering, it's of course the cold.

But when you do that, you will shiver less and less with time. So some people stay very long in the cold when they get adapted to it and wait for the shivering, but the shivering will subside eventually. if you then sit and wait for that, you are waiting for nothing. You don't have to wait for the shivering. So that's it. Yeah. Then the exposure can.

become too long and you will not get the health benefits that you are looking for. So shivering is something that is happening, especially in the beginning, but you should see it as the exposure doesn't have to increase just because of that. The shivering is just not that visual because the mitochondria are increasing both in the muscle fibers, but also in the brown fat cells. So you're just getting better at temperature regulating yourself. And that's why you also...

you are hotter. So that's also one of the outcomes we found in my studies that actually winter swimmers are warmer in temperature. I found that very fascinating that if we measured the temperature on the skin, we could actually measure that they were warmer than the control group and meaning they are just dumping more heat all the time, which means...

they must have an increased basic metabolic research. So it increases your basic metabolic rate. And it must do that because if you are imagining you are dumping heat all the time because you are warmer and you have an increased...

vascularity in your skin, then you must have the ability also to increase the heat in the body. And that is the brown fat. So what I wanted to look at in my studies after we did the... whole winter swimming study and the sauna and we had done all these tests in the laboratory and there were really long test. And I admire my volunteers who came to this study for a year and just went through all these tests. But I asked them.

Would you like to come back to the laboratory and stay at the hospital for a few days? Because I really wanted to study whether this actually impacted their metabolic rate, but also... What about brown fat activation during the day, during the night? Were they hotter? Were they warmer? And what's going on when they're not exposed to the cold or the heat, but just...

in a normal room temperature. Is there any difference? And what we could see here was that they were just physically warmer on the skin all the time, which. must mean that they also increase the activation of the brown fat. And we also did see that during these days where they just were hanging out in the lab. It really is. Interesting in the concept that you don't have to go for longer, because I do think that we are seeing a push for longer and colder, but the outcome and it.

It definitely cools. I mean, it cools your internal organs. I know when I try, and again, this is just anecdotal. When I tried to stay in there, it took me hours to rewarm. Yeah, hours. an hour at least four hours to rewarm that probably was i probably overexposed myself to cold i mean again i can't say for certain but if what we're looking for is the

increase in the central nervous system activation, the increase in brown adipose tissue, it seems that there's diminishing returns for longer cold exposure. You had mentioned something earlier about going up to your shoulders or exposing your clavicle? Is that necessary? Could somebody just get in? waste in their waste, sit in the cold plunge in their waste, stay a bit longer to get the same kind of benefits? Yes. So that is a question that I often get because brown fat activation.

If you look at the location in the body, it's located at six different places in the body and around the central nervous system and especially around the clavicularis, but also down the spine. That's the largest part. When it comes to activation of the brown fat, we would have to think about what is brown fat? Why do we actually have this mysterious organ? It's a temperature regulator in our body. And we had it.

because we needed to survive through ice ages and heat waves. And we actually did that. So compared maybe to other species, maybe we were the one having that survival organ. that could temperature regulate ourselves. And if we look at that, it makes sense that the brown fat is activated as soon as we just get a little bit cold on the skin or blows cold air in our faces.

So it means that this regulator will be activated with almost very little. So if you just depends on what you're going for, right? So if you just want the activation of the brown fat, your metabolism, you can do less. um go up to your waist if you are practicing this and you can do it slowly and slowly you can submerge up to here but it doesn't have anything to do with you have to submerge your clavicular bones or your

your whole spine or something to, to get that activation. It's the cold receptors in your skin, even on your hands is enough actually. So you can dip your hands and this, there are rigid studies on this activating. Your brown fat happens when you dip just your hands in cold water. And it means that it's actually just regulating our temperature in the body and our metabolism.

for survival. So you can go up to your waist or you can go up to your neck, but it's not necessary to do it maybe always or all the time. And especially for women, I think it's a good... thing to think about because during our cycle, we are exposed also to, or we react different to stressors. So, meaning that...

we could have a week, a month at least, where we are more sensitive to stressors such as the cold or the heat. And that means that we will probably feel more uncomfortable in the cold at some... point during that cycle. And that means that you don't have to stay in there for as long as you did last week or last week again. So women really need to, of course, listen to their body.

during the cycle, but also you don't have to overexpose yourself or you don't need to go to a specific threshold all the time. But you will still get the activation of the brown fat even just within minutes. And it helps your metabolism hours afterwards, even four hours afterwards. And is activation enough or are we looking for another level?

