Light as Medicine: How Natural Light Cycles Impact Health and Longevity

The rhythms of nature have orchestrated human biology for millennia, but our modern lifestyle has disconnected us from these essential patterns. Dr. Mark Pettus takes us on a fascinating journey through the science of circadian rhythms, revealing how light serves as crucial information that synchronizes every cell in our bodies with the natural day-night cycle.

From ancient Hippocrates to Nobel Prize-winning research, the evidence is clear: our bodies respond profoundly to light quality and timing. Yet today, we spend over 90% of our time indoors under artificial lighting that bears little resemblance to natural sunlight. This mismatch disrupts our internal clocks and increases risk for depression, anxiety, obesity, diabetes, cardiovascular disease, and even cancer—all conditions that ancestral cultures living in alignment with natural light cycles rarely experienced.

Dr. Pettus explores how different wavelengths of light trigger specific biological responses. Morning blue light naturally stimulates alertness and cortisol production—precisely what we need to start our day. Evening sunset, with its red-orange spectrum, signals our bodies to reduce cortisol and increase melatonin for restoration and repair. When we expose ourselves to bright blue-rich light after sunset through screens and indoor lighting, we essentially trick our bodies into thinking it's morning, suppressing critical healing processes.

The good news? Simple changes can dramatically improve circadian alignment. Just 5-10 minutes of morning sunlight exposure helps anchor your biological clock. Using appropriate lighting throughout the day—brighter, cooler lights in morning hours and warmer, dimmer lights after sunset—can mimic natural patterns. These small adjustments yield profound benefits for sleep quality, mood, cognitive performance, and long-term health. Ready to reconnect with the rhythm of life your body was designed to follow?

Slides and audio can be found at www.thehealthedgepodcast.com
Essential Provision meals Ready to Eat (MREs) can be found at www.essentialprovisions.com

Transcript

Introduction to Circadian Rhythms

Speaker 1 0:03

Hi, I'm Dr Mark Pettis, medical Director of Essential Provisions. This webinar I'm going to review the really fascinating topic of circadian rhythm. How do we tap into that rhythm of life, that day-night cycle which we're now coming to appreciate is a major driver of quality of life and our risk of chronic, complex disease? So let me just share my screen with you here and we will get some slides up for you. Hopefully everyone can see that, okay? So by way of context, we spend very little time outdoors in modern life. In the epigenetic webinar, we talked a little bit about how modern life confronts us with environmental inputs which are very different than the inputs that our DNA, our book of life, was adapted for. An example of that in modern life is how little time we spend outdoors. Over 90-95% of our time now is spent indoors, and that time indoors is spent under non-native lighting, and so this, as it turns out, is more than a trivial change. There's a great deal of research now supporting how disruptive these modern changes are to human health, quality of life and longevity, and it makes me think of what I believe is just a profound illusion that this three-dimensional experience of life confronts us with, and that illusion really takes this form of perceiving that we're separate, form of perceiving that we're separate. We're separate from each other, we're separate from nature, we're separate from other living beings, and that is really a modern, distorted perception of life. All ancient spiritual traditions and ancient cultures saw themselves as inherently connected to nature and the ecosystems within which they lived. As it turns out, our biology, human biology, is tightly linked to these rhythms of nature. When we become disconnected from the normal day-night environmental inputs, our biology becomes disrupted, and we're going to look at what the consequences of that disruption over time can be. And lastly, while this is an issue of disease risk, it's a major issue of quality of life, from depression to anxiety, to changes in cognition. Think is a huge and under-recognized issue, certainly in the clinical community, from which, you know, I've been practicing and teaching over the last 40 years.

Speaker 1 3:36

Now, this is a look at the US from the space station at night and you can see just how lit our country is. This, I would make the case, while extremely convenient, is a relatively new human experience. Really, until Edison developed the light bulb back in the mid-late 19th century, we had never experienced nighttime environments like this. Just to look at Europe, ours is a planet pretty well lit at night. There are pockets of the planet that have remained dark, but they have become far and few. Well, it's also interesting to consider the fact that this planet, that we're on Earth, is rapidly moving, spinning, moving. Everything in the cosmos is moving. If you were at the equator, you would be. The planet is spinning at about 1,000 miles an hour. Be, the planet is spinning at about a thousand miles an hour. If you look at Earth rotating around the Sun, it's moving at about 66,600 miles an hour. And it's this movement, the rotation, the movement that has created these patterns of sunlight and darkness, that have really defined the environmental conditions within which all humans on this planet have existed for hundreds of thousands of years Now.

