:You brought up a lot of really important points for one talking about avoiding bright lights or
blue light exposure in the evenings. And, some people may not be familiar with why that is. So
a key driver of the body's circadian rhythms is melatonin, which, people probably have heard of
it's a sleepiness hormone, but, it rises towards the evening because blue light, inhibits it.
So can you talk a little bit. about Maybe that, and perhaps even the opposite of avoiding
bright light in the evening would be actually seeking it out in the morning.
:Yeah. So, this, discovery of, melanopsin of the blue light receptor was
considered to be one of the top 10 breakthroughs of the year in 2001, when three different labs,
including mine, we discovered it, to give you a context, if you're living
in the nature, and you don't have access to electrical lighting.
then the day length changes between summer and winter. And accordingly, our sleep and
wake up time also has to change our circadian rhythm has to adjust to this changing daylight.
So as a result, our nature has...we have evolved to
have this light sensor, this specialized type of light sensors.
These are called melanopsin or blue light sensing, light sensors that are present in our retina.
These are not necessarily for seeing the outside world, but this light sensor senses
blue light and why blue light? Because the sunlight is the best source of blue light.
When we say blue, it's around 450 nanometer to 500 nanometer that range. So these light sensors in
our retina, they actually are slightly different because they need, a good dose of blue light.
When I say good dose, that means for example, in a full moon night, your regular light sensors
can help you find their way, or you can take a walk. but that level of light is not enough to
activate melanopsin. So that means if you stay awake and you are taking a night hike
in a full moon night, it's not going to reset your circadian clock. and Now fast forward few years,
what we understand now is this melanopsin blue light sensor actually senses light bright light.
during the daytime or blue light from electrical lighting and then tells our master circadian clock
in the brain depending on what time it is and might say, Hey, it may not be evening.
It's actually extension of the day. It's a long summer day, so please stay awake.
Or at the same time, it can also send a signal to this melatonin, which is the
sleep hormone because when melatonin goes up, we tend to feel sleepy. It tells melatonin that, Hey,
it's not time to go up because it's just a long summer day.
So that's the way this blue light sensor in our retina connects to our brain to reset our clock
or to tell when melatonin should rise or fall. So now. What are the functional consequences or
how we can use this information in everyday life? one is since, melatonin has to rise
a melatonin rise correlates very well with, how we, feel sleepy and how we fall asleep.
It's a good idea to let it rise naturally so that we can fall asleep and to let it rise. Naturally,
we have to release the brake and the brake here is blue light. And that's why dimming down light
in the evening is a good idea to release that brake so that melatonin can begin to rise.
And since we know that this is blue light as the cause of
suppressing melatonin, we can also do another thing.
We can change the color of the light
and based on this science, almost all the cell phones. or Laptops now have a night shift or
night light feature and you can program it to turn it on around 8:00 or 9:00 in the evening
when these screens will dim down and will turn it orange in color They may or may not help you to
increase your melatonin, but at least they will, signal that it's time to wind down and go to bed.
Then conversely, during daytime, it's very important to get a good dose of bright daylight.
so that means if you are sitting next to a window, a large window and having your breakfast, although
you don't have sunlight falling on your eyes, you still get around 1000 lux of daylight. And if you
have that exposure for half an hour to an hour in the morning, then that's pretty good enough.
to Again, put a strong brake on melatonin, which might be slowly going down in the morning.
And at the same time that melanopsin receptor, it does slightly different things. During daytime. It
sends a signal to the brain to increase alertness and make us
more functional. So it reduces depression and makes us more happy.
So that way we can use this information that we learn from
a very fundamental discovery in neuroscience to our advantage by getting at least 30 to
60 minutes of daylight, even sitting next to a large window during the first half of the day
and dimming down light and maybe switching to yellow or orange-shifted light or wearing
even blue filtering eyeglasses in the evening to improve our sleep.
:So a couple of questions, one,
You mentioned avoiding the blue...sorry, wearing the blue filtering glasses at night,
perhaps to filter out some of the blue light. What about avoiding sunglasses early in the day to make
sure you're activating the melanopsin receptor and getting that resetting of the circadian clock?
Yes, that's a good question, because we also have to strike the balance between
protecting our eyes and getting enough blue light.
so let's talk about some actual numbers of how much light we
experience. So if you are outside in a sunny day in California or sunny day in any place,
and if you're looking at the sky, not looking at the sun,
you get somewhere between 100,000 to 200,000 Lux of light. so very simple calculation.
And if you're inside your car, And there is no direct sunlight falling on your face or
inside your car. And you're just driving, looking horizontally, Then, you're getting
somewhere between 5,000 to 10,000 lux of light, which is similar to standing outside your car
in a cloudy day, that's also 5,000 to 10,000 lux of light. So now in a cloudy day or sitting inside
your car, there is not enough UV light to hit your eye and damage your cornea or damage your skin.
So in that case, driving without sunglasses is fine because you are not getting too much
UV light exposure, but if you are in the beach or you are outdoors skiing in a very sunny day,
and you have a lot of UV exposure, then it may not be a good idea to abandon your sunglasses.
:Interesting because the, singlet oxygen produced by blue light can damage. the rods and cones.
:There is a ton of UV light outside too.
:And what about, on the flip side of that, people actually being exposed to the bright
light in the evening, oftentimes think, well, I can take a melatonin
supplement and that should sort of help me increase my melatonin.