ANDREW HUBERMAN: Welcome
to the Huberman Lab podcast where we discuss science
and science-based tools for everyday life. [MUSIC PLAYING] 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 part of our
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becoming a premium subscriber is for you. So without further
ado, let's get to answering your questions. The first question is
about colds and flus. And the question
specifically is, why is it that we get more colds
and flus in the winter months? Is it the temperature outside? Is it the fact that people are
spending more time indoors? Or is it a myth that we get more
colds and flus in the winter months? Well, the first thing is that
the research very clearly shows that in winter
months there is a greater prevalence of colds and flus. Now, of course, the words,
"in the winter months" means many things. For instance, in most areas
of the world unless you live directly near the
equator, in the winter months means that days
are going to be shorter and nights are longer
than in the summer months. In general, that's true. It's of course,
especially true if you live very far from the equator. So imagine somebody living up
in Tromsø, Norway, which is very close to the North Pole. In winter, days are very,
very short in Tromsø. And conversely in
the summer months, days are very, very
long in Tromsø Norway. Now, Tromsø Norway represents an
extreme of day length variation according to time of year. The closer you get
to the equator, the less variation there is in
day length and therefore night length across the year. However, in most
locations on Earth, days will be significantly
shorter by about an hour or two at least for certain
parts of the year. And in general,
shorter days correlate with colder temperatures. That's what's really
important to know, which is that shorter days
generally correlate with colder temperatures regardless of where
you live on the planet Earth. OK. So in the winter months
as we're calling it, involves at least two things,
shorter days, which means what? It means less sunlight
and either more artificial light or more darkness depending
on how much artificial light you rely on. It also means, as we
mentioned, colder temperatures. Colder temperatures, of
course, doesn't necessarily mean that you are exposed
to those colder temperatures because what's the third thing? Shorter days and
colder temperatures outside mean that people are
spending more time indoors. So what the research
clearly shows is that one of the reasons,
not the only, but one of the reasons for the greater
prevalence of colds and flus in the short days a.k.a. winter months of the
year is that people are spending more time
indoors and therefore at closer proximity, which
raises a whole bunch of really interesting questions
that have been explored in the peer reviewed research
about proximity cold and flu transmission. There have been
studies for instance where people come into the
laboratory who are suffering from cold and flu and are
sneezing, having them sneeze at different proximity
to other people, obviously people are
doing this under consent. They're agreeing
to participate in these particular experiments. And there does seem to be
a very nice relationship between physical
distance between you, the uninfected person,
and the sneezing, coughing, nose
wiping, eye wiping, we'll get into why I
mentioned all of those things in a moment, person that
is suffering from the flu. In other words,
the closer you are to somebody who's
sneezing or coughing, the higher probability that you
will contract that cold or flu. OK. So we've already
established two things. First of all, physical
proximity is a key variable in terms of transmission
of cold and flu. And at some level that's a duh. I mean, if you think about
it, if you're in the next room or down the hallway from
or across the street from somebody with
a cold or flu, you don't expect to contract
that cold or flu from them. Whereas if you're
in the same vehicle with them or you're sitting
next to them on an airplane or you are on the same bus or
in the same classroom as them and they are sneezing
and coughing, well, then, the probability that
you would get that cold or flu from them is increased. That's just obvious. But the studies that have
explored the relationship between physical proximity and
transmission of cold and flu have actually analyzed things
down to the range of well, if you're standing
one foot apart or you're standing three
feet apart or six feet apart, what's the probability that you
will contract that cold or flu? And it follows a very
direct relationship where the closer the
proximity, the more likely that you're going
to contract the cold or flu from that person. And of course, anything like
exchange of skin contact or exchange of saliva
because obviously in cases of romantic relationships
where people will kiss or in familial relationships or
friendships where people hug, any contact also further
increases the transmission of cold and flu. Not just from stuff emitted
from the nasal passages and from the mouth when
people sneeze and cough, but also when people
wipe their eyes, even when people wipe their
skin because oftentimes they have cold or flu
virus on their skin. It doesn't always survive
terribly long on the skin. But if they wipe their
face or wipe their nose or are using tissues
and then don't wash their hands
thoroughly afterwards, indeed they can transmit
cold and flu simply through handshake. OK. So for all you
hypochondriacs out there, I'm arming you with a
lot of useful knowledge that will justify
staying away from people who perhaps have cold and flu. Now, this particular point
