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Let's end this one with some certainty....there are so many conflicting POVs:

  1. Is supplemental vitamin D somehow different than sunshine in that it uses up magnesium and retinol to be converted?

  2. 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.

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and I know K-2 is a cofactor as well, this post is targeted to the retinol discussion – Chase Aug 16 2011 at 19:40
Aren't you eating enough liver that it wouldn't matter? – Travis Culp Aug 16 2011 at 19:52
what? actually i don't eat liver, but that wasn't the question (vit A from food wasn't the question). the question relates to the vit D/A supplement interaction - and the why behind it. – Chase Aug 16 2011 at 19:56
I'm very interested in this issue, so please don't take this the wrong way, but how is this "finally settling" the question? Or are you asking PHers to finally settle this through discussion...? – Rose Aug 16 2011 at 20:20
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totally not an answer and potentially not helpful, but I just recently listened to a podcast on Superhuman Radio with John Cannell and he has a product with the "necessary D cofactors" - Boron, Calcium, Mag Citrate and Taurine and K2. Interestingly no A. He will be back on that podcast in the near future to talk about the A/D ratio though. I'm going to listen. Sorry for the lack of information here. – none Aug 16 2011 at 21:29
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3 Answers

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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

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Thanks. As far as cofactors and the disagreement between folks, I find it crazy that we just dont know at this point on such an important issue. Supplemental vitamin D is really poorly understood when you think about all of the gaps – Chase Aug 31 2011 at 12:17
Chase read my recent vitamin d blog. I plan on updating it over time. We find new things out weekly about this hormone – The Quilt Aug 31 2011 at 19:28
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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.

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I find it crazy that we just dont know at this point on such an important issue. Supplemental vitamin D is really poorly understood when you think about all of the gaps – Chase Aug 31 2011 at 12:16
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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.

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