Full Transcript: How to Prevent & Treat Colds & Flu
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0:00 ANDREW HUBERMAN: Welcome to the Huberman Lab podcast
0:02 where we discuss science and science-based tools
0:04 for everyday life.
0:05 [MUSIC PLAYING]
0:09 I'm Andrew Huberman, and I'm a professor
0:11 of neurobiology and ophthalmology
0:13 at Stanford School of Medicine.
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1:42 Without further ado, let's get to answering your questions.
1:45 The first question asks, is it possible to get a cold
1:48 or to get sick from deliberate cold exposure?
1:51 And I suppose a related question is, should you even
1:53 do deliberate, cold exposure if you have
1:56 a sniffle, a cold, or a flu?
1:58 I get that question all the time as well.
2:00 So answer both of those questions.
2:01 And I will also touch on some of the immune enhancing effects
2:05 of deliberate cold exposure.
2:06 But just to make sure that we answer
2:08 the specific question asked here right off the bat,
2:11 is it possible to get a cold or to get sick from deliberate
2:15 cold exposure?
2:16 Well, assuming that you're not doing
2:17 the deliberate cold exposure for more than,
2:20 say five or six minutes at one stretch,
2:24 probably not directly from the deliberate cold exposure.
2:28 I mention that because most people
2:30 are doing anywhere from about a minute
2:32 to three minutes, sometimes five or six minutes.
2:34 And maybe for those of you that are really
2:36 pushing it, 10 minutes of deliberate cold exposure.
2:39 And most often after doing that deliberate cold exposure,
2:41 people are either getting clothed,
2:43 or they're getting into a sauna, or they're taking a hot shower,
2:46 and then getting clothed and heading off into their day
2:49 or off to sleep depending on what time of day or night
2:51 you happen to do your deliberate cold exposure.
2:54 We can safely say that if you warm up
2:56 after a relatively brief, meaning one minute to,
2:59 let's extend out to 10 minutes, 10-minute deliberate
3:01 cold exposure, although, I really
3:03 want to caution people to not do 10-minute deliberate
3:05 cold exposure right off the bat.
3:06 If you are somebody who is not accustomed to it,
3:09 don't jump right up to that long exposure to cold water.
3:13 Start with shorter exposures.
3:16 But if you're doing that one-to-10-minute deliberate,
3:18 cold exposure, and then you're getting warm afterwards
3:20 and heading about your day, I can't see how the deliberate
3:23 cold exposure itself would enhance your susceptibility
3:27 to getting sick.
3:29 That said, we know from an enormous number
3:32 of studies that have looked at cold virus transmission
3:35 and other forms of viral and bacterial transmission
3:38 that the environment that you happen to be in
3:41 does impact your susceptibility to colds
3:44 and other types of viruses and to bacterial infections
3:48 in the following way.
3:50 There have been controlled studies in which people
3:52 go into laboratories.
3:54 Those laboratories have rooms, which they can very tightly
3:57 control the humidity, so essentially,
3:59 the water content in the air, as well
4:02 as the temperature in the room.
4:04 And if you look at the total mass of those data,
4:07 we can say a couple of specific things
4:09 in kind of bullet point fashion.
4:11 First off, cold, dry air does seem
4:14 to increase our susceptibility to
4:17 viral and bacterial infections.
4:18 Because whether or not you're a mouth breather or a nose
4:21 breather, and by the way, I suggest everyone be a nose
4:24 breather unless you're exercising hard enough that you
4:26 have to breathe through your mouth,
4:28 or you're talking or something of that sort.
4:30 But if you're a nose breather or a mouth breather or both,
4:34 viruses and bacteria enter through your nose and mouth,
4:38 sometimes through your eyes, but your nose and mouth
4:40 are going to be the main sites of entry
4:42 and your main barriers to viral and bacterial infections.
4:45 In fact, one of the ways you are constantly fighting off
4:48 bacterial and viral infections that you're
4:49 exposed to all the time is by way
4:53 of those viruses and bacteria getting
4:55 trapped in the mucous lining of your nose
4:57 or your mouth, most notably in the back of your throat.
5:01 So if you spend time in cold, dry environments,
5:05 there is a tendency for that mucosal lining to be thinner.
5:08 There is a tendency for that mucosal lining
5:10 to not be as robust in general.