about proximity and people being indoors more
during the winter months, and that's why there's more
cold and flu transmission, raises a whole bunch of
interesting questions, and, in fact, protocols that I
plan to cover in a Huberman Lab podcast episode solely
devoted to colds and flus and how to avoid
getting colds and flus. But one brief mention
or telegraph of what I plan to cover
in that episode is that if people are telling
you that they are sneezing and coughing due to a cold or
flu but that they are quote unquote "not contagious"
either because they are early in the cold or flu
or late in the cold or flu and they have these theories
or claims that oh, I'm no longer contagious. Keep in mind that any time
someone is sneezing or coughing they are in fact contagious. So I'll get back to
that in that full length episode about colds and flus. But I felt it was
too important not to mention right now that
people's theories about when they are quote
unquote "contagious" or "not contagious" are
rarely substantiated by the actual data. The actual data
point to the fact that when people are
sneezing and coughing, if it's due to a cold or flu,
they are still contagious. OK. So we've established that
cold outside means people tend to be indoors more
which increases physical proximity, which
is one of the reasons why there's more cold
and flu transmission. One of the other reasons
why being indoors more tends to increase cold
and flu transmission is that in the cold months of
winter when people are indoors, they tend to be not
under air conditioning, not at neutral temperatures,
but rather they tend to be in heated rooms. And depending on
the type of heating that's used, but in general,
due to all forms of heating, the heated air tends
to be drier air. Now, this is a little
bit counterintuitive because if you ever go outside
on a really cold winter day, you will realize
that the cold weather outdoors is extremely dry. You can almost quote unquote
"feel the dryness of the air." And if you can't quote unquote
"feel the dryness of the air" or imagine what that's
like just imagine this, think of yourself outdoors
on a very cold winter day taking a brisk walk. Then think about yourself
taking that same brisk walk on a very humid summer day. Humidity is, of course,
the concentration of water in the ambient
environment, the air, whereas the dryness is
the lack of humidity. And just that little simple
GedankenNet or thought experiment will
remind you just how dry the cold air is out of
doors during the winter months. Whereas indoors we're
heating that air and indeed the heating
of that air does have the property of drying
the nasal and oral passages but especially the
nasal passages. So another key
reason why there's more transmission of colds
and flus in the winter months is because people are
spending more time indoors. And oftentimes the way
those indoor environments are being heated is drying
out the nasal passages. And the nasal passages
represent a primary site of defense for viral
infections like colds and flus but also bacterial infections
and fungal infections for that matter. Now, I've talked before on this
podcast about the importance of using nasal breathing
under any conditions where you don't have to breathe
through your mouth. So if you are not eating,
if you're not speaking, or if you're not exercising
hard which by the way oftentimes requires that you
breathe through your mouth. There's nothing wrong with
breathing through your mouth if you're exercising
hard and you need to breathe
through your mouth in order to bring
in enough oxygen. There are conditions under which
that's entirely appropriate. You can learn more about
that in the podcast episode I did all about breathing
and breath work. But for the most part it's
best to be a nasal breather except under the conditions
I just mentioned. Why? Well, the nasal passages contain
a number of physical barriers, including the hairs
within your nose. I know that hairs in
the nose, especially if they are super
numerous are not considered aesthetically nice. People will trim
them, et cetera. But those hairs in
your nose actually serve as a barrier
toward infection. This is well established. The lining of the nose, the
mucosal lining of the nose contains a lot of things. First of all, it acts as
its own physical barrier and physical trap for incoming
viruses, fungal infections, and bacterial infections. They literally get trapped
in the nasal passages. And therefore can't enter
deeper into your physiology. And right now is
not the time to go into the whole
anatomy and physiology of the nasal passages. But keep in mind if
you saw the episode that I did with Noam Sobel
or you listen to the episode that I did on olfaction,
both of those episodes highlight the fact that
your brain sits not far behind your nasal passages. There's a bony barrier there
called the cribriform plate, and there are some
other things as well, but it's not far from your
nostrils to your brain. And it is not far
from your nostrils to the rest of your
respiratory pathway, of course. And so the hairs of your
nostrils, the mucus itself, and the microbiome,
the trillions of little micro
bacteria that thrive in the mucosal lining of
your nasal passages actually serve to protect against many
of the incoming infections. This is why it's so
important to keep the mucosal lining of your nasal
passages thriving and intact. How do you do that? Well, one of the
best ways to do that is to make sure that the
air that you're breathing is sufficiently humidified. So while there are many
different claims out there about how to avoid
colds and flus, as long as we're having a
