Childhood Night Light Exposure and the Hidden Cost of “Junk Light”

The clock isn’t just on your wall—it’s in your cells. As autumn settles in and daylight wanes, we dig into how light acts as information for your biology, shaping sleep depth, hormone timing, and metabolic health. A standout 15-year cohort of 200,000+ children links persistent artificial light at night to higher obesity risk, and it pairs with wearable data from tens of thousands of people that reveals how little real sunlight most of us get—even at the height of summer.

We break down what’s actually happening under the hood. Blue-heavy light is a powerful morning cue, but after dusk it sends the wrong signal, suppressing melatonin, shrinking deep sleep, and nudging insulin rhythms off track. That chronic mismatch adds up, especially for kids. Beyond the usual vitamin D narrative, we talk about why full-spectrum sunlight—including infrared—matters for mitochondria, vascular function, mood, and focus, and why energy-efficient LEDs often strip out the very wavelengths that buffer blue and support recovery.

You’ll also get a practical, science-backed playbook you can start tonight. We cover morning outdoor light routines, how to set up your home with full-spectrum lamps for daytime and zero-blue bulbs for evenings, and why programmable circadian lights are a smart upgrade for fall and winter. We share simple screen hygiene, when blue-blocking glasses help, and how to navigate harsh indoor lighting without wrecking your sleep. The goal is coherence: brighter, broader mornings; softer, blue-free nights; and consistent cues your body can trust. If you’re ready to trade “junk light” for light that works with you, not against you, hit play and build your seasonal routine. Enjoyed the conversation? Follow, rate, and share the show with someone who needs a gentler evening glow.

For copies of slide deck: www.thehealthedgepodcast,com

SolShine: https://solshine.org/

Soraa Zero Blue Light Bulbs: https://store.soraa.com/zeroblue/

Korrus OIO programmable circadian lighting: https://www.korrus.com/oio/

Transcript

SPEAKER_00 0:01

Welcome to the Health Edge, translating the science of self-care. I am Mark Pennis, and I'm with my buddy John Bagnulo. John, it's really great to see you, my friend.

SPEAKER_01 0:11

It's great to see you, Mark. It's been too long.