5:12 And when I say robust, what I mean
5:14 is that if your mouth breathing, for instance
5:16 in a cold, dry environment, I'm thinking from the time
5:19 I spent in Cambridge, Massachusetts in winter
5:21 at the T station.
5:23 If you're I'm just imagining myself
5:24 because it was so darn cold back there breathing
5:27 through your mouth or having gone for a run,
5:30 and your mouth isn't covered, or even if you're deliberately
5:33 nasal breathing, you are drying out your nasal passages
5:36 and making them more susceptible to infections.
5:39 Does that necessarily mean that every time you
5:41 go out in cold, dry air that you're
5:43 going to get an infection?
5:44 No, of course it doesn't.
5:45 But to relate this back to the question we have before,
5:49 there are a lot of data pointing to the fact that more humid,
5:52 warm environments are going to make your mucosal lining
5:56 and the general upper respiratory area more,
6:00 I don't want to say immune because I
6:01 don't want to conflate that word with the other meaning
6:03 of immune.
6:03 It's going to make it more robust against
6:07 bacterial and viral infections.
6:10 So if you get into a cold shower or a cold plunge
6:14 or a cold ocean or a cold lake, and then you get out,
6:17 and you're out there shivering and shaking, trying
6:20 to boost your metabolism or whatever
6:22 it is that you're doing it for, and it's
6:24 cold, dry air, and especially if your mouth
6:27 breathing in that cold, dry air, yes, I
6:29 could see how that might lead to a higher
6:32 probability of getting a cold or other type of infection.
6:35 But there's nothing specific about the deliberate, cold
6:38 exposure itself that can induce a cold or other type
6:43 of infection assuming that the water is clean, right?
6:45 We're not talking about bacterial infections
6:47 of cuts on the skin, et cetera.
6:48 We're talking about colds and other forms of being sick,
6:51 namely upper respiratory infections.
6:54 OK, now with that said, I often get asked whether or not
6:58 for people who already have a little sniffle,
7:01 they're feeling a little run down or perhaps a lot run down,
7:04 should they do deliberate cold exposure?
7:06 And what's a little tricky to give a one size fits all
7:09 answer, , but I think we can safely say that if you are
7:13 feeling malaise, if you're feeling like you have to rest
7:16 you're tired, you're not feeling good because of a cold
7:20 or because of a flu or because of a bacterial infection, now,
7:24 I'm not saying just feeling not good,
7:26 I'm saying feeling not good due to a cold or other form
7:30 of virus or bacterial infection, then I would say stay out
7:33 of deliberate, cold exposure.
7:35 Don't use it.
7:36 Now, why would I say that?
7:37 Given the data I'll talk about in a few minutes showing
7:39 that regular deliberate cold exposure if done correctly,
7:43 can in fact increase immune system markers
7:46 and perhaps even make you much more robust to combating
7:49 different types of infection through the release
7:51 of adrenaline.
7:52 We'll talk about what all that looks like
7:54 in a moment in terms of protocols
7:55 and some of the science.
7:56 But to just be very clear and very direct, if you're sick,
8:00 stay out of deliberate cold exposure.
8:03 There, I, would instead recommend
8:05 warmer hot baths warmer hot showers, the sauna, et cetera.
8:09 But I also would caution that if you are getting into saunas
8:13 that are too hot, saunas they're so
8:15 hot that it's stressful for you, and again, a lot of people
8:18 use deliberate heat exposure because of the stress
8:20 it induces, they're doing some heat induced,
8:22 for instance, heat shock proteins and different ways
8:25 of increasing heart rate.
8:26 That's a different sort of thing.
8:28 That's hard, stressful in order to generate an adaptation.
8:33 I don't recommend doing that.
8:34 In fact, I don't recommend doing deliberate cold exposure,
8:37 exercise, or deliberate heat exposure if you're
8:39 feeling really not well.
8:41 Now, if you're feeling just a little bit not well,
8:43 you're feeling a little bit rundown, a little bit
8:46 of sniffle, a little bit of malaise, well then,
8:49 it's kind of an edge case where we could
8:50 say, all right you know what?
8:52 Just take a hot shower and go to sleep.
8:53 That's probably the best advice, that good old-fashioned advice.