So for example, is the threshold to begin to stimulate mitochondria or various other mechanisms of this brown fat is... is it in the activation or is there something else another level that we're looking for so um to put it simply there's no additional outcome other than the activation that we are looking for for a health outcome. Is that correct? Oh, there are other outcomes that comes also from this. So if you can keep activating your brown fat, you would...

exercise your cardiovascular system. And that means you will also have a lower blood pressure in time. But that's also because of other things that are happening in... conjunction with the exposure and the hydrostatic pressure of the water. So the constriction and dilation of your blood vessels, meaning that you will get this better blood circulation when you are going into the cold water.

The blood pressure over time would be lower, which is a really good thing. And it's underrated, I would say. And we should talk more about blood pressure because blood pressure is a fantastic outcome. And I think you can... You would agree with me as a doctor. It's just the first thing that you do with your patients, right? It's just measure blood pressure because it tells everything about your health. At least it will tell you if something's wrong with your...

cardiovascular system. And if you can lower that blood pressure, you are way farther away from getting... type 2 diabetes or any cardiovascular disease. And it also means that you have cleared up some of the plaque or the inflammation, which...

then would lower the blood pressure. So it's kind of like a last outcome, which you can measure if you have cleaned up some of that in your blood circulation. So I really think that... that if we can do anything about blood pressure, then it definitely has to be something that we would... advice to everyone because that would help people keeping them out from the the surgery wards for blood clots and yeah that was just based where it started yes

And just based 11 minutes a week is enough. There's no need to go above that. Is that fair to say? It's fair to say that it's actually shown that it is enough and doing more. There's no research backing up that overexposure should be even better. So more is not better here. I think less is better.

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health outcomes that we see. So blood pressure, when someone begins to go through periods of cold exposure, how long till they begin to see meaningful changes in say, blood pressure? I don't know if they see changes in hemoglobin A1C or blood sugar regulation. I'm assuming over time they do. But if we just stick with one, if we stick with blood pressure, how impactful is cold exposure?

on regulating blood pressure? I think that this is something that surprised me a lot when I did my research and I read through the scientific papers. There's a lot of physiological papers out there going all the way back to the 70s. And if you collect that and look at that, you can see that there are papers showing. I think there's a specific one and I can send you that, but a specific one showing that three months is actually enough to see a decrease in blood pressure with cold exposure.

So it's actually like exercise. If you do exercise, you will probably see the same outcomes after a couple of months or three months. So it seems like it's such a small thing to do. cold exposure, but it has such a huge impact because the body is working so much afterwards. So it's kind of like the aftermath is so important when it comes to this extreme exposure it is.

So even though it's very short and it seems like very little and not much, but it has so much impact on your health afterwards. If you don't overdo it, it would just help you. get that blood pressure down and heart rate actually also basic baseline heart rate also goes down as an outcome of your cardiovascular system getting improved. That makes a lot of sense. And I often wonder about if an individual is obese or overweight and has a higher percentage of body fat, are they better at regulating?

Would they have to be exposed to a plunge that is colder than an individual who is substantially leaner? Yeah, so there are studies on the difference in exposure to cold and having different BMI. And it seems that... It doesn't really have that huge an impact whether you are obese or not when it comes to activating your metabolism and also when do you get a lower core temperature.

So it's a good measure for how much cold you would need. And the activation and the health comes from activating your cold receptors in your skin. So it doesn't really matter if you are obese or you are lean and getting the health benefits also then doesn't matter for the exposure. Then you can ask, well,

How do people with a higher BMI defend that temperature in the body? Do they do that in another way than lean people? But it seems that these studies also show that it doesn't really, they don't defend it. better or worse than a lean person. So when it comes down to how you should do this, it seems that the same amount would be...

just enough and the same actually. So I haven't seen any evidence where it shows that you have to change anything when it comes to this. You can say that lean people... often have more muscle mass and the muscles are also keeping you warm. So sometimes it seems that because you have more muscle, you are warmer and you can stay in the water longer if you can call it that.

Then on the other hand, if you have a higher BMI, more white fat, you have that a little bit more furnished, but it doesn't really help you keep you warm. So the thing is, the key here is actually muscle mass. So you can have a high BMI and have a huge amount of muscle mass also, but you can also be. lean and not have that much muscle mass. And then, I mean, then the one with the higher BMI but have a lot of muscle mass would be warmer than...

the lean with very little awesomeness. But I hope it makes sense. Yeah, it does. Actually, I hadn't thought about that. I often think about when individuals are heavier. And part of this comes from, you know, my husband would say, my husband went through SEAL training and during SEAL training, they go through Winter Hell Week.