New Study: Night Light And Obesity

Wearables Reveal Sunlight Shortfall

Defining Sunlight Obstruction Syndrome

Circadian Disruption Mechanisms

SPEAKER_00 0:14

It's been way too long. And so we've just gotten by another uh autumn uh equinox and uh into this beautiful fall season. And I'm sure everyone is noticing how quickly our daylight is shrinking uh as uh night gets longer and days get shorter, and it it seems a good time of year to uh revisit a topic that we've talked a lot about through the years, but one that I think is gaining a bit more attention and interest in the in the scientific community, the medical community, and that's the importance of light and health and our um awareness that as our seasons change and as we have this expansion of time under dark uh nights and artificial lights in our indoor environments, that there are some unique uh health uh issues there, and there are many things that that people can do to try to minimize the effects of shorter days, longer nights over this long uh win fall winter season. And so uh it seemed uh a good time for that topic, and and we had a a study. And let me just um pull my uh screen up here John. Hopefully this clear is clear. And um this is a uh very recently published uh uh study that uh uh came out of China. This is from uh BMC Medicine, a you know, international journal, excellent uh peer-reviewed uh research. And the the title of this study is Trajectories of Night Light Exposure and Risk of Overweight and Obesity. This was a 15-year longitudinal cohort study of over 200,000 Chinese children. These kids were uh between the ages of five and nine. They were followed over 15 years. And uh, you know, there are things you can do in countries like China where everyone is sort of under the same system and uh uh subject to um testing and the ability to really track large amounts of data over time. And what they were interested in addressing, this again is an observational trial, and as we always talk about, John, you can't draw firm um causation from these relationships. But what they looked at were four patterns of um artificial light exposure in these cohorts of young children. And they essentially fell into four categories. There was uh uh one cohort that got um much less artificial light uh at at night, and uh remained so during that 15-year follow-up. Uh, there were kids on the opposite end of the spectrum that at very young ages of five, you know, that sort of kindergarten preschool age were getting very um high amounts. This was based on uh surveys and exam and historical documentation recording, uh, where they had very high amounts of artificial light at night, which uh persisted uh through that 15-year follow-up. And uh there were um two other cohorts sort of in between, one that started low and ended high, uh, and another that uh started on the high side and came down a little bit over time. But you know, as we'll show from this data, uh when you're exposed at um non-native artificial lighting uh in a in a relatively large uh exposure time at a very young age that persists, what the study ultimately showed is that you have a much greater risk of obesity uh being overweight. And uh, of course, as we know and always talk about many of the metabolic risk factors that that accompany that change in uh body phenotype. And uh and just a few other pieces of data, John, and then I'll and then I'll pause. Um I don't want to dominate our conversation here, but just to set the stage, uh this is some research from Dr. Martin Moore Eid, who's uh uh former Harvard light researcher, one of one of my um go-to experts. This is a topic I love and think a lot about. Uh and um um Martin has done some really superb work. And uh here's an interesting graphic, John, of uh data from almost 60,000 Apple Watch users, right? So now we're in this era where we have these wearable devices and the ability to capture data in ways that historically has not been possible. And this looks at just sort of the average time of those 58,000 Apple Watch users of average daily time that they spend in uh sunlight. And not surprisingly, uh as we go from winter to spring into summer, uh you get this rise in outdoor exposure. And surprisingly, uh the average, even in summer, is still relatively low. It's about a hundred minutes, uh, and then it quickly goes down. So we're we're entering the season of autumn and uh where this curve goes down pretty significantly. And you can see over the winter months uh just how little time people spend outdoors. This is less than 30 minutes on average. One would see that if you track back to December, November. Uh so we know that we spend very little time outdoors to begin with, and and often when we are uh outdoors, we uh are protected to the extent that we don't allow ourselves any meaningful benefit of that sunlight. And uh Dr. Moore Eid has a uh I like this, it he calls it sunlight obstruction syndrome. Yeah. This just general uh public health um issue, challenge of simply not getting enough sunlight at strategic times year-round, uh, which is very important, and many health issues. I mean, this this reads like uh cornucopia of chronic complex diseases, all of which have gone up with tremendous prevalence um in the United States and around the world. Um and again, that brings us to this study in particular, John, and these four trajectories that I had uh talked about, where some kids just got a lot of uh light at night, artificial light at night throughout their uh lives, really through their pretty much their entire development, from young children through um you know their late teenage years. You see one cohort actually cutting down, uh, and then you see these other two with more gradual uh increments. Uh and so it it allowed them to sort of quantify by these quartiles what risk was over time. And and this is just a snapshot of the of the data. Those with the highest risk of obesity and metabolic um changes were those that um started high and continued high, and you see this hazard ratio almost twice the risk compared to those um who uh showed a decline in their uh artificial light exposure at night. And uh, you know, you see this for both boys and girls. So the suggestion was that while artificial light and the amounts that we're getting today are not at all healthy and certainly may be disease promoting, uh it's particularly problematic when you start with high exposures at very, very young ages, you know, whether it be just compact fluorescent lighting or just a lot of time on your smartphones and uh technology. And uh this is a book, John, I just wanted to recommend to folks, uh, and I'll come back toward the end of our discussion. Uh, this was published last year by Dr. Moore Eid. It's the most comprehensive um overview of this subject um that is available. And uh I think he's one of the one of the most noteworthy light researchers, uh certainly in the United States, and his um uh advocacy for uh public health and for getting our regulators to think differently about requirements for lighting, and uh, and I'll touch on this a little bit later, John, it has been very um inspiring. And he's part of uh development of some smart lights, if you will, that I'll I'll share with our uh listeners uh toward the end of our of our discussion. So that that's just an overview of this study, John, and and I think it on some level is not surprising. Um again, these aren't cause and effect, but but as we've talked many times, we know there are many mechanisms that lack of natural light and excess exposures of non-native light uh mechanistically are known to completely disrupt circadian biology. And all of that can be in some way traced to um obesity, weight-related problems, metabolic problems, depression, anxiety, uh right, that that the sunshine obstruction syndrome. Um and so yeah, I'll pause there, John, and just kind of get your preliminary thoughts when you looked at this.

