A Protocol card with the lux × minutes dose, the 60-min window, and the Phase Response Curve citations.
Questions logged on this protocol
How long is enough on a sunny morning?
Direct outdoor sun delivers 10,000-100,000 lux at ground level, so 10 minutes between wake and 08:00 hits the ~10,000 lux-minute dose that Zeitzer et al. 2000 (J Physiol) showed is sufficient to shift the melatonin rhythm. Overcast days drop to 1,000-10,000 lux; extend to 20-30 minutes to match the same cumulative dose. The exact lux-minute threshold varies by individual circadian amplitude.
Does light through a window count?
Partially. A sunlit east-facing window measures ~1,000-5,000 lux at arm's length, depending on glass coating and aspect. That is enough to deliver the dose over 20-30 minutes, but most residential glass filters some short-wavelength (blue) light, which melanopsin signaling relies on most heavily (Brainard et al. 2001, J Neurosci). Outdoor exposure is still the default recommendation; window light is the fallback.
What if I wake up before the sun?
In winter latitudes above ~40 degrees, sunrise can trail wake time by hours. The practical substitute is a 10,000 lux light therapy lamp at 12-18 inches for 20-30 minutes, the dose used in seasonal affective disorder trials (Terman & Terman 2005, CNS Spectrums). Pair with outdoor exposure once civil twilight begins. Lamp use before 05:00 can over-advance phase; keep it within an hour of habitual wake.
Do blue-blocker glasses in the morning ruin the effect?
Yes. Melanopsin peaks at ~480 nm, which is precisely what most blue-blockers attenuate. Wearing them in the morning blunts the phase-advancing signal by 40-60% depending on lens spec (Figueiro & Rea 2010, LRC). Blue-blockers are an evening tool. In the morning, the goal is maximum short-wavelength exposure on the retina.
Does coffee replace morning light?
No. Caffeine boosts alertness via adenosine antagonism, but it does not phase-shift the suprachiasmatic nucleus. Light is the dominant zeitgeber; caffeine is a wake-promoter. They layer (light first, coffee after), but one does not substitute for the other. Wright et al. 2013 (Curr Biol) showed a week of natural light exposure shifted DLMO by ~2 hours with no change to caffeine intake.
Is 10 minutes of morning sun enough?
On a clear day, yes. The 10-minutes-of-10,000-lux protocol that circulates online traces back to Zeitzer et al. 2000, which mapped the dose-response curve for melatonin suppression and phase-shifting. On overcast days or indoors, scale up: 20-30 minutes at 1,000-5,000 lux produces a comparable cumulative dose. The variable that matters is lux-minutes, not clock minutes.
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