The mesmerizing shades of blue and orange in the sky at the beginning and end of a sunny day may play a significant role in setting people’s internal clocks. An innovative LED light that alternates between orange and blue light outperformed two other light devices in increasing melatonin levels in a small group of study participants. These findings, published in the Journal of Biological Rhythms, appear to set a new bar for the ability of humans to influence their circadian rhythms and reflect an effective new approach to combating seasonal affective disorder (SAD).

How Internal Clocks Regulate Our Bodily Functions

A range of health issues and mood disorders are attributed to out-of-sync circadian rhythms. Seasonal changes, lack of natural light, night shifts and flying across time zones can all contribute to this dissonance. “Our internal clock tells our body how to behave at different times of day, but the clock needs to be set, and if our brain is out of sync with the time of day, it won’t work properly,” explained Jay Neitz, co-author of the article and professor of ophthalmology at the UW School of Medicine.

Circadian rhythms are coached and reset daily by the 24-hour solar cycles of light and dark, which stimulate circuits in the eyes that communicate with the brain. With this information, the brain produces melatonin, a hormone that helps organisms become sleepy in sync with nighttime solar hours. People who spend many hours a day in artificial light often have a circadian rhythm that lags behind melatonin production in people who are exposed to more natural light. Many commercial lighting products are designed to compensate for or counteract these delays. Most of these products emphasize the blue wavelength because it is known to affect melanopsin, a photopigment in the eyes that communicates with the brain and is most sensitive to blue.

Effects of Different Artificial Light Sources on Melatonin Production

In contrast, the light developed by the researchers does not affect the melanopsin photopigment. Instead, it has alternating blue and orange wavelengths that stimulate a blue-yellow counter-circuit that works through the cone photoreceptors in the retina. This circuit is much more sensitive than melanopsin and is used by our brain to reset our internal clocks. The lead author of the study was James Kuchenbecker, an ophthalmology research associate at the University of Washington School of Medicine. He wanted to compare the effects of different artificial light sources on melatonin production.

He and his colleagues developed and conducted a test with three devices:

• a 500-lux white light (a brightness suitable for general office spaces)
• a short-wavelength blue LED, designed to trigger melanopsin
• the newly developed LED with blue and orange wavelengths that change 19 times per second to produce a soft white glow.

The goal was to determine which lighting approach was most effective at advancing the phase of melatonin production in six study participants. All participants underwent the following regimen, in which they were exposed to each of the three test lights:

The Device With Alternating Blue and Orange LED Light Worked Best

On the first evening, multiple saliva samples were collected to determine when the participants’ melatonin production began and peaked. For each subject, the onset of this phase determined when they were exposed to the test light for two hours in the morning. That evening, saliva samples were collected again to see if the subjects’ melatonin phase had started earlier compared to their individual baselines. During each test, exposure to other light sources was controlled. The three test phases were spaced out so that subjects could return to their normal baseline phases before starting a new device.

In terms of shifting the melatonin production phase, the device with alternating blue and orange LED light worked best, with a phase shift of 1 hour and 20 minutes. The blue light resulted in a phase shift of 40 minutes. The 500-lux white light resulted in a shift of only 2.8 minutes. Neitz pointed to the light his team had developed and explained: “Even though our light looks white to the naked eye, we believe that your brain recognizes the alternating blue and orange wavelengths as the colors in the sky. The circuitry that causes the greatest melatonin shift wants to see orange and blue.”