如何用冷热暴露改善健康 | Susanna Søberg 博士

完整译文：Andrew Huberman：欢迎收听 Huberman Lab 播客，我们在这里讨论科学以及以科学为基础的日常生活工具。 我是 Andrew Huberman，斯坦福大学医学院神经生物学和眼科学教授。 今天的嘉宾是 Dr. Susanna Søberg. Dr. Susanna Sjoberg completed her doctoral thesis work at the Center of 炎症 and 代谢 and the Center for Physical Activity 研究 at the University of Copenhagen in Denmark.

完整译文：Her 研究 has focused on how 刻意冷暴露 and 刻意热暴露 可以用于 to enhance 人体代谢. She is the first author of a seminal study which discovered the minimum 阈值s for deliberate heat and 刻意冷暴露 for increasing 棕色脂肪产热, which is essentially a mode of increasing heat production and 代谢 in the body, and for establishing actionable 方案 that 可以用于 outside of the laboratory to improve 代谢 and human health.

完整译文：Dr. Søberg's 研究 was published in the journal, Cell Reports 代谢, in 2021, adding to a long and 重要的 history of 研究 focusing on ……的作用 cold and ……的作用 heat in altering various aspects of the body's physiology, including hormone health, 代谢, and changes in 神经递质, such as 多巴胺 and 肾上腺素.

完整译文：事实上, today's discussion with Dr. Søberg focuses on ……的作用 deliberate heat and 刻意冷暴露 on 代谢, but it also includes discussion of the effects of cold and heat on things like 神经递质 production, namely 多巴胺, and 肾上腺素, and 去甲肾上腺素, the so-called 儿茶酚胺, which strongly impact mood and 代谢.

完整译文：此外, Dr. Søberg answers many common 问题s about deliberate cold and 刻意热暴露, including, for instance, ……之间的差异 冷水淋浴s versus cold immersion up to the neck versus total body cold immersion, including 是否 going back and forth between heat and cold changes fundamentally the way that heat and cold impact the 代谢, 激素, and 神经递质 production.

完整译文：And we 讨论 almost every single nuance and variation on deliberate cold and 刻意热暴露 方案 as it relates to the underlying science. In particular, how 冷感受器 在……层面 the skin are impacted versus cold reception and perception 在……层面 the brain and how all of that impacts systems of the brain and body, relating to 心理健康, 身体健康, and 表现.

完整译文：Based on her 科学的 研究 and academic training, as well as her 理解 and use of deliberate heat and 刻意冷暴露 方案, Dr. Søberg is considered one of the world's leading experts on these topics. 事实上, she is the author of a recent book entitled "Winter Swimming," which is, I have to say, a terrific book because it breaks down chapter by chapter the 不同 aspects of deliberate heat and deliberate cold into its various constituent parts, including cold 适应过程, the cold shock response, dangers and safeties of cold water, ……的影响 cold and impact of heat on various aspects of human health, as well as specifics relating to sauna, versus ice, versus cold swimming, showers, et cetera.

完整译文：It's a very thorough read and a very easy and accessible read that if you're interested in deliberate cold or 刻意热暴露 or both, will allow you to embrace those 方案 with the greatest degree of confidence that you're going to obtain the specific endpoints that you're interested in and to do so safely.

完整译文：开始之前，我想强调，这档播客与我在斯坦福的教学和研究工作相互独立。 It is however part of my desire and effort to bring zero cost to consumer information about science and science-与……有关ols to the general public. 本着这一宗旨，我要感谢今天播客的赞助商。

完整译文：Our first sponsor is Plunge. Plunge makes what I believe is the most versatile at home self-cooling 冷水浸泡 for 刻意冷暴露. I've talked numerous times on this podcast about the many 益处 of 刻意冷暴露. And indeed, today's episode is focused entirely on the 益处 and the science of 刻意冷暴露.

完整译文：Plunge uses a powerful cooling filtration and sanitation unit to give you access to 刻意冷暴露 in clean water whenever you want. As we will discuss during today's episode with Dr. Susanna Søberg, 刻意冷暴露, 尤其是 刻意冷暴露 done up to the neck in water, 可以用于 to achieve 一些 重要的 endpoints 与……有关 心理健康, 身体健康, and 表现.

完整译文：I've been using a plunge for more than two years now. I can tell you that it makes it very easy to get your 刻意冷暴露 at home. It doesn't require much cleaning. 事实上, it's very easy to keep clean, which is essential. You don't want bacteria and other things growing in your 冷水浸泡. Basically, everything about the plunge is made easy, so that anyone, including myself, can gather 刻意冷暴露 on a regular basis at home.

完整译文：If you're interested in getting a plunge, you can go to plunge.com/huberman and get $150 off your 冷水浸泡. Again, that's plunge.com/huberman for $150 off. Today's episode is also brought to us by Maui Nui Venison, which I can confidently say is the most nutrient dense and delicious red meat available. Maui Nui spent nearly a decade building a USDA-certified wild harvesting system to help balance deer populations on the island of Maui.

完整译文：The solution they built turns to the proliferation of an invasive species into a wide range of nutrients dense products, from butcher cuts and organ meats, to bone broth and jerky. Their bone broth has an unmatched 25 grams of protein per 100 calories. Several guests on this podcast who are experts in nutrition have pointed to the value of getting at least 1 gram of quality protein per pound of body weight each day. With Maui Nui, that's very easy to do while eating delicious meals and getting it from a sustainable source. If you would like to try Maui Nui Venison, go to mauinuivenison.com/huberman and get 20% off your first order. Again, that's mauinuivenison.com/huberman to get 20% off.

完整译文：Today's episode is also brought to us by Thesis. Thesis makes custom nootropics, and nootropics is not a word that I like because it means smart drugs, and the brain doesn't have neural circuits for being smart, rather has neural circuits for focus, neural circuits for task switching, neural circuits for creativity, and on and on. Thesis 理解s this and designs custom nootropics designed to get your brain and body into a specific state in order to do the mental and/or physical work that's 重要的 to you, such as creativity, or focus, or clarity.

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完整译文：I'm pleased to announce that I will be hosting two live events in September of 2023. The first live event will take place in Toronto on September 12th. The second live event will take place in Chicago on September 28. Both live events we'll include a lecture and a 问题-and-answer period and are entitled The Brain-Body Contract, during which I will discuss tools and science 与……有关 心理健康, 身体健康, and 表现.

完整译文：I should mention that 很多 that content will have absolutely no overlap with content covered previously on the Huberman Lab podcast or elsewhere. If you're interested in attending either or both of these events, please go to hubermanlab.com/tour and enter the code Huberman to get early access to tickets. Once again, that's hubermanlab.com/tour and use the code Huberman to access tickets. I hope to see you there.

完整译文：And now, for my discussion with Dr. Susanna Søberg. Dr. Susanna Søberg, welcome.

完整译文：Susanna Søberg：谢谢。

完整译文：Andrew Huberman：很高兴你来到这里。 I feel like I should give a little bit of the backstory of how we got connected, which was that for many years, I've been interested in cold thermogenesis. It was the topic of my senior thesis in college. And I've of course followed the popularity of Wim Hof. And we've had Dr. Craig Heller, my colleague from biology department at Stanford, who works on cold and its impact on physiology and sports 表现.

完整译文：So, for a long time, I'd been interested in this area. But there's been a real lack of new, let's say, high profile, quality 科学的 information in terms of how, for instance, 冷水浸泡s and sauna, how that impacts human physiology. 我知道 there's been some information out there, but it's been 某种程度上 scattered.

完整译文：And then a little over a year ago, I see this paper in Cell Reports Medicine and was immediately struck. First of all, the fact that it was in Cell Reports Medicine. I've been on the Cell Press editorial board for a long time now. So, press journals are, of course, phenomenal journals.

完整译文：And the title and the content of the paper was directly in line with the sorts of practices that people are very curious about and then are starting to emerge. Things like sauna, 冷水浸泡s, and there was your name first on the author list. And I reached out to you through social media. And we've done a little bit of live content there together.

完整译文：And I've been tracking what you've been doing in the world in terms of your book, and 讨论 the results in your manuscript, and 讨论 the science and impact of 刻意冷暴露 and sauna. And I have to say that it's been a wonderful and remarkable thing to see, and you're bringing so much quality information about this area that for a long time 我认为 was 有点 niche and is now becoming more and more mainstream.

完整译文：So, I'm going to start off with a thank you for being here and a thank you for the work that you've done. And I'm looking forward to talking to you about it today. So, my first 问题, to get things started, is what is happening 当我们 get into an uncomfortably cold environment?

完整译文：So, for instance, if I'm really hot on a hot day, jumping into a cold pool feels really good. But if I'm already 有点 at room 温度, I'm a little bit chilly, getting into that same 温度 of water doesn't feel so good, right? There's a shock there. So, if you could just walk us through what happens 当我们 get into uncomfortably cold water, 是否 it's by way of shower or 冷水浸泡 在……层面 our physiology, and if you'd like, our psychology.

完整译文：我认为 that's a good place for us to start because 我认为 it will orient people to their own experience if they do that. And for those that haven't done it, it might start to peel back some of the layers as to what the underlying mechanisms of cold are.

完整译文：Susanna Søberg：Yeah. 谢谢你的提问。 It's really good to just address what actually happens in our physiology 当我们 get cold, and you can get cold in many ways. So, you can just head out for the one that gives you the most potent stressor, which is submerging into cold water. But you could also go in outside in the cold wind. That's also going to activate your 交感神经系统. So, get all these 神经递质 going in your body and so your 儿茶酚胺.

完整译文：Let's just address that we are taking a 冷水浸泡, 例如. So, 如果你是 very hot, 例如, before you go into the cold water. It's going to feel less 有压力的. But the 温差 from your skin to the cold is definitely going to give you a shock, but your 核心体温 is warmer, and that's going to feel a little bit better.

完整译文：So that's why 当人们 go into a sauna, 例如, and go out and into the cold water, they can do it easily, easier than if they were cold beforehand.

完整译文：Andrew Huberman：Could I just ask you a few 问题s? So, you mentioned the 交感神经系统, which for people listening who aren't familiar with that, is the branch of our 神经系统 that's responsible for creating accelerations and 心率, feelings of alertness, it's accompanied with stress and the 应激反应. But it's accompanied with waking up in the morning for that matter. So, it's not always about stress.

完整译文：And then you mentioned the 儿茶酚胺, which are 多巴胺, 肾上腺素, and 去甲肾上腺素. So maybe a little bit later, we'll 讨论 those individual 神经递质. But you raise a really 重要的 point, which is something I get asked about a lot for people that are curious about using 刻意冷暴露, which is how cold should the water be.

完整译文：And 我知道 it's very hard to give a straight prescription for that because 我认为 it boils down to what you just said, which is it's really ……之间的差异 your current 温度 and really the 温度 at the surface of your skin and the 温度 of the water. So, if you're very warm, getting into cold feels good. If you're already cold, getting into more cold feels 有压力的.

完整译文：Is there any way that 我们可以 start to gauge what is the best way to approach a 刻意冷暴露 方案? I mean, should it feel 不舒适? And that leads into the 问题 of how do we balance the discomfort with the amount of time that we spend in?

完整译文：So, for instance, if it's just a little bit 不舒适, will spending more time in the cold get us the same benefit as getting into very uncomfortably cold water for a very short period of time?

完整译文：Susanna Søberg：Yeah. It's a really good 问题. And I definitely think that this could be a future study on this as well to really unravel what 有点 方案 are the best way or also for which outcomes, of course. So, if the 温度 sure is very cold and you also feel very cold, then you should stay in the water a little bit longer. So, 我认为 you should get 不舒适 cold. So as long as you get 不舒适 cold, it's cold enough, and you get this what we call the cold shock. So, the cold shock is activation of your 交感神经系统 and these activation of the 儿茶酚胺, which you just mentioned before.

完整译文：Andrew Huberman：Does the shock mean that I'm having trouble controlling my breathing? Is that a good gauge?

完整译文：Susanna Søberg：Yeah. You can say so because that's 有点 like how we define it. So, you hyperventilate. So, you have a faster breathing rate. So that 增加s also because you activate your gasping reflex 如果你是 new to this. But 如果你是 adapted, it 有点 subsides with time with 适应.

完整译文：So, what you can do is that you can train this 冷暴露, and you can get adapted to it, so you don't have this hyperventilating response every time you go out in the cold water. So, this is like building up your resilience, building up your 适应. It's going to make this shock like subside a bit. So, it's always harder in the beginning, but you should do hard things, right? It's not something that we-- you shouldn't think about cold water and cold-water immersion as something that is 舒适. It should be hard because that's the point of it, right? If you enjoy it, then yeah, then I'm thinking something is wrong, is not right. You should not enjoy it.

完整译文：Andrew Huberman：Well, this is an 重要的 point that you're making because 我认为 that many people shy away from 刻意冷暴露 because it's 不舒适 in a way that at least from my experience is very 不同 than the discomfort of 运动. Because with 运动, for instance, if running fast and breathing hard is 不舒适, you can slow down or walk. If lifting weights is 不舒适, you can remove some weight, or reduce the number of repetitions, or stop.

完整译文：With 刻意冷暴露, I suppose you can be 某种程度上 halfway in halfway out of the water or partially underneath the 冷水淋浴, but it's very hard to titrate and adjust the level. It's 有点 all or none. And I've seen-- actually, I can tell this by anecdote I've done some work with military special operations. I won't say which country. This was outside the US. And these are very tough individuals. They're 用于 going without sleep and doing hard, high consequence, high risk 有点 work.

完整译文：And they were asked to do some cold-water exposure training, and I was there that day, and it was remarkable. About a third of them just went straight in and just 有点 grinded through it. They looked stoic anyway to me. There were a few whimpers, no cries. About a third talked a lot, and you could tell that they were agitated and anxious, but they made it through.

完整译文：And then about a third of them just simply would not get in past their knees or thighs. It seemed like they were just dreading the whole experience. Some actually didn't actually go in completely. Which was really surprising to me in that you couldn't tell based on their physical appearance or anything else about them, they're all high performers, as to who would have this response.

完整译文：So, it seems like people vary tremendously in terms of their ability to embrace the discomfort of the cold. From your studies, is that your experience as well, or are there these weird mutants who seem to just love going into the cold for the first time?

完整译文：Susanna Søberg：So, some people just feel better in the cold, and some people dread the cold even more. And you can say the more people are pushing the cold away, they might feel the cold pain even more. So, they would definitely-- people who are, maybe the soldiers you just talked about, some of them might be already adapted to the cold.

完整译文：So, if they are not scared of the cold, they go out, and they embrace the cold in a better way. It could also be that some people have a more sensitive 神经系统. And when you are a bit sensitive to the cold, you will, of course, try to get away from it, right? And you also feel the pain more if you avoid it. So, the more you avoid the cold, the more pain painful it will feel when you go into it.

