Blue light as a timing signal

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How light regulate circadian rhythms, mitochondrial function, hormones, and appetite.

Nick & Dr. Alexis Cowan discuss non-image-forming effects of light on the body, from melanopsin-driven circadian signaling in the eye to UV-stimulated pathways in skin and brain that influence melatonin, cortisol, melanin production, and energy balance.

TOPICS DISCUSSED:

• Melanopsin & non-image-forming light: blue light signals daytime to the SCN master clock, suppressing melatonin and promoting alertness.
• UV light, POMC & peptide hormones: UVB exposure in skin and hypothalamus produces alpha-MSH (reduces appetite, boosts energy expenditure) and beta-endorphin (improves mood), independent of vitamin D.
• Mitochondrial effects of light: red/infrared supports function like a gas pedal; isolated blue light acts as brakes, impairing energy production and biophoton signaling.
• Artificial light: Evening blue light from screens inhibits melatonin, poisons mitochondria, and creates discordant timing signals versus balanced natural sunlight.
• Melanin beyond skin: produced via UVB, it harnesses energy, buffers oxidative stress, and links to dopamine pathways; low sun exposure ties to metabolic issues and conditions like Parkinson’s.
• Vitamin D as biomarker: supplementation shows limited benefits because it reflects broader UVB-driven processes, not a standalone fix.

ABOUT THE GUEST: Alexis Cowan, PhD earned her PhD in molecular biology at Princeton in the Rabinowitz lab, a leading metabolism research group, where she studied fasting, ketogenic diets, and exercise; she completed a postdoc at UPenn before shifting focus to circadian and quantum biology. She now educates on light, mitochondria, and quantum biology.

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