Episode 74 - The importance of light exposure for your health

The body does not run on the wall clock. It runs on light. Jonathan Jarecki, an undergraduate researcher focused on circadian biology & light's effects on human health, joined Iris to explain why circadian rhythm governs practically every cell & organ in the body, & why so few of us are giving our bodies the light cues they actually need.

Jarecki stepped away from the pre-med track after realizing his passion was research & science communication rather than the standard medical establishment. He now focuses on translating circadian research for the public, believing that lifestyle-based prevention & reversal of chronic disease starts with understanding how deeply light governs human biology.

This conversation covers the mechanics of the circadian clock, the myth of the "circadian dead zone," why artificial light at night is linked to cancer & diabetes, how women's circadian rhythms differ from men's, & practical steps for aligning with light no matter where you live. What emerges is a clear picture: brighter days & darker nights aren't a wellness trend. They're a biological requirement.

Topics covered

In this episode, we discussed

Jonathan's shift from pre-med track to circadian biology research
Central clock (SCN) & peripheral clocks governing every cell in the body
What happens during first light exposure & sunrise contrast signaling
Circadian dead zone myth: bright light still affects rhythm midday
Artificial light at night classified as probable human carcinogen
Diabetes research linking light exposure patterns to metabolic health
Light exposure strategies for people living in northern, dark winter climates
Fire as ideal nighttime lighting with zero blue light disruption
Women's shorter circadian rhythm & increased sensitivity to light cues
Dermatology's circadian blind spot & DNA repair protein timing
Newborn brain development through non-visual light exposure
Jonathan's personal daily light routine & meal timing practices

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Timestamps

[00:00:56] Episode intro & Jonathan's background

[00:03:09] Why Jonathan stepped away from pre-med

[00:08:12] The 17-year research-to-practice gap

[00:09:16] What is circadian biology & why light is the primary timekeeper

[00:15:07] Circadian rhythm & female fertility, IVF, & reproductive health

[00:15:35] Medication timing & circadian biology

[00:16:16] What happens in the body during first morning light exposure

[00:20:19] The circadian dead zone myth debunked

[00:23:54] Artificial light at night & its effect on melatonin & cortisol

[00:26:43] Brighter days, darker nights: the simple framework

[00:27:22] Downstream health effects: cancer, cardiovascular disease & diabetes

[00:33:04] Light exposure strategies for dark northern winters

[00:38:28] Fire as a nighttime light source

[00:39:24] Circadian disruption in women & the infradian rhythm

[00:42:05] Perimenopausal women, PMDD & circadian research gaps

[00:43:03] What healthcare practitioners get wrong about circadian rhythm

[00:48:00] Children, screens & early brain development

[00:52:02] The Daylight Tablet & blue-light-free devices

[00:53:11] Jonathan's personal daily light & dark routine

[00:56:15] Meal timing & blood glucose regulation

What Circadian Rhythm Actually Is

The body has an intrinsic clock that runs on a roughly 24.2-hour cycle, centered in the suprachiasmatic nucleus (SCN) of the hypothalamus. Left without external cues, in a cave with no light exposure, this internal clock would slowly drift later each day. Light is what keeps it anchored to the 24-hour rhythm of the Earth.

"The circadian system governs practically every single cell and every single organ of our body."

The central clock communicates with peripheral clocks throughout the body, in muscles, the gut, the heart, telling each system when to release hormones, produce proteins, & carry out repair processes. Light is the primary zeitgeber (timekeeper), though food timing & exercise also play supporting roles.

Why Circadian Misalignment Matters

When the circadian clock is out of sync with the light-dark cycle, the downstream effects touch nearly every disease category: diabetes, cardiovascular disease, cancer (particularly breast & colorectal), & even conditions like ulcerative colitis. This isn't a minor wellness detail. It's foundational biology.

The modern reality makes alignment difficult by design. Ninety-three percent of Americans' waking hours are spent indoors. Most people wake up & immediately look at a phone screen rather than getting outdoor light, then spend evenings under bright artificial lighting, sending their bodies a false "daytime" signal well into the night.

The Science of Morning Light Exposure

Morning light exposure isn't just a nice habit. It's a precise biological process. Jarecki walked through the mechanics in detail:

At sunrise, the orange-blue contrast in the sky signals to specialized cells in the retina, intrinsically photosensitive retinal ganglion cells (distinct from the rods & cones used for vision), which then relay that signal to the suprachiasmatic nucleus. As the sun continues rising, the increasing brightness & blue wavelengths further stimulate these cells, anchoring the circadian rhythm for the rest of the day.

"That contrast in and of itself communicates to our cones in our eyes, which then communicates to the intrinsically photosensitive retinal ganglion cells... telling the brain, okay, it's daytime, stimulating that daytime process."

The recommendation: a minimum of 15 minutes of morning light exposure on a clear day, closer to 30 minutes if overcast. Seeing the actual sunrise isn't required, getting outside within the first hour of waking still provides meaningful circadian benefit.

Debunking the Circadian Dead Zone

One of the most useful corrections in this conversation: the popular idea of a "circadian dead zone," a midday window when light supposedly has no effect on the rhythm, is not supported by human research. While this dead zone does exist in nocturnal rodents, diurnal animals (and humans) show a different pattern.

Bright light exposure throughout the day, even if morning light was missed, still strengthens the amplitude of the circadian rhythm. This matters practically: missing sunrise doesn't mean the circadian benefit of daylight is lost for the day. Getting outside at any point still helps, even in shade, where light levels still reach roughly 10,000-25,000 lux compared to just 500 lux in an average indoor room.

Why Artificial Light at Night Is So Disruptive

Exposure to artificial light at night does two things to the circadian rhythm: it shifts the timing of melatonin onset later, & it blunts the overall strength (amplitude) of the melatonin rhythm.

"When we expose ourself to artificial light, not only are we phase shifting the melatonin rhythm, but we're also dampening the melatonin rhythm. So we're not producing as much melatonin as well."

The same disruption pattern affects cortisol, which should stay low at night but spikes with artificial light exposure. The downstream consequences reach far beyond poor sleep.

Night Shift Work & Cancer Risk

International health agencies have classified night shift work as a probable human carcinogen, largely because of the artificial light exposure it involves. Epidemiological evidence links brighter nighttime light exposure to higher rates of nearly every cancer type, with especially strong associations for breast & colorectal cancer.

The mechanism connects to tumor suppressor genes, which operate on their own circadian schedule. When that rhythm is misaligned, tumor suppression & regulation of cell growth become less effective.

The Diabetes Connection

A study of 400,000 participants, tracking roughly 13 million hours of personal light exposure data, found that people with the brightest nighttime light exposure had the highest rates of diabetes, while those with the brightest daytime light exposure had the lowest rates. This held true even after accounting for genetic risk factors.

Lab studies reinforce this: participants exposed to dim artificial light while sleeping (not even bright light) showed elevated fasting blood glucose & dysregulated cortisol upon waking, compared to those who slept in complete darkness.