Speaker 1 5:20

It was well known back in Hippocrates' time. Right, hippocrates often considered the father of medicine. And in Hippocrates' time you know back around 450 to 377 BC heliotherapy, using sunlight as therapy. Therapy was really the gold standard, both for medical and psychological issues. Olympians would train outdoors, in their bathing suits, if you will. It was well established that performance was enhanced when you were outdoors and allowing more of your body to be exposed to that natural light. If you move the clock ahead into the mid-late 19th century.

Speaker 1 6:15

One of the great thinkers, maybe since Da Vinci who I never learned much about in school was Nikola Tesla. Tesla was way ahead of his time and, as Tesla suggested, if you want to find the secrets of the universe, you have to think in terms of energy frequency and vibration. Light and the photons, the little energetic packets of light, is really energy. Each color, each light has a frequency, and if you could measure the electromagnetic vibratory state, you would be able to do so. So humans, all living creatures on this planet, have been bathed in information that takes the form of energy frequency and vibration. Tesla was able to extract energy from the environment, in this case electricity. That allowed him, by simply holding a light bulb, to light that light bulb up. He was generations ahead of his time.

From Heliotherapy to Heliophobia

Speaker 1 7:30

At the turn of the 20th century, dr Niels Ryberg Finsen won the Nobel Prize and he was a Danish physician who basically found that light and specifically looking at skin conditions and lupus, that this was a very powerful form of therapy and it introduced this a bit more of a modern, sophisticated modality for treatment, and a great deal of the clinical establishment used this information, this science. Dr Kellogg of Battle Creek Kellogg, a physician wrote a terrific little book. This is about 110 pages. You can find this on the internet as a PDF. It's really fascinating.

Speaker 1 8:31

Light Therapeutics this was kind of a compendium on how light could be used to treat disease and promote health, and in hospitals, you know, in the early 20th century it was not uncommon at all to see the use of light for treating infection, for healing wounds, for many medical disorders. 1930s was a very sophisticated science, if you will, where over 165 diseases had some information or protocols for how to leverage sunlight as a beneficial treatment. And this was for all kinds of things, from blood pressure to gout, rheumatoid arthritis, anemia, skin conditions, lupus, back pain, sciatica, wounds, burns. This was well-established treatment and if you were in a hospital at that time, chances are you would be brought outside at some time of the day to help whatever you were in the hospital being treated for. Imagine, imagine saying this was the state of the art, the standard of care and our public health messaging was similarly aligned. It was well established that being outdoors was critical to human health and vitamin D. As that story unfolded, production, students learning outdoors again, kids requiring care, more time outdoors this was the standard of care and widely accepted public health practice.

Speaker 1 10:28

And so we've gone from this historical perspective, where we sort of worshiped the sunlight and understood that it was essential to all aspects of life and the ability to thrive, to an all ancient worldviews tended to worship light, saw great power in light to a more modern context of what I would call heliophobia, this universal fear of light. So now we will basically do all we can to avoid any exposure at all, and, like many things in modern life, we're a species with amnesia. We forget of the potential value that we are now depriving ourselves of. It's amazing how these memes, these clinical memes, shift in such a profound way, and so I'm surely not suggesting that you want to go out and get sunburned, but I would suggest, as I'll be emphasizing, that there is a modest dose of exposure, as little as five to 10 minutes twice a day at critical times in the morning and late afternoon, early evening, where we can derive great benefit of this natural therapeutic remedy that most of us, and often without awareness, are depriving ourselves of selves of.