And they would always say, or at least this is what he told me, that if you surround yourself with the heavier guys, they seem to emit a lot more body heat. And it was the smaller... thinner guys that seem to again this is my husband telling me this seem to get much colder faster and uh you know i again i don't know how well that that translates um to

benefits from cold exposure, how long somebody needs to stay in the cold versus not. But if it's skin temperature regulation, it would make sense that it wouldn't matter.

If someone was heavy or not heavy, it really just depends on the receptors in the skin. Yes, exactly. But as you just mentioned, well, if you are... very well trained and you have a lot of muscle mass and you also have the furnish of having some more white fat, then compared to one who is just very lean, then... the one with the higher BMI would end with more white fat as well, or being obese, would have more to stand against the cold just in total, if you understand.

It's kind of like the body compositions here matters when it comes to that. But if you have obesity, if you have obesity, but not. not much muscle mass, then you are not defending your temperature better than a lean person, it seems from the literature. And it doesn't matter how good you get at cold exposure. There is no reason. So an individual could become acclimated, right? You don't have to lower the temperature. You don't have to stay in there longer.

But I do wonder for that central nervous system impact, as you become more trained, it seems as if you don't get this noradrenaline, adrenaline rush as much. I think that's one of the things that I've been wondering so much when I started being a winter swimmer, because the first few times, and you probably remember this as well, the first few times you do this.

you get ecstatic afterwards. You can almost not calm down. It's like out of body experience almost trying cold exposure. And that's because you get that first rush. And that's insane. It feels insane. And over time, you get adapted so quickly to this that you feel that you have to do more.

And you also feel like you want to do more because that dopamine also gets you in a healthy way addicted to this kind of behavior going into cold water. You could almost get addicted, but it's a good thing. It's a good thing. You can you just have to. control yourself a little bit here because you still get that increase in dopamine, but it will not be as high, but it will be enough to keep a higher baseline.

So that is also for your mental health. So if you do this on a regular basis, let's just say you do this three times a week, two to three times a week and up to 11 minutes in total per week, you would get that. increase in dopamine and it will last for hours afterwards. So it doesn't really have to be longer exposure to get that dopamine. rush or get that no adrenaline activation to activate your brown fat, that is already happening.

although your body is recognizing what you're doing. So, and you still get that hormetic stress response in the body. It's just not something you would feel as high as you did in the beginning, but you get still the baseline. could also be because of a change in the sensitivity of the receptors in the brain for dopamine and also for noradrenaline. If you use the sauna, you would definitely get more.

sensitive to the endorphins because in the sauna you would have the activation of endorphins as well. So the sensitivity might also have something to do with it. I love that. We are definitely going to talk about the sauna. From a cold perspective, is there a particular time of day that is best? And does it matter if it is around a workout?

Yeah, so I think that people should do it when they have the time. It's more important that you get it done. Just find a time where it suits you. But I think that people could think about cold exposure as... as coffee because it gets you that kick that you would get from your coffee as well. So if you like me, wouldn't drink coffee after five, because then I wouldn't sleep.

until tomorrow then you should not do your cold plunge after five so it's just a thumb rule that you might could take from me it's not something that i have Study it regularly in a scientific study. It's not something rigid in that way. But just knowing from physiology and knowing the body and the brain, we know that this rush lasts for hours. So you can...

probably feel that you are very energetic if you do a cold exposure before bedtime and that might keep you awake. So I would say in the morning, that is probably the best time to do it because. that rush from the noadrenaline and the dopamine, you would get an oxytocin also. So our love hormone also increases and getting that kick from the morning will get your day started.

off very well, I would say. And you can take that energy into everything you do the rest of the day, right? But doing it in the afternoon actually works very good for me. So doing it just so like at... It could be at 2, 3, 4 o'clock, but that's also because that's when we still have daylight here in Denmark. It gets dark at 4. But in the morning, I often do it.

but also in the afternoon before it gets dark. So as long as you get it done, exactly. Whether it's morning or afternoon, it's just important that you get it done, I think. Is there a temperature that is too cold? For example, many people that I know set their cold plunges anywhere between. So it would be.

13 degrees Fahrenheit. Is there any temperature that is too cold where you would say, you know what, it doesn't have to be that cold. Or for the listener, it doesn't have to be 37 or 40 degrees Fahrenheit. Yeah, that's a good question. I don't think I've been asked that before. I have seen people plunge in very cold water. Totally. Russia? Yeah.

And which would be something I have never done before, but, and they can do it because they adapted to it. It's definitely not something that I would recommend newbies to do. You will have to start. way higher in temperature and then work your way a little bit down, but also maybe up again. It's not about getting colder and colder. It's maybe about the balance and regulation.

telling the body that don't get too comfortable with this very cold temperature, maybe get comfortable with a little bit higher temperature is also good. So it's about like the weights that you put on when you go exercising. Sometimes you... You go up in weight, but you also change the modalities. You change how you do it and how long you do it. Sometimes you do a lot of repetitions and sometimes you just do it faster and that could also increase your muscle mass.