8:57 But if you are determined to do your deliberate cold exposure
9:00 anyway, then I would say definitely get warm
9:03 or take a hot shower afterwards, hot bath, or hot sauna,
9:07 but, not too hot that it's stressful, of course.
9:09 And keep in mind that one of the variables that's
9:11 been measured quite a lot in laboratory
9:13 studies of deliberate cold exposure
9:14 is the increase in immune system markers.
9:16 So I'll provide a few links to some of these studies.
9:20 Although, nowadays there are many, many of them.
9:23 But it's very clear that deliberate cold exposure
9:27 can increase the release and the production
9:31 of different immune molecules and immune cells.
9:34 One slightly older study, but nonetheless a good study
9:37 that has relevance here is entitled
9:39 "Immune system of cold exposed and cold adapted humans."
9:43 Keep in mind that this study is a little bit extreme.
9:46 And there are reasons for that.
9:48 I guess to make a long story short, oftentimes,
9:50 in order to quote unquote "see an effect in a study,"
9:54 scientists will use conditions that are pretty extreme
9:57 compared to control group.
9:58 Oftentimes, you'll see a dose response to,
10:00 but it's a little bit trickier to do with human studies
10:03 of deliberate, cold exposure.
10:04 It can be done, but not too common.
10:06 But here, they used a pretty what
10:07 I would call extreme stimulus.
10:09 It was exposing people to 14 degrees Celsius water,
10:12 so that's 57.2 degrees Fahrenheit,
10:16 which isn't that cold.
10:17 It's like cool, I would say very cool water,
10:19 but not what you might consider cold depending
10:22 on how well you tolerate cold.
10:23 And that will vary, of course.
10:24 But they had people exposed to that for an hour, which
10:27 is a pretty long time.
10:29 Most people, as I mentioned, are using colder temperatures
10:32 of deliberate cold exposure, so even high 30s,
10:35 low 40s, maybe upper 40s for anywhere
10:39 from one to 10 minutes, depending
10:40 on how conditioned they are.
10:42 And again, don't just jump into 10 minutes of deliberate, cold
10:45 exposure, please at 35 degrees or 40 degrees
10:49 or even 45 degrees if you aren't familiar with deliberate cold
10:52 exposure.
10:52 You have to ease into these sorts of things over time.
10:55 And if you're interested in protocols
10:56 for deliberate cold exposure, we have a zero-cost newsletter
10:59 at hubermanlab.com.
11:00 Go to the Menu, go to Newsletter,
11:01 and you can find that.
11:02 We've done several episodes on deliberate cold exposure.
11:06 In any event, this study, "Immune system of cold exposing
11:09 cold adapted humans," as I mentioned,
11:11 had people in 14 degrees Celsius water for one hour.
11:14 And basically what they found is that one exposure to cold
11:17 did not change immune system function
11:20 in any kind of significant way.
11:21 However, what they found was if people did deliver
11:25 cold exposure repeatedly over a period of about six weeks,
11:29 and by repeatedly, I mean three times per week, what they found
11:32 were trends.
11:33 And again, trends are not statistically significant,
11:37 but trends towards increases in plasma concentrations of things
11:41 like IL 6, interleukin 6 or total numbers of T lymphocytes
11:45 and T helper cells and T suppressor cells
11:48 and activated T and B lymphocytes,
11:49 these are all immune cells and immune molecules
11:52 that roughly correspond to an increase in immune system
11:56 function.
11:56 If you'd like to learn more about the immune system,
11:58 I did an episode on immune system function.
12:00 Again, you can find that at hubermanlab.com.
12:02 And it spells out the basic cell types
12:03 of what's called the innate and the adaptive immune system.
12:06 This study, which we will link to in the show note captions
12:08 is but one study of several other studies showing
12:11 that deliberate cold exposure can increase immune system
12:14 markers, especially when deliberate cold exposure is
12:16 done repeatedly over time, so in this case, three times
12:19 a week over a period of six weeks.
12:20 But again, I want to highlight these aren't
12:22 highly significant effects.
12:24 These are trends in the direction
12:25 of increased numbers of immune cells and immune markers.
12:28 Now, what's impossible to know is
12:30 how those trends translate to actual resistance
12:34 to specific concentrations of, say cold virus or flu virus
12:37 or any other virus or bacteria.
