evolvingstuff

As far as I understand it, higher levels of vitamin D3 greatly increases absorption of calcium from the gut, and the K2 is necessary to ensure that the calcium gets deposited in the right places.

Sorry, I don't have an existing set of references for this, but here are a couple things I found:

From http://www.drjessicaseaton.com/Chiropractic_in_West_Los_Ange...

"Increased levels of vitamin D require increased levels of vitamin K, especially of vitamin K2 (menaquinone). Without enough vitamin K2 there is an increased risk of hardening of the arteries and other soft tissues."

From http://en.wikipedia.org/wiki/Vitamin_K

"...high intakes of vitamin D but low intakes of vitamin K were suggested to pose an increased risk of hip fracture."

You might consider switching to a D3 supplement that includes some K2; they play nicely together.

Shameless plug of my dad's website on vitamin D: http://www.vitamindwiki.com/tiki-index.php

* Networks of the Brain by Olaf Sporns

* Set Theory and the Continuum Problem by Smullyan and Fitting

* The Calculus Lifesaver by Adrian Banner

* Discrete Mathematics with Proof by Eric Gossett

* Unix and Linux System Adminstration Handbook by Nemeth, Snyder, Hein, and Whaley

A factor I would like to see controlled for would be the serum vitamin D levels of the subjects. I'm guessing that at least some of these findings could simply be the result of spending more time indoors.