It's like an exercise. So if you go up and down in temperature, that's going to activate your sympathetic nervous system and eventually also your parasympathetic nervous system and lowering your stress. Don't think it's necessary to go anywhere like very, very low in temperature. You already have the activation. Right. So below 13 degrees Celsius is unnecessary. And that's probably. Yeah, probably. But it's also about.

how long you then stay. If you just go down for two seconds and up, then you will have the activation of your cold receptors and you will have the activation of brown fat and metabolism, everything, but you won't get...

over the cold shock response, and you won't use your breath to do that, to get into that parasympathetic activation, where you also get the lowering of the heart rate. And that's kind of also something I think that people should... should aim for because the activation of the parasympathetic nervous system. is decreasing our stress and that's really something we want to do. We lower our inflammation, lower stress and lower that heart rate, lower the blood pressure.

and clean up that inflammation at the same time. So that could be also a good goal. But lower temperature, that makes it, depending on what it is, of course, but it could be impossible. It's definitely cold. What is the minimum length of time? Let's say somebody is closer to between say 13 and 15 degrees Celsius. The minimum length of time at...

during one session to be effective? Yeah, so one to two minutes. When you get over the cold shock, I think that's where you have both the activation of the sympathetic nervous system. where you get that high on dopamine and you get that increase in the noradrenaline, you get your activation of the brown fat, but then when you breathe slowly and preferably through your nose. you will get the activation also of your parasympathetic nervous system and you can splash some water to your face.

That will help it because then you activate the vagus nerve and that's activating the parasympathetic part of your nervous system. And when you do that, you're lowering your heart rate and then you can breathe more calmly. And that's also helping you on the stress and widening that window for how much stress you can take. That's the mindset thing because.

When you then expose yourself to these kinds of stressors, it mimics almost a panic attack, right? It's definitely, you feel that in the beginning, but if you can handle it with your breathing and slow breathing and... get a control over it, then you learn yourself that you can handle this kind of stress and your pain threshold actually widens. And it's not only actually in your mind you do that, it's physiologically you are...

exercising your pain pathway. And in your brain, you're widening the window for how much stress you can tolerate. So stress is actually our pain pathway. So if we can exercise that, we can also tolerate more pain. And we don't need more exercise than just a few minutes. I think that it's something that is important and really not discussed so much, especially regarding leveraging cold for parasympathetic activation. I do think that that is...

Very important. What about talking about parasympathetic nervous system, talking about stress? What about menopause? Are you aware of any research and where can women particularly benefit from cold exposure? Yeah, so I think that menopause is a time where we, I don't know, maybe it's something that we in the research have... not been focused enough about. I think that there is like a gap there that we need to do more research in. And just from looking at my mother, I remember her hot flashes.

oh my God, mom, what is happening? And she didn't have any tools to regulate that. She didn't know what to do and she's not that old. So I figure that there must be something that we could do. Winter swimmers here in Denmark actually use the cold to regulate that as well. It helps on their hot flashes. So this is just something that we know from just being living in this country, but research has also.

come out and this is a research study or a survey actually from UCI from London and they surveyed around 1100 women. and ask them in a questionnaire. So what kind of... you can say, symptoms do you have and how much has it helped you doing cold exposure? And there was actually more than 700 of these women experiencing menopause symptoms. And it seems that 63% of them have symptoms of relief just in general.

Just a lot. That's more than half of the women in menopause feeling that the cold water actually helped them. And more specifically on anxiety, for example, there was 47% of them feeling a relief from anxiety. And 31% felt a better mood. And the hot flashes, which I just mentioned, was actually also relieved or helped with around 30% of them. What happens here is that.

When you expose yourself to code, just to get into the mechanism of it, I'll try to explain. No, no, this audience loves mechanisms, so they will definitely appreciate that. Let's get nerdy about it.

