Light + Health

Alternative Circadian Theory Of Blue-Yellow Opponency


I watched the virtual presentation, Better Than Blue Light, by Dr. Jay Neitz of the University of Washington last week that was presented by LEDucation. I’m not an expert on Light + Health, but I’ll try to explain it as best I can.

Dr. Neitz claims that particular combinations of blue and yellow light have 50 times more melatonin impact than blue light alone. The blue & yellow light combination is termed “Blue-Yellow Opponency.” Sunrise and sunset, each deliver a strong combination of blue and yellow light, are picked up by the retinal cones’ color vision. He has found direct neural connections from these color vision cones to the ipRGCs, a “cone to ganglion cell pathway.” The theory is that the combination of yellow and blue colored light has a much bigger impact on melatonin production than blue light alone (480nm or similar). In this blue-yellow opponency theory, high brightness is NOT required to trigger circadian entrainment when the proper yellow and blue light source combination is experienced.

A company named Tuo produces lamps based on this blue-yellow opponency theory. Tuo lamps alternate between yellowish and blueish colors at 19 Hz. It is like an intentional “color flicker.” The 19 Hz is selected intentionally because it both produces the desired entrainment and no color flicker is perceived by people. The blueish/yellowish “flicker” is perceived as white, at that frequency.

Dr. Neitz and his protégé, Dr. James Kuchenbecker, promoted the Tuo product, which raises some concerns. Overall, from an intuition level, it seems plausible that sunrise and sunset would evolutionarily be a more powerful trigger of circadian entrainment than blue sky light, all day long. Sunrise to trigger alertness and sunset to trigger sleep readiness.

If there are any experts on the blue-yellow opponency theory reading this, I’d welcome corrections or additions. Email me at


Image: Tuo

Top image: Suelynn Shiller

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David Shiller
David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.


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