discussion about why there are more colds and flus
in the winter months because indeed there
are, it's worth mentioning that if you
suffer from colds and flus and you're going to
spend a lot of time in particular
indoor environment, you might be wise to find a
air humidifier, something that brings more moisture
into the air that you're breathing especially
at night while you're sleeping. Now, that's not going to prevent
the person in your environment who happens to
have a cold or flu and is sneezing actively from
transmitting that cold or flu. But it will keep
your nasal passages and the rest of your
respiratory pathways as healthy as they can
be and as resistant as they can be to
any colds or flues that you might be fighting off. And this is another
key point, which is regardless of
whether or not it's the winter months or the
other months of the year, all day long you're combating
different types of infections. Different types
of viral, fungal, and bacterial infections
are bombarding your system and your immune
system counters that both through physical
and through neurochemical and hormonal and pure
immune mechanisms. OK. There's a whole discussion
of this in the episode that I did on the immune system. We'll do more on this. But keeping the air that
you breathe especially at night sufficiently
humidified is one great way to try and offset colds and
flus that you might be combating because you brought
that cold or flu home from work and your immune
system needs to ward it off. OK. If you are having a
hard time grasping how it is that you could
bring home a cold or flu and then ward it
off, do you have it? Do you not have? It is it sitting there trying
to get into your system? Or do you have it a little bit? Well, this is some
of the gray area around cold and flu and
viral transmission generally. I mean, we don't
know, for instance, if you got a mild
sniffle as opposed to a really bad cold
or flu whether or not it would have been a
really bad cold or flu, had you slept less, had you
not humidified your air better, et cetera. Probably it would be. And if you've ever not
slept well for a little bit and you're sick, you
experienced just how much worse that sickness feels. The symptoms of that sickness
go from very mild to moderate or from mild to
moderate to very severe when you are sleep deprived. That said, it's also clear that
some strains of the cold or flu can be more mild than other
strains of the cold or flu. So this can be pretty nuanced. And we'll go deeper
into this in the episode that I do on cold and flu and
how to avoid cold and flu. But nasal breathing whenever
possible day and night time is extremely important for
encouraging the overall health and resistance of
your respiratory pathways to incoming cold and
flu and other types of viruses. Similarly, humidifying the air
that you breathe especially at night but perhaps also during
the day in your OFS environment or home environment can also be
very beneficial for warding off colds and flus. And if you'd like to read more
about the nasal versus mouth breathing components
of colds or flus, I'll just mention one
paper now and again, I'll go into this in more depth in
the future episode on colds and flus. But I want to mention that
this is a bidirectional effect, meaning people who deliberately
breathe through their nose tend to get fewer
colds and flus. Also people who tend to
breathe through their mouth more tend to get
more colds and flus. Now, you might think that's
the same thing or just two sides of the same coin. But actually it's not. There's what we call a
double dissociation whereby if people are mouth
breathers, they are far more susceptible
to colds and flus and other types of
respiratory illnesses. I'll put a link to
one particular paper that I like a lot in the
show note captions entitled association of oral breathing
with dental malocclusions and general health in children. This paper explores a
lot of different things about nasal versus mouth
breathing all of which, by the way point
to the fact that nasal breathing whenever
possible is better for us health wise, aesthetically,
dental health wise than is mouth breathing. But one of the key
components here and this is why I bring it up in the
context of this discussion is quote "oral breathing is
related to a significantly higher prevalence of allergies
and a significantly more likely getting sick and taking
medication for being sick." OK. So lots in this study,
lots in related studies. But nonetheless, being a nasal
breather, humidifying your air, paying attention
to whether or not you're indoors with people
who are coughing and sneezing because it's cold outside,
all of those things are going to be
relevant perhaps keeping a little bit of distance,
maybe a lot of distance from those people or encouraging
them to wash their hands after they wipe their nose. Maybe even sending them to a
little bit of not necessarily isolation although
that might be necessary but keeping them at a distance. I don't think it's too
much to ask somebody who's sick to not get you sick. Personally I think that's the
polite thing to try and do. And there's actually
not many things ruder than someone who
knows that they're sick showing up to something
because they didn't want to miss that particular event
and getting everybody else sick frankly, that's my opinion. I think that opinion is
shared with many of you out there as well. Now, as I mentioned earlier,
when it's cold outside, the air tends to be drier. Not always. I mean, you could live
in an environment that's very cold and very rainy,
obviously very rainy is very humid. It's maximum humidity
