AMA #10: Benefits of Nature & “Grounding," Hearing Loss Research & Avoiding Altitude Sickness
ANDREW HUBERMAN: Welcome to the Huberman Lab podcast,
where we discuss science and science-based tools
for everyday life.
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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.
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So without further ado, let's get
to answering your questions.
The first question is about nature,
in particular about the scientifically-supported
benefits of getting outdoors into nature.
The person asks about the role of sunlight,
the role of calming sounds, the role
of observing wildlife, of observing green colors,
and, quote, "other stuff."
And in fact, I'm glad that they asked about "other stuff"
because I get the question about the scientifically-supported
benefits of nature a lot.
I often also get the question about grounding.
For those of you that aren't familiar with what grounding
is, grounding is a practice of putting your feet on the Earth
directly with bare feet, oftentimes
into soil or on a lawn.
And it's a question that I seem to get more and more.
In fact, every week for quite a long while now, on social media
or elsewhere, somebody asks me about the scientific support
for this practice of grounding.
So obviously there's a lot of interest
in what the scientific research says about getting into nature
and putting one's feet on the ground,
a.k.a. grounding, and so on.
OK, so if I'm going to answer this question,
I first have to be very direct with you.
There is excellent, meaning dozens, if not
hundreds, of quality peer-reviewed studies which
support the value of getting sunlight in one's eyes,
in particular early in the day to set your circadian rhythm.
This is something that I've talked about extensively
on the Huberman Lab podcast and as a guest on other podcasts.
It's one of the first and, frankly, most important
items on the toolkit for sleep, which is a zero-cost toolkit
that you can access by going to hubermanlab.com,
going to the menu, going to Newsletter.
You can see it as a PDF there.
You don't have to sign up for the newsletter.
You can just access that toolkit for sleep.
And you'll notice that very close to the top of that list,
if not top of that list, is to get sunlight in your eyes
early in the day.
You don't have to see the sun cross the horizon.
If you can, that's great.
But if you wake up after the sun has already
risen, go outside, face the sun, blink
as necessary to protect your eyes,
but get some sunlight into your eyes
every single day or as often as you possibly can,
especially on overcast days.
That's an absolutely unequivocally
science-supported tool that will increase daytime mood, focus,
and alertness and will improve your nighttime sleep.
Viewing morning sunlight also has profoundly positive effects
on metabolism.
Now, those effects on metabolism could
be the direct effect of viewing sunlight or, more likely,
they are the indirect consequence
of getting better sleep at night.
So getting sunlight in your eyes early in the day
and ideally in the evening or late afternoon
before the sun sets is a very well supported protocol
that we know is beneficial for numerous aspects
of mental health, physical health, and performance.
And of course, sunlight and getting sunlight in one's eyes
does require that you get outside.
You simply will not derive the same benefits
from viewing sunlight if you try and do it
through a window or windshield or if you
look at a picture of a sun on a screen.
Forget it.
You are not going to set your circadian rhythm.
You are not going to derive all the positive effects
of sunlight by trying to get it from screens
or from looking at pictures of suns or something of that sort.
Now, if you are somebody that, for whatever reason--
seasonality, where you live on the planet, work schedule, et
cetera--
who cannot get sunlight in your eyes early in the day
on a consistent basis, well, then you might consider
purchasing a so-called SAD lamp, which is for seasonal affective
disorder, which is very bright light that you can look
at in the morning for usually about 5 to 10 minutes.
People will put it on their counter
while they make their morning coffee, eat their breakfast.
And that has also been shown to improve mood, focus,
and alertness and set one's circadian rhythm.
But it is not nearly as effective as getting sunlight
in your eyes.
Now, why am I talking about this practice
that I've already talked about extensively
on numerous podcasts before?
Well, because the question is about nature,
and sunlight is a key feature of our natural environment.
But the person is also asking about other features
of nature-- seeing green colors, or blue colors,
or running streams for that matter.
Well, here, too, we can ask, what does the scientific data
really say about things like going
near a waterfall, or a running stream, or being near an ocean?