完整译文：Andrew Huberman：You mentioned being outside in a t-shirt, versus cold immersion up to the neck, versus shower. This is something 很多 people wonder about. What are the 差异s in terms of impact, short term and perhaps even long term, between 冷水淋浴s, 冷水浸泡 to the neck, so that could be an ice water or just very cold water, immersion with dunking one's head and then coming up because obviously, people have to come up for air at some point, and then simply being outside on a cold day in shorts and a t-shirt or something of that sort.

完整译文：Susanna Søberg：So, there are 不同 outcomes because they are very 不同 exposures of the cold to your 冷感受器 in your skin. So, the more you can say you cover your body in the cold, which you would do in cold water because they're, of course, covered totally and the molecules are closer to your skin, you will have a more potent activation of all your 冷感受器 in the skin. So that one will definitely activate your autonomic 神经系统 more and rapid, compared to going out in a t-shirt in the cold wind, just go for a walk.

完整译文：But that is also something that's going to activate your 交感神经系统. Meaning that you will have an 增加 in 去甲肾上腺素, and you will activate something called the 棕色脂肪. So, this is a healthy 有点 fat tissue that we have in our body. And when you activate that, that's going to 增加 your 代谢.

完整译文：Andrew Huberman：Before we 讨论 棕色脂肪, and I'm so glad you brought it up because it's so much to 讨论 there, what about 冷水淋浴? I mean, obviously, 冷水淋浴 is somewhere in between being out outside in the air cold air versus being immersed up to the neck.

完整译文：Susanna Søberg：If we had more studies on 冷水淋浴s, we would learn more about how does that activate our 代谢, how does that 增加 our 神经递质 in the brain, which could also have an impact on our mental balance. So, 我认为 that would be interesting for the future.

完整译文：But what we do know is from activating 棕色脂肪 both from rodent studies but also in humans, is that as soon as we get cold on our skin, we will activate our 棕色脂肪. So, it is 有点 like our first responder in the body to keep our 温度 up. So, our muscles is like the second tissue in our body. We have two tissues, which can 增加 our thermogenesis. So, the 棕色脂肪, which is always like 温度 regulating our body. And then we have the muscles, which will secondarily start to shiver, and that's going to 增加 our 温度 in the body.

完整译文：But as soon as you go into a 冷水淋浴, you will activate your 棕色脂肪 also immediately. So, it could be good also for increasing 代谢 in theory because we haven't really any studies showing how much does it actually activate the 棕色脂肪. So, if someone out there wants to do a study on that, that would be great.

完整译文：Andrew Huberman：I've thought about why there are fewer studies of 冷水淋浴s and cold immersion, and 我认为 the answer to my mind is that from a methodological standpoint, it's just harder to do because if people are getting into cold water up to the neck, they're getting into cold water up to the neck. Whereas if people are getting into a 冷水淋浴, some people are larger or smaller some people are going to stand under the shower with it hitting their head. Some people the back of the neck. You could direct people to do it, but it's a little bit more difficult.

完整译文：Also, 我认为 for-- you and I are both 研究 scientists. There's a little bit of a methodological challenge that might seem silly to people, but it's a real one, which is if people are in a 冷水淋浴 also, the water is going to be-- I'm 有点 pushing their clothing against their skin. There's a certain vulnerability and for most people coming to a laboratory in the first place, let alone being observed while they shower.

完整译文：Whereas when you get into cold immersion, you're getting under the water. And some people might roll their eyes and say, OK, really? Is that the barrier? But science exists in these real-world contexts. And this will vary by culture and things of that sort. But we run human subjects in my lab. And I'll tell you just the process of getting people to the laboratory and having them park and find the lab. And it's a whole new environment with people in lab coats, and people moving around, and where's the restroom? I mean, there's a certain amount of stress just associated with taking part in a study for most human subjects.

完整译文：So, I totally agree, however, we need more studies of 冷水淋浴s. It's just a harder environment to control in my mind. So, it sounds like any form of cold to the skin that people register as what you call a cold shock or an 不舒适, like this is 有点 jarring, activates the 棕色脂肪. Do we know what the pathway is from 冷感受器 on the skin to the 棕色脂肪? I mean, how does the 棕色脂肪 know that we're cold?

完整译文：Susanna Søberg：Yeah. Really good 问题. And it seems that 我认为 that, of course, in the future, we will know much more about these pathways. But what we do know is that the 冷感受器 will send a signal to our 温度 regulating center in the brain, so hypothalamus. And that's going to be taking in this message. And we have so many 冷感受器 in the skin. So, it's going to be very fast. You can say if you immerse the body into cold water, this is going to be so rapid. So, it will have a rapid 增加 in 神经递质 in the brain. So, noradrenaline, adrenaline, and cortisol, which is not that much, it's but it's still there.

完整译文：So, you have this 增加 in noradrenaline, which will then immediately activate the 棕色脂肪 because you can say the activator is the most potent one, cold and noradrenaline, and that's going to activate the 棕色脂肪. But there is also a direct pathway from the 冷感受器 in the skin to the 棕色脂肪, which really shows that because of these 不同 pathways, it shows that it could be that this tissue to keep us warm or was developed in our evolvement as humans to keep us warm and to save us whenever the 温度 on our skin varies just a little bit to keep us in that right homeostatic balance, so we don't get hypothermic, but also so we don't get hypothermic.

完整译文：But because it seems that the 棕色脂肪 is also activated 当我们 get warm on our skin. So, it's also maybe a 温度 regulator in our body. But the pathway is 不同. 我认为 it's also a third pathway directly from the muscles. So, the 棕色脂肪 is also activated, even though the muscles are starting to shiver. So, there's an extra pathway, that way to keep our 温度 up, so muscles and 棕色脂肪 are working together to keep us warm, so we don't suffer too much in the cold water.

完整译文：Andrew Huberman：That's super interesting. And here you're pointing to is the existence of three parallel pathways. And this notion of parallel pathways comes up over and over again in biology, as you and 我知道. And 我认为 it's 重要的 for people to know about because as you said so eloquently, when something is very 重要的 to our survival and/or evolution, the brain and body install multiple mechanisms for it, not just one.

完整译文：And so, it sounds like it's cold on the skin triggers a response in the hypothalamus, which then activates 棕色脂肪, 冷感受器 in the skin directly to the 棕色脂肪, and then shivering in the muscle to the 棕色脂肪. I want to 讨论 棕色脂肪 in depth and learn from you more about 棕色脂肪.

完整译文：Before that however, I want to ask about shiver. I've heard that shiver causes the release of succinate, which then activates the 棕色脂肪. Is it known 是否 inducing shiver is 重要的? And when should people shiver? I mean, I've gotten into 冷水浸泡s and shivered while I was in there. And then I've also had the experience of getting into a 冷水浸泡 or a 冷水淋浴 then getting out or even standing outside on a warm day after swimming in a pool and then starting to shiver, so the shiver comes later. So how 重要的 is shiver, and does it matter when shiver happens?

完整译文：Susanna Søberg：Yeah. Shivering is good because that 增加s your 代谢, and that's going to burn some calories in your body. You shouldn't be so afraid of shivering 我认为 because the shivering, as long as you don't get too hypothermic, so if you don't sit in the cold water for too long. And what you just said by shivering after you get up, that is because of the afterdrop. Something called the afterdrop is when your 核心体温 降低s even after you get out of the cold water. And it always does that, your body, because as soon as you get into the cold water, all your blood vessels is going to constrict because you 需要 keep your blood in your core and keep your vital organs warm. So as soon as you get up, those blood vessels will open again, and the warm blood will flow out and get colder and then flow back again into the core. And that's going to 降低 the 温度 in your core, of course.

完整译文：Andrew Huberman：So that's the drop.

完整译文：Susanna Søberg：So that's the drop.

完整译文：Andrew Huberman：I'm so glad you explained that. I've heard years ago, Wim Hof, I heard him 讨论 the drop, and I've heard colleagues of mine 讨论 the drop. But that's the first time I've ever heard it explained clearly. Let me make sure I 理解 this. So, I get into cold water. Obviously, I'm cold. Vessels constrict to keep blood near the center of my body keep me alive. I get out. The warming up of my body allows those vessels and capillaries to dilate again. The blood goes out to the surface, but the surface is still cold. And so that blood is cooled. And then my core 体温 drops. And that's what you're referring to as the drop, and that's what induces shiver.

完整译文：Susanna Søberg：Exactly.

完整译文：Andrew Huberman：And then am I right in thinking that then the shiver activates 棕色脂肪, which then warms me up again?

完整译文：Susanna Søberg：Yes.

完整译文：Andrew Huberman：Got it.

完整译文：Susanna Søberg：That's why you should end on the cold. We could get back to that.

完整译文：Andrew Huberman：Yeah. Let's 讨论 it. Yes. Ending on cold, it's what I refer to as and what has now become 称为 the Sjoberg principle, which is a really 重要的 principle about the importance of ending on cold and not doing what I do, which is to get into a hot shower or back in the sauna, but we'll get back to that in a few minutes.

完整译文：So that's wonderful that you can explain that so clearly because 我认为 that shiver is something that 很多 people do avoid. People think, oh, I don't want the chattering of the teeth. And it feels like a loss of bodily control, which really, it is. It's an autonomic response.

完整译文：Susanna Søberg：Yeah. But I don't think that people should avoid it that much. It's just like seeing shivering as a way of your body, like it's training for all your cells. It's training for your muscles. It's training of your 代谢. And that's going to 增加 your what's called the 胰岛素敏感性.

完整译文：So, if you can like in your mind get 用于 the thought of shivering is just like when you go exercising in the training center and get that feeling of like, oh, this is tough. Now it hurts a little bit. Yeah. It's going to hurt because that's what shivering also does. But it's just a 不同 way of training yourself and your body. It's going to create what is healthy stress. It's called hormesis in the cells. And the more you expose your muscle cells or your 棕色脂肪 cells to these 有点 healthy stresses, 运动, cold, 热暴露, it's going to make them better at like activating and also keeping you healthy.

完整译文：So as long as the cells get exposed to this, it's going to keep them on its toes you can say because it becomes more robust and increasing these heat shock proteins and cold shock proteins in the cells to make you more robust for the next time. And that is also what happens when you go to the training center. And I keep like drawing that parallel because people today know more about, we know more about 运动 and what that is going to do to your muscle cells.

完整译文：But the same 有点 training is also what you do when you go out and into the cold water and submerge into cold water because that is just your cold training center you can say that and also your heat training center going into the sauna because the cells are getting stronger with hormetic stress. So, it's the same process, just 不同 practices.

完整译文：Andrew Huberman：I'm so glad that you brought up the fact that the discomfort or the embarrassment or both of shiver is still crucial actually to reach for and try and experience the same way that with 运动-- 我认为 很多 people don't realize this, but 当我们 did our series with Dr. Andy Galpin, it became clear to me what should have already been clear to me and 我认为 that most people don't realize, which is that if we were to measure 心率, 血压, stress 激素, and 炎症 in a human being during 运动, it would look as if they were ready to die.

完整译文：血压 would be high. 炎症 is through the roof. But all of that is setting in motion an 适应 or a set of 适应s that allow 血压 to be lower at rest, that allow 炎症 markers to be lower at rest. All the things that everybody is seeking with 运动, 此外 to, of course, the aesthetic changes that people are seeking with 运动.

完整译文：It sounds like the exact same things are happening with the cold. So, the redundant message here seems to be that the more discomfort, provided it's done safely, just like with 运动, the more shivering, the more cold shock provided, it's not to the extreme and stops somebody's heart. 我们可以 讨论 阈值s for that a little bit later. It sounds like all of that is going to set in motion some long-term changes that will make people feel better and will improve health.

完整译文：Could you just touch on a few of the longer-term changes that are known to occur? I mean, I'm well aware of the study showing that, 我认为 it was the European Journal of Physiology showing long lasting 增加s in 儿茶酚胺, 多巴胺, 去甲肾上腺素, and 肾上腺素, for many hours after 刻意冷暴露. What are some of the other things that happen 在……层面 代谢 and 棕色脂肪 in let's say the hours and day after 刻意冷暴露?

完整译文：Susanna Søberg：As soon as you go in, of course, there's an activation. But it seems like you're asking for the later outcomes, like 血压 and stuff like that. Is that what you mean?

完整译文：Andrew Huberman：Yeah, 血压 but also in terms of 代谢. 我知道 that in your study, and we'll 讨论 棕色脂肪 in depth here in a moment, but that there were changes to the 棕色脂肪 that equate to changes in, for instance, people's ability to be 舒适 in colder environments when they're not doing 刻意冷暴露. Or in the same way that I can 运动 on an 运动 bike or go for a hard run. But then if I go hiking with the family on Sunday and it's a steep climb, I can do that steep climb more easily because I'm, quote unquote, fit as a consequence of the 运动. What are some of the fitness 适应s of 刻意冷暴露?

完整译文：Susanna Søberg：Yeah. So, what happens is that you get adapted a little bit every time you go. So, you will like 运动, get a little bit stronger. So, every time you go into the cold water, for every time you will be more exposed to it, you will feel more 舒适 in the cold. So, you're going to build your 适应, which happens on a metabolic level, which is going to be the 棕色脂肪. So, you will have more activation of your 棕色脂肪. The mitochondria in the 棕色脂肪 cells, you'll have more of those, and they will be more efficient at heating you up because it expects the body, expects you to do this again, so you are prepared in a way.

完整译文：The capillaries in your skin will also become better at constricting. So, you will have a better shield of your body to prepare you for the next time. So, you will become better at going into the cold water in that way. So, the body makes these mechanisms and changes your body in a way, so you can expose yourself to the next time, right?

完整译文：And also, your 应激反应 will also subside a bit, so you will have less 增加 of your 儿茶酚胺 with time. With time also, because of this activation of your 棕色脂肪 or your muscles, you will have an 增加 in your 代谢, which will then make your 胰岛素敏感性 better. And this is shown in studies. 例如, there is this interesting study I found just before I started my, which was from Gibas-Dorna et al from 2016, where they measured 代谢 not on 棕色脂肪, but they measured 胰岛素敏感性 in middle aged men and women during one winter swimming season.

完整译文：So, they were not very young like they were in my study, but they were middle aged. And 我认为 this is very interesting. So, during these four, five months they were winter swimming, they saw that they had a lower 血压 after the season, and they had a lower 心率. And they also saw that they have a better 胰岛素敏感性.

完整译文：And 我认为 that is very interesting because if you can have a better 胰岛素敏感性, you can prevent lifestyle diseases and will lower 血压, which is a very strong outcome also for telling how much 炎症 you have in the body. And because they didn't measure 棕色脂肪, I figured that it could be that was the missing link. That was one of the explanations to why we see this less 炎症 in the body.

完整译文：So, the long-term outcomes could be that you lower your 血压 and have a lower 心率, you also have a better 胰岛素敏感性 and better glucose balance, but that is shown in my study.

完整译文：Andrew Huberman：I'd like to take a quick break and acknowledge one of our sponsors, Athletic Greens. Athletic Greens, now called AG1, is a vitamin mineral probiotic drink that covers all of your foundational nutritional needs. I've been taking Athletic Greens since 2012. So, I'm delighted that they're sponsoring the podcast.

