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ANDREW HUBERMAN 4 | Early daily get sunlight or blue artificial light…sets cortisol/melatonin cycles
presents episode 436 | Dr Andrew Huberman
Huberman Lab podcast

How long do you need to be outside early in the day to set
your circadian clock (stimulate cortisol & set up melatonin)?
-bright winter day, snow covered ground, lots of light:
~30 to 60 seconds will do it
-dense cloud cover? still getting 10-50k lux
~sufficient to set clock

Can light from phone do this?
-early in day, retina not very sensitive….so
you need a lot of photons (ideally from sunlight)
-if you cannot see sunlight, must opt for artificial sunlight
-blue light is great for circadian clock
-you want lots of blue & yellow light
early in the day
NEVER look at light of any type
-that is painful to look at

Blue and yellow light from sunlight is best, or
-artificial light with lots of blue wavelengths will work well
-to set the circadian clock
“I should wear blue blockers throughout the day!”
WRONG—reserve those for late in the evening
-because light suppresses melatonin
-sunlight inhibits the pineal gland
-prevents release of melatonin
-darkness allows the release of melatonin
“melatonin is the sleepiness signal
correlated with darkness”

Artificial lights: sunlight simulators work well, but also:
-ring lights, used for selfies, have lots of blue light
-the app, “Light Meter” enables your phone to measure
amount of photon energy in environment
Example, early morning outside, cloud cover
-could still have 10-20k lux
-indoors, seems bright…
only 500-1k lux

The circadian systems in the body work by averaging…
-when you look at the brightest blue light
-most wake up and look at their phone…
~does not trigger circadian clock
-then drive car with sunglasses
CAREFUL: Safety first!
-if you need to wear prescription
sunglasses…do so!
-they won’t filter out the blue light

The circadian systems in the body work by averaging…
-if you have a retinal degenerative disorder
(or it runs in your family):
-avoid excessively bright light at all times
~perhaps see dimmer sunlight for a longer period of time
Blind people, if eyes still intact, still have
neurons that set the circadian clock
-this is a subconscious mechanism, where
these neurons (melanopsin ganglion)
-activated by light in atmosphere
(you don’t have to see the sun itself)


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