Insulin, Pancreas, And Night Light

SPEAKER_01 11:02

Yeah, no, to your point, Mark, I mean, it's uh affirmation of you know, previous studies and and what you know, I think what researchers have observed with you know, with really the global population now spending too much time in front of artificial light and all of the kind of downstream effects that has, is um I think it's pretty well established. This is a great paper given the population size, and to your point, the way that it was um, you know, carried out over those that amount of years is really remarkable. Um you know, the analogy I like to use with light that I know you agree with, Mark, is that, you know, much like we're an overfed yet malnourished population now, it's the same thing with light. So we're we're we're like kind of drowning in artificial light, especially at the wrong time of day. And then yet we're also malnourished with respect to real sunlight, full spectrum light. And it's you know, again, I think it's it's the exact same situation. So we have all these effects on human physiology from light exposure, like you know, 10, 11, midnight. I mean, God, most, you know, most people are on their phones now around midnight. And, you know, that, as you know, Mark, that initiates a lot of hormonal changes in the body. Um it can uh it can really stop or arrest kind of the the hormonal production that you want, the endocrine function, you know, want to have more human growth hormone, right? You want to have that window of time in complete darkness where your body can really recover, repair. That's true rest, but you don't get that with that kind of light exposure. All of those things are stopped. And then we know that the pancreas, for instance, really is very, very sensitive to this circadian entrainment or deregulation. I think that's really what comes into play here, specifically with this paper, where you see that you know, these children um have such a much higher prevalence of obesity with that nighttime exposure. I, you know, the pancreas uh is just gonna produce a little more insulin over years and years and years. And then as young adults, um, a lot of these kids end up with mild to severe insulin resistance. And, you know, that diet aside, to your point, this is an association observation. So we while we can't prove prove cause and effect, obviously there's a mechanism at work with the highest risk uh group here. And you know, when you take a look at what the primary driving factor is for obesity and insulin resistance, it's the way the pancreas is uh kind of deregulated over time. So I I you know I think it's uh you know, I take, you know, we talk about core, like these kind of core issues for human physiology in the modern world. And I think this is phenomenal, Mark, because it it ties so many things together.

SPEAKER_00 13:59

And I love that comparison, John, of uh uh being overfed and undernourished to the current state of light exposure. Uh, you know, this kind this sort of notion of solar nutrition being nourished by light. And the um, you know, we often make the comparison of junk light to junk food. Right. And you know, it takes so long for what would seem obvious to ultimately hit the radar of the of the of the medical community, like, oh, is it junk food is actually bad for you, right? You you pick up papers today, and the hot papers are about how processed and ultra-processed food isn't good for you. Uh it's like, well, okay, that's that's you know, it's it's good to have that um affirmation, you know, to use your word, John. Um, but it uh the the amount of time it takes for uh the clinical community to really begin to pivot and and address policy and recommendation around these things is is just very, very slow. And you know, we we often talk about health from the perspective of evolutionary biologic adaptation, and this is a really good example of how the modern environment has changed much faster than our innate ability to adapt. And so uh humans really up until maybe three, four generations ago, uh relied on natural light. Uh when they used light, it was candle light, you know, very low magnitude of light, not as disruptive at night, because the quality of dark is just as important as the quality of light. And uh, you know, it they just spent more time outdoors. And and so um a lot of these uh chronic complex disease epidemics are really emergent. 20th century, these are 20th century phenomenon that um uh sadly are continuing to challenge all of us to a greater extent. And and so we see the prevalence of all these chronic complex diseases going up, not going down.

unknown 16:24

Yeah.