if you think about it. But if you are going
to spend time out of doors in cold days of
winter, which by the way, is a really good thing
for other reasons, I'll get into those
reasons in a moment because they relate
directly to why there's such a prevalence
of colds and flus because in general,
people are not doing what I'm about to tell you to do. But there are two things
to keep in mind if you're going to be out of doors. First of all, the things
about proximity still hold. There have been
studies of people who have colds and flus
sneezing in indoor environments versus outdoor environments and
how much transmission there is. Again, it boils
down to proximity. Yes, you can get a cold or
flu from somebody sneezing out of doors next to
you just as well as you can if they
sneeze next to you indoors There's a slightly
higher probability that you'll get it from them if they're
sneezing at that same distance but you're indoors as opposed
to outdoors obviously sneezers, coughers-- sneeze and cough
in the other direction, cover your mouth and nose. If you don't have a tissue
or something, we are told and I subscribe to the idea
that sneezing into your elbow or coughing into your elbow
is probably the next best thing to not covering up at all,
as opposed to into your hand, which then you touch
other things and yourself. Anyway, without getting into
the mechanics of sneezing and coughing too
deeply, if you're going to be outside in
the cold winter months and you'd like to avoid getting
colds and flus, when you run, when you exercise,
when you walk, when you're in conversation,
try to nasal breathe unless you have to mouth breathe. And if you can sense your
nasal passages or your mouth drying out because of
that hard breathing, and by the way exercise
during the winter months is still important. So I'm not discouraging people
from exercising outdoors during the winter months as
long as you can do it safely. But if you feel those
air passages drying out, just be aware that when
you take those dried out air passages in doors and
you're around other people that might have colds
and flus, you are going to be more susceptible. So that's cause for taking a
hot shower, perhaps if you have access to a steam
room or humidifier, and rehydrating those
nasal and oral passages. Now, if you're
outside and running and you're breathing hard and
your nasal passages are drying out, does that mean that you're
more susceptible to colds and flus that are just
out in that environment if no one else is around? Chances are no. However, what we
were all told when we were kids which is if you
go outside and you get a chill, it's a good idea when
you come back inside to take a hot
shower or a hot bath or if you have access to
it a sauna to heat back up. That's also true, why? Well, it does seem that
there's a relationship between core body temperature
and susceptibility to cold and flu. And this is something
I'm going to go deeply into in the
episode on colds and flus. Keep in mind that fevers that
are the response to exposure to a cold or flu or being full
blown sick with a cold and flu are an attempt of your immune
system to heat up that virus and destroy it. Keep that in mind if
you're considering taking any medication to
lower your fever, of course, know that highly elevated
body temperatures a.k.a. fever can be very dangerous
to the brain and body. There's a fairly
limited upper range of temperatures that we
can go into before we start damaging ourselves. But also keep in mind that
fever is an adaptation designed to destroy viruses. So if you blunt the
fever, you are actually letting a cold or
virus to proliferate more readily than it
would if you allowed a slight fever to combat that. OK. So there's a whole discussion to
be had there because obviously you don't want people
cooking their brains due to elevated fever and
not treating that fever. But you also don't want
to reduce your core body temperature too much which
raises the question of things like cold plunges. Should you be
taking cold showers and doing cold plunges
in the winter months when it's already cold and
you're susceptible to colds and maybe you're coming
down with a cold, should you do that? Well, that segues
into the next question that I'm going to answer
for this AMA, which relates directly to cold exposure
and so-called cyclic hyperventilation breathing
sometimes associated with so-called Wim Hof breathing
but other forms of deliberate breathing as well. And how specific forms of
deliberate breathing and how deliberate cold
exposure can indeed be used to offset or even
prevent entirely infection due to bacterial or viruses. But if you're
already coming down with a bacterial
or viral infection, why cyclic hyperventilation
breathing or why deliberate cold exposure may actually
be the worst thing if you are already contracting
or have contracted, if you are contracting or
have already contracted a cold or virus. So we'll answer
that question next. In the meantime, just know
that yes, indeed in the winter months you are more
susceptible to colds and flus because there's more
of them going around. We talked about some of
the reasons why they're going around, and
some of the things you can do to protect yourself
against those colds and flus. There are a bunch
of other things that you can do that are very
valuable that will explore in the full length
episode on colds and flus and how to avoid getting them. And I'm hoping you all
stay clear of colds and flus these winter months. And now you have some
tools to try and reduce the duration and severity
of those colds and flus should you get one. Thank you for joining
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