Sunlight
More than just vitamin D. Sunlight is an essential environmental signal that humans evolved under for millions of years. It regulates your circadian rhythm, boosts nitric oxide and blood pressure, influences mood, and affects mitochondrial function. Modern indoor living may be a massive, unrecognized health problem.
What Sunlight Does
Vitamin D Synthesis
UVB converts cholesterol in skin to vitamin D3. 10-30 min midday sun can make 10,000-20,000 IU.
Circadian Rhythm
Morning light signals SCN to set daily clock. Suppresses melatonin, triggers cortisol awakening.
Nitric Oxide Release
UV light releases NO from skin stores. Lowers blood pressure. May explain cardiovascular benefits.
Serotonin & Mood
Light exposure increases serotonin. SAD (seasonal affective disorder) linked to light deficiency.
Mitochondrial Effects
Near-infrared light (NIR) penetrates tissue, may affect cytochrome C oxidase. Red light therapy basis.
Beta-Endorphins
UV exposure triggers endorphin release in skin. May explain why sun feels good.
The Sunlight Spectrum
UV Light
- UVB (280-315nm): Makes vitamin D. Causes sunburn. Blocked by glass.
- UVA (315-400nm): Releases nitric oxide. Deeper penetration. Ages skin.
- Sunscreen: Blocks most UV. May prevent vitamin D and NO benefits.
Visible & Infrared
- Blue light (450-495nm): Strongest circadian signal. Suppresses melatonin.
- Red light (620-700nm): Penetrates tissue. Photobiomodulation.
- NIR (700-1400nm): Deepest penetration. Mitochondrial effects.
The Power of Morning Light
What Happens
Light through eyes signals SCN. Melatonin suppressed. Cortisol awakening response triggered. Clock set.
How Much
10-30 min within first 1-2 hours of waking. Cloudy day still works (10x brighter than indoors).
Benefits
Better sleep that night, improved mood, enhanced focus, proper hormone timing, metabolic benefits.
No Sunglasses
Light needs to hit special receptors (ipRGCs) in eyes. Sunglasses block the signal.
The Modern Light Problem
Too Little By Day
Indoor lighting 300-500 lux. Outdoor overcast 10,000+ lux. We're chronically light-deprived.
Too Much At Night
Screens, LEDs, artificial light after sunset. Blue light suppresses melatonin. Disrupts sleep.
Wrong Spectrum
LED/fluorescent light lacks red/NIR that sunlight has. Full spectrum matters, not just intensity.