完整译文：The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or usually twice a day is that it gets me the probiotics that I need for gut health. Our gut is very 重要的. It's populated by gut microbiota that communicate with the brain, the immune system, and basically all the biological systems of our body to strongly impact our immediate and long-term health. And those probiotics and Athletic Greens are optimal and vital for microbiotic health.

完整译文：此外, Athletic Greens contains 一些 adaptogens, vitamins, and minerals that make sure that all of my foundational nutritional needs are met, and it tastes great. If you'd like to try Athletic Greens, you can go to athleticgreens.com/huberman, and they'll give you five free travel packs that make it really easy to mix up Athletic Greens while you're on the road, in the car, on the plane, et cetera. And they'll give you a year's supply of vitamin D3 K2. Again, that's athleticgreens.com/huberman to get the five free travel packs and the year supply of vitamin D3 K2.

完整译文：We'll get back to the 胰岛素敏感性 and glucose balance. That's an impressive list of 益处. 血压. Of course, most people are aware of, 血压 and what it is. It's what they measure 当我们 go to the doctor. And it's not very sexy nowadays. 血压, people are, oh, 血压. People want to hear about the inflammatome and the microbiome, and all of that stuff is really interesting. But 我认为 that 血压 doesn't get enough attention.

完整译文：And we have spoken to, on this podcast, to Dr. Peter Attia, who is an expert in longevity, and healthspan, and things of that sort. And I was surprised to learn again, I shouldn't have been surprised, that the number one reason people die worldwide is cerebral vascular disease and cardiovascular disease. And there are basically three things on the list of things to address. One is not smoking or vaping, by the way. There are a few other things 与……有关 blood markers, ApoB and things of that sort.

完整译文：But then the big one is 血压. And so, it's interesting because we don't think about 血压 that much anymore as the 有点 people interested in health optimization and health. But 血压 is so vital to control. So, it's wonderful to hear that 刻意冷暴露 is one way to control 血压, I'm guessing in concert with other forms of 运动.

完整译文：Let's 讨论 棕色脂肪. And if you're willing, I'd love to drill into 棕色脂肪 at a deep level. Again, my 理解 of this is far more elementary than yours obviously. You're the expert. My 理解 about 棕色脂肪 is that it's located in specific areas of our body, maybe more widespread than when I learned in school. I was taught it was just at the clavicles in the back of the neck and upper back, but who knows?

完整译文：I learned that there's more of it 当我们're 儿童, maybe more distributed throughout our body, and that it's rich in mitochondria. But what is so special about the 棕色脂肪? Like if we could just go into the biology of 棕色脂肪 a little bit, what does it look like? You've measured it in human subjects. Where is it distributed really? Can it expand its distribution? Can we activate and expand the amount of 棕色脂肪 as adults?

完整译文：And for those of you that are cringing already thinking we're 讨论 getting fatter, it's quite the opposite. We're 讨论 not subcutaneous fat, but fat located around the organs. But please educate me, tell me where I'm wrong, and expand my knowledge on 棕色脂肪.

完整译文：Susanna Søberg：OK. Yeah. You're not wrong. But it's true that there are more locations of the 棕色脂肪 than we previously thought. There's this very nice study from 2017 by Leitner et Al, where they had made these opacities overlays of their subjects, where they could see where in the body do we have 棕色脂肪 and where can we grow more 棕色脂肪 so to say.

完整译文：So, the 棕色脂肪 is very plastic. So, it means that it can grow, and it can 降低. And this is proven in studies where we have seen people with pheochryocytoma, is like a very specific cancer type where from the '70s where 我们可以 see that if they have this specific 有点 cancer type, they have this tumor on their adrenal gland. So, they have a huge 增加 in noradrenaline.

完整译文：And because of that, they have this continuous activation of the 棕色脂肪. And they have grown 很多 棕色脂肪 in whole body, abdomen or where it's located in these six 不同 places, but it is less like very much compared to normal people. And what they then see, what we learned from this study is that 棕色脂肪 can apparently grow if you have an 增加 in noradrenaline in the body. It's not like you want that because when that happens, you have a high 血压. You don't want it chronically, right? You just want it on like short amount of time. And then it can grow for a bit.

完整译文：But you don't want it chronically, of course not. But because it activates also your 交感神经系统, so they also showed they have high 血压. They lost 很多 weight, of course, because this is activating your 代谢. So, they found luckily that when they removed this benign tumor, that the 棕色脂肪 降低s again to normal size. And they gained weight again, and they had normal 血压. So, the story ends well.

完整译文：But it's 有点 like proof of concept of the 棕色脂肪 can actually grow. So, it's plastic in its way of like it can grow, and it can 降低 again. So that's very good. Good studies to see what the body is capable of. But we don't of course want all that 棕色脂肪. We just want to keep it actually and keep it activated because what we see in studies is also that after the age of 40, studies have shown that there is an association with having less 棕色脂肪 but 增加 obesity.

完整译文：So of course, we don't know yet whether 棕色脂肪 降低s with age and 因此 we get obese, or we get obese and 因此, we have less 棕色脂肪. But as 棕色脂肪 is an insulin-sensitive organ in our body and we get obese, just like the muscles get less insulin sensitive, the 棕色脂肪 does as well. And 因此, it maybe 降低s. It could be a theory that 我认为 could be one of the reasons why we don't see that much 棕色脂肪 in elderly people. Some have a lot, 尤其是 people working outside. There are studies showing this.

完整译文：Andrew Huberman：People who--

完整译文：Susanna Søberg：Work outside.

完整译文：Andrew Huberman：Do physical work outside. Farmers.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：Interesting.

完整译文：Susanna Søberg：They expose themselves to it. So, they will just keep it in that way.

完整译文：Andrew Huberman：And I suppose 我们应该 clarify for people in case they don't know that 胰岛素敏感性 is a very good thing. You want that you want your cells to be sensitive to insulin. Insulin insensitivity is type 2 diabetes and is associated with obesity. So just a point of clarification there.

完整译文：Yeah. It's interesting to me. I usually work out at home, but I go to a gym once or twice a week if I can because it's good if I see the outside world. And there are a few individuals at the gym who, they're not particularly large or muscular, but they are incredibly lean, and their posture is great, presumably from the musculoskeletal work. And they're in their 70s and 80s. I mean, it's remarkable.

完整译文：And 我知道 all the telltale signs of hormone augmentation. I'm very good at spotting that. There are a few telltale signs. I've talked about this on other podcast. And that's not why they're fit. They're clearly of that look, and you see this outside the gym too, of course. For people that look like they've done 很多 physical labor their whole life, they're just moving a lot. They have strong hands and features. And they're not necessarily excessively lean, but you can tell that they've been using their musculoskeletal system.

完整译文：And I like to talk to these people and ask them like not what are you doing now for your workout, but what did you grow up doing? And 我会说, and obviously, I haven't run statistics on this. But more than 75% of them respond that they grew up on a farm, or that they did some 某种程度上 manual labor, or a postman, or a postwoman, or doing something where they moved a lot for their early years and throughout middle age. And most of them are now in retirement, but some of them are still working, and they all still moving a lot.

完整译文：So, the relationship between shiver and 棕色脂肪 makes sense to me. But is it the case that as we're just moving around, and I've heard of NEAT, non-运动 induced thermogenesis. So, if we're just moving around that we are activating 棕色脂肪 or does there 需要 be this stressor? Does there 需要 be shiver and a cold stimulus or a heat stimulus to activate the 棕色脂肪? In other words, is just staying active enough, or do we 需要 do some 某种程度上 温度, shock type thing like 刻意冷暴露?

完整译文：Susanna Søberg：Yeah. 我认为 that is a really good 问题 because how-- also, why do we have this tissue then? If it has to be extreme, then you can 问题 what do we need this tissue for? But it seems that you can activate the 棕色脂肪 with just a little bit of exposure to cold. So cold is the most potent stressor activator of our 棕色脂肪 because it's our 温度 regulating organ in our body. So, first responder to that. So, the muscles will be a little bit too late, and 因此, we have maybe these two 有点 tissues.

完整译文：So actually, just exposing yourself or a hand actually just to cold water. So, studies have shown that if you just put your hand in cold water, not that you're going to do that all day, or every day, or anything. It's not something you have to do but. It just shows that you can activate your 棕色脂肪 just by getting a 温度 change on your skin.

完整译文：So, you can go outside in a t-shirt. That's why also, we were just 讨论, well, people who work outside, or move a lot, or get in and out of, like changing the 温度 of their body all the time, they will have more 棕色脂肪. And activating that is going to keep your 代谢 higher and your 胰岛素敏感性. Studies have also shown this.

完整译文：So, the 棕色脂肪 can be activated as soon as you just change your 温度 in the skin. So going outside in a t-shirt, wearing cooling vests, also studies have shown this. For 10 days, it's going to also grow your 棕色脂肪. So, you can get more 棕色脂肪 if you expose yourself to the cold. You don't have to start in a 冷水淋浴. You don't have to start in a 冷水浸泡 if you're not really ready for that yet. But just exposing yourself to the cold wind has also shown to activate your 棕色脂肪.

完整译文：Or if you don't want to be like in this awake state, then you can also just sleep in the cold. And you won't notice it that much maybe. But studies have shown that if you sleep in 19 摄氏度. Then you will activate your 棕色脂肪, and you will grow your 棕色脂肪, so you have more of it. So, this very nice studies from Hansen et al from 2017 showed that a group of subjects who slept in a room at 24 degrees. And then they made this PET CT scanning to see how much 棕色脂肪 do they have from the beginning, so what we call baseline. Then they measured again after a month of sleeping in 19 degrees. And they saw, 我认为 it's remarkable, just one month at 19 degrees sleeping there, they had a duvet on. And they still had clothes on when they're sleeping.

完整译文：Andrew Huberman：So, they're under a cover, under a duvet.

完整译文：Susanna Søberg：Under a duvet. Yeah. The subjects were sleeping at 19 degrees for one month had 增加的 its 胰岛素敏感性. The next month, they slept at 24 degrees. They measured this again, and they had 降低的 actually a little bit. And then they slept at the 27 degrees. So quite warm room actually for the fourth month. And they saw even less activation of the 棕色脂肪 and also 胰岛素敏感性.

完整译文：So, it seems that you can expose yourself, and pretty rapidly, the 棕色脂肪 will respond to this because it's so sensitive to noradrenaline. So, if you keep exposing yourself to a little bit of cold, you will also get a little bit adapted to it, but that's because the 棕色脂肪 has grown these more mitochondria in the cells. So, these small energy fabrics that's going to activate the cells, and that's going to take up glucose and fat from the fatty acids, from the bloodstream, to keep the thermogenesis up.

完整译文：And that's going to clear up some sugar, and it's going to clear up so in the bloodstream and some fat as well. So, the 棕色脂肪 can in that way 降低 our unhealthy fat, which is the white fat. And the white fat is what we don't want too much of, but we still need some, of course. And it's our energy storage, so it's very 重要的 that it's there. We just don't need 很多 it. So, on our thighs and also around our inner organs, that's where it's located.

完整译文：So, if 我们可以 have activation of the 棕色脂肪 just by going out in the cold and just by sleeping in a cold room. Or if you have courage for it, you can go out and expose yourself in a 冷水浸泡. 冷水淋浴s is also going to do the trick. So, you can do 不同 variations of this. Just exposing yourself to various 温度s is going to activate the 棕色脂肪 because it was involved to keep us in a perfect homeostatic balance regarding 温度. So, to keep us alive.

完整译文：Andrew Huberman：Incredible. I just get a clarification around this 19 摄氏度 room that they're sleeping in. So, they're under a comforter, a duvet. And you mentioned they have clothes on. The room is 19 摄氏度, but the 温度 underneath their blanket might not be 19 摄氏度. So presumably, it's the cold on their face that's activating the 增加 in 棕色脂肪 that was observed. Is that a reasonable expectation?

完整译文：Susanna Søberg：我认为 so, yeah, because you have so many receptors in your face. Actually, it's enough. And 我认为 it corresponds very well with the studies showing that you can activate the 棕色脂肪 just by putting a hand into a bucket of cold water. And I did this experiment myself in my studies just to see how well did they respond to cold water. So, it was 4 摄氏度 cold water for 4 minutes. And then I just measured 血压 and 心率 to see, do they have an activation of this?

完整译文：I actually also measured the 棕色脂肪 during this 冷暴露 for 4 minutes with an infrared thermography camera to see, can I see that the 棕色脂肪 is activated? And just to go back to the location of the 棕色脂肪. So usually, you cannot really see activation of your 棕色脂肪 because it's located centrally around your central 神经系统.

完整译文：And the biggest depot, as you mentioned before, is up here under the clavicular bones and very close to the skin surface. And because it's so close to the skin surface, I could measure it with this very expensive camera. And it's not very feasible for people to go home and do this don't because it takes 很多 practice, I can tell.

完整译文：But we measured the 棕色脂肪 with this. And I could see that after a few minutes that the activation was there, an 增加 in 温度 arose from that activation, just 4 minutes. So, it's very rapid and I'm also measured in my study how deep was the 棕色脂肪 under your skin. So, it's very close to the surface, which also shows that it needs to be there to heat you up and heat your inner organs.

完整译文：Andrew Huberman：Well, I'm delighted to hear all of this, and I'll tell you why. One is by way of anecdote. I mentioned a little bit earlier that as an undergraduate, I worked in a lab that studied thermogenesis. And we were doing that in animals. But we had this room that was very cold. The whole room was cold.

完整译文：The guy who I worked for at the time, Harry Carlisle was a very accomplished physiologist. He came from this lineage. I don't know if this literature is still discussed much, but it's a beautiful literature from Rothwell and Stock. They were the ones who discovered non-运动 induced thermogenesis. The fact that people who bounce their legs a lot, and move around a lot, and have 很多 stochastic movement burn up to 1,800 calories more per day than people who sit more still.

完整译文：Susanna Søberg：Fascinating.

完整译文：Andrew Huberman：Incredible. Just incredible. I don't think that work gets as much attention as it deserves. Published in journals like Nature, so very fine journals. But in any event, one of the things that I noticed when I started working in that laboratory was that I was cold because the room was cold.

完整译文：And Dr. Carlisle, Harry, said, well, the key is to wear a t-shirt in here for about two or three days, and then you will cold-adapt. I thought, well, wouldn't I want to put on a hoodie and get warm in there, so I was 舒适? And he said, no. Actually, what you want to do is get yourself uncomfortably cold, activate your 棕色脂肪.

完整译文：And indeed, when I did that, 我认为 it was just two days of being in that cold environment. Then I could come back on the third day and be perfectly 舒适 because the 棕色脂肪 had expanded, or added mitochondria, or both. And I was perfectly 舒适 in that environment. I also got very, very lean in those days and weeks.