Light Frequencies and Health Benefits

Speaker 1 12:11

Just a quick reminder that if you're outside, you're getting a full array of light frequencies this is the electromagnetic spectrum where you know shorter, higher energy wavelengths of light ultraviolet x-rays, gamma rays, cosmic rays on the higher energetic end, as contrasted with longer, lower energy wavelengths from infrared, microwave, radar, radio broadcasting bands. Full spectrum light and sunlight is really a very narrow slice of this broad electromagnetic frequency right what Tesla referred to as energy vibration frequency. And when you look at the light that we're exposed to from the sunshine, we get sun. From the ultraviolet range we have the visible light spectrum. You can all remember in physics in high school right or middle school, holding the prism up to light and then seeing these colors emerge, each with different wavelengths, from lower wavelength to higher wavelengths, to infrared light on the other end of the spectrum, now sunlight, the light that reaches our planet is predominantly infrared, about 40% and so it helps to understand that, like food, food is medicine, food is information. The quality of that information will influence the quality of your biology. The quality of your biology will be the quality of your biography. The same is true of light. Light is information, and if we are depriving ourselves of quality information at certain times of the day and substituting that with artificial light, which, as I'll show you in a minute, is very poor quality, then this is a perfect storm for setting up the risk of disease and diminished quality of life.

Speaker 1 14:17

Now we know today and this research is exploding that in the ultraviolet range we make vitamin D. I think many people know that UVB makes vitamin D. Uva is associated with nitric oxide. This dilates your blood vessels, allows more oxygen to flow. The Nobel Prize some 20 years ago was awarded to the scientists that discovered nitric oxide. We know that ultraviolet light is antimicrobial. Many hospitals now will use ultraviolet light to sterilize a room where a microbe might have been prevalent. We know that blue light will help the body get rid of bilirubin. When my son, alex, who has Down syndrome, was born 32 years ago, he was jaundiced and he went home with a biliblanquet. This was a blanket that we surrounded him with that had blue light. So blue light stimulates the liver's metabolism of bilirubin and many other compounds as well.

Speaker 1 15:36

Blue light is also and this is really the heart of this talk blue light is the on switch as circadian rhythms go, morning sunrise being the on switch, evening sunset being the off switch. Blue light is the wavelength of light that turns our chronobiology on. We want that to happen earlier in the day. We know that green light certainly is what plants use for photosynthesis. It's also very good for many other things, like migraine. There are long lists and a deep history, as I shared with you here.

Speaker 1 16:20

This is a lost art form here. This is a lost art form Wound healing in the red end of the continuum, stimulating collagen under our skin, skin integrity, more youthful skin from red and near-infrared light. Nitric oxide, also produced at this wavelength of light. Our body's ability to detoxify in the liver we call that sulfation, excuse me is largely produced by these longer wavelengths of light, and we know that our mitochondria are powerhouses of our cells that are now implicated in most chronic, complex diseases can be traced to disruptions of mitochondrial function. Near-infrared light, red light, is a powerful stimulus for mitochondrial energetic function, which is one reason why we feel so energized when we're in light. I mean, rarely do I meet a person who does not feel good when the spring season comes around. Their days are getting longer, warmer, they're outside in that sunshine. I mean, you know who doesn't feel better in that, and that's not just humans, but all species of living creatures. And then this is another topic.

Circadian Disruption and Disease Risk

Speaker 1 17:47

But water will actually change its quantum alignment in relationship to red and near-infrared light frequencies. This is work by Gerald Pollack University of Washington and this is probably of critical importance to human health. When we are exposed to those wavelengths of light, the water and humans are predominantly water. We're about 60% water by weight. We're about 99% water in terms of number of molecules in the human body. Most of them are water. Water will change its configuration in response to red, near-infrared light and actually becomes a battery. It creates a charge, a capacitor. We are our photoreceptors and these are key frequencies of light across the health spectrum. This is just an example of a billy blanket for kids that are born with neonatal jaundice.

Speaker 1 19:00

Many people are aware that our hormones, for the most part, are on a circadian clock. For most of us, the early morning hours around, right before and soon after sunset, the on switch goes on. We're getting ready to hunt and gather, our adrenaline goes up, our cortisol goes up and toward the end of the day, as the softer orange, red, right late day, sun setting light occurs, the switches turn off and cortisol and adrenaline go down. And then melatonin goes up, preparing us not just for a night of sleep. Melatonin is commonly thought of as the sleep hormone. It's really. It does so much more. It's an antioxidant, anti-inflammatory, it helps protect against cancer. Most of our healing, our restoration, our rejuvenation is facilitated by melatonin at those dark cycles of the overnight period. This is powerfully entrenched human circadian biology and every human that's ever lived on this planet has been wired for this kind of circadian response.

