Are you Preserving a Healthy Circadian Rhythm?


Yesterday, late afternoon, was my trip to the eye doctor.


The appointment took a little longer than expected!


Partly, due to some nutrition discussion. But mostly lecturing on my poor behavior with the use of my contact lenses. We will talk more about this later and the health of your eyes because it is pretty interesting.


I had my eyes dilated. Always fun. Friday night ruined, as I typically take longer to detox these anti-cholinergic agents. And as usual, was given an in-the-moment, massive appreciation for the suffering of those dealing with chronic photo sensitivity.


But also a reminder of how much more intense the light outdoors is relative to most indoor environments. Even outdoor light during late afternoon-early evening!


I had no issue cruising around in Walmart, grabbing some toilet paper and piecing together a few things for an afternoon meal. But when I got outside, I was stumbling around, squinty-eyed, hand over my brow, trying to locate my car. I am certain it was a lot of fun to watch!


This reminded me of the importance of natural light, or something similar to it. At this point in time, I am convinced that the number one needle mover for health in the context of most is the state of your circadian rhythm.


Light and Circadian Rythms


There is a lot of unknown in this area. But it seems pretty obvious we had much more exposure to sunlight than we do now. And more importantly, variations in the intensity of our exposure.


Zeitgebers are environmental cues that entrain our circadian rhythms. The word literally means “time giver” or “synchronizer.” The most potent we know of being light, and the variation in the intensity of that light.


These zeitgebers effect central oscillators in our brain and peripheral oscillators throughout the rest of our body. These events impact just about everything. Some fun mentions… sex, feeding behavior, metabolism, possibly the profile of bacteria in your intestines, how your body handles pharmacologic agents. And of great importance, your sleep-wake cycle.


What does this mean for you?



Most of you are concerned with preventing chronic disease.


It would likely benefit you to increase your exposure to the intensity of light that is similar to that of outdoors. And vary that intensity throughout the day.


I achieve this by doing my best to ensure I have at least 5 outdoor exposures in sunlight when possible lasting 5-10 minutes throughout the day. Away from shade and cover matters, because the angle at which light enters the eye is also important. Even on a cloudy day.


My routine looks like this:


Sometime after rising.

Later morning.

Another mid-day, typically longer to assist with Vitamin D synthesis.

Another late afternoon.

Just before sunset.


For what it is worth, when I deviate from this behavior, I do not wind down automatically for bed as usual. And I do not rise without the assistance of an alarm.


And yes, the “right time” for certain exposure is relevant.  More for some than others. Meaning twilight exposure to blue light is probably not serving you. But I find this does not matter as much if I follow the pattern above.


This is not an awful lot of time we are talking about here. 25 minutes minimum. You can do it. Take a call, check an email, have a snack outside. No big deal. Bonus points if you can expose at least half of your skin surface area for a few more minutes in the middle of the day! (I actually got busted for this one afternoon at school for breaking policy. Sort of ironic… being a naturopathic medical school).


Another way of doing this would be with a light box that can mimic the intensity of outdoor light. I do not have any experience with these devices, but do plan on experimenting with them at some point. I’ll keep you posted!


If you already rise easily and wind down easily, then you probably get the right exposure variation. If you are in a building all day and rarely emerge, it might serve you to pay attention to your exposure and make modifications.




Further Reading



Huang, Yuanwei, et al. “Efficacy and safety of chronomodulated chemotherapy for patients with metastatic colorectal cancer: a systematic review and meta‐analysis.” Asia‐Pacific Journal of Clinical Oncology (2016)


Dallmann, Robert, Steven A. Brown, and Frédéric Gachon. “Chronopharmacology: new insights and therapeutic implications.” Annual review of pharmacology and toxicology 54 (2014): 339-361


Usui, Setsuo. “Gradual changes in environmental light intensity and entrainment of circadian rhythms.” Brain and Development 22 (2000): 61-64


Voigt, Robin M., et al. “Circadian disorganization alters intestinal microbiota.” PloS one 9.5 (2014): e97500


Zanquetta, Melissa M., et al. “Body weight, metabolism and clock genes.” Diabetology & metabolic syndrome 2.1 (2010): 53



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