So when you expose yourself to the cold, you have the activation of the sympathetic nervous system. We talked about that. But the parasympathetic nervous system activation... helps you regulate that anxiety, but also the mood thing because of the dopamine increase and the new adrenaline, the energy rush that you get from that, it changes how you...

um, regulate your mood. So if you look at, um, depression, um, medication, what they actually give you is, uh, no adrenaline in this medication. So it. And this medication can get all the way into that center in the brain and it can increase the noradrenaline. But we do it naturally when we are exposed to the cold. So if you want to get into that center.

where your mood is regulated, you need to increase your neuroadrenaline. So it makes sense from a mechanistic point of view that they feel these relieves. And I think it's quite a lot asking 1100 women, but of course we should. have some more studies on this but i think it's it's it's a good

thesis or hypothesis generating survey, which means that we can go out and do more studies on this. What about menopause and vasomotor symptoms? Do you think that the cold water helped them temperature regulate? Yeah, so I would suspect that even though they didn't do this physiological test on them, I wish they had, but I think this is just the first step that they did in this study. But what I would suspect happened, which... happens to everyone.

who does cold exposure is that you get the vasoconstriction and vasodilation when you do this kind of like gymnastics for your blood vessels. And that helps also regulate your temperature even better. And the brown fat has something. to do with that because it helps you get warm when you need to get warm and not warmer during the night when you don't have to.

good way to help the body temperature regulate. And when you look at our winter swimmers, which we actually did do a lot of measures on the body and to see how well temperature regulated they were. They were almost perfect all the time. They didn't freeze. They were not too warm, but they just dumped a lot of heat.

when they were in a room temperature and when they were cold because I cooled them down actually for hours because we needed to measure their brown fat. But they were comfortable where other people weren't. So who didn't do? winter swimming. So the temperature regulation gets even better.

than people who are not. So I guess that could be an explanation why these women would say that it helps them with the night sweats and it helps them with the hot flashes. I would suppose it has something to do with the physiology. I have another question about women. And I don't know if you have read anything about this, but what about in pregnancy while individuals are pregnant? And I do know that there are other cultures that do cold.

exposure, plunging while they are pregnant. Yeah. I think that the Finns do it. I know that many Finnish women... But they have done cold exposure their whole lives probably and continue to do that while they're pregnant. They are so familiar with doing this and they would have a regulation which... women who are starting, I don't know, today and being in the, yeah, I don't know, mid-age or something, or even just not growing up with it, wouldn't know how to regulate.

their body temperature as good as someone from Finland who has done it all their lives. So that might explain why Finnish women do this while they're pregnant. But in general, I would say that. If maybe you're not finished, I wouldn't even recommend it to a Finn, actually. If you're pregnant, I say that you should stay away from doing cold exposure and actually also sauna.

But we can get back to that. But for cold exposure, I think it's very important to say that you have a huge stressor when you go into the cold water. The cold water will switch and mix with the warmer blood when you get up. So when you're in the cold water, you are not the coldest you will be. So when you get up, you should always think about that. When you get up from the water, your vasodilation will make the warm blood.

mix with the cold blood and then go back to your core. And in your core, in your aorta, you have these temperature receptors sending a signal to the brain that suddenly that blood has become very much colder. that suddenly change in temperature will also affect the fetus. And we don't know the impact of that. And I mean... I wouldn't do that to my unborn children. I would just stay away from the water for the nine months and knowing that.

Studies actually show that you're still adapted to the cold water when you get back. Studies have shown that if you take a pause for a year and go back, we can still see that you are adapted to the cold water measured on. breathing rate. So whether people are hyperventilating as much as they did in the beginning of the year before. while they got adapted so they can see that you don't go back to zero it's just a pause and i think that people should just

Women should just enjoy their pregnancy and then go back to the cold when they're done with the pregnancy. Just take a break. Not bad advice. Let's talk about sauna and then the combination of... hot and cold. Where does all of this fit in, in terms of overall health and wellness? Yeah, so...

Sauna is definitely something that I would also recommend. That's why we put it into my research because there is a lot of research on... the effect of sauna and how that affects our cardiovascular system, how it increases heat shock proteins and heat shock proteins, I guess your audience must have heard about that, but it's...

It's the key, you can say, mechanistic regulator in our cells when it comes to the healthy stress part of it. And heat is an activator of that. And it repairs our cells from the inside. does a lot of good things on our cardiovascular system, even longevity. So sauna in combination with the cold water, which I call contrast therapy, is what we...

also do in Denmark or we are starting to do more. We are more of a winter swimming country, but Saunas has also come into our culture and doing the contrast will, you can say, push your cardiovascular system. So it's a really good exercise for your vessels. It's a good exercise for actually your... even your mental health, because you are doing an increase in the neurotransmitters on a different way when you go into the cold and then when you switch to the heat.

I always say you should start in the cold, though, and then you should end in the cold also. Okay, tell us about that. How hot... Is hot enough? And for how long? Does it matter if it's an infrared sauna versus a traditional sauna? I know that there's a lot of Finnish data out there that they use traditional hot saunas. Where are we in terms of our understanding of number one, how hot and for how long? Yeah, so I think it's very interesting that.