And actually, this is quite interesting.
There is actually a peer-reviewed literature
on negative ionization, as it's called,
which is a pattern of ionization that's
present close to bodies of water and particular types of bodies
of water, such as waterfalls, running streams, et cetera.
There's actually a laboratory at Columbia University School
of Medicine that has published fairly extensively
on the health benefits of negative ionization
as it relates to setting circadian
rhythm and some other aspects of mental and physical health.
I intend to host the head of that laboratory
on the Huberman Lab podcast in the not too distant future.
For now, we can safely say this--
there does seem to be some positive health
benefits to placing oneself near bodies of water,
in particular moving bodies of water.
And of course, as is always the case when there's
a discovery about how the natural world can impact
health, there have been some technologies developed
to create negative patterns of ionization
within a home environment.
But as with viewing sunlight exposure
and comparing it to, say, SAD lamps,
the negative ionization machines that one can purchase and put
in their home environment have been shown in a few studies
to produce some positive health benefits.
But those positive effects in no way
reach the level of positive effects
that have been demonstrated in studies where people
are actually spending a dedicated
period of time outdoors as near a moving body of water.
So in thinking about nature, natural environments,
there's strong evidence for getting sunlight in one's eyes.
There is some evidence for being near moving bodies of water,
perhaps--
again, I really want to highlight perhaps--
because of negative ionization created by those moving
bodies of water.
There is far less evidence for sunlight simulators
or negative ionization machines used indoors.
And then the asker of this question also, quite correctly,
asked about things like calming sounds,
watching wildlife, green colors, et cetera.
And herein lies a really important point for everyone
to digest.
While, of course, answering a question
about the natural world or about health
requires that we first pose a hypothesis-- for those of you
that aren't familiar what a hypothesis is,
a hypothesis is a stated prediction.
So it's not a question.
A question would be something like,
is getting out into nature good for our health?
A scientific hypothesis is where one actually takes a stance.
For instance, you could take the stance
and make the hypothesis that getting out
into nature for 30 minutes per day, three days per week,
improves mood and nighttime sleep.
So that's a hypothesis that then one would go on
to design an experiment to test and then evaluate
the data from that experiment and compare it
to the hypothesis, either validating or negating
that hypothesis.
That's essentially how science is done.
There's a lot more to it, but that's essentially
the scientific method.
And while, of course, the scientific method
is a fabulously powerful tool, for some questions,
it is a less potent tool.
And the question of is getting out into nature
helpful for enhancing our mental and physical health is
the sort of question that while ideally you
could design a really well controlled study to address,
it's actually quite difficult to design such a study.
And here's why.
In order to perform a study that's very well controlled,
meaning where you can isolate individual variables--
like sunlight, like the sorts of color contrast that one sees
in a natural scene outdoors in a forest or near a river--
in order to address whether or not
the calming sounds or the presence of squirrels running
through your environment are the relevant factors,
it becomes incredibly difficult to try and isolate
individual variables, meaning as soon as you bring people
into the laboratory, yes, you have more control over which
variables, as they're called, you present them,
by bringing them into a room that essentially has
no art on the walls and then having them look
at a picture of a sun or looking at sunlight
or listening to soothing sounds or looking
at a picture of a forest, of course,
you're controlling the individual variables.
However, there is a sort of gestalt,
meaning a collective picture of being
in nature that brings together lots
of different elements-- the element of surprise,
for instance.
The other day I was out for a Sunday hike,
and that morning I saw a squirrel running
across my path, and it was interesting
because the squirrel had a pinecone in its mouth.
It had been chewed down to the cob.
And the squirrel was probably only about 7 or 8 inches long,
and the pine cone was probably about 9 or 10 inches long--
the cob of the pine cone, that is.
And the interesting thing is that the squirrel
was carrying it long ways from the tip of the cob.
And so I delighted in the fact that this little squirrel
was working so hard to carry this object through the woods.