Circadian Rhythm & Women's Hormonal Health

Women's circadian rhythms are, on average, shorter than 24 hours, making them more sensitive to light cues than men's. This has direct implications for hormone health, fertility, & menstrual cycle regulation, an area Jarecki noted remains significantly under-researched.

"For the vast majority, especially in the very beginning of circadian research, pretty much everything was just on men and male animal models."

Iris connected this to her own work with clients, noting the emerging research linking circadian disruption to premenstrual issues like PMDD, & the particularly difficult combination of perimenopause & night shift work. While the research base remains limited, existing findings suggest circadian alignment deserves far more attention in fertility & hormone health conversations, including in IVF clinics, which rarely factor circadian biology into treatment protocols.

Practical Steps for Circadian Alignment, Wherever You Live

For people living in northern latitudes with limited winter daylight, individual light sensitivity varies significantly, but several strategies help:

Sleep & wake consistency matters more than sleep duration alone. Research tracking mortality found that sleep regularity had a greater protective effect than simply hitting seven to eight hours nightly.
SAD lamps (10,000 lux) can help supplement limited daylight during darker months.
Red & infrared light exposure indoors supports mitochondrial health, particularly valuable when natural daylight is scarce.
Firelight is an ideal nighttime light source as it contains no blue light, is naturally dim, & sits low to the ground, minimizing circadian disruption.
Consistent meal timing supports circadian alignment alongside light exposure, though individual needs vary (Jarecki practices intermittent fasting; Iris noted this approach tends to suit male physiology better than female).

Jarecki's own daily rhythm reflects these principles: watching sunrise most mornings, prioritizing outdoor light throughout the day (including lunch breaks), & maintaining a nighttime environment with no overhead lighting, only warm, blue-light-free lamps.

The Bottom Line

Circadian rhythm isn't a niche wellness topic. It's the operating system underneath nearly every biological process in the body. From cancer risk to fertility, from a newborn's brain development to a dermatology patient's skin cancer risk, light exposure timing shapes outcomes in ways the medical establishment has only recently begun to acknowledge.

What makes this conversation so valuable is its simplicity. The guidance isn't complicated: bright light in the morning, bright light throughout the day, & minimal light at night. Yet the modern built environment actively works against this rhythm at nearly every turn, from phone screens as the first light of the day to artificial lighting stretching long into the evening.

For women in particular, this conversation carries added weight. With circadian rhythms that are shorter & more light-sensitive than men's, & a research base that has historically excluded female subjects, there's still so much to learn about how circadian alignment intersects with fertility, menstrual health, & hormonal transitions like perimenopause. What's already clear is enough to act on: brighter days, darker nights.

Key Takeaways

Circadian rhythm governs nearly every cell & organ in the body, not just sleep, through a central clock in the suprachiasmatic nucleus & peripheral clocks throughout the body
Morning light exposure (15-30 minutes) anchors the circadian rhythm through specialized non-visual retinal cells that respond to light contrast, brightness & blue wavelengths
The "circadian dead zone" is a myth in humans - daytime light exposure still strengthens circadian rhythm even without morning sunlight
Artificial light at night shifts & blunts melatonin production, with downstream links to cancer, particularly breast & colorectal, & elevated diabetes risk
Women have shorter, more light-sensitive circadian rhythms than men, with likely implications for fertility & menstrual health that remain under-researched
Skin cancer repair mechanisms are circadian-controlled, meaning aligned light exposure supports the body's natural UV damage repair capacity
Newborn light exposure affects brain development, mediated by the same non-visual retinal cells responsible for circadian regulation
Sleep consistency matters more than sleep duration for long-term health outcomes
Firelight, red/infrared light & SAD lamps offer practical support for circadian alignment during darker months or in northern latitudes

Transcript

[00:00:00] Iris Josephina: You are listening to the podcast of Iris Josephina. If you are passionate about exploring the menstrual cycle, cyclical living, body wisdom, personal growth, spirituality, and running a business in alignment with your natural cycles, you're in the right place. I'm Iris. I'm an entrepreneur, functional hormone specialist, trainer and coach, and I am on a mission to share insights, fun facts, and inspiration I discover along the way as I run my business and walk my own path on earth. Here you'll hear my personal stories, guest interviews, and vulnerable shares from clients and students. Most people know me from Instagram where you can find me under @cycleseeds, or they have been a coaching client or student in one of my courses. I'm so grateful you're here. Let's dive into today's episode.

[00:00:56] Iris Josephina: So for this episode, I had the honor to sit down with Jonathan, and Jonathan is actually an undergrad student at Davidson College, and he studies biology and neuroscience, and he's on the PhD track. And he has an absolute passion, and you'll feel this and hear this and see this in the episode. He has an absolute passion for translating complex science and health topics for the general public so that all of us can understand it, so all of us can improve our lives by doing certain things that are super easy to do. And the topics that we mostly dove into were the topics of light and circadian biology, why this is so important for us, why we are so passionate about bringing this wisdom out and helping people understand their relationship with light, our relationship with screens and how we can do better around that, what happens in our bodies when we don't honor the natural relationship with light that our bodies have, what happens to our hormones, to our metabolism, and we also tied it in to women's hormone health. And I genuinely loved this episode so much. I hope you will love it as much as I did, and we hope that you learn something new. If you feel that you want to talk to us after, if you want to share your feedback or your aha moments, we are both very open to receive your messages on Instagram, which is the platform that both of us are most active on. And I just can't wait for you to dive into this episode and learn all these super cool things about your body, about light, and I cannot wait to hear from you after you've finished the podcast what you thought about it. Enjoy listening.

[00:02:48] Iris Josephina: Hey, everyone. Welcome to a new episode of the Inner Rhythms podcast. I am here with Jonathan Jerecki and I'm very, very excited to speak with him today because he is as passionate about circadian biology as I am. Welcome to the show, Jonathan.

[00:03:06] Jonathan Jerecki: Yeah, thank you so much for having me on, Iris. I'm excited for the conversation.

[00:03:09] Iris Josephina: Yeah, me too. So, you mentioned before that you went through pre-med school and then as you were going through all of that you kind of decided to step away from that. And when you mentioned that on your Instagram I was very curious what led you to take that step. What did you see in there that made you want to take a different direction?