You can say, well, any heat, just like with the cold, any heat is good for you. So if you have no... access to a sauna or you don't have an infrared sauna, but an infrared blanket or sitting in a steam room or whatever you have access to. So any heat. it would actually do you good. So just to get that clear. So any heat is good. But there are a lot of research, I think, on the dry sauna.

at 80 degrees Celsius, which I'm not really sure if that is 176 degrees Fahrenheit, around that number, right? So 80 degrees. Celsius is what is recommended, you can say, because most Finnish saunas are around that temperature. And that is where we see health benefits also and also on longevity. So there are Finnish studies showing that if you go into the sauna two to three times per week, or even just one time is really good. But if you can do two to three times per week, then you will have...

Lower risk of early death on 24%. And if you can do four times per week and you have... all that amount of time, or even every day, so seven times per week, you will lower your risk of early death by 40%. And I think that's quite amazing. And you can ask now, why is that? When you go into the sauna, you almost mimic an exercise in zone two. If you sit there for around 15 minutes or maybe a maximum of 30 minutes, but...

Then again, it's overexposure and you don't need to do that. If you go longer, you might exhaust yourselves. That's something I always say. So shorter is sometimes also just enough and better. your body will get adapted over time. So your sweating rate will start earlier and earlier. So meaning that when you sit in the sauna for around 10 minutes, it could actually be enough.

to both activate the heat shock proteins, which are regulating and repairing our cells on the inside. So they live longer. And when they live longer, we also live longer. the exercise of the cardiovascular system is what's mimicking the exercise. So that is, I think, amazing. And it clears the inflammation. And that is why we see that people have this longer life or they have a lower risk of early death on these studies from Finland where they have followed people for.

around 25 years, more than 2000 sauna bathers. And it's 15 to 30 minutes at 176 degrees Fahrenheit, which is 80 degrees Celsius. One question for you is that when we think about exercise, and I might be thinking about this wrong, but if you become more trained, then you require more effort to move into zone two. The more well-trained an individual is, the more you have to increase the stimulus. That is not the same for sauna. Is that correct?

Well, this is about temperature receptors more than it is, I think, about it is for exercising the muscles. So the pathways for activating... sweating is probably not the same when you are exposed to the heat and when you are moving your muscles. But I think it's a very good question. I would say that it means that there is a difference on exercise and heat. So you don't have to do more and more and more in the sauna to get the health benefits or to get into soon too.

It means also that the increase in sweating might actually increase over time. meaning also you will be able to sit in the sauna for a longer time because the heart rate will not increase that much after you get adapted. But that's also where, just like the cold, you will have to... control yourself a little bit and say, well, I can sit here for an hour if I want to, but maybe ask yourself whether you should do that and expose yourself that long to the heat.

That makes a lot of sense. You start with cold. If in your ideal world, what would be an ideal protocol for you? Perfect world. Perfect world. I think that people should start in the cold water because, well, and this is just my observation and through my... I did a lot of field studies before I actually started my research because I needed to figure out what is actually this cold exposure and winter swimming and what do they actually do when they go out.

and plunge and they go into the sauna what happens and what i noticed is that when we dip in the cold water we activate our fight and flight system, right? So that is a noadrenaline, dopamine and oxytocin. And that increases something that makes us so happy and joyful. And when people go up from the water and you observe them and go into the sauna, they are so happy, ecstatic actually, but they're also so grateful.

Why I say start in the cold water is because then when you land in the sauna and you sit there. You can do an internal thing where you can feel more gratitude for being where you are, for what you do. You can do that as a mindset for yourself, but also you feel so grateful for it. nature for being here for the people that you sit around and you will enjoy that sitting in the sauna the first session more than if you started there because that's almost just painful sometimes because you are

already and you don't have that increase in all the neurotransmitters and you just sit there and wait until you had enough. And it could feel awful for some people, especially in the beginning because... That's because when you are not exposed or adapted to the heat. you will suffer a little bit. You will feel that suffering from the heat. Oh my God, I need to get out. And with time, you get more adapted to that because the sensitivity of those endorphin receptors will get better.

And you will receive the endorphins in your brain better over time, meaning that over time you will feel better in the sauna. But if you want to have a really good experience, then... you will have the increase of all those neurotransmitters when you start in the cold and then take that into the heat. So I always say start in the heat also, but you should also end on the cold. And is it because of the change in vasodilation?