Evolution, Junk Light, And Health

SPEAKER_00 16:24

And uh I think I think light is um uh uh when one looks at light as information, we often we often look at at the uh environment, all these environmental inputs is information. Ultimately, I think uh it can be said that humans are these complex uh uh uh systems, biologic systems that are designed to sense what's going on in the environment. Uh we receive information, all kinds of information, uh much of which we're not even aware that we're receiving, we then interpret and respond to that information, and that leads to our thoughts and beliefs and behaviors, which is information that we then fast forward into our environments. And so you you see this cycle of feed forward, feedback. And if you're not mindful of the quality of the information that that from the feedback that you're getting, then you really find yourself kind of behind the eight ball. And um, so it it really is a fascinating subject uh because light, I think, is not recognized as information. It's just it's it's an it's convenient to make it easier to sort of navigate your environment because you can see better. Uh who thinks about the fact that all those wavelengths of light from non-visible ultraviolet on the on the uh sort of lower uh uh end of the light continuum to infrared on the higher end of the light continuum, um all those things we know hugely impact human biology. And then all the colors in between, and we probably have only recognized a fraction of the ways in which all those frequencies of light influence our biology. And so that that information has fundamentally changed for all of us with each passing generation, and um, you know, who you look at kids today and they're all just connected to devices. Um I'm often struck, John. I live in this beautiful neighborhood in the Berkshires, and we have a lot of young families, and I hardly ever see kids outside. Uh every now and then I'll see a kid on a bike. Uh you'll drive by fields and you might see some kids playing because they're in a league. Um but but kids generally aren't out playing baseball unless they're on a team and there's a game. Uh it's not something you do if it's not sort of on your calendar, you know, not something already scheduled. Uh and that I I think this is to some extent the elephant in the room from a public health perspective.

Sunlight Beyond Vitamin D

Seasonality And Heart Risk

SPEAKER_01 19:20

Yeah, and you know, what you let in with, Mark, about you know, this time of year and then showing us that that slide with uh how much of a drop-off there is in time. It I mean it's bad to begin with, even in the summer. I mean, you know, about an hour a day, I think, is what that that slide showed or less. And then it gets down to, yeah, that's that'd be really helpful. Just take a look at that. That's that's minutes per day. So around a hundred minutes is as good as it gets in June when it's not dark, you know, northern latitudes until 8 30, 9 o'clock at night. Um you know, for like I said earlier, when I use the analogy that we're malnourished with respect to quality light, you you know, you and I have talked about this in the past, Mark. It's like how many chemical reactions does sunlight exposure on the skin drive? I mean, there's so many that people aren't aware of. I one of the biggest misconceptions that I find when talking to people about this is that they they think it's all about vitamin D. I mean, you know, taking vitamin D in lieu of inadequate sunlight exposure, in my opinion, it's like taking a multivitamin and not eating any vegetables or not eating anything that is nutrient dense. I it's just I understand the you know, the effort to try to kind of cover your bases, so to speak, um, with a vitamin D supplement, but that's not going to influence sulfation. That's not going to influence your body's ability to generate um, you know, heparin sulfate, which is what maintains, you know, kind of more ideal or optimal blood viscosity and hemodynamics. I mean, there's just so many components to what natural light does for us. And our mitochondria, I mean, we're not even, we won't even have time to get into that today, but how our mitochondria look just like photoblasts, and we know that there's a role for sunlight in terms of maintaining mitochondrial health. So there's all these different layers to it where sunlight is just like for plants, like you could you could really argue that it's as essential for us in so many areas of our health and physiology, but all of that is, you know, it's just it's just not really appreciated as much as the research suggests it should be. And if you start to look at seasonality and chronic disease, and and there's a lot of different examples of this, we could look at cancer, we could look at heart disease, but it's really clear that, for instance, in North America, just I'll use one example, the months with the absolute really clear highest incidence of heart disease in the way of a myocardial infarction are December and January. You think about it, that's when for most of North America, you'll have the least amount of sunlight exposure, right? To the point that you illustrated with that slide. I mean, it's all it all dovetails. And so, you know, what's going on in December and January? People would say, oh, it's the, you know, it's the holidays, it's, you know, well, no, it's a lot of it's time indoors, almost no sunlight exposure. And so a huge area of our physiology gets kind of deregulated, and that really lends itself to more people having heart attacks. And I I just think it's uh, you know, again, we we have to get to a place, I think, from a public health perspective here where light is appreciated more. We help uh populations understand that they they need there's an essential amount that you need per day. And it's gonna be really tough from now until here in New Hampshire, it's gonna be really tough like from now until probably March. You gotta make the most of those days you get. But I think this is where, you know, different there's whether it's uh, you know, red light, full spectrum light, um, UVB light, there's there's ways to live in a northern latitude and still get some of that. And it may not be ideal as full spectrum sunlight, but it's gonna be a lot better than not having any of it at all.