[00:03:35] Jonathan Jerecki: Yeah, for sure. Great question. So I'm an undergrad right now. I go to Davidson College in North Carolina here in the States. And going into my undergrad, my freshman year, I knew I wanted to do something in STEM and in sciences. I had a great experience with my science classes in high school. And so I wanted to major in biology, minor in neuroscience, and that was definitely the path I wanted to take in terms of my major and minor and what I wanted to study in undergrad. And at the same time there was also a ton of, at Davidson there's a ton of students who are pre-med, so they're on the pre-med track wanting to go to med school after undergrad. And so I was around a lot of those students and that definitely had an influence on it and I sort of had this idea like, all right, it would be awesome if I could have this influence on the medical establishment being in it with a different perspective. So that was sort of the track I wanted to go down, and yeah, so I was on the pre-med track. And it wasn't until a few months ago that I decided to quit it. So I was raised in a very holistic household. We focused a lot on alternative medicine and didn't really go to the doctor very much growing up, didn't go to the doctor at all besides yearly checkups. So my mom raised us with this idea that if you take the right approach you don't necessarily need the doctor, at least to the extent of how people are using the doctor today. Obviously there's a time and place, like if there's a tragic accident or something like that, it's good to go to the doctor. But for the most part, like, we never took medications or anything like that. So I had that mindset already from my childhood and growing up and I'm still of the same mindset today. And so it was definitely interesting because I was one to have much different perspectives on many different areas in this field than pretty much a lot of my peers, and different than the standard medical establishment, and I have a lot of disagreements with the standard medical establishment. So after a lot of thought and some other stuff, I decided that it probably wouldn't be best for me. And at the same time, I also had this passion and have this passion for research. I love research, and really, research is the foundation of what doctors take on for their understanding, and textbooks are obviously all built on the research that we have. So if we can advance research in these areas, then hopefully we could have a big effect on and influence on the medical establishment. So I think research is key, and I just love it so much. I mean, obviously you're seeing on Instagram, I share a ton about the research around a ton of different topics, mainly being light, of course. And so I decided to quit. I think it was the best option. So right now I'm currently focused on research. I'll be doing some research next semester with one of my professors, and also wanting to continue that in the long term. And one of the big things is continuing that on a more science communication background. So wanting to communicate the science with the public, because I think if we can get the science in the hands of the public, I think that's the biggest thing, and giving them the information that they could utilize for their health to hopefully improve their lives and improve their health so they don't have to rely on the standard medical establishment. Because I mean, we see it today, chronic disease is at an all-time high, cardiovascular disease, diabetes, cancer, all these things, and quite frankly they're not for the most part lowering, right? They're only going up, and we need big change, and it comes from lifestyle, right? We can prevent the vast, vast majority of these diseases with lifestyle approaches, and it starts young, right? So it's like we need to start this as soon as possible in terms of babies and children. But obviously even if you're in your older ages, you can have dramatic effects reversing chronic disease as well. So it's not only prevention, but it's also reversal. So yeah, that's sort of a little bit about why I wanted to step away from that. And ultimately it just wasn't aligned with the views that I had and what I wanted to do. At the same time, I have a bunch of my friends who are going into med school after undergrad and a lot, more than I would expect, have this understanding of lifestyle on health. So I think things are coming around, especially with the newer generation going into the medical field. They're seeing all the chronic disease that is burdening our society, and I think they're understanding gradually that lifestyle can have an effect on that, and you can prevent it, and you can reverse these diseases.

[00:08:04] Iris Josephina: Mm-hmm.

[00:08:04] Jonathan Jerecki: So I'm very hopeful for the future in terms of the medical establishment. But yeah, for me, I wanted to take a step back there.

[00:08:12] Iris Josephina: Thank you for sharing that, and I think it's such a good angle to really want to focus on research and specifically want to bring it to the public. I once read an article and it stated that it takes about 17 years for research to actually land into clinical practice, which is an insanely long time. Like, people need help now. Like, what are you talking about? The research is there. Apply it.

[00:08:34] Jonathan Jerecki: Yeah.

[00:08:35] Iris Josephina: So yeah.

[00:08:36] Jonathan Jerecki: Yeah, exactly, and that's sort of just the fault of how science works. But I think what's really great is that if we can get... a research paper can come out, and the next day you can post something on social media about it and get the word out that way. So I think that's what's really great about social media. Obviously social media has its pros and cons, but one of the pros is that we can get this information out more readily and more easily, whereas a textbook, I mean, textbooks are 20 years behind what we currently understand, you know? And what we currently understand is many years behind what is actually reality. So there's a big delay in research and medicine for sure.

[00:09:16] Iris Josephina: Yeah. And I also like that you mentioned that there is really this movement where people understand that lifestyle is really at the foundation. It's interesting because in my language, all of these newer diseases and chronic things that come up, we actually literally translate them, we call them lifestyle diseases that are induced by how people create their environments and create their lifestyles. So yeah, so you mentioned before that you are mainly focusing on light, and light in relation to human bodies is really part of the field of circadian biology. For someone hearing circadian biology for the first time, why is that important and why is light the thing that we should organize everything else around?

[00:10:07] Jonathan Jerecki: Yeah, great question. So let's first take a step back and look at what is a circadian rhythm, right? So our bodies have this clock in them. It's this intrinsic clock that runs throughout our body, and there's a central clock. So the central clock is in our brain. It's called the suprachiasmatic nucleus in the hypothalamus of the brain, and this central clock is essentially a clock, right? So it's this roughly 24-hour clock. So on average, humans' circadian clock is around just over 24 hours, so it's around 24.2 hours, which is important. So let's say we put someone in a cave where they're not exposed to any environmental cues like light, right? Put them in a cave for long periods of time. What's going to happen is their intrinsic clock within their body is going to run at a 24.2-hour rhythm, so it's going to start getting delayed as the days go on because it's not getting entrained by the 24-hour light-dark cycle. So the circadian rhythm will run automatically whether we have light exposed to us or not, but the primary timekeeper of the circadian rhythm is light. We do utilize light to entrain that circadian rhythm, so our internal clock is aligned with the rhythm of the light-dark cycle of the Earth wherever we're located, right? So that's really important there. And the circadian system governs practically every single cell and every single organ of our body. So we have this central circadian clock that basically talks to all of our cells, telling all our cells what time of day it is, which then tells our cells, "Okay, release this hormone at this time, release this protein at this time. Translate and transcribe this protein in X." So it's doing all these processes and it's controlling all these processes as well. At the same time, we also have peripheral clocks. So we have clocks in our muscles, we have clocks in our gut, we have clocks in our heart. So we have these peripheral clocks that talk to each other and communicate with the central clock. These clock systems within our body govern pretty much every single facet of biology. And we want that entrainment to occur, and light is the primary thing. So our clocks can also get entrained by other cues, which are called zeitgebers or timekeepers. The main one is light. There's also food. Food affects the rhythm, so what time we're eating, right? We don't want to eat late into the night, things like that. Exercise also affects the circadian clock, things like that. But the main timekeeper is light. And this makes sense, right? Because when we look at it from a primordial standpoint, our primordial existence would have been we would have been outdoors twenty-four/seven being exposed to the light-dark cycle of the Earth, and that is going to affect when we need different hormones being produced and all things like that. So that's really the foundation there. And the circadian system, I think it makes sense, if it governs every single cell and every single organ in our body, well, it's going to have effects on health outcomes, right? So we can look at epidemiological evidence and also mechanistic evidence. If we misalign the circadian clock, if the circadian clock is not aligned to the light-dark cycle, well, we have downstream effects. So this has effects on pretty much every single disease. It has effects on diabetes, it has effects on cardiovascular disease, on cancer. Specific cancers like breast cancer and colorectal cancers are big ones there. But it really has an effect on pretty much every single disease that we know of. Like ulcerative colitis, there was a paper that came out a few months ago on ulcerative colitis on how the circadian system affects that. So pretty much every single thing has a circadian component. So the circadian system is vital to living properly in alignment with how your body is meant to be living. And I think when we look at our current society, right, we are having very dim days. So we're indoors a ton. We're not being exposed to light a ton in our mornings. We're not really getting outside very much, right? I know for Americans the stat is 93% of Americans' day is spent indoors, right? And a lot of the times people wake up and the first light they're exposed to is their phone, and they'll start scrolling on their phone, and they probably stay indoors for the rest of their morning, not exposing themselves to bright light in the mornings. And then at night, the opposite, right? We have bright nights. So we turn on the lights at night. Everywhere you go, we have light pollution just in general from outdoor lights like lampposts and things like that, but also the indoor environment has tons and tons of artificial light at night, and that again is affecting that circadian system. Essentially, the nighttime one I think is easy for people to understand. It's like when you're exposing yourself to bright light at night, it's essentially telling your body that it's daytime when it's not. Right? So it's giving the wrong cue to your body when you should be getting the cue, "It's nighttime. Do the nighttime things," right? So that's essentially a little bit of a rundown of what the circadian system is and why it is so important. Again, it's affecting everything, everything we do.

