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Understanding Blue Light

June 24, 2020

Light is critical to shaping life.

For the vast majority of human history, our exposure to light came only from the sun, moon, stars and (eventually) fire. From morning to night, our existence was intimately tied to the environment and we adapted to live in alignment with seasonal and solar rhythms.

While our physiology hasn’t changed, our use of non-native, artificial blue light certainly has and we’ve traded our connection with nature for convenience. Only in the last 100 years or so has it become possible to enjoy the luxury of light 24/7, utilize technology at our whim, consume virtually any food in any season, and maintain a state of constant warmth. In the same time period, disease rates have skyrocketed and dysfunction has become the norm, which begs the question—at what cost?


What Is Blue Light?

At the most fundamental level, light is the collection of electromagnetic particles traveling in waves. The length between the waves is called the wavelength, which is measured in nanometers and dictates what we perceive as the color; the full range of wavelengths comprises the electromagnetic spectrum. Light also carries energy in the form of photons and the amount of energy is inversely related to the wavelength. Warmer colors with longer-wavelength on the spectrum, such as red, orange, and yellow, are lower energy. However, cooler colors with shorter-wavelengths like purple, green and blue carry higher amounts of energy1.

We typically classify light into two categories: visible and non-visible. Visible light is perceived by the human eye in varying colors and occurs between approximately 380nm and 740nm on the electromagnetic spectrum. Radiation below 380nm is referred to as ultraviolet light and radiation above 740nm is referred to as infrared and recognized as heat1.

Blue light is found in the visible light spectrum, from 380nm to 500nm and carries more energy due to its shorter wavelength. We are exposed to varying amounts of natural blue light everyday based on time of day, weather and location, which plays an important role in our physiology2.


Not All Blue Light Is Created Equally

It’s just light right? No!

Life is programmed by the environment and we have evolved to utilize natural light to initiate action throughout the body. All parts of the spectrum are important, but blue light plays a unique role in modulating our circadian rhythm, the 24 hour cycle of physiologic and behavioral changes.

Circadian alignment is controlled predominantly by the Suprachiasmatic nucleus (SCN), which is responsible for synchronizing our physiologic functions to the rhythms of natural light3. The SCN receives it messaging from non-visual photoreceptor cells located in the eye and skin, which become excited by the presence of specific spectrums of light3. As the solar spectrum and intensity changes throughout the day, these messages stimulate processes to begin and for others to shut off. In its natural form, blue light plays an especially important role in regulating these processes. When circadian timing is aligned with nature, optimal health can be achieved.

Natural blue light is strongest in the morning and is always balanced by red wavelengths. These signals prompt the body to stop melatonin secretion; up regulate cortisol, dopamine, and serotonin; stimulate metabolism; increase cognitive function; and super charge mitochondrial energy production—these processes give you the boost required to start your day4. At night when the spectrum is dominated by red and absent of blue, the opposite occurs—we begin to wind down, shutting off cortisol, initiating cellular repair and synthesizing melatonin after several hours of darkness. These natural cycles are critical to maintaining normal function and recovery and deviating from them can be disastrous4.

In a world where solar light dominated, staying in alignment was natural. But, due to the gradual advancement of technology and lighting over time, blue light now has a dark side: non-native, artificial blue light.

To say artificial blue light is everywhere would be an understatement. The modern world almost exclusively makes use of technology and light sources that peak in the blue range without the natural balance found in the sun’s full spectrum3.

The problem: we simply have not evolved to distinguish between native and non-native blue light and we live in a state of perpetual daytime. Every time you pick up your phone, look at a computer, watch the TV, open your refrigerator or turn on an LED/CFL, you are being bathed by junk light and your body responds accordingly. This is especially detrimental at night, when you rely on the absence of blue light to initiate melatonin secretion for quality sleep and repair processes4.

To make matters worse: we spend 90% of our lives indoors without exposure to unfiltered, natural light and completely disconnected from nature5. This serves only to further increase our exposure to harmful blue light and negatively impact our health.

Given the non-linear impact of light on our physiology, it’s safe to say the proliferation of artificial blue light has been devastating to our individual and collective wellness. Hormonal imbalance, poor sleep, cognitive dysfunction, retinal damage, inability to conduct cellular repair and mitochondrial inefficiency are now the unfortunate norm.


A Brief History Of Artificial Blue Light

Humans are uniquely capable of altering their environment and subverting nature’s principles in exchange for comfort and convenience. The rapid increase in the complexity of artificial lighting serves as a perfect example.

The first improvements to the traditional use of fire and natural light came in the form oil based lamps and candles, which lit the lives of people for hundreds of years. Lamps and candles offer a more natural, balanced spectrum and made light more accessible and portable; but, the demand for improvement persisted. Many would try to meet the demand, but only one would ultimately succeed. In 1879, Edison would patent the first commercially viable light source in the form of the incandescent lightbulb. Paired with the rapidly developing power grid, this would eventually bring light into the homes of billions of people very quickly. The continued desire for innovation and efficiency would eventually result in the creation of the light emitting diode (LED) and the compact fluorescent lightbulb (CFL). While they’ve proven to be harmful, due to their efficiency and performance, these light sources now dominate our modern lives6.


Where Is Blue Light Found Artificially?

The modern world is full of artificial sources of blue light—here are the most common:

  • Computers and laptops
  • Televisions
  • Smartphones
  • Tablets
  • E-Readers
  • Electronic devices
  • Digital screens
  • LED and CFL lights and lightbulbs
  • Refrigerators
  • Fluorescent light
  • Windows and windshields

What’s Next?

Blue light is undeniably harmful to our health and the story goes far deeper. Stay tuned as we explore the ways blue light may be an obstacle to optimal and what you can do to mitigate and eliminate its impact in your life.



  1. http://www.columbia.edu/~vjd1/electromag_spectrum.htm
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7065627/?log$=activity
  4. http://photobiology.info/Roberts-CR.html?fbclid=IwAR04N-lvc_z56kChYW3M5SLnPiBCM3W9qVPs9-SBvZSL1h0sja0lx-9Ogb4
  5. https://indoor.lbl.gov/sites/all/files/lbnl-47713.pdf
  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763140/?log$=activity



Medical Disclaimer: This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Dr. Monette nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement or lifestyle program. Statements made on this website have not been evaluated by the U.S. Food and Drug Administration. Products sold on this website are not intended to diagnose, treat, cure, or prevent any disease.

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