12:39 That would be great, but that's a very difficult study
12:42 to do, especially in the context of deliberate cold exposure
12:44 as well.
12:45 Now, we can all be scientists about this and say, what is it
12:50 about deliberate cold exposure that would increase
12:52 immune system function?
12:54 And there, we can confidently say the molecules
12:57 epinephrine and norepinephrine, which
12:58 are released in both brain and body in response to cold water
13:02 exposure, as well as things like deliberate hyperventilation,
13:06 the release of norepinephrine and epinephrine into the brain
13:09 and body is known to have a number of different effects
13:12 related to the immune system.
13:14 It can be pro-immune, at least in the short term.
13:17 And in the long term, meaning if noradrenaline and adrenaline,
13:21 again those are just different names for norepinephrine
13:24 and epinephrine.
13:24 I'm sorry, those are the same thing,
13:26 but that's why I use them interchangeably so
13:28 that you don't get confused.
13:29 If you see noradrenaline or norepinephrine,
13:31 that's the same thing you hear, epinephrine or adrenaline,
13:34 same thing.
13:36 Deliberate cold exposure or deliberate hyperventilation
13:38 will increase those molecules, norepinephrine and epinephrine.
13:43 And their increase is pro-immune.
13:46 It can trigger the activation of immune cells
13:50 and immune molecules that can make
13:51 you more resistant to certain forms of infection.
13:54 However, if norepinephrine and epinephrine
13:57 are elevated chronically, and especially
13:59 if they are elevated late in the day repeatedly
14:02 over many, many days, that can cause reductions
14:06 in the number and efficiency of immune cells
14:09 in combating infections.
14:10 So getting cold in this context of
14:12 whether or not you can get sick from it
14:14 should really be considered more as
14:15 what happens when you spike your adrenaline and norepinephrine?
14:19 And there's one other study that we can look to,
14:21 which is now really a famous study published in proceedings
14:24 of the National Academy of Sciences
14:26 looking at so-called Wim Hof breathing.
14:28 But really, that just translates to cyclic hyperventilation.
14:31 So this is inhaling through nose,
14:33 exhaling through the mouth repeatedly 25 times or so.
14:36 [BREATHING]
14:38 If you do that, you notice you feel quite warm,
14:41 lots to do with some things relate to vasodilation,
14:43 has some things to do with release of norepinephrine.
14:46 And epinephrine, we know that pattern
14:47 of deliberate hyperventilation, much like deliberate
14:49 cold exposure, deploys or releases
14:52 noradrenaline and adrenaline into your brain and body.
14:55 And we know from this study entitled
14:57 "Voluntary activation of the sympathetic nervous system
14:59 and attenuation of the innate immune response in humans"
15:02 showed really nicely, I think.
15:04 That if people are injected with E. coli, a bacteria
15:09 it's actually an end-- they did this
15:11 through endotoxin injections.
15:12 People got really sick.
15:13 They'd get feel like they had the flu,
15:16 they vomit, diarrhea, get a fever, et cetera.
15:19 However if they did the sorts of breathing
15:21 that I talked about just a moment ago, prior to that,
15:24 they were able to ward off a lot of the symptoms associated
15:29 with the endotoxin infection.
15:31 And you would say, OK wow, their immune system just fired up,
15:33 and they were able to fight it off.
15:34 But it's trickier than that, actually.
15:36 What happened was the release of epinephrine
15:39 and norepinephrine from cyclic hyperventilation, which
15:41 is really what [BREATHING] really
15:44 is, cyclic hyperventilation, also called Wim Hof breathing,
15:47 also called tummo breathing, et cetera, that actually had
15:50 a suppressive action on certain arms of the immune system
15:55 in a way that allowed people to avoid symptomology
15:59 such as fever, nausea, et cetera.
16:01 And we would imagine the same thing would
16:03 occur with deliberate cold exposure done
16:06 prior to bacterial infection or viral exposure.
16:10 So if you're sensing that I'm saying two things at once,
16:13 I am.
16:14 I'm saying deliberate cold exposure,
16:16 and cyclic hyperventilation can both cause deployment
16:19 of molecules such as epinephrine and norepinephrine
16:23 that lead to enhanced immune system
16:24 function if done repeatedly.