[00:15:07] Iris Josephina: Mm-hmm, for sure. And I mean, I work with female hormones and fertility and all that kind of stuff, and I really dove deep into how circadian rhythm and circadian clocks connect to fertility, spermatogenesis, ovarian health. Like, it's insane how all of that is connected. And I don't think IVF clinics even think about that. But as you say, it's connected to every single process in the body.

[00:15:35] Jonathan Jerecki: Yeah. I mean, even there's some great research coming out now. It's like even with cancer therapies and just medications in general, we're giving these medications and cancer therapies, which in and of themselves have problems, but we're also giving them at a time of day where we're not even considering that there's actually an effect on the time of day we give these therapies and these medications on the system. And again, there's a whole rabbit hole of these medications also having all their side effects in and of themselves. But we're increasing those side effects by giving them at times of day when we shouldn't be giving them, right? So it really governs so, so many things.

[00:16:16] Iris Josephina: Yeah, so let's take it back to this first light in the morning, right? Could you walk us through what is actually happening inside the body in these first few minutes or 15 minutes that we are exposed to this first light? And I'm sure it needs to happen in a specific timeframe. You can't have your first light at 1:00 PM, for example. Could you walk me through it?

[00:16:42] Jonathan Jerecki: Yeah, so ideally, right, the ideal scenario is we're exposing ourselves to sunrise. Now obviously the time of that is going to depend on where you are located. I would say let's just think about this as at the equator, right? I mean, our primordial existence is at the equator, and obviously as humans evolved we moved away from the equator. But at the equator it's a roughly 12-hour day, 12-hour night. And when we get up in the morning, right, we're ideally exposing ourselves to sunrise. And what's happening when we're exposing ourselves to sunrise? A couple of things. So one, there's a contrast in the sky at sunrise, and that contrast in and of itself, that orange-blue contrast in the sky, communicates to our cones. So we have different cells in our retina. We have rods and cones, which most people are familiar with. We also have what's called intrinsically photosensitive retinal ganglion cells. So these are non-visual forming cells within the retina. So the rods and cones affect the visual system, so they allow us to actually see stuff. The intrinsically photosensitive retinal ganglion cells don't allow us to see stuff. They simply communicate these light cues. So when we expose ourselves to the sunrise and we see that contrast, what's actually happening, there was a beautiful paper published in Cell, I believe in 2020, so this is actually a recent finding, where that contrast in and of itself communicates to our cones in our eyes which then communicates to the intrinsically photosensitive retinal ganglion cells, enhancing that signal to those ganglion cells, which then those ganglion cells will send a signal to our suprachiasmatic nucleus, the central circadian clock within the brain, telling the brain, "Okay, it's daytime," stimulating that daytime process. Now, as the sun continues to rise, that contrast starts to go away. The sky starts to get much more brighter and much more blue. So now you're having more blue light coming to you, and you're having a much brighter light coming to you as that sun is rising. And that blueness and that brightness and also that angle is directly affecting those retinal ganglion cells. So now this is a different process than that contrast. So that brightness and that blueness and that angle stimulates those retinal ganglion cells, again stimulating that circadian system, essentially entraining the circadian system. So what you're doing is you're anchoring in that morning time. So that morning signal for the circadian system, you're anchoring that in, like all right, now we have that system in place. So we're entraining the rhythm because, again, that rhythm will start shifting if we're not getting the light. So if we get that light in the morning, we're anchoring the system for it to go for the rest of the day. Now, that's the phase, right? And so we're getting that bright light into the eyes and ideally a minimum of fifteen minutes is really what we want. Now on an overcast day, we want to have more than that. We want to do probably thirty minutes. But on a bright, clear day, fifteen minutes is that minimum that we want. Now, it's not necessary that you see the sunrise, although that is obviously the ideal scenario. It's not necessary. Even if you wake up early but the sunrise already occurred, still getting outside within the first hour of waking up and viewing just that brightness and that blueness and that angle of light is still going to stimulate and entrain that circadian system. So the sunrise plus the continued sunrise is going to have the largest effect, but you don't necessarily need the sunrise. So that's sort of how we anchor the circadian system for the morning hours. Now, what's really interesting, and you mentioned the timing, right? So when we look at the circadian system, we have two main things. There's the phase of the circadian system, so that is sort of like the length of it, but then there's the amplitude as well. And the amplitude of the rhythm is basically how high up that rhythm, that wave, goes. And that's like the strength of the rhythm. Now, when we expose ourselves to bright light in the morning, we're affecting the phase of the rhythm, entraining that phase, but we're also affecting that amplitude. We're strengthening the amplitude. Now, what's really interesting, and I'm actually just becoming aware of this within the past few weeks. I had a conversation with Dr. Sean Kane, who's one of the leading circadian biologists out there. He's had some tremendous papers that him and his team have published. I talked to him about what's considered a circadian dead zone. So there's this idea of a circadian dead zone, meaning in the middle of the day we cannot affect the circadian system at all. And this is sort of what has been talked about within the circadian realm on social media and things like that. I talked to him and I asked him about this circadian dead zone. Turns out that nocturnal rodents, so mice that are awake at night but asleep during the day, they do have a circadian dead zone. So you shine bright light on a nocturnal rodent during their day, in the middle of the day you cannot affect the circadian system. However, when we look at diurnal rodents, which we are diurnal, right? When we look at diurnal rodent models in mice who are awake during the day and asleep at night, we can shine bright light in the middle of their day and throughout their day, and we can affect the circadian system. So there is no circadian dead zone for these diurnal mice. The specific thing that we're affecting is the amplitude. So it doesn't seem that we can shift the phase of the rhythm, but we can affect the amplitude of the rhythm and the strength of the rhythm. I was talking to Sean Kane, and he even argues that it's an even more important factor, that amplitude, that strength of the rhythm, than the phase of the rhythm. And so we can strengthen the phase with bright light on these diurnal rodents. Now let's look at the human studies. We actually have a handful of very well done human studies doing the exact same thing. Irrespective of morning light, so irrespective of getting bright light into the eyes in the morning, getting bright light into the eyes during the day, in the middle of the day, increases that strength of the rhythm, increases the amplitude of the rhythm in humans. These are human studies. So there doesn't seem to be a circadian dead zone to the extent of you cannot affect the rhythm. You can still strengthen the rhythm in the middle of the day. So that's really to say, if someone doesn't get their morning sunlight, although it's extremely important to still get your morning sunlight, right when you wake up get out there as soon as possible, but if someone doesn't get that, it's not like you've now lost the circadian effect that you can get if you just go outside to get bright light into the eyes during the middle of the day, right? And this doesn't have to be direct sunlight, so even if you're under shade, you're still getting tons and tons of bright light. We measure brightness of light in lux. And when we measure lux outdoors on a bright, sunny day we can have up to 250,000 lux. Indoor environment you'd be lucky if you're at 1,000 lux. Now, if you have a ton of windows, maybe you can get to that 1,000 lux mark, but for the most part the average indoor environment is like 500 lux. So much, much dimmer indoors than it is outdoors. So even under shade you're getting tons and tons of bright light. So that's the thing that I think about there in terms of the morning and the daytime.

