AMA #7: Cold Exposure, Maximizing REM Sleep & My Next Scientific Studies
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Welcome to the huberman lab podcast, where we discuss science and science space tools for everyday life. I'm Andrew huberman and am a professor of neutral logy and optimal gy at stanford school of medicine today. Isn't ask me anything episode or A M A.

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And for those of you that are not human and lab podcast premium subscribers, you can still hear the first twenty minutes of today's episode and determine whether not becoming a premium of subscriber is for you without further a do. Let's get to answering your questions. The first question asks, is IT possible to get a cold or to get sick from deliberate cold exposure? As was a related question is, should you even do deliberate cold exposure if you have a snifter, a cold or a flu? I get that question all the time as well.

I answer both of those questions, and I will also touch on some of the mune enhancing effects of deliberate cold exposure. But just to make sure that we answer the specific question asked here, read off the bat is IT possible to get a cold or to get sick from deliberate cold exposure. Well, assuming that you're not doing the deliberate cold exposure for more than, say, five or six minutes at one stretch, probably not directly from the deliberate cold exposure.

I mention that because most people are doing anywhere from about a minute to three minutes, sometimes five or six minutes. And maybe for those of you, they're really pushing IT ten minutes of deliberate cold exposure. And most often after doing that deliberate old exposure, people are either getting closed or they getting into a sa, or they are taking a hot shower and then getting closed and heading off into their day or off to sleep.

Depending on what time of day or night you happen to do, you're delivered cold exposure. We can safely say that if you warm up after a relatively brief, meaning one minute to, let's extend out to ten minutes, ten minute deliberate called exposure. Although I really want to caution, people do not do ten minute deliberate called exposure right off the back.

If you are somebody who is not a custom to IT, don't jump right up to that long exposure to cold water. Start with shorter exposure. But if you're doing that one to ten minute to deliberate cold exposure and then you're getting warm afterwards and heading about your day, I can see how the deliberate cold exposure itself would enhance your suspect ability to getting sick.

That said, we know from an enormous number of studies that have looked at cold virus transmission in other forms of viral and bacterial transmission that the environment that you happen to be in does impact your suspect ability to colds and other types of viruses into bacterial infections. In the following way, there been controlled studies in which people go into laboratories. Was laboratories have rooms which they can very tightly control the humidity, so water content in the air as well as the temperature in the room.

And if you look at the total mass of those data, we can say a couple of specific things in kind of bullet point fashion. First off, cold, dry air does seem to increase our suspect ability to viral and bacteria infections because whether or not you a mouth breather or a nose breather and by the way, I suggest everyone be a nose breather unless you're exercising hard enough that you have to breathe your mouth or you're talking or something in that sort. But if you're a nose breather or mouth breather, or both viruses and bacteria enter through your nose and mouth, sometimes through your eyes, but your nose and mouth are going to be the main sites of entry and your main barriers to viral bacteria infections.

In fact, one of the ways you are constantly fighting off bacteria and viral infections that you're exposed to all the time is, by a way, of those viruses and bacteria getting trapped in the mucus lining of your nose or your mouth, most notably in the of your throat. So if you spend time in cold, dry environment, there is a tendency for that mucosal lining to be thinner. There is a tendency for that mucosal lining to not be as robust in general when I say robust mean is that if you're mouth breathing, for instance, in a cold, dry environment, i'm thinking um from the time I spent in cambridge masaccio in winter at the t station.

You know, you're i'm just imaging myself because I was so down called back there. No breathing through your mouth. You are having fun for a run and your mouth is uncovered.

Or even if you're deliberately nasal breathing, you are drawing out your nasal passages and making them more acceptable to infections. Does that necessarily mean that every time you go out in cold, dry air that you're going to get an infection? No, of course, IT doesn't.

But to relate this back to the question we have before, there are a lot of data pointing to the fact that more humid and warm environments are going to make your mucosal lining and the general upper respiratory area more. I don't want to say immune because I don't want to conflict that word with the other meaning of immune. It's going to make IT more robust against bacterial and viral infections.

okay. So if you get into a cold shower or a cold plunge or a cold ocean or a cold lake and then you get out and you're out there shivering and shaking, trying to boost your metabolic, whatever is that you're doing IT for. And it's cold, dry air and especially if your mouth breathing in that cold, dry air.

Yes, I could see how that might lead to a higher probability of getting a cold or other type of infection, but there's nothing specific about the deliberate cold exposure itself that can induce a cold or other type of infection, assuming that the water is clean, right? We're not talking about bacteria infections of cuts on the skin at sea. We're talking about goals and other forms of being sick, namely upper respiratory infections.

Now with that said, I often get asked whether or not for people who already have a little sniff le, they're feeling a little run down or perhaps a lot run down should they do deliberate old exposure. I wants a little tRicky to give a one size fits all answer. But I think we can safely say that if you are feeling malaise, if you're feeling like you have to arrest, you're tired.

You're not feeling good because of a cold or because of a flu or because of a bacteria infection. okay. I'm not saying just feeling not good. I'm saying feeling not good due to a cold or other form of virus or bacterial infection, then I would say, stay out of deliberate cold exposure, don't use IT.

