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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can still hear the first 20 minutes of today's episode and determine whether or not 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 that 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 intro emsa and conversely in the summer months days are very very long in Trump's in 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.
Cross 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.
Okay. So in the winter
months as we're calling it involves at
least two things shorter days,
which means what it means
there's less sunlight and either more
artificial light or more Darkness
depending on how much artificial light you rely on. It also means as we mention 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 cold.
Flus in the short days AKA winter months of the year is that people are spending more time indoors and therefore 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.
Allure
experiments and there does seem to be a very nice relationship between physical distance between you the uninfected person and the sneezing coughing knows wiping I wiping will get into why all I mentioned all of those things in a moment person that is suffering from the flu. In other words. The closer you are to someone
who's sneezing or coughing the higher probability that you will contract that cold or flu
Okay. So we've already established two things. First of all physical proximity Is a
Variable in terms of transmission of cold and
flu and at some level that sort of 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 a contract
that colder flew 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
Lord the relationship between physical proximity and transmission of Cold and Flu have actually analyze things down to the range of well, if you're standing one foot apart or you're standing three feet apart or 6 feet apart. What's the probability that you will
contract that colder 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 kind of contact also
further increases the transmission of cold and
flute 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.
Did they can transmit cold and flu simply through handshake? Okay. 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 human 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 colder flu or late in the cold or flu and they have these theories or claims that oh, you know, 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
Okay. 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
a 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 gedanken or thought experiment will remind you just how dry the cold air
is out of doors during the winter months.
Whereas in doors were heating that are and indeed the heating of that are does have the property of drawing 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
Often times 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
Knows especially if they are super numerous are not considered aesthetically nice people will
trim them etcetera. 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 gnome 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's 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
use 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 and 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
Our 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 flus that you might be
fighting off and this is another key point, which is regardless of whether or not the winter months for 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 in your immune system
counters that both through physical and through
neurochemical and hormonal and pure immune.
Seems okay. There's a whole discussion of this in the episode. I did on the immune system will 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. Okay. If you
are having a hard time grasping how it is that you could bring home a cold or flu and then awarded off like you have it do not have it at sitting there trying to get into your system or do you have it?
Little bit. Well, this is some of the gray area around cold and flu and viral transmission generally 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 last. How do you not
humidified your are better at cetera? Probably it would be if you've
ever not slept well for a little bit and you're sick you experience just how much worse that sickness feels the symptoms of that sickness go from very mild to moderate or from mild to
it 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 and your office
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 bi-directional effect meaning people who deliberately breathe through their nose tend to get fewer colds and
flus also people who
Ooh 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. No 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,
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. Okay,
so lots in this study lots and related studies.
But nonetheless being a nasal breather humidifying your are paying attention to whether or not you are 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, right? I don't think it's too much to ask somebody who's
sick to
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 a very humid its 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
they're 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, all the things about proximity still hold right? There have been studies of people who have colds and flus sneezing.
An
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 you indoors so 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 coffers 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 subscribed 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 send
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 are passages drying out just be aware that when you take those dried out are 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 Andre
rehydrating those nasal and oral passages
now if you're outside and running and you're breathing hard in 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 a hot bath or if you have access to it a sauna it 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
or an attempt of your immune system to heat
up that virus and destroy it
keep that in mind.
If you're considering taking any kind of medication to lower your fever, of course know that highly elevated body temperature Zack.
A 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. Okay. So if you blunt the fever you are actually letting a colder
virus to proliferate more readily than it would if you allowed a slight fever to combat that okay. So there's a whole discussion to be had there because obviously you don't want people cooking their brains due to elevated fever 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 coal 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? Ah,
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 a 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
Iris, 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 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 for the beginning of this ask me anything episode to hear the full episode and to hear future episodes of these ask me anything sessions plus to receive
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