[00:23:54] Jonathan Jerecki: And then at night I think it's important to touch on this as well. When we expose our eyes to artificial light at night, and Sean Kane has a beautiful paper published on this looking at just the indoor home environments, right? When we look at the melanopic lux, so the ability for light to stimulate the melanopsin within these ganglion cells in our eyes, when we look at sunset, melanopic lux drops dramatically until the sun is obviously set, and then there's no light outdoors in the environment. Within like a 20- to 30-minute frame you're going from high melanopic lux to practically zero. Now, when we look at the built environment, that melanopic lux, that ability for light to stimulate the circadian system, continues all the way out through the night because people are being exposed to artificial light at night that's stimulating those cells, stimulating the circadian system, telling your body it's daytime well into the late, late night hours. And what's happening there, going back to the phase and the amplitude, you're shifting the phase. I think it's easy to think of melatonin and cortisol for these scenarios, right? Melatonin, we want high amounts of melatonin at night. Now, what's happening when you're exposing yourself to artificial light at night, you're shifting that melatonin onset. So now melatonin is going to start being produced much later into the night, once you start not exposing yourself to artificial light. We're extending that far into the night with our current modern environments. At the same time you're also reducing and blunting the amplitude of the rhythm when you expose yourself to artificial light. So let's just think about, you go camping. Sun sets, it's dark. What happens is you have a nice melatonin onset, so melatonin starts getting produced early, but also you have a nice amplitude in that melatonin rhythm. So you have a ton of melatonin. The strength of that rhythm is strong, so you're producing a lot of melatonin. Now, when we expose ourselves to artificial light, not only are we phase shifting the melatonin rhythm, but we're also dampening the melatonin rhythm. So we're not producing as much melatonin as well. So you're having those two effects that are going to obviously have downstream effects, and that's just the melatonin example, but there are a ton of other ones. I mean, cortisol, artificial light at night is going to spike the cortisol. We want low cortisol at night. But again, this is affecting everything. So it's not just those two hormones, but everything else. Those are just two easy ones to understand. So that's really how I think about morning, daytime, and nighttime light on the circadian system. And the best thing is it's super simple to get back in line. It's not any crazy thing. So it's like get bright light in the morning, get bright light throughout the day, and get as little light as possible at night, and that's really the main thing for people to do.

[00:26:43] Iris Josephina: Yeah, I usually tell my clients brighter days, darker nights. Simple.

[00:26:47] Jonathan Jerecki: Exactly. Yep. Exactly.

[00:26:48] Iris Josephina: Yeah. And you've mentioned how our screen exposure basically almost messes with the ability of our bodies to respond to that. What are some of the downstream effects that you have seen or studied or heard about when people don't honor this circadian rhythm, specifically of light, and don't have red lights in their house or dim the lights at night? What are some of the downstream effects that could happen for people that they're maybe even not aware of?

[00:27:22] Jonathan Jerecki: Yeah, so I think this is a huge one that people are not aware of. The international agencies have literally classified night shift as a probable human carcinogen. So a group two carcinogen, a probable human carcinogen for night shift workers. And what's happening with night shift? They're being exposed to artificial light throughout the night. And I would make the argument that pretty much every modern human is a night shift worker at this point, you know? So night shift, and just getting artificial light into the eyes at night, and getting that bright light at night when we're not supposed to, is going to have an effect on cancer, right? So we see when we look at epidemiological evidence, brighter nighttime light and getting exposed to artificial light at night is correlated with higher rates of pretty much every single type of cancer. It's very emphasized with breast cancer and colorectal cancer and things like that. But for many, many cancers we have higher rates with getting more light at night. And then when we look at more mechanistic stuff, we can do these same experiments on animals. We can shine light onto these animals at night, and we see increased rates of tumors in these animals. And again, that's going to have, there are a lot of mechanisms at play there, but one of the main things is tumor suppression. So all of our tumor suppressor genes and proteins are governed by the circadian system. These tumor suppressing proteins that suppress tumors and regulate tumor growth are expressed at certain times of the day and are not expressed at other times of the day. Now, if that rhythm of these tumor suppressor proteins is misaligned, well, then we're going to not be able to regulate tumor growth and cancer growth and things like this. So that's really what we're seeing there. And there are other effects on that, but that's really the main mechanism. I think also, cancer is a big one. Cardiovascular disease, the American Heart Association actually came out with a public statement, I think it was late 2025, expressing how a big player of cardiovascular disease is circadian rhythm and circadian misalignment and circadian disruption. So this is the American Heart Association acknowledging this. So there are players there. Again, your heart has a circadian clock, so there are cardiometabolic effects there. And again, pretty much all the epidemiological evidence that we have shows that as well. I would say another big one, and we have great human lab experiments on this, is metabolism and diabetes and things like that. So I'll first start with the epidemiological observational evidence. We do have correlations showing that people who get brighter nights have increased diabetes. Sean Kane and his team did a great paper on this. It was 400,000 participants looking at their personal light exposure. So it was around 13 million hours of light exposure data where they wore a wristband, tracking how much light they were exposed to day and night. And what they saw, and then they correlated that with diabetes, was that the people who got the brightest nighttime light, so getting a lot of artificial light at night, had the highest rates of diabetes. And then also at the same time, the people who got the brightest daytime light, so getting a lot of bright light during the day, had the lowest rates of diabetes. And the vice versa. So people who got the lowest daytime light had higher rates of diabetes. People who got the lowest nighttime light had the lower rates of diabetes. So again, like you said, brighter days, darker nights is going to have the best effect on metabolism and diabetes. Now again, that's correlation. What's really interesting with that study is they accounted for a ton of confounding variables, but they also accounted for genetic risk. So irrespective of these participants' genetic risk, the light exposure itself still had an effect on their diabetes. So the light exposure itself had these increasing rates of diabetes irrespective of genetics. Now, getting to these interesting human lab experiments. So this isn't going to look at diabetes, but still a marker. There are some papers where they bring people into a lab and they sleep there overnight for a few days. And what they do is they just have light shining on these participants while they're sleeping. So very dim light, though. This is not like they flip the lights on at night. It's a super dim light, but obviously enriched in those blue wavelengths of light while these people are sleeping, and they monitor their blood glucose. They look at blood glucose before they go to bed and then looking at blood glucose after they go to bed. They have a control group, an experimental group, and all these things. And they see that the people who got exposed to the dim, still very dim, artificial light at night while they're sleeping had much elevated fasting blood glucose levels upon waking. Cortisol was also affected, so they had dysregulated cortisol rhythms when they were waking up. And these are things going back to metabolism. Cortisol is a glucocorticoid, so it actually regulates when glucose goes into our muscles and things like that. And then obviously elevated blood glucose is a sign of poor metabolic health, which can lead to prediabetes and Type 2 diabetes. So there's plenty and plenty of evidence. We have obviously a ton of animal model experiments on this as well. Observational experiments and the lab experiments all corroborate on this one idea that getting artificial light at night has negative health consequences on multiple levels. Not just cancer, I mean obviously the cancer is a huge one, but on pretty much every single chronic disease. So again, it just points to what you said. We want dark nights, and we want bright days, and that's how we're going to reduce our risk for these chronic diseases.