Just the contraction, maybe there's a synergistic effect. Is it amplified for health outcomes, this contrast therapy? Yes, definitely. If you... You can see it as gymnastics or like an elastic. When you go into the cold water, you would definitely have the vasoconstriction. And when you get up, you will not have immediately a vasodilation, but when you go into the heat, you actually help.

bit. So the increase in, now it's a little bit nerdy, but so you have the increase in nitric oxide because of that and it helps. in the cold water, increasing that, but also when you go into the sauna and that ability to contract and dilate and, and doing the heat, the cold and the heat helps with that.

that is an ability you really want in your body because then you will have a better oxygenation. Is it called that? Yeah. So you have a better oxygenation of all your cells in the body because you will get... more oxygen out to all your cells because of the increase also in nitro oxide. And that will help your blood circulation. And then once they've spent two minutes in the cold.

they go to their 176 degrees in their sauna, how long are they gonna stay there, 15 minutes? Yeah, so 10 to 15 minutes should be enough. But they don't need to stay any longer. And then they go back to the cold for another two minutes or so? Yeah. So get over the cold shock and get back into the sauna. I always say that... take a breather before you go directly from the sauna to the coat plunge. And that is just to...

Maybe just a little bit temperature regulate. That could be if you are outside, that's a good way to just stand at the wind for just a moment, depending on temperature and wind, of course. But cool down. before you jump directly into the cold water, because it can be very shocking for the body going from extreme sweating to extreme cold.

you could have that fast activation of your sympathetic nervous system and a decrease in blood flow to the brain that you could almost pass out, actually. So it's just a precaution that... Be careful not to go straight and very fast. And if someone is thinking about fertility, let's say men, and they want to have a baby, would you... recommend against sauna versus cold or both extremes in temperature might not be ideal? Is there any data on those kinds of things? Yeah, so that's a good question.

There's actually some data showing apparently that if you sit in the heat, you would have a lower level of production of... I think it's sperm. I... I've absolutely heard that. Just so you know, I have seen research and I'm just curious if you saw something else, but we definitely don't recommend individuals who are trying to conceive go into this online.

just going down that road, but now I couldn't stop. Yes. And then I'm just going to repeat it. So yes, if, and we also don't recommend using that as a form of birth control, but no, exactly. Yeah. Exactly. It's not something that we would recommend. What do you think about, are there myths out there that you continuously see?

One of the things that you mentioned, of course, was this idea that you have to really suffer, that you want to go in to frigid temperatures for long periods of time or tough it out in the sauna for long periods of time. That seems to be one myth. that extremes are better. Is there, is there anything else in the science perhaps that, and maybe even in the scientific community that you see perpetuated versus what is out in the public sphere?

Yeah, so other than that, that extreme or longer is better, which is taking over, I think it's going a little bit crazy. I think we're good to stop that a bit and see if we can stop the circus. of longer exposure, but I also see that some people are very nervous about doing cold exposure in conjunction with exercise. And I don't think it's really necessary to think about it as something like very bad or not doing it at the same time or just after. I mean, it.

It really depends on what you want, of course. So if you say you are a bodybuilder and you want every inch of growth of your muscle mass after exercise, and you don't want to lose that. very, very small percentage, then maybe don't do the cold exposure right after exercise and you can wait four hours and do it then. Because what happens when you do the cold exposure right after?

is that you increase something called TNF-alpha, which is our inflammation marker. And when you lower that, you also stop, you can say that... the disruption of muscle fibers. And that maybe doesn't help the muscle grow, but it's so little percentage that I actually think that if you are a... Um, if you are an athlete or maybe, or maybe not an athlete, but you want to go exercise tomorrow or you exercise every day, then it's better to actually do the cold plunge because you.

eventually grow your muscles even more because your performance would be better because you're not sore. So I think that this is... I think it's just math. It's just looking at when would you have enough energy and not be sore to go and do your exercise again. So I don't think that people should be too rigid about this, but people are. And I see huge discussions online on this. And I think it's just...

A bit ridiculous, actually, because top athletes has done this for 25, 50 years. I don't know, but it's like so many years they have done this. And they do it to actually increase their performance. the next day and they can go out and play football and compete without being sore and they can perform even better. And there are actually studies also showing that they can perform better.

when they have done a cold exposure. So I think that it's just a myth that's taking over a little bit. And probably not very meaningful. The impact that... hot or cold would have on, say, hypertrophy or gains. Again, it doesn't make a ton of sense. And I think that the mechanism of action that we're talking about... And then a lot of your research is highlighted is activation of brown adipose tissue and other various mechanisms that are different than...

the pathways that would relate to muscle protein synthesis, and things of that nature. So I totally agree with you. And I'm so glad that you said that. What about age? Does it matter? I'll tell you this, both my five-year-old loves putting her face in the cold plunge. And again, she loves it. She's like, put me in, put me in. And my mid 70 year old dad loves going in the cold plunge. Okay. I mean, as long as, well, as long as they don't have.

