Let's end this one with some certainty....there are so many conflicting POVs:
Is supplemental vitamin D somehow different than sunshine in that it uses up magnesium and retinol to be converted?
Do you need more supplemental retinol (vit A) when taking Vit D?
Ive seen the WAPF and Chris Masterjohn POVs, as well as John Cannell. These disagree. I've experimented personally for ~6 months now and can't come to a conclusion. I've seen other posts where people raise the issue but it's never really settled to the point where someone described the WHY for the correct point of view. I think its simple, does supplemental D make us need retinol (and why)?
I think it could make sense because the only source of vit D in nature (eggs, fish) is also coupled with vit A.
However, the other point of view would be that we need 5-10 k IU of D per day...and it is not safe (and actually antagonistic) to take higher amounts of retinol to offset that much vit D.
On top of all of this, I personally dont seem to do well taking isolated vitamin D, but am also not clear what combo of co-factors make it effective and tolerable.
asked byChase (480)
Get FREE instant access to our Paleo For Beginners Guide & 15 FREE Recipes!
on August 31, 2011
at 01:12 AM
Main reason for vitamin A is that it is a co factor for endogenous steroid genesis with T3 to convert cholesterol to pregnenolone. As for supplementation vitamin A can inhibit D to a certain extent. CM has a theory that vitamin A protects from vit k depletion from gut bacteria. Nothing is written in stone about this. Plausible theory but I have not seen a lot of data on it and I bet neither has Dr Cannell. Eating offal does not always mean you have enough D. I have a patient who eats offal three times a week and has a vitamin D level of 22. If you just eat offal and never test you just don't know. Turns out my patient had two issues. A VDR snp and vit D binding protein. So he needs to be overwhelmed to saturate his receptors to get his level optimal. There are 27 known VDR snps......it's pretty common
on August 31, 2011
at 12:38 AM
How can we "end this one with some certainty" when there is no certainty by the experts? The logical approach is to not supplement to extreme, and be sure of a good amount of A and K2. Likely sun exposure does not present harmful interactions due to lack of A. Obviously much is not known.
on August 16, 2011
at 10:50 PM
I know your looking to an answer to the supplemental factor of this, but as a point I would purpose that supplementation is not optimal nor necessary unless you can prove that what you are supplementing is unatainable in today's food sources or lifestyle. The amounts you get from these sources are "optimal" unless you can prove that these sources have changed so drastically as not to be viable.
Doesn't answer the question to why A/D, but its a philosophy that I am comfortable confronting most problems like this from.