[00:33:04] Iris Josephina: Mm-hmm. So a lot of my audience lives through darker northern winters. Like, I'm from the Netherlands, so we have pretty gray, dark winters, and a lot of people work indoors a lot of the time. And you mentioned before that our primordial state as human beings, years upon years ago, we used to live around the equator where the days are equally long as the night. And obviously through human migration, we migrated away from the equator over thousands and thousands of years. So we ended up up north, experiencing very dark winters. Some people don't even experience daylight during their winters. How would you say that we should be going about our light exposure when we live in environments like that?

[00:33:59] Jonathan Jerecki: Yeah. So this is a great question, and I think there's a lot of individual variability here. So I'll take a step back and just look at the circadian rhythm and the sensitivity of light on the circadian rhythm. It's actually very variable on an individual basis. So some people could be super sensitive to light at night in effects on the rhythm, but some people can be very resilient to light at night, where artificial light at night doesn't actually affect their rhythm as much. It's still going to have an effect on the rhythm for sure, but not as much. So the individual variability is pretty large. So for each person it's going to differ a little bit. Now, to your point, right, it's like we are designed, for the most part, to be in a more equatorial area as it relates to circadian rhythms. Now, that's not to say we haven't, there are definitely some populations that have adapted to longer days or shorter days. And like you said, some people don't get any light into their eyes at all just because there is no light where they are if they're super far up north. So I would say there are a few things people can do. I think it is very important to still, especially people who are working normal shifts, it's still very important to keep that rough 12/12 in terms of 12 hours of day, 12 hours of night roughly. Obviously it doesn't need to be exactly, but it's still important to keep that consistency. So there are some things people can do artificially. So you can get like a SAD lamp, a 10,000 lux bright light lamp that people can utilize. That can be effective. And there are different ways to utilize light in that scenario. I think a big one is, and this is sort of separate from a circadian perspective but looking more at the mitochondria and light's effects on the mitochondria, we also want these longer wavelengths of red and infrared light, especially during the winters when we are indoors a ton and our indoor environment doesn't have any longer wavelengths of infrared light. Utilizing incandescent light bulbs, utilizing devices that have these longer wavelengths of light can be very beneficial, especially during the winter months and especially when you are not getting outside a ton. I would say that's a big one, and really just being consistent with sleeping and waking. So again, like I mentioned, your rhythm is going to still go on even if you're in a cave, right? So the rhythm still runs. It's not like it just shuts down completely. Again, you're entraining your rhythm with the light, but you're also entraining your rhythm when you go to bed and when you wake up. So having a consistent wake-up time and sleep time is probably going to be one of the biggest things and levers that people can utilize, especially people who are up north and things like that. There was, again going back to Sean Kane and his colleagues, a paper that he published in I think 2023, where they were looking at mortality among a large population size, and they were looking at sleep regularity versus sleep duration. And what they actually found is that what affects mortality the most, and at a much greater scale, is sleep consistency rather than sleep duration. So if we can keep the consistency of sleep, so waking up at the same time every day and going to bed at the same time every day, that's going to have a larger effect than actually sleep duration in general. So everyone talks about get your seven, eight, nine hours of sleep every night. Yeah, that's great, but we want to keep that consistency. We want to keep that seven to eight hours consistent in terms of when we are getting that seven to eight hours of sleep. So I think that's a really big lever people can utilize, consistency. And again, utilizing bright lights indoors can be great. But if you are in an area that has daytime light during the winter months, still just try to get out there as much as possible. Being near a window like you are right now and I am, that's really important as well. Having that dynamic lighting throughout the day is great. So those are some tips that I would probably recommend for people. And again, for people who are exposed to no sun, if it's literally just nighttime all day long, very far up north, still turning on those lights when you wake up and turning them down when you go to bed. So that's probably the biggest thing that people can do.

[00:38:28] Iris Josephina: Mm-hmm. One of the things that I usually tell my clients when they are far up north, to have them support the infrared spectrum, is fire. Like working with fire, being in front of a fire, opening your fireplace to make sure that at night you have that cue.

[00:38:46] Jonathan Jerecki: Yes. Yeah. Exactly, yeah. That would be huge. If people have access to fire and a fireplace at night, that should really be the only light that they are exposed to at their nighttime. So that is great. And why is fire such a great light to use at night? I mean, it's really like the first artificial light that humans created. But one, fire has no blue light. It is very dim, and it's very low to the ground. So you're having those three things stacking up on each other that makes fire such a great light to use that doesn't affect the circadian system very much. So yeah, that's a great option to do.

[00:39:24] Iris Josephina: Yeah. So as you know, I work with women mostly, and I'm interested to know, does circadian disruption as we know it in our society today, does it happen differently in women's bodies given that they go through a bigger infradian rhythm than men? Obviously a sperm cycle is also very infradian. Like, there is this idea right now like, "Oh, men are circadian and women are infradian." I'm like, "No, people. That's not how it is." We all have both. But given that women go through such a more expansive infradian rhythm and bigger hormone drops and rises, how does circadian disruption impact that from your perspective, from what you've seen and learned?

[00:40:11] Jonathan Jerecki: Yeah. I'll even say something on the circadian rhythm for men versus women. So women actually have, like I mentioned, the on average human's circadian system is 24.2 hours. Women have a shorter circadian rhythm typically. Again, that's going to vary, but on average women have a shorter circadian rhythm than men, so it's actually going to be shorter than 24 hours, which actually makes them more sensitive to light cues on the circadian rhythm. So I would say for them it's probably even more important. And again, going back to hormones, right? It's probably even more important to really lock in the light cues in general, and really focus on not getting artificial light as much as possible at night, because they're going to be even more sensitive. So I think one of the also faults of science is a lot of studies aren't looking at women. I mean nowadays we're getting a lot more, but for the vast majority, especially in the very beginning of circadian research, pretty much everything was just on men and male animal models. I don't think they were utilizing very much female models at all. And that's really true in much of endocrinology and in a lot of just hormone-based research. It's definitely coming around, but definitely in the very beginning they weren't utilizing women at all because it's harder for the researchers quite frankly, and they want to just make it easy for themselves, so they'll just use the men who don't have these big fluctuations as women do. So I would say hopefully we can get some more research on this, but it is definitely apparent that women are going to be more sensitive to this and it's going to have a larger effect on them.

