Love the detail, but really? We get immediately chastised for not taking in VitD “naturally” via exposure to sunlight?
Oh, kiss my Arshe! What the ‘Ell is someone supposed to do in the midst of winter in the north? Run around naked in the sunlight until something freezes off?
Bloody idiot.
FYI, older skin does not process sunshine into vitamin D as well as it did when younger.
Vitamin D in diet is there, but the minimum levels that were achieved from diet and sunshine when young stop being achieved with the same diet as when young because that second sunshine source fails.
And so, ingest concentrated form. It’s not guesswork. You can see the blood levels elevate with the supplement.