heart diseases or unregulated high or low blood pressure. And then I would say it doesn't have an edge actually. A funny story is that the house that me and my husband bought was owned by... a man who was very known in the community for, he was very, very old, but he had done winter swimming.

his whole life. And one of the last things that he also said when he got very, very old is that I will keep winter swimming. I want to go to the water. So the club up here went to his house and they carried him. all the way down to the water and they plunged him into the water and up again. He didn't have heart diseases. He didn't have any unregulated heart rate or anything related to that. So he could just still do it.

until his last day. So as long as you don't have those issues, then I think that we can recommend it. When you go down in age, I would say that we would have to think about... the body size because children are just much smaller in mass, right? And they're... mass ratio is or surface to mass ratio is just very much higher compared to an adult. In research, there's this study where they have compared 12-year-old kids to adults who were in their 30s.

and looked at how well does 12 year old defend their body temperature in cold water compared to adults. And it seems that the mechanism of how they do it was different. But they could, for these minutes, they did the cold plunge, they could stand it and they could defend the cold. But when they then got out of the cold water. the kids were way colder than the adults. And I think it just makes a lot of sense because they have so much surface, but so little mass to keep them warm.

So it's that ratio that is important to look at. So when you have a kid that is only five years old, you have a large surface to mass ratio. she would not be able to defend their temperature as well as an adult because there's just so much more mass, so much more muscle, so much better maybe also temperature regulation. kid would need to be

very short in the cold water. If they want to do a cold plunge, they maybe just dip and up and make sure they can come into heat right after, meaning into a living room or warm clothes or something. But the face, I don't see any problem with that. That would be... Just great. Technically, because it's a cold receptor, it would be effective, right? Yes, exactly. Yeah. When in Denmark do they typically, what is the age people typically start doing winter swimming?

They would typically start winter swimming when people become so like older teenagers because nobody is like... Of course, nobody's forced or anything to do it here, but we have a culture. But we don't see many small kids. they cannot become members of our winter swimming clubs either so it's you have to be a certain age to become a member and that is also for safety because hypothermia

is a risk when you have the smaller mass, the smaller bodies. So winter swimming is, I would say, for teenagers and adults. I mean, kids in Russia do it. So it's like, depends on culture, I would say, and how you do that. You should ask a Russian, how do you get your kids adapted to this groundwater? I don't even know if they should, actually. But it's interesting because I talk a lot about that.

When our ultimate goal is to raise strong humans, they all watch what we are doing. They don't listen to what we say. They watch what we do. And if we are engaging in these activities, which I do. you know, with the sober principles, my kids want to do it. And I think it's amazing whether they can do it or not at that moment, they are seeing it, they are being primed.

to be interested in the physical nature of themselves, the environment. Where do you envision the future going with these environmental exposures? How would you like to see it fit in to health and wellness? Yeah, so I think that's the cold exposure and heat exposure is definitely something that I'm sure will be mainstream. And I think it is already moving in that direction, but there are so many people not really recognizing it and still think it's like...

something funny to do, just a funny activity, and accepting the health of it is just as difficult as exercise actually was back in the 70s. I remember when I was in high school. seeing a short movie clip from the 70s where people were jogging around in California in small hot pants. And I remember the palm trees and the voiceover said, well, we are now jogging in California.

And we can actually see that people are running around here. It's crazy. It's something called jogging. Is it actually healthy? And there were actually policemen. driving after people who were running because it seemed so stupid and why would they run? If they run, they must be running from something. And I think that we can... We can look at that and see how research has catched up with that and shown how.

healthy it actually is to do exercise. And today it is completely recognized and it's accepted by everyone. And I think that coat and heat exposure is on the same path. But it takes some time for people to recognize that, oh, it's not just something funny to do or something crazy people do, the crazy winter swimmers from Denmark. Yeah, I think it will be recognized. Dr. Susanna Soberg, I'm so grateful.

for you that you joined us. I do believe that you cleared up a bunch of myths and you made everybody at home happy because now two things. Number one, they realize that they no longer have to cold plunge at frigid, frigid temperatures. long periods of time, nor do they have to sit in the sauna also.

extreme temperatures for long periods of time. I think that your work is amazing and you are doing so much for the world. There is, of course, there's the nutrition and the exercise space and the environmental influence space, which you have really contributed quite. bit too. So thank you so much for coming on the show. Oh, thank you so much for letting me coming on your show. I'm sorry that I didn't have the chance to send you actually my book because it was so fast that we got this.

call on. But if people want to read more, I have a book about it. And it's not only about winter swimming, it's also about sauna. the combination. Well, we will link all of that. And I am going to hold you to a signed copy, considering you will be in LA. So you'll have to send me one of those. And again, thank you for all your wonderful work. Thank you so much.