[00:42:05] Iris Josephina: Mm-hmm. There is quite some research out there. Like we spoke about this earlier connected to fertility, but there is also some research on perimenopausal women because their hormones are obviously fluctuating and shifting and changing, and they're more sensitive to even circadian disruption. Specifically shift workers who are perimenopausal, it's like the worst combination that you can go through. And then there have also been some connections between premnstrual issues, PMDD, and circadian disruption. So there is some stuff out there but it's a bit of a tiny pile of research. Like, we need much more.

[00:42:49] Jonathan Jerecki: Yeah.

[00:42:49] Iris Josephina: For sure.

[00:42:50] Jonathan Jerecki: 100%.

[00:42:50] Iris Josephina: Yeah. So what are some of the things that healthcare practitioners and people in general get wrong about this whole circadian rhythm thing?

[00:43:03] Jonathan Jerecki: Sure, yeah. A few things. I'll say just one quick thing since we already touched on this, but that circadian dead zone, that concept of that in humans is obviously, like we mentioned, wrong. We need to understand that even getting bright light throughout the day is very important. So that's one thing I think a lot of people get wrong, and quite frankly I got wrong until having this conversation with Sean Kane. A couple of other things. I would probably say the biggest one, and I'm in college right now so I'm really focused on younger people and people my age and in my generation. I think the biggest thing is they just don't understand that light at night, and also getting light during the day, is important and has an effect on the rhythm. Now, obviously I've been in some entry level bio classes and other more advanced bio classes, and we do learn about the circadian rhythm for the most part, but it sort of just talks about mechanisms and things like that, not a whole ton on outcomes and consequences and things along those lines. So I think getting people, especially my generation, to understand that these effects are dramatic and they're real, and yes, perhaps you're not going to see a negative effect right now because the body's very resilient, which is great. But down the road there are going to be consequences for getting artificial light at night and not getting enough bright light throughout the day. So I think making that message more known in that space and within my generation. And then again to medical doctors, for them to understand the circadian rhythm is super important. And when they're dealing with patients and things like that, circadian biology isn't even a focus. Now, one of my favorite things to touch on here is dermatology. So, you know, dermatology obviously advocates to get as little sunlight as possible, as little direct sunlight as possible. And there are obviously risks and benefits to everything. There are risks and benefits to sunlight. We need to utilize the sunlight properly. But one of the big things is, like I mentioned, every tumor suppressor protein and every regulator of skin cancer, and DNA repair mechanisms, are all under circadian control. So it's really interesting. One of the main DNA repair mechanisms for UV-induced DNA damage is this protein called NER, N-E-R, and NER gets expressed the most if our rhythm is aligned. It gets expressed the most in the middle of the day when we would be exposed to those high amounts of UV light from the sun, and it starts going down at night when we don't really need NER to be expressed. We don't need to be cleaned up as much. So in that circadian-aligned scenario, it's perfect. We're getting exposed to a lot of UV light in the middle of the day. DNA is breaking just as that naturally happens, and there are actually some beneficial effects of that. But for the most part, we don't want DNA to be damaged long term, and that's why NER gets expressed the most during that time when DNA is going to be damaged the most. Now, if our central circadian rhythm is misaligned, that's going to have an effect on all the circadian systems, and one of those being the NER rhythm. So NER can either be shifted, so now we don't have NER being expressed in the middle of the day, or it can be blunted. The amplitude can be blunted. We don't have enough NER being expressed. So even when we look at skin cancer and dermatology, they're not even taking into consideration circadian biology, right? So I think if dermatologists told their patients, "All right. Get your circadian rhythm aligned," well, then they probably wouldn't have to be dealing with so many skin cancers. Obviously it's not the perfect cure. Getting your circadian rhythm in line isn't going to prevent you 100% from skin cancers, but it's going to have a dramatic effect, no doubt about it. I mean, we look at animal models where if we misalign the animal's circadian system, looking at skin cancer specifically, we have skin cancer increase right? Simply because their rhythm is misaligned. So I think getting this into dermatology, but getting this into the medical establishment as a whole, and like I said, I think things are hopefully changing with the American Heart Association coming out with their statement on circadian biology and cardiometabolic effects. So I think things are changing hopefully. But just coming to this realization that it has a profound effect, and if we understand that, if we start preaching it more, if we start telling patients that, we can have a big effect on patients' health.

[00:48:00] Iris Josephina: I definitely agree with that. And it's like so under-discussed in so many fields, and then we haven't even talked about children and children on screens. Like, it's something that I'm at the age where we're exploring having kids, and seeing people around me, like their babies are two years old, three years old, and the first thing that they get in the morning is their iPad. And I'm like, wow. What kind of effect does that have on these little brains that are still neurologically developing in such a crucial stage of development where the foundations of all the neurological connections are laid. And yeah, it's just something I'm really worried about, and I personally believe that doctors should advise parents to not expose their children to artificial light up until a certain age, because it's so damaging to their development. And you can't redo your development when you are a kid.

[00:49:00] Jonathan Jerecki: Yeah. Touching on newborns a little bit, there was a paper published in Cell not too long ago where, this was on mice, but what they were looking at is newborn mice from neonatal day one to day nine. In these mice, and also in humans, our rods and cones aren't functioning, but our intrinsically photosensitive retinal ganglion cells are. And what they were seeing is that when we get bright light into the eyes of these newborn mice within that first one to nine days of being born, a few things occur. One, synaptogenesis, the formation of synapses within the brain, actually increases. And the mechanism there involves oxytocin and things like that, but synaptogenesis increases. What they also saw, they looked at these mice over time and into adulthood, their cognition was improved, simply by just getting the bright light in the first nine days of life, right? And again, this is not visual. This is all intrinsically photosensitive retinal ganglion cells, so non-visual forming, having an effect on literally brain cell formation and development. So yeah, it has an effect. And even those researchers, obviously this was done on mice, but they talk about the human relevancy, and there's definitely a lot of relevancy. All the mechanisms and everything is conserved in humans, so it would make sense that this also happens in humans. So even within the first few days of your baby being born, getting them outdoors, and again, you don't need to expose them to direct sun exposure. They can be under shade, but just getting that brightness of light into their eyes is going to be so, so helpful for right then and there on their brain development, but then long term on cognition. So it's super important for children as well, and you're right. We need to not have children being on these devices all the time. And circadian aside, you know, it's also having short wavelength blue light in isolation that's going to have effects on cell viability just from a cellular perspective, and the retina is the most sensitive. I mean, the eyes are basically just a projection of the brain, so you're having this layer of brain that isn't being protected much. Our internal organs are protected because we have skin, so our skin is protective of that. But we have the retina that isn't protected very much. Blue light penetrates completely through the lens of the eye and reaches pretty much 100% of the spectrum of blue. Yes, 100% of the spectrum of blue reaches the retina. And so we're exposing a very vulnerable layer of tissue to artificial isolated blue light that is going to have cellular damaging effects as well. And we see high rates of myopia and all these things in children. So yeah, there are a lot of problems with screens and things like that, and we want to limit them as much as possible.