完整译文：Now I've never been somebody who's very lean, nor am I somebody who carries 很多 excess adipose tissue. I'm 有点 somewhere in the middle. I'm sure I could adjust that with feeding if I want to. But it was striking what a powerful effect it had on my entire system of thermal regulation. And one of the things that I also delighted in when Cell Reports Medicine published your study is they had an accompanying press release that went out to those of us that receive press releases.

完整译文：And it described a saying in Scandinavia which is essentially, I'm not going to attempt to speak Danish, even though I have much of my family is in Denmark, believe it or not, from Denmark. We have 很多 Danes in my family. I won't embarrass myself by trying to speak Danish as I did before the microphones were rolling.

完整译文：That there's a saying that 我认为 essentially translates to in the fall, when you're approaching winter, you want to actually wear fewer layers, not bundle up, when you go outside, so that you can prepare yourself for the cold of winter and be able to heat yourself up using your 棕色脂肪. And that in the spring, as the 温度s are warming, rather than removing layers, you want to wear more layers in order to be a little bit uncomfortably warm, so that in the heat of the summer, you're better at cooling your body. Do I have that right? And maybe do you know the saying, and would you be willing to share it? Only the Swedes and Danes will be able to 理解. Maybe the Norwegians too. If you don't know it, that's OK.

完整译文：Susanna Søberg：Yeah. So, 我知道 the concept of it because we say it. You should wear a less before winter and more before summer.

完整译文：Andrew Huberman：So, there it is in English. So, it doesn't have to be esoteric.

完整译文：Susanna Søberg：Yeah. And you're completely right. And 我认为 this is just something that we know in the Scandinavian countries, 我认为 that we intuitively know this. But if we just go back a little bit in history, 我认为 that around the 1950s, the Russian government went out and said, well, 我们应该 do something about tuberculosis pandemic or epidemic there was at this time. So, they wanted to have the people be more resilient to the cold and also 增加 our immune system.

完整译文：So, in Scandinavia, and actually also in Russia, we put our babies outside to sleep in the prom. And that is like to also to get more resistant to the cold but also to 增加 our immune system. And we still do that in Denmark.

完整译文：Andrew Huberman：Do you really?

完整译文：Susanna Søberg：Yeah, we do.

完整译文：Andrew Huberman：Babies are taken out in the cold?

完整译文：Susanna Søberg：In the snow, in frosty rain, everything. My two boys have been sleeping out in winter, or at least their first many three, four, five years because it's very good for them, and they get a better immune system and get resilient to the cold, so they will have less colds. And also, they run around in a t-shirt when it's super cold because they have activated all their 棕色脂肪. I didn't 理解 at that time, I must say. But I 有点 intuitively also knew because we have inherited this way of doing things with our culture.

完整译文：And I have heard people coming from the US saying Danes are crazy. They put their babies outside in proms and leave them there. And then they go inside and drink coffee on the cafes.

完整译文：Andrew Huberman：Well, I don't think Danes are crazy. I adore the Danes, their amazing culture and people. I'm so fortunate to have family members from Denmark. But I did notice. So, 当我们 were in Copenhagen, and 我知道 we saw you there not long ago. That was June. The water in the harbor was cold, even though the Pacific is close to here, which is very cold. I felt pretty cold. But it was summertime-ish. So, people were in summertime mode. T-shirts, and shorts, and things of that sort.

完整译文：But it did strike me that people in Copenhagen are dramatically fitter than they are in the United States. I mean, first of all, everyone's bicycling everywhere. Not many people wearing sunglasses. So, trying to extract as much photon energy from the sun as possible, which I support. As everyone knows, I'm a big fan of getting sun.

完整译文：But also, 当我们 did see swimmers, they were swimming in this cold water like it was nothing. And the range in age of the swimmers was remarkable. You saw the 有点 fit, triathlete-looking types but also young kids, like really young kids. And then people probably in their again their 70s, 80s, maybe even 90s. Really remarkable. Vastly 不同 than what you she have to go to the ocean here in Los Angeles or elsewhere. So yeah, you Scandinavians are on to something with this.

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完整译文：I'd like to 讨论 your study. If you could give us a little bit of the backdrop about what motivated that study. And then walk us through what you did. Who the subjects were, what you had them do, what you measured, in as much detail as you would like to share because 我认为 it's such an 重要的, even fair to say, landmark study because it also explored not just cold but sauna and the co-use of cold and sauna as a way to probe 代谢 and 棕色脂肪 and other markers as well.

完整译文：And as you do this, I'm hoping at some point that you might tell us some of the observations that you might have made that interested you that perhaps were not in the paper because that's one of the great 益处 of sitting across from somebody who did the work in detail. So yeah, if you could tell us about your study, and what you did, and what you discovered.

完整译文：Susanna Søberg：Thank you for that 问题, Andrew. I'd love to also explain a little bit what did we do because 当人们 read this 有点 paper, they just see the numbers. They don't see what happened before that. And human studies are very 不同 from my study. My studies, you can do a knockout of something, and then everything is like perfectly matched and controlled. Doing human studies is very 不同 from that because people are 不同, even in the groups. So yeah.

完整译文：When I started this 研究 in 2016, I did not really know what the 棕色脂肪 was. So, I started reading up on all this. And I was very interested in preventive medicine. And also, the studies that I did before, 棕色脂肪 was also very much in the preventive side, like how can we-- that was about something else, but the sweet tooth, and how can we lower our sweet tooth, and stuff like that. But after that I, wanted to do something new.

完整译文：So, I looked into the 棕色脂肪, got hired in this fantastic 研究 group, where it's the cell group. So, they mostly did cell studies, and they didn't have anyone to do a human study yet. But they really wanted me to do that. So, I read up on 很多 研究 about how does the 棕色脂肪 get activated? What have been done already? And I mentioned the paper before with sleeping in the cold. I found that particular paper very fascinating.

完整译文：And that was also where at that time, I was like, OK. So 冷暴露 as an intervention of sleeping in the cold could be a good thing to go out and say, well, people do this. But on the other hand, first of all, it was already done. That was one thing. But the other thing was like, well, I wanted to see if 我们可以 do some 有点 activity. So, 我们可以 have people move also, go and do something. Do something together or whatever.

完整译文：And the cold made us think about, well, what about winter swimming? It was 有点 like a bit of a joke in the beginning. I was like, winter swimming. Yeah, it's going to activate the 棕色脂肪, right? But 当我们 read the literature, we couldn't really find anything about activation of the 棕色脂肪 with cold water besides hand in a bucket of cold water. That was already there.

完整译文：So, we were just thinking, OK. So, it should be very potent activation of the 棕色脂肪 if it's cold water but very 不同 from cold air. So, it was 有点 also a new thing we were going into. And we knew that we were going to do more of a proof-of-concept study at the beginning of it because it was like winter swimmers must in theory activate the 棕色脂肪, right? But we 有点 didn't really was this 有点 stressor too much, too little, or what will happen actually?

完整译文：But we had this idea about, well, we always say that cold water winter swimming will activate your 代谢. But do we know if it does that? No, we don't. And while this idea was a little bit fun at the beginning, we 有点 accepted. It was like, OK, let's just try this out. But because we didn't have the funding for it, we was like, OK, let's do a proof-of-concept study. Let's go with a small number but enough to see a 差异 between the groups. So, the power calculation of that study is done on what we know from PET CT scannings of the 棕色脂肪. So that's the main outcome, of course.

完整译文：And we wanted to go a little bit smaller on the numbers of participants because we wanted to dig a little bit deeper into the 不同 mechanisms and also redo some of the days. So, I really wanted to do that to see if I can replicate also the findings. And that's going to take 很多 funding, but it's also going to take 很多 time to do it.

完整译文：So, the proof of concept was just going small but looking at 不同 mechanisms. We also took fat biopsies, 例如, and looked at the white fat to see if there was any 差异s between the groups before and after and stuff like that. So that's 有点 like how it started. And the first year was like a field study for me. So, I was not a winter swimmer when I started this.

完整译文：Andrew Huberman：Oh, really?

完整译文：Susanna Søberg：No. I wasn't at all. And I will say I was a bit afraid of the cold myself. A bit of a cold sissy. Always cold, having big socks on and sweaters and stuff like that. So, I was like, I am so 舒适. I'm just like everybody else. Very 舒适. I like being completely 温度 neutral.

完整译文：But I started like playing with this thought, like, well, if this is so healthy, in theory, I should not pack myself up. I should start not doing that. But the first year, observation of winter swimmers on the jetty. They 有点 joked about it and say, come on, Susanna. You 需要 try this. You cannot study this unless you have tried it. And I was like ha, ha. Very funny. Of course, I can do that. But I couldn't.

完整译文：I read the literature. I understood in theory what happens when you go into cold water. But I completely understood it when I first tried it. The first few times, not so funny. It felt painful. It was just like running too long after a long break, and your muscles hurt the day after, right? You completely regret that you took that extra mile.

完整译文：Andrew Huberman：What about, when you say 不舒适, you mean 不舒适 when you got in and when you were in, or 不舒适 afterwards? Because I find that on rare occasions-- I should just, full disclosure, I do 刻意冷暴露 every morning for about a minute to 2 minutes in a 冷水浸泡. There are days that I miss. But when I'm at home, I do that. And when I travel, I do a 冷水淋浴. I do finish with a warm shower. And we'll 讨论 why that's probably not the best idea.

完整译文：And I've been doing it for some years now on and off. So just full disclosure, I'm a devotee, and I have family members that hate the cold but have gotten into it and are starting to like it. And I don't necessarily like the experience in the cold water, but I love the way I feel when I get out.

完整译文：And I'm 100% on that statement about loving it when I get out. Occasionally, it feels good to be in there. It feels invigorating. And 我认为 I've learned to control the gasp reflex and the hyperventilation, and I just have told myself what we know, which is that the forebrain struggles to engage for the first 20 or 30 seconds. But if you can get past that wall, it's far easier to push through. But when you say that it was really 不舒适, do you mean the experience of getting in, or you also felt lousy afterward?

完整译文：Susanna Søberg：Yeah. And very 重要的 to clear that out. I only felt very 不舒适 doing it at the moment. But afterwards, the first time I went with a group, and actually, my husband was there as well because I really wanted someone I knew coming along. Because it's very normal if you haven't done this before, you feel a little bit anxious about it. This is shown in studies as well because 血压 and 心率 goes up in those who are new to this 有点 activity.

完整译文：So, I was a little bit anxious about it. So, it was really 不舒适 just doing it. But afterwards, as soon as I got up, I felt fantastic. And we went into the sauna. And I did three rounds because I just loved it. I loved the feeling afterwards because you have all these 神经递质 going in your brain, and you feel more positive. I feel invigorated. I had so much energy. And like I could totally see why people would do this to get energy throughout the day because I definitely had that. I didn't have to do three dips to get that. 我认为 one would be enough.

完整译文：And I often do that also now today. I do one dip. 有时, I do two or three dips in one round, you can say in one day. But often, it's just one or two times a week. For me, that is enough to get that energy and to get that positive feeling. And 我认为 that is also why I put up my study in that way. I wanted to study the lowest dose, you can say, the lowest amount that 我们可以 get away with but still see health 益处.

完整译文：So, what I observed there on the jetty was that some did it a long time. They were in the water for a very long time. And to me it seemed maybe a bit extreme.

完整译文：Andrew Huberman：Could you give me an example of a long time?

完整译文：Susanna Søberg：Well, so maybe they were really swimming, and they could be 20 minutes or half an hour.

完整译文：Andrew Huberman：That's a long time.

完整译文：Susanna Søberg：That's a long time. And there was like ice. And people who came up-- I mean, I just didn't really feel that this is something that I wanted to go out and recommend to people after my Ph.D.--

完整译文：Andrew Huberman：You don't want any 研究 subjects dying either because if you're not adapted. I mean, people can do that. Also, a 20-minute 冷水淋浴 or 20-minute 冷水浸泡, 我知道 people do it, but it's probably not a good idea.

完整译文：Susanna Søberg：No. Probably not. It's going to exhaust your cells and make them age too fast. So exactly. When you pass that hormetic stress, the healthy stress level, that's what is happening. The quite opposite is almost chronic stress actually in the cells.

完整译文：Well, what happened then was that I found out that if I want to have this 方案 get through ethical committee, I really needed to go very sleek with the not too long and make sure that they were also very healthy and to get approval, of course, of this study.

完整译文：But what I did was to recruit winter swimmers who already had been swimming for two or three seasons. And I just observed them. I said I'm not going to do an intervention study yet. I did that after. But I wanted to do like a proof of concept where they were already adapted to the cold and then compare them to a matched control group who were matched on, you can say diet. So were they vegetarian or not. And one of them was in each group.

完整译文：Andrew Huberman：They weren't all vegetarians?

完整译文：Susanna Søberg：No, no, no. Just one in each group. Yeah.

完整译文：Andrew Huberman：I'm going to say, with all the amazing fish and meat in Denmark, I'd have a hard time being a vegetarian. The breads are amazing, the fruits and vegetables too. OK. So, there were a couple of vegetarians in each group.

完整译文：Susanna Søberg：Yeah. One in each. Yeah. OK.

完整译文：Andrew Huberman：Token vegetarian. I have family members who are vegetarian. So, I'm just poking fun.

完整译文：Susanna Søberg：Yeah. But they were matched on 不同 things. So, what we usually match them on is also BMI. And we chose one gender in this study. And we would always choose both men and women normally. But we do see that there are 不同 棕色脂肪 levels depending on gender. So, women have more 棕色脂肪 than men.

完整译文：Andrew Huberman：Really? Interesting.

完整译文：Susanna Søberg：Yeah. 我认为 it's interesting.

完整译文：Andrew Huberman：That deserves a study.

完整译文：Susanna Søberg：Yeah. Why, actually? 我认为 it's interesting because women are also smaller in size and mass, right? But they also have a lower peripheral 温度, 尤其是 on hands and ears.

完整译文：Andrew Huberman：Is that right? That's documented that women do run colder than men?

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：Physiologically. I didn't say psychologically.

完整译文：Susanna Søberg：No, no. No.

完整译文：Andrew Huberman：We won't go to the psychological cold-heat.

完整译文：Susanna Søberg：That's 不同. Something else.

完整译文：Andrew Huberman：That's a 不同 podcast.

完整译文：Susanna Søberg：Yeah. Another time. So, women are just colder physically. So, on hands and ears, it's measured on that. And feet as well. So compared to men. And men have bigger hearts than women. And they can pump out more blood peripheral than in a woman's body. So that could be an explanation for the colder hands, 例如. Thermo舒适 state is also 不同 between genders. So, men are more 舒适 at 22 摄氏度, and women are thermo舒适 at 24 摄氏度.

完整译文：Andrew Huberman：So, the thermostat wars of home have been now validated.

完整译文：Susanna Søberg：Yes.

完整译文：Andrew Huberman：2 摄氏度. By the way, prior to starting recording, I made the executive decision that we were going to go with Celsius throughout the podcast because the majority of the world uses Celsius. So, for those of you that think in Fahrenheit, the internet is your friend in making those conversions. So, we're sticking with Celsius. So, men tend to be thermo舒适 at 22 摄氏度, women at 24. OK, interesting.

