Once a person floods the system with the hormone, D3, there is a lag of about 2 weeks for that proper, higher concentration to drop low. Once a 2 week regimen of 20,000 IU establishes the proper fill, a 5,000 to 6,000 IU daily replenishment is adequate to maintain an expected D3 hormone level.
This level is usually established by being outside in the direct sunshine causing the skin to generate as much as 20,000 IU with just 30 minutes of direct, full Sun exposure when shirtless. Humans aren’t designed to be building or cave dwellers.
Unless they're Irish, in which case they are expected to stay under a constant layer of thick clouds, or in a pub.
CIS: Crappy Irish Skin. It can happen to you if you're not careful.
This level is usually established by being outside in the direct sunshine causing the skin to generate as much as 20,000 IU with just 30 minutes of direct, full Sun exposure when shirtless. Humans aren’t designed to be building or cave dwellers.
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Exactly. In our modern world, we’ve become indoor dwellers. We live at home. We work in offices. We drive to work in cars. Few, other than perhaps construction workers, are outdoors for a meaningful portion of the day.
I know for myself, since I started taking a daily 5,000 IU vitamin D3 capsule, I basically never get a cold. I use to reliably get 3 or 4 colds per year.