[00:51:55] Iris Josephina: Yeah, I really wish that there's more and more awareness around this because people, this is another thing people don't know. People have no idea.

[00:52:02] Jonathan Jerecki: Yeah. Well, I will say, I have here, let me see, it's over here. I don't know if you've seen this. It's called the Daylight Tablet. Have you seen this?

[00:52:08] Iris Josephina: I have seen that, yeah, but I've never, I've seen it online, but I don't know anyone who has one.

[00:52:13] Jonathan Jerecki: Yeah, yeah. So this thing is awesome. I've been using it for a while now. But it doesn't emit any blue light. It's meant to be used outdoors, so it works the best when it's outdoors because it doesn't emit any light. It only reflects light. So when you're outdoors, obviously since it's much brighter, you're going to have a lot more reflecting light coming back, so it's going to be more visible. You can still utilize it indoors super easily, but it's best to be used outdoors. So no blue light, no flicker, meant to be used outdoors. It's a great device. And for kids I think they have a kid-friendly one specifically for kids. They're a great company. I'm a big supporter of what they're doing.

[00:52:49] Iris Josephina: What's the name of it?

[00:52:51] Jonathan Jerecki: It's called the Daylight Tablet, or Daylight Computer.

[00:52:54] Iris Josephina: Daylight Computer. Yeah, I'll remember that.

[00:52:57] Jonathan Jerecki: Yeah.

[00:52:57] Iris Josephina: And to finish, I would love to ask you what your own daily relationship with light and dark is, and how that could potentially translate to all of us in doing better with our light and dark exposure.

[00:53:11] Jonathan Jerecki: Yeah, great question. So I'm fortunate enough, I'm in South Florida right now, so I'm much closer to the equator, so I have tons of natural daylight throughout the year, which is amazing. But what I do, I'm also fortunate I live super close to the beach, so I live like five minutes from the beach. So in the mornings, I typically wake up before sunrise. I'll drive five minutes to the beach. I watch the sun rise up on the horizon at the beach, which is lovely. And again, this isn't a necessity, so if you don't have access to this, it's not the end of the world, like we mentioned in the beginning. But yeah, so I see the sunrise at the beach, and then I try to just get as much light exposure throughout the day. So back at home during the summer, I'm fortunate enough I can work just outside. I have a nice desk outside, so I'm pretty much outside most of the day. Back up at school, I'm in classes indoors and have to work in the library sometimes. So I'll be outdoors a little less, but always for lunch I'm outdoors. Lunch break is your best time to go outside. There's no commitment to being indoors, you can always take it outside. So I'm always outdoors for lunch. And yeah, just being consistent with trying to mitigate artificial light during the day and trying to get as much bright daylight throughout the day as well. And then nighttime is really the big one for me. So at night I have no overhead lights on. I only have little lamps, and the lamps are either amber incandescent light bulbs. I've tested the spectrum on the ones I use. There's basically no blue light. And then I also utilize, there's a company called Raw Optics. They just came out with a new light bulb called Lumios. I have one in front of me right here. But their nighttime bulb, the candle bulb, is blue light free, has a very nice spectrum, tons of near infrared, and very nice and dim. So my nighttime light environment is very dim, no blue light, nice and amber. A lot of people will utilize red light bulbs but I'm not a fan of them personally. I just don't like how they make me feel, the deep red ones. Some people actually find them really relaxing. Some people find them stimulating, so it's going to affect individuals differently. I tend to lean more towards just amber. And again, that's more like firelight, you know? Firelight's not just one monochromatic red. It's a broader spectrum and it's amber. So super, super, super dim environment. And then, this is obviously after the sun sets. I do try before the sun sets to be outside for a period of time while the sun is setting. I don't see the sunset, but obviously the atmosphere is getting dimmer, so just being outdoors during that period, coming back indoors afterwards, having that light environment on after the sunset. And then again, trying to get to bed early so I can naturally wake up early in the morning for sunrise. So that's sort of my day-to-day light environment and how I do it.

[00:56:15] Iris Josephina: Mm-hmm. And do you also have specific times that you cue your meals?

[00:56:19] Jonathan Jerecki: Yeah, great question. Yeah. So I don't eat, I've just grown up never eating breakfast. I intermittent fast until lunchtime. So I have lunch in the middle of the day. And then for dinner I try to have it as early as possible. So typically my dinner is like 5:00 PM during the winter. During the summer I will extend that a little bit later just because the sun is setting later, so I'll extend that to 6:00. Sometimes it's still 5:00, but 5:00 to 6:00 is usually when I have dinner. Trying to keep that earlier is better, so I don't go to bed with a super full stomach. I always go on a walk after I eat, which is great for glucose regulation. Not only are you contracting your muscles to take in glucose, but you're also exposing yourself to longer wavelengths of light from the sun, which is going to have a dramatic effect on blood glucose levels as well. So yeah, that's what I do for meal timing.

[00:57:18] Iris Josephina: Yeah. Cool. I do the same things except I have a huge breakfast.

[00:57:22] Jonathan Jerecki: Yeah, yeah.

[00:57:23] Iris Josephina: I think as a woman it's a bit different. I think for male bodies, intermittent fasting is just easier to do, and it's more in alignment with their nervous system.

[00:57:32] Jonathan Jerecki: Yep, for sure.

[00:57:33] Iris Josephina: Thank you so much for coming on and sharing all of your wisdom and your knowledge. I'm really excited to see what's in store for you, what kind of research you're going to be publishing all throughout your life. So if that comes out, please post about it. And yeah, it was a pleasure talking to you.

[00:57:53] Jonathan Jerecki: Yeah, thank you so much, Iris. This was a fun conversation. I appreciate you having me on.

[00:57:56] Iris Josephina: Okay, this wraps up today's episode. Thank you so much for listening. Want to know more about me? The best way to reach me is via @cycleseeds on Instagram, and if you heard something today and you think, oh my God, wow, I learned something new, feel free to share the podcast on your social media and tag me or leave a review or rating. In this way, you help me reach more people like you. Thank you so much.

About the Host

I’m Iris Josephina, a functional hormone specialist, orthomolecular hormone coach, circadian biology practitioner, and entrepreneur. Through Cycle Seeds and The Inner Rhythms Podcast, I support people in reconnecting with their cyclical nature, deepening body literacy, and reclaiming hormonal harmony from a place of sovereignty and embodied knowledge. Most people know me from Instagram, where I share stories, tools, and inspiration on cyclical living, menstrual cycles, fertility, hormones, and more.

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