My understanding is that if we're supplementing with Vitamin D, then D3 is a better choice than D2. (Also: http://heartscanblog.blogspot.com/2007/04/vitamin-d2-vs-vitamin-d3.html)
So I was surprised to learn that from some samples of Green Pasture's Fermented Cod Liver Oil, the "majority of D is D2."
I realize that the Vitamin D content of fermented cod liver oil is only one of the reasons to take it (others being for e.g. A, K2 and E, as well as omega 3). And so I wouldn't necessarily not take it because of its D2 content. Although I did read somewhere that it's much easier to overdose on Vitamin D2 than D3.
However, I am looking for natural / whole food sources of Vitamin D3, and am wondering, if that's one of my top reasons for taking Fermented Cod Liver Oil, should I reconsider?
I'm also thinking that there's so much we still don't know about Vitamin D - is it possible that D2 taken in this natural form is somehow better than D3 taken as a standalone supplement?
Edited to update:
I asked a slight variation of this question on Chris Masterjohn's blog post at WAPF about vitamin D.
For the fermented cod liver oil that WAPF recommends, what do you make of the majority of vitamin D being D2? (http://www.greenpasture.org/re...=test-data)
My understanding is that it's D3 that we should be supplementing with?
Also, I've read that D3 is found in animal sources whereas D2 comes from plants? So where does such a high level of vitamin D come from in the cod liver oil? I try to eat natural / whole food sources of vitamins rather than supplements, which is why I like the idea of cod liver oil - I was just surprised about the D2 and am trying to get a better understanding.
Here is his answer:
I don't know the answer and I think there are many unresolved questions about the vitamin D's in marine oils. Obviously it's false that D2 comes from plants and D3 from animals, as fish are animals (though this may be accumulated from plankton or other non-animal sources). I think it's important to realize that we don't know the biochemistry as much as the hysteria-driven vitamin D movement maintains that we do, and therefore we should look at clinical effects of foods, and not try to extrapolate from specific chemical forms in foods or rely too heavily on 25(OH)D levels in and of themselves.
I definitely agree that there's a lot we still don't know (and I appreciate Chris' response).. still hoping to get some more insight..