Now why would I say that, given the date we'll talk about in a few minutes, showing that regular deliberate cold exposure, if done correctly, can in fact increased immune system markers and perhaps even make you much more robust to combating different types of infection through the release of a drennen will talk about what all that looks like in a moment in terms of protocols in some of the science. But to just be very clear and very direct, if you're sick, stay out of deliberate cold exposure there, I would instead recommend warmer hot baths, warmer hot showers, the sona etta. But I also would caution that if you are getting into songs that are too hot, you know on as there are so hot that it's stressful for you.

And again, a lot of people use delivered heat exposure because of the stresses induces. They're doing some heat induce, for instance, heat shock proteins and different ways of increasing heart rate. That's a different sort of thing that's hard, stressful in order to generate an adaptation. I don't recommend doing that. In fact, I don't recommend doing deliberate cold exposure exercises or deliberate heat exposure.

If you're feeling really not well now, if you're feeling just a little bit not well, you're elling a little bit run down, a little bit of sniffle, a bit of malaise, well then it's kind of an egg case where we could say, all right, you know, I just take a hotch shower and go to sleep. That's probably the best advice, that good old fashion advice. But if you are determined to do your deliberate cold exposure anyway, then I would say, definitely get warm or take a hot shower afterward, a hot bath or hot sona, but not too hot.

That is stressful, of course. And keep in mind that one of the variables that been measured quite a lot in laboratories studies of deliberate cold exposure is the increase in immune system markers. So i'll provide a few links to some of these studies, although nowaday, there are many, many of them, but it's very clear that deliberate cold exposure can increase the release and the production of different immune molecules and immune ells.

One slightly older study, but none there's a good study that has relevance here is entitled immune system of cold exposed and called adapted humans. I keep in mind that this study is a little bit extreme and there are reasons for that um is to make a long story short often times in order to quote a sea and effect in a study, scientists will use conditions that are pretty extreme compared to control group. Often times they'll see a dose response to that's a little bit tRicky to do with a human studies of deliberate cold exposure can be done but not too common.

But here they used are pretty, what I would call extreme stimulus. IT was exposing people to fourteen degree south IaaS water. So that fifty seven point to degrees fair height, which is in that cold, is because, like, cool, I would say, very cool water, but not what you might consider cold, depending on how well you tolerate cold.

And that will very, of course, but they had people exposed to that for an hour, which is pretty long time. You know, most people I mentioned are using colder temperatures of deliberate cold exposure. So even.

High thirties, low forties, maybe upper forties for anywhere from one to ten minutes, depending on how conditions they are. And again, don't just jump into ten minutes of deliberate cold exposure please. Um at you know thirty five degrees or forty degrees or even forty five degrees, if you aren't familiar with deliberate cold exposure, you have to eased into these sorts of things over time.

And if you're interested in protocols for deliberate cold exposure, we have a zero cost newsletter that your woman lapt outcome. Go to the menu, go newsletter and you can find that we've done several episodes on deliberate cold exposure. In any event, this study, immune system of called exposing, called adapted humans, as I mention, had people in fourteen degrees sales as water for one hour. And basically what they found is that one exposure to code did not change immune stem function in any kind of a significant way.

However, what they found was if people did deliberate cold exposure repeatedly over a period of about six weeks and by repeatedly, I mean, three times per week, but they found where trends, and again, trends are not statistically significant, but trends towards increases in plastic concentrations of things like I L six influent sex or total numbers of t emphasize, and t helper cells, tea suppress our cells and activated t and b emphasize. These are all immune cells and immune molecules that roughly core respond to an increase in immune system function. If you like to learn more about the immune system, I did an episode on immune system function again.

You can find that that he room lab ed a command IT spells out the basic cell types of what's called the innate and the adapt of immune system. This study, which we will link to in the shown of captions, is but one study of several other studies showing the deliberate cold exposure can increase immune system markers, especially when deliberate cold exposure is done repeatedly over time. So in this case, three times a week over a period of six weeks.

But again, I want to highlight, these aren't highly significant effects. These are trends in the direction of increased numbers of immune ells and immune kers. Now what's impossible to know is how those change translate to actual resistance to specific concentrations of, say, cold virus or flu virus or any other virus or bacteria. That would be great, but that's a very difficult study to do, especially in the context of deliberate cold exposure as well.

Now we can all be scientists about this and say, what is IT about deliberate cold exposure that would increase immune system function? And there we can confidently say the molecules, epiphone and nor epa effort, which are released in both in and body in response to cold water exposure, as well as things like deliberate hyperventilation, the release of north, an african, an effort into the brain body, is known to have a number of different effects made to the immune system. IT can be pro immune, at least in the short term and in the long term, meaning if, or Jenny and Jenny again, those are just different names for np and ef and f and F N.

I'm sorry, those are the same thing, but that's why I use them interchangeably so that you don't get confused. If you see nor journal or nor appan afra the same thing, you hear em, f or journal same thing. Deliberate old exposure or deliberate hiper ventilation will increase those molecules, euan effort and epinephrine, and their increase is pro immune that can trigger the activation of immune cells and immune molecules that can make you more resistance to certain forms of infection.