Simple Daily Light Habits

Spectra: Sun vs. LEDs

Blue Light, Efficiency, And Policy

Mitochondria And Infrared Needs

SPEAKER_00 23:25

That's a really good segue, John, into some relatively easy things that people can do to tweak their environment in an effort to better align time of day, light quality exposure, uh, as compared to what what their current state may be. And I'm always um looking at emerging technology. Some of it is just not rocket science, right? Uh, like certainly get being outdoors every day year round, particularly in the uh morning hours and late afternoon hours, even for five or ten minutes, uh is is powerful, even if you're not getting uh some of those stronger um magnitudes of light, ultraviolet light, of course, uh, you know, you're you're not gonna get much of that living in North America for the most part. Um but just uh let me just I want to come back to something real quick. John, I had a few other slides that I can share. Uh, you know, this um this in my view would be an example of uh the gold standard, right? This is sunlight. And uh this would be uh a snapshot of the uh color spectral pattern of morning daylight. And uh again, uh, you know, none of the non-native artificial lighting will give you any ultraviolet exposure. And for those that are worried about ultraviolet light and its connection to uh cancer, uh, yeah, I mean nobody would question that relationship. Uh but low doses, low exposures of ultraviolet light can allow one to re realize the optimal effect of that frequency of light and at the same time mitigate longer exposures that that might put them at increased risk for skin cancer if they have a family history or maybe they're just very fair skinned. But you see this very broad and um uh uh pretty much even distribution across the color spectrum into the red and infrared range, also a non-visible frequency. And um, you know, as some of our listeners might know that most of the light that hits the surface of this planet is in the infrared range, about 40% of it. So that's a really important frequency of light. No non-native lighting, artificial lighting, with a few more recent exceptions that I'll share, have any infrared light in them. Um and so uh one of the problems is that the regulations that require uh companies to produce light that uh provides a certain brightness, which is this L is lumens, a measure of brightness per watt of energy used in an effort to conserve energy. The mandate was any light bulb you produce now has to have a minimum of 40 lumens per watt of electricity used. And the best frequencies to do that are the blue and some of this green. Uh so most of the artificial lights on the market today, in an effort to meet these regulatory standards, have a lot of blue light, some green light, and leave everything else out because with with just these LED frequency ranges, they can produce plenty of lumens, brightness, and use much less electricity. Uh and the and the the problem there is that that blue light, while it's great during the day after sunset, this is the light that ordinarily turns on our circadian clock. So when we look at that Chinese study, John, and look at the amount of uh um artificial light that people are exposed to at night, much of that is coming in the form of these blue frequencies. And that is sending the exact opposite information to the brain that our bodies have evolved to be in relationship with. And that's where you start to get disruption of circadian rhythms and all that comes with that disruption that we've we've talked about. You also eliminate frequencies of light with these more energy efficient alternatives that, as you alluded to, John, and we just don't have much time to talk about this. Um, you know, we get into the red, infrared, these are critical for energy production, mitochondrial health. And I think we would agree, John, that uh mitochondrial disruption is probably a driver of most chronic complex diseases and may be particularly important in those systems that are very high energy, like the brain. So degenerative neurologic diseases, Alzheimer's, Parkinson's, ALS, um, probably uh one could add autism and other manifestations of disrupted brain function, are very dependent on these frequencies of light, which have been all but eliminated in the uh non-native artificial light industry innovation and development. Uh, you know, they check all the boxes for uh efficiency, but they are really poor for human health. And um a couple of companies, and I I have no vested interest in these companies. I use their products, I've researched them, and I and I really um believe in the uh integrity of the data and science that supports what they are doing. Um this is a a company, Soul Shine, and and I love this. It sort of relates to your analogy of sunlight as nutrition, John. Uh they have uh full spectrum light. Uh ideally for the morning, if if somebody uh I recommend most people living, you know, in North America have full spectrum morning light. Uh and so when you look at the specs, uh it's over 10,000 lumens, so it's what you want in morning exposure, it's brighter light. It has it really pretty much mimics all of these wavelengths of light. There's there's mild UV, low levels, uh, but it also has infrared light. Um many of the light boxes out there just have bright light, mostly blue, green. And that and the brightness is is important for seasonal um shifts and and uh reinforcing that circadian clock, but it will tend to omit uh many of these other frequencies. So the the Solray folks have come up with um options that provide not only the brightness, but you're getting the infrared and the full spectrum of visible light, um, which is really desirable. Uh another emerging company, and I give these companies credit because they are really butting up against the regulatory environment, um uh understanding the health implication. And so uh this is a company called uh Sora, and they have uh one of the first to market zero blue uh light bulbs. Um these are ideal to put in a room that you're spending more time in at night, a family room, a bedroom. Uh and um uh again, you're getting all the other frequencies, but they're just eliminating that that narrow band of blue light for nighttime exposure. And then the last uh, and I've got some of these now that I'm um um kind of experimenting with, if you will, uh John. These are the first to market programmable um circadian compatible lights. Um and um this is OIO, uh a company that uh Dr. Martin Eid is part of. Um I've spoken with their some of their science uh folks, and they are um really bringing to market what I think is one of the true innovations that um will be available to anyone. And so what these lights do, and again, they look like um you know LED lights, they look like the old incandescent lights. Uh you can program from your phone based on the where you live, the latitude that you're at, and which times of day you you wish uh the light to uh to shift. These so these lights are programmable. And uh during the day, you can set it so that you're getting right you're getting this beautiful full spectrum or blue light. Um during the uh overnight hours, uh, and you can just control this from your phone. Uh the light will shift uh to totally eliminating this blue band, which has been the most um important wavelength for mitigating disruption of circadian rhythm. And um, and again, you they even give you a little um handheld prism. You can hold it up to the light and see these differences in frequency. So um this is IOI. Uh, they're a new company. Um, and again, I have no financial um ties to any of these companies. Uh, I just really believe in uh the the technology. And um so I I do my checklist, John, for this time of year is some full spectrum lighting in the morning uh for 20 minutes minimum. Uh I then uh will have either either a warm LED or one of these newer technology lights in rooms that I'm spending more time at night in after sunset when it's dark. I I want to try to manage the blue light exposure that I'm getting. These are really nice ways to do that. Um I will you know wear blue glasses, you know, if I'm in an environment where I don't have as much influence over the lighting. Um, you know, you go into a uh you know a big box retailer at at 8 p.m. and you know, you're gonna under the baked under those fluorescent lights, you're gonna buy something that you definitely don't need. Uh and so uh there are strategic times where I will wear these. Um and so uh you know, these are all, and then just getting more time outside as we talk about John. I think these are these are you know, they're so simple that it's hard for people to appreciate how powerful they can be. But this I this is um uh definitely an opportunity.

