Does supplemental Vitamin D3 suppress endogenous melatonin production, hence it would be prudent to not take D3 later in the day or evening to avoid disruption to sleep? Some sources on the Internet make this assertion, but it does not seem to be universally held. My hunch is that sunlight or blue light (not D3) triggers the pineal gland to suppresses endogenous melatonin production, but some people have jumped to the conclusion that it is the D3 (the effect, not the cause) instead.
Well Robert I had a friend once that asked me when I took my Vitamin D. I did not understand her question at first and eventually I realized she meant morning or evening. She said she took hers before bed and was actually getting much better sleep. There have been no studies that say one is better than the other.