After reading a bit about Vitamin D3, I also thought that you can justify taking Vitamin D3 in the morning this way.
I however had to rewrite my post because it doesn’t seem to be as easy. The Wikipedia article used to suggest that cholecalciferol gets directly transformed into calcitriol but it seems it has to be converted to calcifediol first. This process takes time and as a result it’s harder to make the argument about Vitamin D3 that you take (cholecalciferol) directly effecting the circadian rhythm.
What time did you take it? D3 is a strong cellular modulator of our clock genes https://www.vitamindcouncil.org/new-research-finds-activated-vitamin-d-regulates-genes-involved-in-the-circadian-rhythm/
After reading a bit about Vitamin D3, I also thought that you can justify taking Vitamin D3 in the morning this way.
I however had to rewrite my post because it doesn’t seem to be as easy. The Wikipedia article used to suggest that cholecalciferol gets directly transformed into calcitriol but it seems it has to be converted to calcifediol first. This process takes time and as a result it’s harder to make the argument about Vitamin D3 that you take (cholecalciferol) directly effecting the circadian rhythm.
Do you have any data on how long the conversion takes?
Unfortunately, I don’t.
I have opened a biology.SE question about the question of how long it takes till Vitamin D3 is biologically active a while ago.