Speaker 1 20:24

The Nobel Prize in medicine in 2017 went to some researchers in Boston that elucidated the circadian clocks. Every cell in your body has a clock is on a timer, and we know that the greatest stimulus, the most sensitive environmental condition for these timers when they turn on and when they turn off into the deepest parts of your brain, specifically designed to respond to light and light quality. Now the research on the health effects of disruptions of this circadian biology are very well established. A lot of it comes from night shift workers, health care workers, emergency responders. Anyone who has chronic disruption of day-night cycling is at much greater risk for all chronic, complex diseases, from disrupted sleep to depression and mental health issues, heart disease, hypertension, diabetes, fatty liver, chronic inflammatory conditions. All of this becomes a consequence when we have chronic disruption, whether it be shift work, jet lag. With aging, our ability to adapt is not quite as robust, which is why we have to be especially mindful of the light quality in our environments, and that's where I'm going with this. In much the same way, we know that people who have really good alignment of their lifestyle and environment with circadian biology tend to be in much better health. And again, this is just a tip of the iceberg of the research. A lot of this is from the Harvard Nurses Study.

Ancestral Light Patterns vs Modern Lighting

Speaker 1 22:34

I've spent most of my life in hospital settings. You're under these bright fluorescent lights at two in the morning. Your body has absolutely no idea what time it really is. You could not create a more disruptive circadian environment. So many healthcare workers are at greater risk If you look at nurses, much greater risk of breast cancer, of depression, of obesity, of diabetes. This is true in other occupations where shift work and disruption of day-night cycles are common, and we know that many health issues are quite pronounced with these disruptions. Most heart attacks, for example, will tend to occur in the early morning hours when the adrenaline response for the day is getting ready to start. In much the same way that when we change our clocks forward or back, you will see a higher prevalence in the 24, 48, 72 hours around those time changes, of a greater prevalence of heart attack, stroke. We know that again, cancer and cardiovascular disease much more common in night shift workers, anyone who's ever been in the hospital or has ever had a loved one in the hospital.

Speaker 1 24:02

Generally, when you're discharged from the hospital, hopefully you're feeling better. People spend more time recovering at home, which is the ideal place to be recovering in, but it can take a while to regain circadian rhythms because in hospital settings they will be very disrupted, so much so that we have diagnoses we call them post-hospital syndrome, where people may, for many months after a hospitalization, be more depressed, feel more anxious, have more chronic disruption of sleep, may put on weight, many manifestations of metabolic disruption and again, from depression to post-traumatic stress, general anxiety disorder, bipolar these are all very well established to be at much greater risk when these circadian rhythms are disrupted. Now this is where we're really getting to what I think is the most important part of what I'm going to share with you, and again I come back to this concept of ancestral health. Every generation before us tended to be just more innately connected to these. You know, life was just different.

Speaker 1 25:14

We, you know we didn't have as much non-native light. We spent more time outdoors. The foods that we ate were not processed, so sunlight is the gold standard. And again, I'm not suggesting people spend hours in sunlight, particularly midday. You don't want to burn, but we need to be getting more light, not just on our skin but through our eyes. Sunlight has all of the wavelengths of the visible light. What you don't see here is you get ultraviolet light and infrared light as well. They're all perfectly represented in full-spectrum outdoor lighting.

Speaker 1 26:00

During the morning hours we tend to have more blue light, because it's blue light that turns our clocks on and you see that sky blue. That's the color. That's the color that says it's time to wake up, it's time to get ready to hunt and gather. Now's the time to move. Later in the day you see a shift away from the blue light into a greater percentage of yellow, orange, red light, and then, after the sun goes down, there's no blue light and it's all pretty much red, red, infrared, that end of the light continuum. This is the frequency of light that turns the clock genes off, that stimulates melatonin, that turns off the adrenaline and the cortisol. This is the light condition that is ideal for sleep, for restoration, for rejuvenation, to get you ready for another day. More blue in the morning, no blue and mostly red orange later in the day. This is the gold standard. All humans, for generations before us, experienced copious quantities of this light over the course of the day. And when you look at many ancestral cultures that continue to embrace ancestral ways of living, like, as you see in the Blue Zone communities, sardinia, icarus, a Greek island, costa Rica, the Nicoya Peninsula, okinawa, japan, if you look at ancestral the Australian Aborigines, the Hadza, the Aigon tribes, the Inuit Alaskans, they are very attuned to outdoor lighting and are getting the right exposures at the right time and they have much lower prevalence of chronic, complex disease. Now this is when you look at sort of natural light as the gold standard.

