This topic has been nicely discussed but I'd like to ad one thought before it goes away. I've perused the web myself to learn more about this topic, and found numerous references, from sources including medical universities, which suggest that warfarin leads to osteoporosis. The problem with the sources is that they can't help but have bad information since warfarin ACT patients have been told for so long and by so many to avoid eating K rich foods, and especially to avoid K supplements. Perhaps not coincidentally, some of the references also referred to Warfarin as a 'blood thinner', and indication of how much we ought to value them as sources of information.
For Example:
http://umm.edu/health/medical/altmed/supplement/vitamin-k
For Example:
http://umm.edu/health/medical/altmed/supplement/vitamin-k