完整译文：Susanna Søberg：解释 a lot about also some arguments in the homes where men are turning down the heater, and women are turning up the heater, and they cannot really-- I'm on both sides here. I 理解 the men. We 理解 the women, but there is a 差异 there. Which was also one of the reasons why we in this proof-of-concept study chose one gender. So, it is not like only because we wanted to study men. It was just to eliminate all the confounding factors which could have an impact on our results. So that was one of the reasons.

完整译文：But also, because yeah, so women have more 棕色脂肪 than men. And otherwise, we would have to do four groups or something like that. And not having funding yet, we were like, OK, we 需要 do like just one group, just a control group, and a group who were always the winter swimmers.

完整译文：So recruited winter swimmers who have been swimming for two to three seasons because I wanted them to be already adapted. But not going too long in the water. So, they told me, I did 很多 screening here, of course, beforehand and interviews to ask them how much do you do and how much do you how long do you stay in the water. And I monitored how long did they didn't stay in the water and recruited based on that they only did like two to three times per week. It seems reasonable for Denmark at least to do that.

完整译文：And they stayed only in the water for 1 to 2 minutes. So, the cold shock subsides very quickly, and you will get this activation of your rest and digest system, which is your 副交感神经系统. So, the other branch of your autonomous 神经系统. And you get that activation because you submerge into cold water. And when you do that, you have an activation of your diving response. And that's going to slow down you can say the consumption of oxygen also in your body. And that's going to slow down your 心率.

完整译文：Andrew Huberman：Could I pause you on this because I've heard this before that 当我们 get into cold water, shower, or immersion, we get this sympathetic autonomic response. So 增加的 血压, 增加的 心率, release of 去甲肾上腺素 from the locus coeruleus in the brain, release of adrenaline, 多巴胺, adrenaline from the adrenals, 多巴胺 presumably within the brain.

完整译文：But that the parasympathetic response is activated 当我们 put our face into cold water or go underwater. And that's a calming relaxation response. So, this brings us back to, I don't want to take us off track from you describing the study, but this brings us back to the first 问题, which is if I go completely underwater for a moment when I start my 冷水浸泡, does that change the physiological outcome as compared to if I just submerge myself up to the neck?

完整译文：And actually, nowadays, there seems to be a little bit of a movement online of people putting a bowl of ice water on their countertop and submerging their face into it. Did you see this? As a start, I've seen more and more posts about this. So, could you just touch on what the dive reflex is, and why it perhaps activates the parasympathetic response, this calming response?

完整译文：Susanna Søberg：Well, so the diving reflex is activated when you submerge into cold water.

完整译文：Andrew Huberman：Even just to the neck?

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：Or I thought you had to get your face under. I'm not arguing 不同. You're the expert.

完整译文：Susanna Søberg：I haven't read that. I just seen that you can activate your diving response as soon as you go underwater with your body. So, you don't have to do it with your face, as far as I 理解. I could be wrong. Yeah. So, when you activate your diving response, you will slow down your oxygen consumption in your body. And that is because the body tries to preserve oxygen, so you will not get hypothermic too fast. So, it's 有点 like a survival system in your body.

完整译文：So, this survival system is very 重要的 for us, of course. So that would be activated. And because of that, you will have to, maybe 1 minute or so. I can't be precise on that because maybe it also varies a bit in humans. So, 1 to 2 minutes, you will have full activation of the 交感神经系统 but also the 副交感神经系统.

完整译文：And that's going to activate, 例如, something like serotonin in your brain, which is also good for mental balance and people feeling in mental balance afterwards after they go up. So that is like measured on a 问题naire and also measured like on anecdotes. Of course, people tell all the time that they feel good afterwards. We need studies on this. So, if anyone's sitting out there thinking that's interesting, then please do some studies on that to get more out on that.

完整译文：Andrew Huberman：So, you observed these winter swimmers who have done this for a few seasons.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：They're coming around for a new season of winter swimming, and you've decided to recruit them as subjects. They are getting into cold water climbing down a ladder or jumping into the water up to their neck.

完整译文：Susanna Søberg：Yeah. Climbing. Yeah.

完整译文：Andrew Huberman：OK. Climbing down a ladder because this is done outdoors. What a fun study to do. My graduate thesis was done under fluorescent lights with no windows in a building that-- I mean, I had a ton of fun as a Ph.D. student. I actually lived in the laboratory as a Ph.D. student. I loved it so much. But not something required to do a Ph.D., by the way. But they're climbing down the ladder, getting in up to their necks, staying in for 1 to 2 minutes, and then getting out. And how many times a week are they doing this?

完整译文：Susanna Søberg：So, they do this two to three times per week. And for each time they go, each day they go, they take three rounds, so three dips and two sauna sessions. So, they start in the cold, and they end in the cold water.

完整译文：Andrew Huberman：OK. So, it's get in for 1 to 2 minutes. Then get out and get into the sauna.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：What is the 温度 of the sauna?

完整译文：Susanna Søberg：About 80 摄氏度.

完整译文：Andrew Huberman：OK. Then how long are they in the sauna?

完整译文：Susanna Søberg：So, they stayed there for 10 to 15 minutes. So, depending on if they went two times per week or three times per week.

完整译文：Andrew Huberman：OK. And then they get back into the cold for a few minutes? 2 minutes.

完整译文：Susanna Søberg：Up to 2 minutes. Yeah.

完整译文：Andrew Huberman：OK. Then back into the sauna 15 minutes or so.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：Then back into the cold for a third round.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：Back into the sauna. And then they're--

完整译文：Susanna Søberg：Ending on the cold.

完整译文：Andrew Huberman：And then back into the cold again and then ending on cold. And we will 讨论 why it's 重要的 to end on cold, the so-called Sober principle. How cold was the water in this particular, given the average, because I realize it's outdoor winter swimming, so it's going to vary depending on wind chill and things as well.

完整译文：Susanna Søberg：Of course. So, it's a very uncontrolled environment to do this 有点 study. But I wanted to do something that was also very close to something people could do for free, going out in nature and use that, and also have the nature. It's very healthy impact on us. It lowers our stress level as well. So, by doing so, I also measured the 温度 every time they went.

完整译文：So, I have this graph. And it's actually in the "Winter Swimming" book. It shows the 温度 in Denmark going like from October to April. And it's like that's at 12 degrees. 我认为 it's around 12 摄氏度, the water. And then it goes down to 2 degrees on average in January and then up again. So, it's within the spectrum of very cold water, 我会说, from around 15 摄氏度 and down. But it was actually not colder than like two to 4 degrees on average when it was the coldest. So, it doesn't have to be that cold to be good enough and enough to activate our 代谢.

完整译文：Andrew Huberman：And what time of day are the participants doing this cold sauna alternation?

完整译文：Susanna Søberg：So, 我认为 they did this throughout the day. So, I didn't control whether they wanted to go in the morning, in the afternoon, or in the evening. At that time where I set up this study, I was not controlling it in that way. I wanted them to go whenever they had time. And I also think that is the most 重要的 message to give to people, is do it when you have time.

完整译文：If doing it when you get home from work, and it's 6:00 in the evening, and this is the time where you can do it, then try out if it's going to impact your sleep or not. If it doesn't impact your sleep, then fine. But you have to try for yourself and find out what works for you. It's the same for coffee, 例如, right? Some people can drink coffee in the evening and go to bed, and they can sleep. I can't.

完整译文：Andrew Huberman：Or 运动.

完整译文：Susanna Søberg：Or 运动. Exactly. So, I can't do that. And that's because the coffee, 运动, 冷水浸泡 is going to activate your 交感神经系统. You have an 增加 in 应激反应 in your body. And that's going to make it really hard to fall asleep for some people at least. Maybe you are super exhausted anyways, and then you will just crash anyways. But yeah. But that's the only thing. So, I just told them to do this if they can during the daytime. And that's primarily what they also did.

完整译文：Andrew Huberman：And then all along, you're measuring 棕色脂肪 by way of this infrared camera, right? So, what did you observe in terms of changes in 棕色脂肪? How quickly did that occur? And then I'd like to ask also about sauna a bit more because earlier, you mentioned that you can activate 棕色脂肪 with sauna as well, with heat on the surface of the skin.

完整译文：How long did it take before you observed significant 增加s in 棕色脂肪, and was it 增加的 density of 棕色脂肪 or distribution? Was it showing expansion to 不同 regions throughout the body? And maybe you could also touch on some of the changes in 胰岛素敏感性 and 代谢.

完整译文：Susanna Søberg：Yeah. Very good 问题. And I didn't mention this before. But besides measuring 温度 as an outcome for 棕色脂肪 activity, we also did PET MRI scanning of the 棕色脂肪. So, this is like the golden standard for measuring 棕色脂肪. And it's not very feasible for normal people to get a CT or PET MRI scanning of the 棕色脂肪. It's super expensive.

完整译文：So, we had both to see if we could have a continuous measure of 棕色脂肪 in humans because that was already not out there. So, I wanted to see during both the experimental days but also during day and night what 有点 like circadian rhythm do we have in our 棕色脂肪 activity. So that's why I wanted to have that as well.

完整译文：So, the PET CT scanning or the PET MRI scanning was to see upon cold activation stimulation for some hours. Do we have activation? Can we see the 棕色脂肪 in this subject. And also, during thermoneutrality or thermo舒适 state, how is that activated in each of the group, of course?

完整译文：Andrew Huberman：So, you want to see how 舒适 people were away from the cold water and sauna, just at 不同 温度 environments. Is that right?

完整译文：Susanna Søberg：Yeah. So, I also measured that how 舒适 are you. I made this scale, like visual analog scale, and asked them, how 舒适 do you feel with this 温度? And throughout the study days, during 冷暴露 and thermo舒适 day. I had a whole day where I just kept them thermo舒适 to see do they activate the 棕色脂肪 if they are just completely thermo舒适 as good as we could get with that because we were asking people on a scale from 1 to 10, and 5 being thermo舒适, where are you on this scale? So, 1 would be very cold, and 10 would be super burning hot. Yeah. And so that was a way to try to figure out how do they actually feel also during this study. I also measured in electromyography, so of muscles, to see, do they shiver during the cooling day? 有时, people shiver before they know they're really shivering.

完整译文：Andrew Huberman：Oh, interesting.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：So, our conscious perception of shivering might not be the best readout of shiver.

完整译文：Susanna Søberg：Yeah. Well, if you also get adapted to the cold water, you will have less shivering. There will be less vigorous. There will be very small. So, you wouldn't probably know that you are shivering because the shivering is so small, and the mitochondria in the muscle cells will be so dense that it doesn't 需要 shiver maybe that much to get that thermogenesis going, compared to when you're completely new to cold water exposure, and you're not adapted. Then the body needs to create these mitochondria, these energy fabrics to keep you warm. And that's also what the 运动 is in the beginning.

完整译文：But 当我们 measured this, we did see that the winter swimmers were shivering less or having less vigorous shivering when they said I'm cold. So even though their perception of the cold was pretty similar in the groups, we could see that the activation of the muscles that we measured on were 不同 and more vigorous in the control group.

完整译文：Andrew Huberman：Were the subjects incentivized to be in the study? Were they paid or anything of that sort? Do they just happen to like doing cold and sauna, and so that's why they did the study?

完整译文：Susanna Søberg：Well, they got paid a little bit for it, but not much. And that's how we do this study--

完整译文：Andrew Huberman：I was just curious. I was just curious. There might be some folks that wonder. So, what did you discover in terms of changes in 棕色脂肪 insulin resistance, or 胰岛素敏感性 rather, and 代谢?

完整译文：Susanna Søberg：So, what we saw was we had this 有点 不同 measures to see what to try and unravel what's actually going on when they are already adapted to the cold water, compared to a control group who was matched on various parameters.

完整译文：We did see that the winter swimmers had an 增加的 胰岛素敏感性. They produced less insulin on all the experimental days. So besides from just cooling them and measuring the 棕色脂肪 on each of these cooling days. There were two cooling days and one thermo舒适 day. So, I wanted to measure insulin when they were fasting, meaning that they hadn't eaten in 8 hours before the study day.

完整译文：And they were completely lying still, not moving, just in a bed. And we measured insulin during the experimental day just to see what level are they on. And we could see that the winter swimmer had lower production of insulin. And they also, when they had a glucose drink, so we give them that to test before we enroll them in studies to see if they have diabetes, 例如, and not knowing, 例如. That would ruin maybe the study. So, we test for that and see if they have a normal curve. So, what we did see in that the winter swimmers had a faster glucose clearance in the bloodstream. So, after two hours, we could see that they had a lower level, and the curve went down faster than in the control group.

完整译文：Andrew Huberman：So, despite having lower insulin release, they have better blood glucose clearance, which is really what we all seek. Excessive insulin is bad. Insulin being a more or less a chaperone for blood glucose can do all sorts of other things as well, of course. And having high blood glucose, obviously terrible for cells, 尤其是 brain cells. I don't think people realize how toxic high blood glucose is, having high glucose is.

完整译文：If you want to kill neurons, you put them in an environment where there's too much sugar. Oh, yeah. Very neurotoxic. And there are mechanisms like insulin that buffer that, keeping blood glucose in reasonable range, so that doesn't happen. I mean, 我认为 that's why people will go into insulinemic shock. Hypoglycemic shock is also possible. So that range in which neurons are happy is not a tremendously large range.

完整译文：Incidentally, the range in which neurons are happy and surviving is much greater as one gets colder than when you heat up. I mean, you can basically destroy brain cells by getting too hot for too long.

完整译文：Susanna Søberg：Oh, yeah.

完整译文：Andrew Huberman：You can definitely destroy brain cells permanently by getting too cold for too long, but you have to get really, really cold for a really long time.

完整译文：Susanna Søberg：Yeah. Yeah. Very interesting.

完整译文：Andrew Huberman：Yeah. We're thinking about doing an episode on 某种程度上 survival of the brain after death 有点 things, which actually happens. You hear about these people who are declared dead and then come back. And there's actually now 很多 cryopreservation-type approaches for that. Anyway, we risk going into the esoteric now. So I'll steer us back to our discussion about your study.

完整译文：So, if I do the math, these subjects are in the cold. Let's say they're doing three rounds of cold for 1 to 2 minutes, two or three times a week, what were the 阈值s that you discovered were 重要的 for getting these positive changes, such as reduced blood sugar or clearance of blood sugar being more efficient, reduced insulin, improved 棕色脂肪 distribution and density. How much 冷暴露 do people need, how much 热暴露 do people need in order to extract these 益处?

完整译文：Susanna Søberg：Yeah. So, 当我们 then calculated the numbers together, we could see that this ended up being 11 minutes in total per week. So not in one session, of course. But they had two to three visits to the water and the sauna per week. So, 当我们 divide that out, it corresponds to being in cold water 1 to 2 minutes at a time. But also, in the sauna 10 to 15 minutes at a time.