16:26 I'm also saying that increasing norepinephrine and epinephrine
16:29 too much can suppress your immune system.
16:33 In this study, the PNAS study that I mentioned a moment ago,
16:36 that suppression of the immune response
16:38 was actually one of the reasons people avoided symptomology.
16:40 But they were still injected with endotoxin,
16:42 so they just weren't fighting off the endotoxin with fever.
16:45 Remember, fever is an adaptation to fight infection.
16:48 It's designed essentially to heat up the infection
16:51 and kill it.
16:52 So what are we to take away from this?
16:54 Here are what I think are the key takeaways.
16:57 One, if you are feeling good to great,
17:00 do your deliberate cold exposure.
17:02 And perhaps don't worry so much about using your body's
17:05 natural metabolism and thermogenic abilities
17:08 to heat back up afterwards.
17:10 But I don't suggest anyone ever allow themselves
17:13 to stay really cold after deliberate
17:15 cold exposure for more than 10, 15 minutes or maybe
17:19 half an hour, right?
17:20 Get bundled back up, or put on clothes.
17:22 If it's a nice hot, sunny day, get out in the sun and warm up.
17:25 Again, temperatures and conditions
17:27 will vary for different people, different locations, et cetera.
17:32 If you are not feeling great, you're
17:33 feeling a little rundown, and you really
17:35 want to do your deliberate cold exposure,
17:37 do it, but then warm up really well afterwards.
17:39 Maybe even drink some hot tea or other fluid afterwards as well.
17:44 And if you are not feeling good, you're feeling malaise,
17:46 you're feeling run down.
17:48 Despite what you read about deliberate,
17:51 cold exposure or cyclic hyperventilation,
17:54 allowing for the deployment of immune molecules
17:57 or increasing the number of immune cells
17:59 that you're making, avoid anything
18:01 that's stressful or challenging whether or not
18:05 it's a cold challenge, a heat challenge, or an exercise
18:08 challenge when you're feeling run down.
18:10 Because under those conditions, what you really want to do
18:12 is slow your circulation down, probably
18:14 find and take a little walks or something
18:15 provided you're not doubled over in bed and vomiting,
18:18 and things like that.
18:18 A little bit of movement, probably
18:20 good to circulate your blood.
18:21 But in general, the advice that you
18:23 get to rest when you're sick and not push yourself,
18:27 that's really good advice because you
18:28 want all of your body's resources
18:30 to be devoted to getting over that infection.
18:33 And if you're interested in sickness and sickness
18:36 behavior and the sorts of behaviors
18:38 that can combat infection, check out the episode
18:40 I did on the immune system.
18:41 We'll link to it in the show note captions.
18:43 Because it talks about how when we
18:44 have a viral or bacterial infection,
18:46 a whole set of brain circuits get
18:48 activated that encourage us to be more in the fetal position,
18:52 to move less, to be eyes down, to kind of slump down.
18:56 That's not a coincidence.
18:57 That's because of the activation of these so-called sickness
18:59 circuits that are really designed
19:01 to help you heal yourself.
19:02 So I both apologize, and what do the kids say?
19:07 Sorry, not sorry.
19:08 Don't apologize for the somewhat nuanced answer here.
19:12 Because a lot of information out there says,
19:14 oh, cold boosts your immune system.
19:16 And yeah, that's true under certain conditions.
19:18 It can also deplete your immune system
19:20 and limit your ability to fight off infections
19:23 under other conditions.
19:24 And perhaps the last thing to say about this
19:27 is that I am a big believer in using nasal breathing whenever
19:31 you don't have to breathe through your mouth.
19:33 So if you're exercising hard, by all means breathe
19:35 through your mouth.
19:35 If you're doing martial arts, and it
19:37 requires that you breathe through your mouth,
19:38 go ahead and do that.
19:40 But if you're doing, say a zone two cardio, low level
19:42 cardio, or you're just walking along,
19:44 it's very clear based on a growing amount of data
19:46 that being a nasal breather is better
19:48 than being a mouth breather.
19:49 And there are a number of different reasons
19:50 for that we've talked about on the podcast and elsewhere.
19:53 But one of the additional reasons is a main site of entry
19:56 for infections is through the mouth.
19:58 So keep that mouth shut unless you need to talk.
20:02 Thank you for joining for the beginning of this
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