0:02 So, what is the perfect day? What What does that look like from a circadian sleepwakefulness standpoint? Well, I'm about to summarize what I've said in the three previous podcast episodes as well as now countless Instagram posts. Here's the deal. You basically want to get as much light, ideally sunlight, but as much light into your eyes during the period of each 24-hour cycle when you want to be awake, when you want to be alert. And you want to get as little light into your eyes at the times of that 24-hour cycle when you want to be asleep or drowsy and falling asleep. How much is enough? Well, you don't want
0:48 to go so high with the light exposure that you damage your eyes because as many of you have heard me say before, the eyes are actually two pieces of your brain, your central nervous system that were extruded out of your skull. And as pieces of the central nervous system, aka your brain, they will not regenerate. At least right now, the technologies don't exist to regenerate those neurons in humans. You do not want to damage them. So, what is too bright? Well, when it's painful to look at, when you have to blink or close your eyes in order to bear it. Please don't look at very bright lights. So painful that they're likely going to damage your eyes. However, if you get up in the morning and it's still dark out and you want to be awake, you would be wise to turn on artificial lights, in particular
1:33 overhead lights for reasons I've discussed previously. But those overhead lights will optimally trigger the neurons, these melnops and cells in the retina that will activate your circadian clock when the sun comes out. Even if there's cloud cover, the sun does come out every day regardless of where you live. Unless you live in a cave. People have said to me, "Well, I live in an area where I can't really see the sun." Well, the sun is there. It might be hiding behind clouds. Unless it's very very dark where you live like Scandinavia in the depths of winter, which case you might want some artificial light. Get some sunlight in your eyes when you can. Here's the deal with sunlight and artificial light that I have not discussed previously. A lot of photon energy, a high amount of
2:20 lux lux comes through even cloud cover. A good number to shoot for, as a rule of thumb, is to try and get exposure to at least a 100,000 lux before 9:00 a.m. 10:00 a.m. maybe, but before 9:00 a.m., assuming you're waking up sometime between 5 and 8:00 a.m. Okay, so get 100,000 lux. Now, you do not, I want to repeat, you do not want to stare at a 200,000 lux or a 100,000 lux light. It's very very bright. The mechanism of circadian clock setting, and this is very important, the mechanism of circadian clock setting involves these neurons in your eye that send electrical signals to this clock
3:06 above the roof of your mouth. And that system sums, meaning it adds photons. It's a very slow system. So, let's say that I wake up and I look at my computer screen briefly or my phone screen. That's probably 500 to a,000 lux. If I were to look at that for a full minute, I would get that photon energy transferred into electrical energy of neurons and it would be communicated to my circadian clock. However, the signal that it's morning will not have registered with the circadian clock. Unless I looked at that for 100 minutes or more, so 100,000. Now, the problem is if you wake up at 8:00, you're not going to get enough light from artificial light before you reach what's called the circadian dead zone. So, you have this opportunity before 9:00 a.m., maybe
3:52 10:00 a.m. to capture enough photons, and you have to do it with your eyes. I've discussed why that's important in previous episodes of the podcast, but you have to do it with your eyes. There is no extracular photo reception. This is not about vitamin D in your skin. This is about setting your circadian clock, which is paramount for mental and physical health. So, here we're talking about trying to get that at least 100,000 photons, but not all at once, but you got to get them before 9:00 a.m.ish, maybe 10 a.m. So, what do you do? You go outside. If you want to get nerdy about this quantitative, you could download a free app like light meter and take a look around your house with light meter and you'll notice that even bright overhead lights are only emitting about 4,000 or 5,000 lux. It's going to take a long while of looking at those lights
4:38 with eyes open in order to set your circadian clock and tell your brain and body that it's morning. Going outside, even on a cloudy day, could be 7,000, 10,000 lux. It's really remarkable how bright it is. Meaning, how much photon energy is coming through. So, try and get 100,000 lux before that 9:00 a.m. Now, if you can't do that because you live in an area of the world where it's just not bright enough, some people have sent me pictures from Northern England. It's just not bright enough in winter. Then, sure, you can resort to using artificial lights in order to get enough photons. And I'm putting out this 100,000 lux number as a as a target to get each day before 9:00 a.m. You can in theory get it all from
5:24 artificial lights, but there are some special qualities about sunlight that make sunlight the better stimulus. First of all, it's free if it's available outside. There is a a number of different there are, excuse me, a number of different technologies kind of like this one, like a light pad that this one says it's uh 930 lux. I'm not I'm covering this up because I'm not trying to promote any specific products. I actually bought this just with my own money on Amazon. They're not a sponsor. And it lets you toggle the brightness. I think by holding this on uh holding down this button, you can make it dimmer, brighter. This is about 1,000 lux. It seems really bright, but a cloudy day outside will have five times more photon energy coming through. So, some people set these lights or ring lights that they use for selfies and that kind of thing near their coffee or workstation first thing in the morning. But you
6:10 really want to get sunlight. Okay, so those things are kind of nice because they'll travel and we're going to talk about jet lag. But I can't emphasize this enough that light has to be captured and summed before you enter the circadian dead zone which is the middle of the day. This is again trying to achieve kind of perfect schedule. Then I've recommended based on scientific literature that you look at sunlight sometime around the time when the sun is setting. And the reason for that, of course, is because it adjusts down the sensitivity of your eyes. Because here's the diabolical thing. While we need a lot of photon energy early in the day to wake up our system and set our circadian clock and prepare us for a good night's sleep 14 to 16 hours later, it takes very little photon energy to reset and shift our
6:57 clock after 8:00 p.m. And that's why you want to as much as you safely can avoid bright light and even not so bright light between the hours of 10 or 11 p.m. and 4:00 a.m. A number of people have asked me some questions about this and the last episode I went into red lights. I discussed blue blockers, all that kind of stuff. So, I'm not going to repeat all that. But here's the thing. If you see afternoon light, you're going to adjust down the sensitivity of your eyes so that you have a little bit more wiggle room, a little bit more leeway to view lights from screens and overhead lights even late at night without disrupting your circadian clock. But it is a kind of a a double-edged sword
7:43 where you need a lot of light early in the day and you need to avoid bright lights later in the day. I've mentioned studies on here. A number of you have asked about getting the references. We are in the process of trying to get a web page going with full links. There's some copyright issues that we have to deal with, but wherever possible, I'll try and reference these studies and when people ask, I'll generally put them in the response to their comments on YouTube or Instagram. There have been two studies done from the University of Colorado, both published in current biology. You can easily find these online by just uh you know googling the words uh current biology, camping and reset circadian clocks that have shown that 2 days of waking up with the sun and avoiding light at night. They actually took
8:28 graduate students camping. Really cool experiment to be a part of. reset the melatonin and cortisol rhythms for these people that had otherwise drifted quite far from their natural rhythms. There are other things that you can do to shift your clock and to reinforce your clock, like exercising more or less the same time, eating more or less the same time, etc. That's not what today's episode is about. So, I just described perfect schedule. Get at least 100,000 lux of light exposure to the eyes. Not all at once, but summing across the morning. Again, you know when it's too much because it's painful to look at. So, that's obviously something to avoid. But then once the middle of the day, let's say you're waking up at 10 or 11, you go outside, the sun's overhead, forget it. You're not going to shift your clock. You're just not. It doesn't work that way.
9:14 In the evening, you see the evening light, and you want to get that light to adjust down your retinal sensitivity to afford you a bit of a buffer so that late at night, if you happen to look at screens or go to the bathroom in the middle of the night, it's not going to shift your clock. Because it takes probably only about 1,000 to,500 lux of light energy to shift your clock in the middle of the night.