完整译文：And 我认为 this is very like also similar to what we see in other studies 当我们 look, 例如, to the observational studies from the Finnish cohort study from Laukkanen et al, 例如. They published this very amazing paper in 2015. Some results from this long cohort study where they show that up to 30 minutes in the sauna was healthy, and you lower your risk of cardiovascular disease. And that's like the 阈值. And if you go further than that, then there is not more healthy 益处 to gain from that.

完整译文：And before that, it's like 90 minutes, then you will have this dose response relationship up to 90 minutes that's really decreasing your risk of cardiovascular diseases.

完整译文：Andrew Huberman：That's per week. 90 minutes per week.

完整译文：Susanna Søberg：90 minutes per session now.

完整译文：Andrew Huberman：Per session.

完整译文：Susanna Søberg：Yeah. Per session. If we then compare that with my study, which was 10 to 15 minutes per session, then 我认为 it fits very well with what we call the hermetic stress or healthy stress that you expose the cells to this 有点 like potent, very 有压力的 situation, where they 增加 heat shock proteins in the cells. And that will repair the cells. But if you then overdo it and you go beyond the maybe 30 minutes in the sauna, this observational study from Finland with more than up to 2,000 sauna bathers where they followed these for 20 years, they see that 30 minutes per session is like enough. And if you go above that, you don't get more health 益处 out of it. So, 我认为 there's a window where 我们可以 say the healthy stress corresponds to 10 minutes.

完整译文：Andrew Huberman：Per session.

完整译文：Susanna Søberg：Per session. And it's not much actually. So, it shows that you don't have to expose yourself very much to the heat or very much actually to the cold to get this healthy 益处 from going into cold, going to heat, and have healthy 益处 on your cardiovascular system.

完整译文：So, 我认为 this is very 重要的 also message to get out that you don't have to go extreme. You don't have to swim for half an hour in the cold water. You can go in the water for 1 to 2 minutes per session but go up to 11 minutes per week in total. And for the sauna, my study showed 57 minutes in total per week. And if we also then divide it out on these two to three days and two sessions each day, corresponds to 10 to 15 minutes.

完整译文：So, it's a low 阈值, but 我认为 it's good to have that too. Maybe 我们可以 aim for that if people 需要 have something to aim for. And 我认为 it's really good to have that because then you don't overdo it. And if you overdo it, you exhaust the cells. And that will 增加 your risk of cardiovascular disease also.

完整译文：Andrew Huberman：I get 很多 问题s about this, and I did solicit for 问题s for this podcast on Twitter. And one of the 问题s that I got was as one becomes more cold adapted, do the 益处 start to wear off? Or can people do too much 冷暴露? Of course, the answer to that is, yes, you can become hypothermic.

完整译文：But I'm sensing a 不同 answer now, which is if I 理解 correctly, the 阈值 is 11 minutes total per week of 刻意冷暴露 divided into two or three sessions of maybe 1 to 3 minutes, depending on how long somebody stays in. And then 57 minutes. I want to be careful not to round up to an hour but divide it into maybe three 20-minute sessions or so. So, one doesn't have to be perfect as long as you get beyond that 阈值.

完整译文：But I wonder something, which is it the case that if somebody said, oh, you know I'm just going to do one 11-minute session per week. That might actually not be as beneficial as dividing it up because what you told us earlier is that the hermetic response depends on having that cold shock. You actually don't want to become too cold-adapted. I mean, once the 血压 response drops down, so in minute 4, 5, and 6, you're getting very cold, and you're shivering. But one is not getting the autonomic stimulus that they want.

完整译文：I guess I could liken this to if 运动 worked in a way where it was only the first few minutes of 运动 that really triggered the 适应. Of course, this is not how it works. But 事实上, probably quite the opposite. But if that were the case, then it's not simply the total amount of 运动 but dividing up the sessions into little bouts where every single time it acts as a stimulus. That seems to be the key here.

完整译文：This is very 重要的 because having watched the landscape of this on social media but also in books and generally-- 我认为 you're the first person to really touch on this, that the goal is not to get so cold-adapted that you can sit in for the full 11 minutes in one session, where the goal isn't to be able to do an hour of very hot sauna. If you want to, I suppose people could do it for other reasons. But if the goal is to improve these health metrics, then the idea is to keep the stimulus a stimulus.

完整译文：Susanna Søberg：Short. Exactly. Yeah.

完整译文：Andrew Huberman：Great. Well, this also, 我认为 there's practical feasibility as you pointed out because getting into a 冷水淋浴, or cold immersion, or natural body of water for a couple of minutes is far less challenging to most people than finding a full morning to go spend there. But I've never really heard it articulated that the longer sessions might not be beneficial and might actually be detrimental.

完整译文：That's very 重要的. Were there any other observations that you made that did not make it into the paper or that were 有点 in the margin notes in terms of psychological 益处 or anything of that sort? There was this recent study on soldiers that talked about weight loss as 某种程度上 a controversial study for 很多 reasons.

完整译文：But one of the things they remarked in the paper was that there were 很多 psychological changes. Improved buffering against anxiety. The men and women in that study reported one of the significant effects was significantly improved sexual satisfaction. They didn't tell us what that meant for these subjects. So, we won't go there. But 一些 subjective improvements. Was there anything that you observed or took note of in your study that perhaps didn't make the main abstract but that 我们应该 be aware of?

完整译文：Susanna Søberg：Yeah. There were some. And today, I regret that I didn't measure on sleep, 例如. I frankly didn't really think about that when I designed the study. So, we were very much occupied with the 代谢 and 有点 had the thought maybe this could impact sleep quality.

完整译文：And I wish I had the thought that why don't you just ask them in a 问题naire? But I ask them every morning-- or every morning, it was not many mornings. Just two mornings actually we measured on. But the winter swimmers told us before I wrote them that they had a really good sleep quality. The control group also had that. But they told me on the day where we measured the 棕色脂肪 on a day and a night. So, for actually two days and two nights.

完整译文：They told me that they had a good night's sleep, but they also woke up. So, it's just telling me that they also had a quick wake-up, and then they fell asleep again. And the winter swimmers, they have a really good sleep. So, it's like in general, they also say we sleep very well. I sleep very well. So, it's anecdotally general corresponds to what I heard in my study. But nothing that I measured on, which could be fun to do in the future, but we didn't measure on sleep quality. That would have been a really good idea to do.

完整译文：They also told me that they were very 舒适 when they were cold. They don't mind, winter swimmers, they don't mind going out, 例如, in the cold with a t-shirt. They were also less scared of showing their skin. That was also one observation.

完整译文：Andrew Huberman：Interesting. So, 有点 a reduced social anxiety.

完整译文：Susanna Søberg：Yeah. They were just so 舒适 in the lab. As you just mentioned before, coats on, and everybody's running around. It was very busy. And all the other scientists out in the hallway. And also, my supervisor had her office down the hallway. And one of the winter swimmers one day just got out of bed after had been in the study for 8 hours. It was a long day, right? He jumped out of the bed and had his clothes in the bathroom, and he went out completely naked. He didn't care. He just went out. It was like, oh.

完整译文：Andrew Huberman：So that's a side effect perhaps of getting too 舒适 with the cold. We're not recommending that. Although in your book, you dedicated some-- let me start that again. Although in your book, you dedicated some pages to naked winter swimming, or I should say naked cold-water exposure, as opposed to with bathing suit. Are there any data on this? I'm sorry, chuckling. But 我认为 in most places in the United States, skinny dipping is not legal most public beaches. There are few.

完整译文：事实上, my laboratory before moving to Stanford was in San Diego at the Salk Institute for Biological Studies. Beautiful building. Incredible science is done there. The beach right below that is called Black's Beach. And it's a known nude beach. And so, whenever tourists were heading down the stairway there, I would 某种程度上 let them know, 尤其是 if they had kids, I'd let them know.

完整译文：And it's a nude beach of a particular genre. So, I'd give them a little Warning about what they could expect down below. In any event, those beaches are quite rare in the United States maybe compared to Europe, I don't know. So, is there anything special about clothed versus clothed exposure?

完整译文：Susanna Søberg：Yeah. 我认为 in that sense, we are a bit more free with this 有点 like-- but remember, we also had this winter swimming culture for hundreds of years in Denmark. And the oldest winter swimming clubs that we have, 尤其是 the one we have in Copenhagen where did my next study, which we haven't talked about, and it's also not published yet. But in that winter swimming club, it's the oldest one we have, and it's huge. And they swim naked at this facility.

完整译文：Andrew Huberman：Men and women.

完整译文：Susanna Søberg：Men and women. And they have sauna where they can go in together. And they also have separate saunas. But it's very much a Danish thing. And 我认为 我认为 it's good if people want that. And I had it in my book because people want to know if they have to swim with their bathing suit on, or if they can take it off, or what's the 差异. Is there any 差异 in this? And if you ask me, there is no 差异.

完整译文：If you have your little skinny bikini on, it's not going to do any 差异 to your 冷暴露 or your 适应. It's not going to do any 差异 for your 益处, of course. But 我认为 that it has something else. It has something to do with how you also observe yourself, how you observe your surroundings. And there's some sense of freedom in skinny dipping.

完整译文：So, 我认为 people in Denmark who does this is they do the winter swimming because they feel free when they do it. They come home from work. They go to this club, and they skinny dip, and they feel like in touch with nature. And they have maybe done this their whole life. So, this is an old tradition in Denmark in some of the clubs. But the newer clubs that are coming, they don't skinny dip. So, everyone has bathing suits. I never skinny dip because there are people around. People with phones and taking pictures all the time.

完整译文：Andrew Huberman：不同 nowadays. Everything's recorded.

完整译文：Susanna Søberg：Yeah. And also, this old tradition is also fading away because of that.

完整译文：Andrew Huberman：Yeah. I use sauna and cold at home. But when I travel there, there's a banya, so Russian banya, has hot sauna and 冷水浸泡. There's one in San Francisco called Archimedes Banya. And that one is clothing optional. So, some people are clothed, such as myself. And then other people are not. And it's co-ed most of the time. 我认为 they have female separated evenings or something like that.

完整译文：And then the other banya is Spa 88, which is on Wall Street in New York, is an amazing banya as well. And these are starting to crop up in 不同 cities. Or maybe they've been there for a long time, and as 刻意冷暴露 and sauna gets more popular, more people are using them. The one in New York, that Spa 88 is always closed.

完整译文：And it's interesting because people hear naked or skinny dipping, and they might get certain ideas in mind. All these places are very well lit, and they all have a tone of health. It's about the 有点 health and wellness. I guess the point being that there's no requirement to do one thing or the other. Although in the studies that you did obviously, people were clothed. But I did I did pay attention to those pages in your book. I thought it was interesting that you put some dedicated passages in your book 与……有关 this.

完整译文：Susanna Søberg：My publisher wanted that.

完整译文：Andrew Huberman：Oh, your publisher wanted that. Interesting.

完整译文：Susanna Søberg：Yeah. It was not me. It was like my publisher really wanted to have a little discussion about that. So, I was like, OK.

完整译文：Andrew Huberman：Well, 我认为 it points to a larger theme, which is 我认为 for 很多 people who already do these practices, there's no shock there. For people that 不要 do 刻意冷暴露 or sauna, 我认为 that there is this idea perhaps that, oh, you know, these traditions that are 有点 fringe or that they're--

完整译文：And I just I want to cue that point because there are so many things that are happening right now in biomedical 研究 and medicine. Serious, quality, peer-reviewed studies published in excellent journals like your paper on things like 刻意冷暴露, sauna, the use of particular supplements. Natural herbs and supplements. I mean, there's an entire branch of the National Institutes of Health in the United States dedicated just to the study of supplements and behavioral interventions for health, like meditation and breathwork. Really incredible. It's really incredible.

完整译文：And psychedelics, of course, being something that for a long time was part of a certain community and feel and now is being frankly adopted by mainstream medicine, even pharma. So, the times are changing. And so yes. 我认为 it's 重要的 to know that it's perfectly acceptable and encouraged to wear clothing.

完整译文：Susanna Søberg：Absolutely absolutely. Yeah. And one other thing that I wanted to mention going back to your 问题s around if there were any observations in the studies which we really maybe haven't discussed yet, and maybe it's in the back of the paper and not mentioned that much was one of the winter swimmers didn't have any 棕色脂肪 当我们 measured him.

完整译文：Andrew Huberman：Zero.

完整译文：Susanna Søberg：Zero. And we do see this in previous studies as well that some humans don't have any 棕色脂肪.

完整译文：Andrew Huberman：Did he carry 很多 white fat adipose tissue? Was he obese?

完整译文：Susanna Søberg：No. He wasn't. No. He was not obese because he would not have been in the study then.

完整译文：Andrew Huberman：Oh, right. Yes. You mentioned this earlier. Forgive me.

完整译文：Susanna Søberg：No, no. But what I did observe before I knew that he didn't have any 棕色脂肪 was that during the cooling experiment where I cooled him for 2 hours before they go into the PET CT scanner, he was not able to control his shivering like the winter swimmers could. So, he got he got very cold very easily compared to the others.

完整译文：And I didn't know what was 不同 about him. But all or me and the three others were working on the experiment, we were like, OK, what's going on because we turned down the 温度. But he started like shivering and then we had to turn it up again. And it was just all over the place. The 温度 is not, it wasn't that controlled like the others. It was pretty similar 方案. I could just do pretty much the same because they're the same size and also same gender.

完整译文：So, it was easier to foresee what was going to happen and when will they start shivering. I quickly learned that. But with this subject, with this volunteer, it was just very much 不同. And then 当我们 scanned him and didn't find any 棕色脂肪, I didn't even think about it. So, 当我们 scanned him and we didn't see anything, I told the PET CT people, like, oh, you put up the wrong scanning.

完整译文：Andrew Huberman：Right. Blame the technology.

完整译文：Susanna Søberg：Yeah. The technology. It was like this scanning look like the thermoneutral day, the thermo舒适 day where we also scanned them to see if they have any 棕色脂肪. So, you have made a mistake I was pretty sure. And the reanalysis analyzed this scanning, and they just concluded, well, the scanning was fine. The experiment went well. It was just that he didn't have any 棕色脂肪.

完整译文：So, he was like what we just in the paper called a 棕色脂肪 negative. So, he didn't have any. And in my studies, it would be called a knockout. So, he didn't have any 棕色脂肪. So, what the observation with him and 我认为 that's interesting is that he both shivered very early on and didn't regulate his 温度 as well. He also told me that then he was like a 5 on the scale of how 舒适 he felt with the cold.

完整译文：Andrew Huberman：Out of?

完整译文：Susanna Søberg：So, it was from 1 to 10, and 5 being thermo舒适, and 10 being very cold, and 1 very hot. So, on this like scale up and down. And he was like more up and down on this scale than any of the others. It was an observation that I did. But we did see in his blood samples also that his blood samples looked a bit more like the control group. And also, his insulin levels were like the control group. So, a little bit 高于 the other winter swimmers. And his blood glucose clearance was not as fast as the other winter swimmers.

