Welcome to the huberman live podcast where we discuss science and science based tools for everyday life. I'm Andrew huberman. And I'm a professor of neurobiology and Ophthalmology at Stanford school of medicine. Today is an ask me, anything episode or AMA. This is
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hear the first 20 minutes of today's episode and determine whether or not becoming a premium subscriber is for you. Without further Ado, 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 and I suppose a related question is, should you even do
deliberate, cold exposure? If you have a sniffle, a cold or a flu? I get that question all the time as well.
So I'll
answer both of those questions. And I will also touch on some of the Munich enhancing
effects of deliberate cold exposure.
But just to make sure that we answer the specific question asked here right 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 that are really pushing it, 10 minutes of deliberate, cold exposure and most often after doing that. Deliberate cold,
exposure. People are either getting closed or they're getting into a sauna, or
they're taking a hot shower and then getting clothes and heading off into their day or off to sleep,
depending on what time of day or night. You happen to do your deliberate cold exposure.
We can safely say that, if you warm up, after a relatively brief meeting,
A minute to, Let's extend it out to 10 minutes, 10 minutes, deliberate, cold exposure, although I really want to
caution people to not do 10-minute. Deliberate cold exposure right off the bat. If you are
somebody who is not accustomed to it, don't jump
right up to that long. Exposure to cold water, start with shorter exposures,
but if you're doing that one to ten minute deliberate, cold exposure, and then you're getting warm afterwards and heading about your day, I can't see how the deliberate cold, exposure itself would enhance your susceptibility to getting
That said we know from an enormous number of studies that have looked at cold virus transmission and other forms of viral and bacterial transmission that the environment that you happen to be in does
impact your susceptibility to colds and other types of viruses and to bacterial infections in the following way, there have
been controlled studies in which people go into, Laboratories was Laboratories have rooms, which they can very tightly control, the humidity.
Aditi. So essentially the 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 and kind of bullet point fashion. First off, cold dry, air does seem to increase our susceptibility to viral and bacterial infections, because whether or not you're a mouth-breather or nose breather. And by the way, I suggest everyone be a nose breather. Unless you're exercising hard enough, that you have to breathe through your mouth or you're talking or
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 and bacterial infections. In fact, one
of the ways you are constantly fighting off
bacterial and viral infections that you're exposed
to all the time is, by way of those viruses and bacteria getting trapped in the mucus
lining of your nose, or your mouth, most notably in the back 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. What I mean, is that, if your mouth breathing, for instance, in a cold
dry environment? I'm thinking from the time I spent in Cambridge Massachusetts in winter at the
T Station, you know, if
you're just imagining myself because it was so darn, cold back there. You know, breathing through your mouth or having gotten for a run
and your mouth isn't covered or even if you're deliberately nasal.
You think you are drying out your nasal
passages and making them more susceptible 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 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 conflate 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 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 metabolism or whatever it 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 bacterial infections of cuts on the skin at cetera. We're talking about colds and other forms of being sick. Namely upper respiratory infections
right now. With that said, I often get asked whether or not for people who already have a little sniffle, they're feeling a little rundown or perhaps a lot.
Run down. Should they do deliberate cold exposure? He 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 rest, you're tired. You're not feeling good because of a
cold or because of a flu or because of a
bacterial infection, okay? Now 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 data I'll talk about in a few minutes showing that regular deliberate cold exposure, if done correctly can, in fact,
increase immune system markers, and perhaps, even make you much more robust to combating different types of infection through the release of adrenaline will talk about what all that looks like in a moment in terms of protocols and 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 warm, or hot baths, warm, or hot showers
the sauna Etc. But I also would caution that if you are getting into saunas,
that are too hot. You know, it's honors. There are so hot that it's stressful for you. And again, a lot of people use deliberate heat exposure because of the stress that induces. They're doing some heat-induced. 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
And doing that. In fact, I don't recommend doing deliberate cold exposure exercise or deliberate heat exposure if you're
feeling really not well. Now, if
you're feeling just a little bit, not well you're feeling a little bit rundown, little bit of sniffle, little bit of malaise. Well then it's kind of an edge case where we could say. All right, you know what, just take a hot shower and go to sleep, that's probably the best
advice, right? 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 afterwards, hot bath or hot sauna, but not too hot that it's stressful, of course
and keep in mind that one of the variables that's been
measured quite a lot in laboratory 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 nowadays 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 cells.
One slightly older study, but nonetheless a good study that has relevance here is entitled immune system of cold exposed and cold-adapted humans. Keep in mind that this study is a little bit extreme and there are reasons for
that. I guess to make a long story short,
oftentimes in order to quote unquote, see an effect in a study, scientists will use conditions that are pretty extreme compared to
control group. Oftentimes, you'll see a dose response
to, but it's a little bit trickier to do with human studies of
Burt cold exposure can be done but not too common but here they used a pretty what I would call Extreme stimulus. It was exposing people to 14 degrees Celsius water. So that's 57.2 degrees Fahrenheit. Which isn't that cold? It sounds 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 vary of course.
But they had people exposed to
that for an hour, which is a pretty long time. Most people, as I mentioned are using colder temperatures of deliberate called exposure, so,
You know, high 30s, low 40s, maybe upper 40s for anywhere from 1 to 10 minutes, depending on how condition they are.
