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nightsurfer on 2009-12-07"As far as I can tell, MK-4 is capable of performing all the functions of vitamin K. MK-4 can even activate blood clotting factors, which is a role traditionally ascribed to vitamin K1. Babies are often born clotting deficient, which is why we give newborns vitamin K1 injections in the U.S. to prevent hemorrhaging. In Japan, they give children MK-4 to prevent hemorrhage, an intervention that is very effective. Could that have to do with the fact that Japan has half the infant mortality rate of the U.S.?
Today, I found another difference between MK-4 and MK-7. I was reading a paper about SXR-independent effects of vitamin K2 on gene expression. The investigators found that MK-4 strongly activates transcription of two specific genes in osteoblast cells. Osteoblasts are cells that create bone tissue. The genes are GDF15 and STC2 and they're involved in bone and cartilage formation. They tested K1 and MK-7, and in contrast to MK-4, they did not activate transcription of the genes in the slightest. This shows that MK-4 has effects on gene expression in bone tissue that MK-7 doesn't have.
That being said, MK-7 may still have a place in a healthy diet. Just because it can't do everything MK-4 can, doesn't mean it has no role. It may be able to fill in for MK-4 in some functions, or reduce the dietary need for MK-4. But no one really knows at this point. Hunter-gatherers would have had a source of longer menaquinones, including MK-7, from livers. So it's possible that we're adapted to a modest MK-7 intake on top of MK-4. "