完整译文：So, he was like an outlier what we call it. And in the analysis, we also had to take him out of the analysis because he was an outlier. So, the results showing that the 棕色脂肪 is more efficiently activated in the winter swimmers is without having him in that group. But it didn't ruin the study if I tried to put him in as well, and it didn't ruin the results or anything. But just to keep it more clear, we took him out of the analysis.

完整译文：Andrew Huberman：Yeah. So, he was a mutant, a knockout. Yeah. And I'm sure they're out there. Very interesting. So, if you shiver early, then perhaps you have less 棕色脂肪 to begin with, although it's hard to conclude from one person. That's 某种程度上 the implication there.

完整译文：Susanna Søberg：Or you haven't adapted to the cold. So, you should build that up. Yeah.

完整译文：Andrew Huberman：So, 此外 to looking at regulation of blood sugar, 棕色脂肪, 代谢, and so on, were there any markers that you examined in the 刻意冷暴露 group as compared to controls that revealed to you that deliberate, 冷暴露 could have additional 益处, say, for immune system function or for any function for that matter?

完整译文：Susanna Søberg：Yeah. So, we looked at 炎症. Of course, we measure the outcome of 血压 and so on. But we also measured the IL-6 in this study, just to see also inflammatory and inflammatory markers. So, IL-6 went up, and it also follows with the IL-10. So that is like also very known in the literature.

完整译文：So, we measured that and 我认为 it's very 重要的 to think about the 冷暴露 and the 热暴露 as something that then lowers the 炎症 in the body. And if 我们可以 do that, we will have an open door for preventing lifestyle diseases, right? So, for type 2 diabetes but actually also for some mental diseases as well. So as 称为 depression and anxiety and also Alzheimer's disease, which are all associated in 研究, also newer 研究 showing that 炎症 增加s the risk of depression, anxiety, and Alzheimer's disease, neurological diseases.

完整译文：So, if 我们可以 降低 炎症 in the body, we will 降低 our modern lifestyle diseases, but also these increasing mental diseases that we see in these modern lifestyle times. So, 我认为 it's very interesting that 我们可以 go out in nature, and 我们可以 use these natural stressors. And I don't want to have it sound very romantic or anything. It's just exposure to 温度 actually, just to cold or to heat, that is going to trick our body into a natural state again and reset it where the homeostasis, the balance is lost a bit.

完整译文：So, the body is going to repair itself in that way. And 我认为 it's beautiful that 我们可以 do that just by changing the 温度 of our body. And although people are very scared of doing this because in our times, we have been away from cold, away from heat 温度 for decades now since we isolated our houses better, and we are more sedentary. We also sit more indoor. We don't move as much. So, this very modern sedentary lifestyle has made us more 温度 舒适 or just neutral. So, no wonder, I mean, that obesity is increasing.

完整译文：We don't expose ourselves to the natural stresses that we did earlier on in our environment but up until maybe the 70s the 60s, where we started having more like 舒适 lifestyles, right? And obesity 增加s in the 80s. 我们可以 see that from statistics. So, 我认为 that if 我们可以 take in cold and heat, and you mentioned other things also before. But of course, 运动 is very 重要的 here. And also, a bit of fasting actually because it all 增加s the hermetic stress in the body. So, it doesn't have to be other than natural stresses to the body, which then could keep us in that natural balance again.

完整译文：Andrew Huberman：Could we 讨论 what I refer to as the Søberg principle, which is to end on cold? And the reason I called it the Søberg principle is because in reviewing-- Oh, by the way. I wasn't a official reviewer of your paper. But I mean in reading and reviewing your paper for its after published contents, I noticed that you had people end on cold. And this has been a long-standing debate in the 刻意冷暴露 community. Should you warm up with a warm shower afterwards or get back in the sauna? What should you end on? End on cold or end on heat?

完整译文：And the Søberg principle says end on cold, as I 理解 it, in order to force your body to heat itself back up and thereby 增加 代谢 further still. Is that right?

完整译文：Susanna Søberg：Yes. So, when you end on the cold, you force your body to heat up by itself. And that will require that you keep your 棕色脂肪 activated and also your muscles, which is a good thing. It's a good collaboration to keep your thermogenesis up. And that's like an 运动, even when you go home. So, in that way, you don't have to think about your 冷暴露 or dipping in your plunge or open sea or what it is as just an 运动 that you do for 1 to 2 minutes, and then it's over.

完整译文：If you end on the cold, you have an 运动 for your body going on for hours afterwards. And that's not only on your 代谢, but it's also going to keep your 神经递质 activated as well and 增加 that because your body is still cold. So, you need those 神经递质 to activate the 棕色脂肪 as well. So that's going to make your 棕色脂肪 cells more efficient and also your muscle cells more efficient. So increasing mitochondria in the cells, which will then generate heat very fast.

完整译文：So, if you have done this for a few times, so maybe three, four, or five times, being new to this but have tried it a few times, you will notice a switch where you like feel that you get easily warmer, and you can keep yourself warmer. And that is also what was shown in my study, is that the winter swimmers were physically warmer on the skin compared to the control group.

完整译文：Andrew Huberman：When they are out of the cold.

完整译文：Susanna Søberg：When they are out of the cold. Just relaxing. And we tested this in on the days where they were sleeping in the lab. So, we could see that they had a more activation of the 棕色脂肪, higher 温度. So probably because they also lose heat, they have a higher heat loss to the body compared to the control group because they have a more vascular skin because of the contrast of cold and heat. So, they lose heat faster from the body during the day but is that a bad thing. No. Probably not because that's going to keep your 棕色脂肪 and your muscles a little bit activated. So, it has to work to keep you warm.

完整译文：Andrew Huberman：And I would hypothesize that it also might lead to some of the subjectively reported improvements in sleep because in order to fall asleep, you need your core 体温 to drop by about 1 to 3 degrees. So, it's not just sufficient to be sleeping in a cold room and under the blanket. You also need your 体温 to drop.

完整译文：Susanna Søberg：Yes.

完整译文：Andrew Huberman：And so, what you're saying, if I 理解 correctly, is that by ending on cold and forcing oneself to heat up naturally, that 增加s the 棕色脂肪 stores, which I 某种程度上 see as 有点 like the oil in the candle of the furnace that is thermogenesis. And that in turn leads to 增加的 heat loss, which people might think, oh, I don't want to lose heat from the body. But there are times when you want to lose heat from the body.

完整译文：Basically, it sounds like what we want is to be a very efficient heating and cooling system. That it's not about being cold or being hot. It's really about keeping the system tuned well. Keeping the oil in the candle, this 棕色脂肪, functioning.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：What could I ask one 问题 about fed or fasted? Are there any known 益处 of doing 刻意冷暴露 and/or sauna fasted, versus after a meal, say within the last hour or something of that sort? I do my 刻意冷暴露 first thing in the morning. So, in general, I'm fasted because I don't eat until a little bit later in the day. But what's known about that, and was that looked at in your study? 我知道 you measured glucose, but that was as a separate test away from the cold.

完整译文：Susanna Søberg：Away from the cold. Yeah. But I also tested glucose on the days on the cold. So, we measured that as well on the cooling days. Specifically, on fasting and fat, I don't know. I don't think that I have seen studies specifically on this.

完整译文：Andrew Huberman：OK. More science needed. 一些 people ask about the use of deliberate, 冷暴露 to offset some of the symptoms of various diseases. Now here we're not 讨论 curing disease. We're 讨论 offsetting symptoms. One 问题 I've seen quite often is 是否 people with Raynaud's syndrome. This is a syndrome-- my high school girlfriend had this syndrome, and I'll never forget we were at a school dance together. And this was 当我们 first started dating. And she had Raynaud's, which leads to very poor 血流 to the extremities. And she was very cold.

完整译文：So, she left to go to the bathroom and warm up her hands in the warm water. And I was left standing there at the dance. And people came up to me and asked you why I was there and who I was there with. And I kept telling them who I was with. And they didn't believe me because they couldn't believe that she would be with me. It made total sense if you knew me at the time. I was way out of my league with her at the time. I like to think eventually, I caught up.

完整译文：But in any case, she was in the bathroom for about an hour. So, at one point, I did consider the possibility that she had just left. But indeed, she hadn't. She warmed her hands back up. But people with Raynaud's suffer from this thing of very, very cold extremities. Their fingertips will even turn blue as if they were starting to get frostbitten. It's quite dramatic.

完整译文：And that 问题 gets asked 是否 there's any use of cold to try and 增加 the elasticity, the plasticity of the small capillaries and vessels. But everything you've described up until now, it seems like that would be a logical thing to do.

完整译文：And 此外 to that, 是否 people with autoimmune, conditions people with any other types of conditions are known to benefit from 刻意冷暴露. I'm not aware of any studies, but I get asked about this a lot, and there were 很多 问题s about this for you in the Twitter feed.

完整译文：Susanna Søberg：Yeah. Thank you for those 问题s, and I get them as well on social media. And I have to say that I haven't seen any studies directed on this outcome in measuring Raynaud's syndrome. I do know that it's not that rare actually a problem. And 我知道 that many women or more women than men suffer from this.

完整译文：But logically, it would help them if they exposed their hands to cold and also heat to make the vessel more vascular. And I have heard from people saying that it had helped them but also hurt for some others saying it didn't help them. So, studies are needed on this specific topic, 我认为. I hurt my hands when I go into the cold, and I don't have this syndrome at all. But I keep my hands above the water.

完整译文：Andrew Huberman：You do?

完整译文：Susanna Søberg：Yeah. And I do that. Often, I take a little bit of a swim. And then of course, I have to have my hands in the water. But it helps me when I then get back to the jetty and then take my hands up because then I can stand there for a little bit and get my 1 to 2 minutes exposure. And then I can go up because then otherwise, that would stop me from being in the water enough time as long as I would like to.

完整译文：So, if people suffer from having this pain in the fingers, and it can be very intense. So just take the hands up a bit from the water. And that's going to help you. Also boots, neoprene boots. It's going to help on the feet. Some people feel the pain in the feet and in the ankles. And that's going to help them also a little bit.

完整译文：Andrew Huberman：OK. So, there is no problem with keeping hands out or feet in neoprene booties if people feel the 需要 do that. If pain of the hands or feet is a barrier for people doing 刻意冷暴露, then it would be to keep hands out or to keep your feet in booties.

完整译文：Susanna Søberg：Yeah. Because you do get the exposure. But of course, hands and feet are very potent places in your body to get a fast activation of your 神经系统, of course. But you can also just dip them and then take them off. It's still going to activate that. But your full body is covered in the 冷感受器. You have a full activation anyways.

完整译文：Andrew Huberman：You are providing very reassuring information to people because 我知道 一些 people that 不要 like to put their hands in. I find that the more of my body I get in, the more 舒适 I am. So, I don't know if it's psychologically and/or physiologically. I find that where there's an interface between the water and the cold, it's most 不舒适. So, I prefer to just get everything under. I keep my head out.

完整译文：Although these days, I've been dunking all the way in and then coming out and then dunking once more with my head under before I get out after the plunge. That raises a 不同 问题. Now we're getting into the practicalities of 刻意冷暴露, which 我认为 are 重要的. 有时, I'll experience, and I hear from 很多 people that they'll get a 有点 back of the head headache at the interface of the water when they're in doing cold immersion to the neck.

完整译文：I assume this has to do with 血流, that there's vasoconstriction right up until the neck and in the region surrounding it, but that maybe there's still 血流 to the head. But do we know what the origin of these headaches is? And again, this doesn't happen for everybody, but some people do experience them.

完整译文：Susanna Søberg：OK. Yeah. I haven't really heard about that one specifically. But 我会说 that there are 不同 reasons for maybe keeping your head out of the water, but it seems like maybe for some, that could be a reason for like just getting like a quick head dunk to--

完整译文：Andrew Huberman：Going all the way in once.

完整译文：Susanna Søberg：Yeah.

完整译文：Andrew Huberman：That's what I've started doing to eliminate-- I wasn't getting headaches, but I noticed that interface. And I wasn't in the rest of the experience of it so much. So, I started dunking all the way in. I noticed in some of the photos that you've put out and, in your book, that you'll 有时 wear a cap while you go in.

完整译文：Susanna Søberg：Yeah. Well, it comes from 不同 reasons. So, let's 讨论 some of the physiological reasons. So, when you submerge in cold water up to the neck, studies have shown, and this is from Denmark studies from Bispebjerg Hospital that when you submerge into cold water up to the neck at 0 degrees, so 0 摄氏度, very cold, you have a 降低的 血流 to the brain by around 30% to 40%. And makes sense because you activate the 交感神经系统. And 因此, you will have a less 血流 to the brain. Makes you maybe a little bit dizzier.

完整译文：Andrew Huberman：Proof again that you need a heart more than a brain because when the 交感神经系统 gets activated 血流 is maintained to the heart to keep you alive but obviously taking away from the brain to keep you from thinking. That's why it's hard to think when you're stressed.

完整译文：Susanna Søberg：Yeah. Well, the muscles and your vital organs 需要-- you have to be able to run away from that tiger, right?

完整译文：Andrew Huberman：The rationale, it makes total sense. And who am I to disagree with mother nature?

完整译文：Susanna Søberg：But yeah. So, one of the reasons being that you should keep your head out of the water is that you could 降低 in 血流 to the brain further if you dunked the head. So, there's this very nice paper from a 研究 group in Canada, where they have collectively looked at 不同 papers where they compared heat loss in a group in the papers where they dunked the head and compared it to heat loss submerging up to the neck to see how much extra heat do we lose from our core 当我们 dunk the head.

完整译文：And 我认为 it's very interesting that if you submerge up to the neck, you have a heat loss of 11% from the body core. And when you then also dunk the head, you 增加 that heat loss rate by 36%. I'm not here to say what is right and what is wrong. I just think that people should know the information, so they can for themselves evaluate what is best for them.

完整译文：But if you 增加 your heat loss rate by 36% from your core, that's going to 增加 your afterdrop, which we touched upon a little bit earlier, even further. So that's meaning that you are closer to hypothermia than you are if you just submerge up to the neck. So, you should really think about whether this is like something that you want to do or if it's just better for you not to get that cold in your core.

完整译文：The beanie is also because I have a little bit of sensitive ears. So, meaning that if there's wind, and because we swim in the open sea in Denmark, we have 很多 wind. Our conditions are just very rainy, very windy. And when the 温度 is also freezing, you could get this-- what is that called? So very cold and lightheaded just from wind. So, if you also submerge into cold water and you then get up, you would get a brain freeze immediately.

完整译文：So, it is enough to just go up to the neck wear a beanie to just not get dizzy also because the heat loss is 增加的 of course, but also, the 血流 to the brain has 降低的. So, the beanie will keep you a little bit warmer, so you can stay for 1 to 2 minutes. So, it's just a way of getting around some of the conditions also. So, people can choose that if they feel that, but it's quite normal to do in Scandinavia, wear a beanie.

完整译文：Andrew Huberman：Love it. And so, for those of you afraid of doing a 2-minute 冷水淋浴, what Dr. Søberg just described. You see how she and others are capable of doing things far harder than that. The way you describe it with the cold wind and Scandinavia is quite striking.