Speaker 1 28:13

Incandescent light you know the sort of the Edison light bulb really did a pretty good job of mimicking a little less blue, but you really got that nice full spectrum. Now you can't get incandescent bulbs anymore because your regulations. You know the EPA and the USDA have regulations now because these bulbs consume too much energy, they're not compatible with sort of a green emphasis and so they've been removed. What might be one of the most therapeutic non-native light sources was eliminated and it was replaced ultimately with these you know sort of LED energy conserving bulbs that had to meet regulatory criteria. And in order to do that, you have to cut out most of these therapeutic wavelengths of light, most of these therapeutic wavelengths of light, and you're left with mostly blue and a few of these peaks. But this is nothing like this, and the blue light, particularly after sunset, will convince your brain that you're about to start a day when, in fact, you're about to start a day when, in fact, you should be winding down from day's end. Now.

Practical Light Management for Better Health

Speaker 1 29:48

Halogens and warm LEDs are a bit of better quality in terms of mimicking this, with less blue and more of the red later in the day, while the cooler, brighter white lights are ideal earlier in the day, with these peaks of blue. This is a great daytime light bulb, but you do not want this late in the day, as the sun is setting, certainly after sunset. We call these full-spectrum lights the color rendering index. Ideally, with a warm LED, you're going to get a color rendering index of 95 plus percent, which is what you know, if you're interested in this, what you would want to look for and late in the day, you want a color temperature that is consistent with these warmer shades of light. So again, the cool white earlier in the day, warm LED late in the day.

Speaker 1 30:50

The compact fluorescent curlicue bulbs are just. I think they're really, really problematic. Yes, they meet regulatory code. They produce a lot of light, don't use a lot of energy. That checks all the boxes. If you're a regulator. It doesn't check any box if you're committed to human health. And so we know that. The quality of light through our eyes. Meal timing our ancient ancestors didn't eat right close to bedtime. You know they might have one or two meals during the day, you know. So meal timing, or what we might call time restricted eating you know consuming most of your food during sunrise and sunset and then giving yourself a few hours between last consumption and bedtime. Movement All of these things are known to stimulate circadian rhythms in a normal way.

Speaker 1 31:50

So all of these heart rate higher in the morning, body temperature higher during the day than at night, same with blood pressure and the hormones again, that we looked at, what you want to be high during the day and what you want to be turning off at night, and higher at night like melatonin is made possible by better alignment of these information sources, if you will, these environmental inputs. In much the same way, if we're getting too much of that blue wavelength that night after sunset, your brain will interpret that as the sun is about to rise and so it might be 10 pm. You've had a long day, you're stressed out, you're hoping for a good night's sleep, but you're on your laptop or maybe you're watching your high definition TV. You're sitting or laying down under a compact fluorescent light bulb and your brain thinks that it's time to get up. All of the things that you would want to happen in that circadian pathways becomes disrupted and so your clock your internal clock, the information it's getting will suppress melatonin when it should be turned on. We know this increases cancer risk. Cortisol is elevated at night, when it should be down. We know this increases cancer risk. Cortisol is elevated at night when it should be down. We know this increases obesity risk, diabetes risk, chronic sleep disruption.

Speaker 1 33:25

People who have a regular schedule during the week but are out socializing up later on the weekend. We call that social jet lag. Those are two different circadian schedules. You know we call that social jet lag. Those are two different circadian schedules. And and if, if things aren't aligned each day, each week, then that will be disruptive. So blue light is really a very stimulating light. I like to think of it as the equivalent of a cup of coffee. You don't want to be getting this after sunset. And again, we, we know that.