4 ms·

>I could see how taking vitamin D in the evening would actually be harmful if it disrupts melatonin synthesis. How would this work? From my understanding, vita

>I could see how taking vitamin D in the evening would actually be harmful if it disrupts melatonin synthesis. How would this work? From my understanding, vitamin D blood concentration takes quite a while to build up due to the fat soluble nature, and taking a single pill doesn't cause an immediate spike just like staying inside for an entire day doesn't cause a drop.

macawfish 6y ago
Here's a study showing a marked circadian rhythm in serum 25-hydroxyl vitamin D levels. There are actually lots of theoretical papers about this kind of thing, yet somehow so many of these nutritional studies seem oblivious to them or something. https://pubmed.ncbi.nlm.nih.gov/25788054/ https://pubmed.ncbi.nlm.nih.gov/25788054/ If you dig a little you'll find a similar situation with Mg/Ca/vitamin K/vitamin D. There are lots non-controversial evidence and understanding of the relationships between them, but the nutritional studies on vitamin D supplementation seem all but oblivious to that information.
- indecisive_user 6y ago
  So that study seems to conclude that the blood concentration of vitamin D varies according to circadian rhythms. That's an interesting finding, but what I'm saying is that I don't think taking a vitamin D pill has an immediate effect on your body's vitamin D levels. That's why it takes weeks or months of supplementation before you see it reflected in blood tests.
  - macawfish 6y ago
    One issue here I'm realizing is in a difference of assumptions... I'm used to taking vitamin D3 drops under my tongue, which I imagine absorb differently than capsules. But even so, fat soluble substances can get into the blood pretty quickly when you ingest them, well within the timespan of one day. So I'm not sure if I understand your reasoning. Can you link to a source? Something I'm reading now that sounds similar to what you're saying is that during supplementation, it takes a while for serum vitamin D levels to reach a steady state. Maybe that's what you're referring to? Edit: check this out https://www.sciencedirect.com/topics/medicine-and-dentistry/vitamin-d https://www.sciencedirect.com/topics/medicine-and-dentistry/... > After an oral dose of vitamin D, blood levels begin to rise at 4 hours, peak by 12 hours, and return to close to baseline by 72 hours. In this article, I take "baseline" to refer to what I called "steady state" earlier in this comment.

macawfish 6y ago

Here's a study showing a marked circadian rhythm in serum 25-hydroxyl vitamin D levels. There are actually lots of theoretical papers about this kind of thing, yet somehow so many of these nutritional studies seem oblivious to them or something. https://pubmed.ncbi.nlm.nih.gov/25788054/ https://pubmed.ncbi.nlm.nih.gov/25788054/ If you dig a little you'll find a similar situation with Mg/Ca/vitamin K/vitamin D. There are lots non-controversial evidence and understanding of the relationships between them, but the nutritional studies on vitamin D supplementation seem all but oblivious to that information.

indecisive_user 6y ago
So that study seems to conclude that the blood concentration of vitamin D varies according to circadian rhythms. That's an interesting finding, but what I'm saying is that I don't think taking a vitamin D pill has an immediate effect on your body's vitamin D levels. That's why it takes weeks or months of supplementation before you see it reflected in blood tests.
- macawfish 6y ago
  One issue here I'm realizing is in a difference of assumptions... I'm used to taking vitamin D3 drops under my tongue, which I imagine absorb differently than capsules. But even so, fat soluble substances can get into the blood pretty quickly when you ingest them, well within the timespan of one day. So I'm not sure if I understand your reasoning. Can you link to a source? Something I'm reading now that sounds similar to what you're saying is that during supplementation, it takes a while for serum vitamin D levels to reach a steady state. Maybe that's what you're referring to? Edit: check this out https://www.sciencedirect.com/topics/medicine-and-dentistry/vitamin-d https://www.sciencedirect.com/topics/medicine-and-dentistry/... > After an oral dose of vitamin D, blood levels begin to rise at 4 hours, peak by 12 hours, and return to close to baseline by 72 hours. In this article, I take "baseline" to refer to what I called "steady state" earlier in this comment.