Circadian Rhythm

Blue Light: A Red Alert for Health

Heightening your alertness to light exposure is a cornerstone of environmental health that directly impacts circadian rhythm.

Far too many people exist in a state of low variability when it comes to light exposure – both in timing and types of light (blue light vs. red/others).

Types of Light

Blue light is not the devil, but like so many things in health, context matters. Naturally, various colors are blended in the exposures we experience. This is a great graphic from Mercola.com1

Blue light suppresses melatonin – a fact now widely known – a beneficial traight in the daytime. Red light is beneficial as well, helping energy production in the mitochondria. As you can see, the light exposures in our daily environment, vary widely. The biological interaction also varies widely depending on the spectrum. This is a control point we have to exert influence over.

Timing of Light Exposure and Intensity

As the sun rises, we experience a rising intensity of brightness, measured in lux. This can be done conveniently by a free iOS app, myLuxRecorder. Typical exposure can go from single digit lux readings in the dark hours rapidly up to ~1,000 lux on a cloudy day to easily 10,000+ on a clear sunny day. Then a decrease to near zero in the evening before bed is the standard.

Where we get timing and type wrong

Our modern society deviates from what our biology expects in terms of light timing, intensity, and spectrum. Instead of a predictable rhythm of the increaseing intensity of a broad spectrum of light wavelengths, we tend to experience the following:

  • Wake up to Cool White LED light bulbs with blue light emitting phones, somewhere less than 500 lux.
  • Go to work in a building with less than 500 lux, likely near 100 lux, and fluoresent or cool white LED.
  • Come home with cool white LED, bright and clear LED TV screens, and devices emitting blue light until bed, at the same 100 lux range.

In this scenario, the expected variance in light and intensity is replaced with near ZERO variance. Hard to have a circadian rhythm when there is no rhythm!


There is a large field of circadian biology that I can’t delve into in a complete fashion in a summary post. The consequences of this lack of rhythm are broad and will be expanded upon. For now, the basics.

  • Sleep Disruption. The unbalanced blue light suppresses melatonin. The ramification of sleep disruption fill numerous books.
  • Blue light speeds blindness 2
  • Cancer

Optimization Tactics

As this point, there are a few simple things that can provide benefit.

  • Get outside a few times per day with no sunglasses! Sunglasses can reduce light exposure 7-15 fold. 4. Getting the bright light during the day makes it easier for your body to notice the shift to evening light levels. Going from 5,000 lux down to 50 lux is much better than 100 lux at the office to 50 lux at home.
  • Have some incandescent lights in the house, at least in areas used most in the evening. As you can see above, they have more red and less blue.
  • Reduce blue light exposure from computers and devices. There are native settings on phones, such as Apple’s Night Shift. For computers, there is a free program, f.lux, that will reduce blue light from your screen on a schedule. A paid app with more features, Iris, is one I have used that works very well too – there is more control available. Some TV’s have controls to reduce as well.
  • Blue Light Glasses: There are many available. Plenty of economical blue light filter type glasses on Amazon and other places. They tend to block JUST blue light. As we can see from the spectrums above, there is more to the picture than blue light. Enter True Dark. They have three different ways to filter many different colors on the light spectrum, and taget those for the time of day. Daytime, evening, and prior to bed (blocks everything but red and a little green). I have noticed a great benefit from using True Dark glasses, as shown in my Oura ring data. It allows for things such as device and TV viewing up until bed with no noticeable impact on sleep onset – my time to fall asleep is most always less than 15 minutes.

Get Some Rhythm & (less) Blues

While the goal of this post is not meant to be all-encompassing on circadian biology, it contains a primer that I wished I would have read many years ago. For further reading, this Book Report on The Circadian Code is a good start, or you can now view ALL the notes (searchable) I have saved from my kindle library here (the book report posts only have a fraction – and I haven’t got all the books written up in the summary form yet). This site also has a tool that allows collection of various data points from your day to assess rhythm, one of the metrics is light exposure. It is free, go ahead and check it out!

  4. What About Sunglasses? Sunglasses can reduce bright light reaching the eye by seven- to fifteenfold. That means if daylight inside a car is around 5,000 lux, sunglasses cut the exposure down to between 330 and 700 lux. Thinking about this math and knowing that my major source of daylight is when I drive to and from work immediately made me quit wearing sunglasses during my regular day’s activities. Satchin Panda, The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight, loc. 2743

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