And this object was literally longer than its own body
length, and it looked so dedicated in its running
across the path in order to do whatever it
would with that pine cone cob.
So something like that obviously stuck in my memory.
It delighted me.
And at the very same time, there were a number
of other things happening besides the presence
of that novel wildlife experience.
There was the sound of a stream.
There's the sunlight.
There's the color contrast everywhere.
I'm breathing fresh air because I
was far away from any cars or any civilization, in fact.
And so here's what we know.
There are dozens, if not hundreds,
of studies that show that if people get out
of doors into nature--
this could be parks.
This could be near a stream.
This could be an ocean, any number
of different natural environments.
And if they do that for anywhere from 10 to 30 minutes,
three to seven days per week, indeed there
are demonstrated significant reductions
in things like blood pressure, resting heart
rate, improvements in sleep, improvements in mood.
And so I think we can very reliably say that, yes,
or perhaps even absolutely yes, getting outside into nature
can enhance various aspects of mental health, physical health,
and thereby performance in different aspects of life.
However, when talking about the benefits
of getting into nature, we are talking about hundreds, if not
thousands, of variables, some of which we are aware of,
such as the presence of wildlife or sunlight or color contrast.
And then, of course, there are going
to be dozens, if not hundreds, maybe even
thousands of other variables that we're not even aware of.
Perhaps it's negative ionization.
Most people aren't measuring the ionization of the air
when they go out into nature.
But perhaps it's also the presence
of certain smells from the soils that are being broken down
and then they're changing the oxygenation state of the air
around you, the plants, et cetera.
Again, so many variables, that, frankly,
to try and isolate any one of those variables
in the laboratory seems not just artificial,
but I think that it actually would just
lead to a diminished sense of just how valuable nature is.
So while, of course, the Huberman Lab podcast
is a podcast where we always center
on science and science-related tools,
meaning protocols that are grounded
in quality peer-reviewed studies that have been subjected
to control conditions where some people are getting,
say, the drug treatment or taking the supplement
or doing a particular behavioral practice and other people
are not or doing some variant of those and dose response curves,
all of that stuff, when it comes to the question of
whether or not it's valuable to get out into nature,
I think it's a very straightforward yes.
Absolutely yes.
Get out into nature as often as you can and safely can,
of course.
I realize some of this is weather permitting.
People live in different areas.
Some people are in cities.
Some people are in deserts.
Some people are near the ocean.
But getting out into nature has been shown over and over again
to have numerous positive health effects.
And yet, unless we're talking about sunlight exposure
and isolating the variable of setting one's circadian
rhythm by viewing sunlight early in the day, all
of the other features of getting out into nature,
things like forest bathing--
this is a term coined from some, frankly, pretty nice studies
that were done in Japan in which people placed themselves
into forest-like environments for a certain period of time.
There were control groups where people were not
placed into those environments, and the people
that did this so-called forest bathing experienced
enhanced mental and physical health.
That brought on a practice of people who could not get out
of doors into forests bringing plants
into their home environment, which I think all of us
would agree look nice.
They often will add pleasant odors to the air,
and perhaps they do actually shift our mental and physical
health in significant ways.
I suppose it depends on how much you like plants,
how much you pay attention to them, and, of course,
how many plants there are.
But-- and I think this is a really important
"but" to emphasize--
while most all questions about tools and protocols
for enhancing health immediately lead me to say, ah,
this study or that study or, yes,
there's evidence or, no, there isn't evidence, when it comes
to questions about nature and grounding in particular,
I take the stance that this is a unique instance where
we know there are just so many benefits of getting out
into nature that trying to isolate
any one of those variables in a quality,
rigorous way within the laboratory
almost seems too artificial to really justify
the conclusions that arrive.
Now, I'm sure there are some of you out there who are aware--
and if you're not, I'll tell you-- there
are studies that have explored this practice
of so-called grounding.
They've had people come into the laboratory
and place their feet on soil that is contained within a box
or there are other studies where they actually
have people go out of doors and place their feet
onto the grass or the ground.