And again don't just jump into ten minutes of
deliberate cold exposure, please at, you know, 35 degrees or 40 degrees or even 45 degrees. If you aren't familiar with deliberate cold exposure, you have to ease into these sorts of things over time. And if you're interested in protocols for deliberate cold exposure, we have a zero cost newsletter at your room in laptop cam. 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 cold exposing cold-adapted humans. As I mentioned at people in 14 degrees Celsius water for 1 hour and basically what they found is that one exposure to cold did not change immune
system function in any kind of 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,
what they found were
Then again, Trends are not statistically significant, but Trends towards increases in plasma concentrations of
things like il-6 interleukin 6
or total numbers of T lymphocytes and T helper cells and T suppressor cells and activated T and B lymphocytes. These are all immune cells and immune molecules that roughly correspond to an increase in immune system function if
you'd like to learn more about the immune system, I did an episode on immune system function again. You can find that at huberman labs.com and it spells out the basic cell types
Of What's called the innate and the Adaptive immune system,
this study, which we will link to in the show. No captions is, but one study of several other studies showing that deliberate cold exposure can increase immune system markers. Especially when delivered 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 cells and immune markers. Now what's impossible to know
is how those Trends 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 epinephrine and norepinephrine which are released in
both brain and body, and response to cold water exposure as well.
As things like deliberate hyperventilation,
the release of norepinephrine and epinephrine into the brain, and body is known to have a number of different effects
related to. The immune system, it can be
Pro immune at least in the short term and in the long term meaning if noradrenaline. And adrenaline again, those are just
different names where norepinephrine and epinephrine. 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 noradrenaline or
norepinephrine is
the same thing you hear.
Lenore Drennan. Same thing.
Deliberate cold, exposure, or deliberate. Hyperventilation will increase those molecules
norepinephrine and
epinephrine and their increase is pro immune. It can
trigger the activation of immune cells and immune molecules that can make you more resistant to certain forms of
infection. However if norepinephrine and epinephrine are elevated chronically and especially if they are elevated late in the day, repeatedly over many many days.
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 adrenaline and norepinephrine and
there's one other study that we can look to which is now really a famous study published in proceedings of the National Academy of Sciences, looking at so-called Wim Hof breathing but really, that just translates to cyclic
hyperventilation. So this is inhaling through the nose, exhaling through the
Out repeatedly, 25 times. Or so, if you do that, you know what, you feel, quite warm. It's to do with some things really do. Vasodilation has some things to do with release of norepinephrine and epinephrine. We know
that pattern of deliberate hyperventilation much like deliberate cold exposure deploys or releases noradrenaline and adrenaline into your brain and body. And we know from this study entitled voluntary activation of the sympathetic nervous system and attenuation of the Nate immune response in humans showed really nice.
Nicely. I think that if people are injected with E coli,
right a bacteria, it's actually, and they did this through endotoxin injections, people got really sick. They get, you know, feel like they had the
flu, they vomit diarrhea, get a fever Etc. However, if they did the sorts of breathing that I talked about, just a moment ago prior to that, they were able to ward off a
lot of the symptoms associated with the endotoxin infection and you would say, okay wow, their immune system just fired up.
They were able to fight it
off but it's trickier than that. Actually what happened was the release of epinephrine and norepinephrine from
cyclic hyperventilation which is really what
really is cyclic hyperventilation also call with cough breathing also called to mow breathing Etc. That actually had a suppressive
action on certain arms
of the immune system in a way that allowed people to avoid
symptomology such as fever. Nausea Etc.
And we would imagine the same thing.
NG would
occur with deliberate cold, exposure, done prior to bacterial 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 cyclic hyperventilation can both cause deployment of molecules such as epinephrine and norepinephrine that lead to enhanced immune system function if done repeatedly. I'm also saying that increasing norepinephrine and epinephrine too much can suppress your immune system.
This study, the pnas study that I mentioned a moment ago that suppression of the immune response was actually one of the reasons people avoided symptomology but they were still injected with endotoxins, they just weren't fighting off
the end of 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. Takeaways
one, if you are feeling good to Great, do your deliberate cold exposure? And perhaps don't worry so much
So much about using your body's natural metabolism
and thermogenic abilities to heat back up afterwards.
But I don't suggest anyone ever allow themselves to stay really cold.
After deliberate cold exposure for more than 10-15 minutes or maybe half an hour,
right? Get bundled back up or put on clothes. If it's a nice hot sunny day, get out in the sun and warm
up, getting temperatures, and conditions will vary for different people. Different locations, Etc.
If you are not feeling greatly feeling a little rundown and you really want to do your deliberate cold exposure, do it, but then, warm up really well
afterwards maybe even drink some, you know, hot tea or other fluid 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 cyclic hyperventilation
allowing for the deployment of
immune, molecules, or increasing the number of immune cells that you're making
avoid anything.
That's stressful or challenging, whether or not, 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 it. Take a little walks or something provide you're not doubled over in bed and vomiting and things like that. You know,
little bit of 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, check out the episode I did on the immune system will link to it in the show, no captions. Because it talks about how when we have a viral or bacterial infection, a whole set of brain circuits get activated, that kind of encouraged us to be more in the fetal position to move last to be eyes down to kind of, you know, slump down. That's not a coincidence. That's because of the activation of these so-called sickness circuits that are really designed to help.
Heal yourself. So I both apologized
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, cold 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 breathe through your mouth. So
if you're exercising hard by all means, breathe through your mouth. If you do martial arts and it requires that you breathe through your mouth, go ahead and do that. But if
you're doing say Zone to cardio, low-level cardio or you just walking along, it's very clear based on a growing
amount of data. That being a nasal breather is better than being a mouth breather. And there are a number of 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.
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