SPEAKER_01 35:22

It's awesome stuff, Mark. Those I think those light bulbs are that's revolutionary, you know. We we try to use incandescence um wherever we can, but those are you know those are tough to find nowadays.

SPEAKER_00 35:34

Yeah, they went off the market in you know, like 2019 when when uh the EPA, you know, they changed. You had to meet this 40 lumen per watt standard, right? And every incandescent bulb immediately no longer met those current. So unless you hoarded them as I did and others have, it it's they're hard to find now. But that was one of the original great light sources.

SPEAKER_01 36:00

Yeah.

Smarter Lighting Solutions

SPEAKER_00 36:00

Um what I love about some of these newer lights is that they are more energy efficient and they do um, particularly some of the um uh daytime lights, uh full spectrum lights, also include infrared. So that's a nice plus. And so the technology really is evolving in a in a really positive way. I think people just need to be more aware of how important all of this is.

SPEAKER_01 36:26

Right. It's great stuff, Mark.

SPEAKER_00 36:30

So, John, it um always a pleasure connecting. And um all of this will end up on our website, uh, the health edgepodcast.com. Um, we haven't had a chance to do as many recordings. Life has been very rich and complicated, and uh we'll come back when the spirit moves us, but we appreciate that people still listen in and uh share with their friends. And uh, news to use is what we love to share, and uh it's it's a joy as always, John.

SPEAKER_01 37:05

Yeah, absolutely. Thank you so much, Mark.

SPEAKER_00 37:08

You bet.