However, if north pf an ef an are elevated chronically, and especially if they are elevated late in the day, repeatedly over many, many days, that can cause reductions in the number and efficiency of immune cells in combating infections. So getting cold in this context of whether or not you can get sick from IT should really be considered more as what happens when you Spike your journal in the north and american. And there's one other study that we can look to, which is not really a famous study, publishing purses in the national academy of sciences, looking at so called wim hop breathing.

But really, that just translates to sick c hyperventilation. So this is inhaling through the nose and selling through the mouths repeatedly twenty five times or so. If you do that, you know, you feel quite warm to do with some things really to visit illative as things to do with released in north ef and up and effort.

We know that pattern of deliberate hydroid ventilation, much like deliberate old exposure, deploys a releases nor journey, and a journey into your brain and body. And we know from the study, entitled voluntary activation of the sympathetic nervous system in of the nata mn response in humans, showed really nicely. I think that if people are injected with equi, right, a bacteria, actually, and they did this through and talks and injections, people get really sick, get you feel like they had the flu, they ve vomit diary, get a fever at seta.

However, if they did the sorts of breathing that I talk about just a moment ago, prior to that, they were able to ward off a lot of the symptoms, associate with the end talks and infection, and you would say, okay, wow, their immense system just fired up and they were able to fight IT off. But it's tRicky than that. Actually, what happened was the release of een effort and nor upon effort from a stickle kype ventilation, which is really what really is prevention also with breathing, also got two more of a thing at a that actually had a suppressive action on certain arms of the immune system in a way that allowed people to avoid symptoms ology such as fever, naja, eeta.

And we would imagine the same thing would occur with deliberate cold exposure done prior to bacteria infection or viral exposure. So if you're sensing that, i'm saying two things at once, I am. I'm saying deliberate cold exposure and cyclical APP ventilation can both cause deployment of molecules such as happen after an and nor up an effort that lead to enhance immune system function.

Have done repeatedly. I'm also saying that increasing no rap and f an, f an, f an too much can suppress your immune system. In this study, the pn study that mention a moment ago that suppression of the immune response was actually one of the reasons people avoided symptomatic, but they were still injected with toxin, so they just weren't fighting off the end toxin with fever.

Remember, fever is an adaptation to fight. Infection is designed essentially to heat up the infection and kill IT. So what are we to take away from this? Here are what I think are the key takeaway.

One, if you are feeling good to great, do you deliberate cold exposure? And perhaps don't worry so much about using your body's natural metabolism and thermogenesis ilium to heat back up afterwards, but I don't suggest anyone ever allow themselves to say really cold after deliberate cold exposure for more than ten, fifteen minutes or maybe half an hour, right? Get bungled back up or put on close if it's a nice hot, Sunny day, get out in the sun and warm up again.

Temperatures and conditions will vary for different people, different locations. At SATA, if you are not feeling greatly, feeling a little run down and you really want to do your deliberate cold exposure, do IT, but then warm up really well afterwards, maybe even drink some hot tea, other flew at afterwards as well. And if you are not feeling good, you're feeling malaise, you're feeling run down despite what you read about deliberate cold exposure or cyclical cup of ventilation, allowing for the deployment ment of immune molecules are increasing the number of immune cells that you're making.

Avoid anything that stressful or chAllenging, whether it's a cold chAllenge, a heat chAllenge or an exercise chAllenge when you're feeling run down. Because under those conditions, what you really want to do is slow your circulation down, probably find to take walks or something, probably not doubled over in bed, dominating and things like that, know a little bit movement, probably good to circulate your blood. But in general, the advice that you get to rest when you're sick and not push yourself, that's really good advice, because you want all of your body's resources to be devoted to getting over that infection.

And if you're interested in sickness and sickness behavior and the sorts of behaviors that can combat infection, and check out the episode did on the immune system will linked to in the show, no captions because he talks about how when we have a viral or bacterial infection, a whole set of brain circuits ts get activated that encourage us to be more in the federal position, to move less, to be eyes down, to kind of, you know, slum down. That's not a coincidence. That's because of the activation of these so called sickness circuits that I really designed to help you heal yourself.

So I both apologize. And what are the kids say? Sorry, not sorry. Don't apologize for the somewhat nuanced answer here because a lot of information out there says, oh, you know, called boost your immune system and yeah, that's true.

Under certain conditions, IT can also deplete your immune system and limit your ability to fight off infections under other conditions. And perhaps the last thing to say about this is that I am a big believer in using nasal breathing whenever you don't have to break through your mouth. So if you're exercising hard, by all means breakthrough your mouth.

If you doing martial arts and IT requires that you break your mouth, go, hadn't do that. But if you're doing a zone to cardio, low level cardio or you're just walking along, it's very clear based on a growing amount of data that being a nazzal breather is Better than being a mouths breather. And there are number different reasons for that we've talked about on the podcast and elsewhere.

But one of the additional reasons is a main side of entry for infections is through the mouth. So keep that mouth shut unless you need to talk. Thank you for joining for the beginning of this asked me anything episode to hear the full episode and to hear future episodes of these.

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