And there are a bunch of theories
as to how grounding could improve
one's mental and physical health that aren't just about getting
outside.
So the theories go that this has to do
with the exchange of electrons with the Earth
and the Earth's surface in particular.
There's been the argument made that shoes,
in particular shoes that have rubber soles,
may block some of this electron exchange
with the surface of the Earth.
There have been theories about the tactile--
that is, the touch sensation-- with the Earth being important.
Not a lot of science published in, let's just say,
blue ribbon journals, which is not
to diminish some of the journals that these have been published
in, but just to say that, again, there are so many variables
associated with a practice such as grounding that I'll simply
say, yes, please do get out of doors into nature.
I try every Sunday to do my zone 2 cardio by rucking or jogging
or hiking, often with other people
if I'm trying to be social with family or others.
But the point is getting out of doors
has myriad positive effects on mental health
and physical health.
And of course, when you're moving out of doors,
you're also getting that zone 2 cardio or other forms
of physical benefit by elevating your heart rate
or perhaps you could even do your resistance training out
of doors on other days.
Now, I also try to get out of doors other days of the week.
But oftentimes, I'm, by way of weather
or by way of other commitments, forced to be indoors,
on planes, here at the podcast studio
where certainly I'm indoors.
But I try and get out of doors at least a few minutes
each day for a morning stroll, looking at sunlight, et cetera.
So the long and short of this is, yes, there's
some evidence for grounding.
Is it super strong evidence?
No, it's not.
We don't really know what it is about placing one's feet
onto the Earth that is producing the positive effects that
were observed in those studies.
And those studies made some reasonable attempt
to isolate the variables and figure out whether or not
it was ion exchange with the Earth or the tactile,
meaning the touch sensation, of having
one's feet on the ground.
Frankly, I don't think there's enough quality science
to really draw any firm conclusions about that.
However, if you like the idea of grounding, by all means, do it.
In fact, if it feels good to you,
I recommend getting your morning sunlight out
of doors with your bare feet on the ground.
Or if you're like me, you put on your shoes,
and you take a walk most days.
Although, I've tried this practice of grounding,
and it feels pretty good, meaning
it feels nice to have my feet on the Earth,
provided I'm on clean soil or clean lawn.
Definitely don't do this at the dog park.
Hookworm is a real thing, by the way, folks.
So pay attention to the sorts of surfaces
that you're putting your feet onto.
But the question about whether or not nature
is valuable for our mental and physical health is an easy one.
It's an absolute yes.
But isolating the particular variables about nature
that are most beneficial, well, that's a much tougher question,
and it's one that, frankly, the scientific method is not
and, to be honest, I don't think ever
will be in a position to isolate and really
nail down specifically, because as soon as you get specific
about that question, you start to diminish
the value of the study itself.
So the long and short of this is get out into nature
as often as you safely can.
If you can exercise out of doors, even better.
If you want to make it social, great.
If you don't want to make it social, fine.
It's your life.
It's up to you.
But there certainly is value in getting out into nature.
It's also just beautiful from a visual perspective,
from an auditory perspective.
And I myself try and take at least a few trips each year.
None of these are particularly expensive trips
where I try and get out hiking, camping.
The weekly walks in nature are an absolute must for me.
If I miss one because of weather conditions or travel,
I make it a point to try and get into nature
more during the following week or whenever I can.
And frankly, I don't have a scientific explanation
for why nature is oh-so beneficial,
except for the sunlight piece and perhaps this grounding
piece and the negative ionization piece.
And frankly, I don't worry so much
about the lack of variable-isolating, quality,
peer-reviewed studies that support the benefits of getting
out into nature.
I simply like getting out into nature
and into different natural environments
as much as I possibly can, because, for whatever reason,
imagine those reasons have something to do with serotonin,
dopamine, hormones, oxytocin, probably
a bunch of different things that are
rooted in how our nervous system evolved
in natural environments.
Well, it just feels really good.
Thank you for joining for the beginning
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