完整译文：Along the lines of covering the head, there's this seemingly paradoxical thing of people going into hot saunas and wearing wool caps. If you go to a banya or you go to a sauna, and there are people who are, well, from Eastern Europe typically, or Finland, or Russia, or Ukraine, or elsewhere. What you'll see is that many of them are wearing wool caps in the sauna, which many people think is to make it hotter, but it's actually not the case. It actually insulates you from the heat environment.

完整译文：The sense of urgency to get out of the hot sauna is a brain-driven mechanism. And so, the reason that people wear wool hats in the sauna is it actually lets you stay in the sauna longer because it takes 很多 heat to the skin before you feel that you, quote unquote, have to get out. Whereas so when you insulate the brain, you don't get that signal. It's pretty interesting. I've tried this before just by putting a towel over my head in the sauna, and you can stay in there much more easily and for much longer.

完整译文：As we 讨论 these 不同 stimuli for the hermetic response, the 适应 to stress, it occurs to me that the big ones in our evolutionary history have been light. I mean, you were 讨论 seasonal changes. We know, 尤其是 as you go up to Nordic countries, there are seasonal changes in the amount of light by time of year. Dramatic ones, 事实上. Less so at the equator, of course.

完整译文：Light, 温度, food, movement. And it's 某种程度上 interesting. And at the same time, perhaps it should have been obvious to us that there are stimuli that our bodies have evolved to adapt to in very powerful ways. And so, the idea that 温度, heat and cold, could evoke these tremendous physiological changes that are beneficial for us probably shouldn't surprise us at all. I mean, these are not esoteric mechanisms. They're actually the foundational mechanisms by which our body and the bodies of other animals adapt.

完整译文：So, I do have a 问题 about the 不同 ways that people could approach 刻意冷暴露. So, for instance, 儿童. I've been to banyas where there are kids 6 or 7 years old with their parents at the banya. And so, they're in hot sauna. I'm not suggesting people do this if they're not adapted to it. And talk to your parents, kids. And talk to your kids, parents. Talk to your doctors. But it is remarkable.

完整译文：I mean, 儿童 doing sauna from a young age or 刻意冷暴露. Are there any data on this, and is it safe assuming that, obviously, that they can swim or they're doing this in a tub or shower? And then I'd also like to ask you about are there any additional male-female 差异s? 我知道 your study focused on men. But other studies have focused on both. And you, of course, are a woman and can attest to your own experience with this. So, 儿童, men, women, 差异s there in terms of 方案? Is there anything that people should build into the structure of their 刻意冷暴露 that's unique to that?

完整译文：Susanna Søberg：Yeah. So, this was on 冷暴露. So yeah. 我认为 that starting with the 问题 about 儿童. 我认为 that it's 重要的 to think about as 儿童 are smaller than adults, so 我们可以not really completely transfer all the information and the 益处 and also 方案 for how long and stuff like that to 儿童. 我们可以not do that because they are just smaller in mass.

完整译文：And one study that actually proves this is a study where they have compared heat loss in 儿童, boys who were 12 years old, compared to adults, men, and looked at heat loss of the 核心体温. And exposed them to a 1- or 2-minutes 冷暴露. So, immersion up to the neck.

完整译文：And what they saw was that the boys in this study could actually defend their 核心体温 in the same way as the adults could, but they had to use their muscles way faster. So, it means that they couldn't stay for as long, and they use more energy to defend their 核心体温 compared to the adults. But for 1 minute, it seems that they could actually, but they will be colder when they then come out because they are smaller in their mass to their ratio, right?

完整译文：So, it means that if the surface is so large on 儿童 and their mass and muscles being smaller to that ratio, it means that they can be in the water less time before they get hypothermic. So just think about that. They are just smaller. They can't defend their 温度 for a very long time. But in this study, they saw that for up to, 我认为 it was a minute or so.

完整译文：Andrew Huberman：1 minute.

完整译文：Susanna Søberg：1 minute. Yeah.

完整译文：Andrew Huberman：I'm glad you mentioned hypothermia in smaller bodied people, 儿童. I 用于 do some Pacific Ocean swims in the morning without wetsuits, and I adapted to it pretty quickly. And these are fairly long swims, and we brought an excellent swimmer with us that was interning with me for a while, is 16 years old at the time and very lean. And he wasn't small for his age, but he was smaller than us. It was all guys on the swim that day. And 有时, women join us.

完整译文：And he got hypothermic. And he's an excellent swimmer. And he didn't report feeling overly cold. But fortunately, we got him to shore and heated him up again. So, he lived. I don't think his mother is going to ever let him go swimming with us again. He's thriving in the world. He's a university student now. And he recalls that swim. I mean, this is why you always want to ocean swim with a buddy, with people. Yeah. He became hypothermic. His teeth turned yellow. He was slurring his words. He wasn't making sense. We got him on to shore, and he was 有点 drooling and a little bit semi-euphoric. Hypothermia is no joke.

完整译文：Susanna Søberg：It's no joke.

完整译文：Andrew Huberman：Yeah. So, I'm really glad that this is coming up because the cold is a powerful stimulus, and kids and smaller bodied people are at a greater risk of hypothermia. So, a good reason to approach it with caution. Maybe start with 冷水淋浴s. Get then cold immersion in still water. Natural water and open bodies of water of course are always going to be more 危险的 for other reasons, currents and things of that sort.

完整译文：Susanna Søberg：Yeah, exactly. And drowning. Yeah.

完整译文：Andrew Huberman：So 重要的 note there. What about any additional male-female 差异s or similarities that 我们应该 be aware of? And this comes up all the time on social media. Any time I post anything about a study, it's what about women? Because oftentimes, there are 差异s.

完整译文：Susanna Søberg：Yeah. And we also just talked about the 差异 in 温度 in men and women. So, it means that if we replicated my study in women, it could be that they would have enough, you can say, 冷暴露 with just 9 minutes per week. It could be because they apparently are also just colder, and they have 增加的 代谢, and their 棕色脂肪 is just they have more 棕色脂肪. It could be, but this is just something that I frankly don't know.

完整译文：But women also do 冷暴露, winter swimming with the 11 minutes 方案. I do it myself and feel good about it. So, 我会说 that women, also regarding activation of the 棕色脂肪, it should be the same in theory. But I don't know if women actually do 需要 have another 方案 when it comes to this rapid 冷暴露.

完整译文：我认为 that it's another 问题 if we are 讨论 ice swimming when it comes to how far can you be in the cold water without getting hypothermic. Then there will be 差异s in men and female. But if you do this 冷暴露 for a very brief amount of time, which is what I try to 讨论, what we call also microstressing the body to 增加 the hermetic stress, the healthy stress. Then this is such a short amount of exposure that it's fairly the same. 我认为 women can look at this as a fairly good 方案 for them as well.

完整译文：Andrew Huberman：I always say that if you really dread the cold and don't like the cold, then you are a perfect candidate for using 刻意冷暴露 because the sympathetic, aka the 应激反应, will be greater. And thereby, the 适应 to that shorter 1 or 2 minutes is going to be much greater.

完整译文：For people that are perfectly 舒适 in the cold, it's harder to get an 适应 response. The same way that if somebody is very strong and they can lift a very heavy weight, that that very heavy weight is unlikely to evoke the same 有点 or same degree of adaptive responses if somebody is not quite as strong. So, another reason to keep these exposures relatively short and more frequent than to do longer duration exposures frequently.

完整译文：However, let's say somebody only had two days a week to do 刻意冷暴露. Maybe they don't have access to a sauna. Maybe they do. Would you suggest that they get in for 1 or 2 minutes, then get out, then get back in for another couple of minutes, then get out, and call that for 4.5 minutes to try and get to that 11 minutes total per week, as opposed to getting in for a full 5 minutes, and then getting out, and coming back a second time that week?

完整译文：我知道 this is getting down into the weeds, but these are the sorts of things that 我认为 people really want to know because 很多 people either don't live close to a body of water or don't have a 冷水浸泡 that they can do this with, although 冷水淋浴 apparently works too. So, most people live close to a shower.

完整译文：Susanna Søberg：Yeah. Definitely. 我认为 the changes in 温度 is what is strengthening your cells in the body. So, if you can do the short amount of exposure and then get out and get back in, that is going to, you can say, strengthen your cells because you are challenging them to adapt to changing 温度s.

完整译文：So, during one session, you can change this, right? You can do it 如果你是 able to go to cold water but also a sauna. Then you just do that automatically, and you will have a change in 温度. But you could also do it while variating the 温度. In your 冷水浸泡 if you have a plunge, or if you have an open sea, or you have seasons even. We have that in Denmark. So, we have four seasons. And the 温度 is going to vary with that.

完整译文：So, we have nature who can just change this for us, and we don't have to think about it. But if you have a 冷水浸泡, well, then 我会说 that changing the 温度 is what is going to create this hermetic stress and also keep your cells on its toes, you can say, because right the body will still be stressed to try to adapt to the new 温度 as it's seen as something actually toxic to the body, right? It's a small piece of toxicity that you are exposing yourself to. You don't have to swallow it, but it's enough that you touch it actually.

完整译文：Andrew Huberman：Yeah. A great way to frame it. That brings me back to this idea of circadian time. In your study, you didn't control for specific time of day. And now I'm realizing that may be a great asset to the whole thing. So, we know, for instance, that our bodies go through pretty dramatic shifts in 温度 from the time we wake up. Our body starts heating up as we wake up and continues to heat until the afternoon. And then starts to drop in the later afternoon. And then assuming all things are working correctly, that 体温 drops, and we sleep.

完整译文：So, I could imagine that doing 刻意冷暴露 at 不同 times just by way of convenience or by way of intention could be very beneficial because my 体温 is going to be quite a bit warmer at one time of day versus another. And in that way, keeping the system tuned.

完整译文：And that's really what I keep hearing coming through as you explain these data and all these beautiful studies, yours and others, is that it's not really about getting cold. It's about going from warm to cold and from cold to warm. And I love this idea because I probably said this 100 times on my podcast and a million times in my life, and I'll continue to, which is that biology is not an event. It's a process. Like these metabolic and thermoregulatory processes are indeed like the turning of a knob. It's a verb as opposed to a noun.

完整译文：And so, 我认为 if people can internalize that idea, that they're going to have a lot more flexibility, a lot more fun, and get a lot more benefit as opposed to thinking, OK, I 需要 get into x degrees of water for x amount of time on x number of days in a very rigid way.

完整译文：Susanna Søberg：I get this 问题 all the time. How much and how cold? And I mean, it's just like, well, because we also don't have studies showing exactly if you just keep 5 degrees in your water and you do that for a month, then what happens? Maybe in the future, we will know much more about this, and I'm sure it's going to come, and I really hope so. But I just think by logically changing that 温度 up and down, up and down, and you also do that in your water, it's not that 重要的 what 温度 you will have your water then. They'll just keep changing, going up and down. It could be all up to 12 摄氏度.

完整译文：You're going to activate your 棕色脂肪 anyways. I mean, 12, 19 degrees cold air is enough to activate your 棕色脂肪. So maybe we don't have to go as cold as 我认为 many people think and putting ice even all the time. You don't have to. I don't think it's necessary to expose yourself to that cold 温度 all the time but vary it a bit.

完整译文：Andrew Huberman：So, keep the system off balance. It's the way to keep it tuned. You mentioned a study that is more recent and ongoing that's not published. If you're willing, could you share maybe some of the data from that findings from that study with, of course, the cue to everybody that these are not yet published data, so the conclusions could change. The data could change for that matter.

完整译文：Susanna Søberg：Yeah. So, we haven't analyzed all the data yet, and 我知道 from the study that we did publish that we would 需要 look more at the data. So, I don't really have any results yet that I can share because we are still in very preliminary analysis of this. So, I wouldn't know yet what to exactly say about it. But what we looked at was both men and women. So that's coming.

完整译文：Andrew Huberman：Oh, that's fantastic. That answer is going to please a great number of people and intrigue everybody. Well, I want to really thank you for coming here today to 讨论 your work and the incredible direction that it points to because 我认为 that no one study is definitive, but your study really again stands as a landmark in the landscape of exploring 刻意冷暴露 and heat, how it can impact and potentially impact our health.

完整译文：Because frankly, there just haven't been that many high resolution detailed modern studies of this. There have been studies of sauna. There have been some studies of cold. There are 很多 groups in physiology that work on hypothermia and very 冷暴露. But most of the 温度s used in those days just aren't practical.

完整译文：So first of all, I just want to thank you for viewing the work that you've done and for the work that you continue to do. I'm waiting with bated breath as I say to hear the results of this study that's ongoing on both men and women. So, we'll have to have you back to inform us about that soon.

完整译文：And I want to thank you for the incredible public education efforts that you've been doing on social media with respect to your book. And we, of course, will put links to all of those things in the show note captions, so people can learn from you and can continue to learn from you. We certainly need more scientists who are both experienced with doing hard core 研究, as it's called, and who also do the practices. 我认为 that's a wonderful additional asset. You're not just behind a lab coat or bundled up in a down feather jacket as everyone else is getting into the cold. You do these things. And that you are so open and generous in the way that you share knowledge, which includes coming here today to share knowledge with me and our audience. So, thank you ever so much.

完整译文：Susanna Søberg：You're very welcome. I am so pleased to be here. And thank you so much for inviting me. And I could explain my study, and I can share some of my insights from doing that. So, I'm very grateful for being here.

完整译文：Andrew Huberman：Delighted, and we'll have to have you back again.

完整译文：Thank you for joining me for today's discussion all about deliberate cold and 刻意热暴露 science and 方案 with Dr. Susanna Søberg. If you'd like to learn more about Dr. Søberg's 研究 or you would like to learn about the 研究 of her institute, the Søberg Institute, please see the links in the show note caption.

完整译文：Also, in the show note caption, you can find a link to Dr. Søberg's excellent book, "Winter Swimming." If you're learning from and/or enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero cost way to support us. 此外, please subscribe to the podcast on Spotify and Apple. And 此外, on both Spotify and Apple, you can leave us up to a five-star review.

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完整译文：For those of you that haven't already subscribed to our so-called Neural Network newsletter, this is a completely zero cost monthly newsletter that has summaries of podcast episodes and so-called toolkits. Toolkits are lists of about a page to two pages long that give the critical tools, for instance, for optimizing sleep, or for neuroplasticity, or 刻意冷暴露, or 刻意热暴露, or optimizing 多巴胺. Again, all available to you at zero cost. You simply go to hubermanlab.com. Go to the Menu tab in the corner. Scroll down to Newsletter. You provide us your email. We 不要 share your email with anybody.

完整译文：And 此外 to that, there are samples of toolkits on the hubermanlab.com website, again, under Newsletter. And you don't even have to sign up to access those. But 我认为 most people do end up signing up for the newsletter because it's rich with useful information and again, completely zero cost. Thank you once again for joining me for today's discussion with Dr. Susanna Søberg. And last but certainly not least, thank you for your interest in science.