One of the major reasons people take Vitamin K-2 for cardiovascular support is because it supports the formation of Osteocalcin, a protein carrier which helps to transfer calcium into the bone. Nattokinase helps breaks down fibrin, which is the webby structure that forms the basis of clots to help support circulation.
Vitamin K-2 does support the formation of clotting factors in the liver, which under ideal circumstances will simply remain on stand-by until the body has a legitimate need to initiate the clotting process, leading to production of fibrin.
The two could actually be considered as “balancing” one another. Generally, there is a cycle going on for most substances in the body with the substance being built up or formed and then being broken down. In other words, Nattokinase and Vitamin K-2 have very different effects on the body, but like many other supplements can have some overlapping areas of benefits. They don’t exactly work against each other because the clotting factors will allow your blood to clot when needed, but won’t force it to clot.
If you have any history of blood clots or anything which might compromise the integrity of the blood vessels and contribute to abnormal clotting, you wouldn’t want to take either product without consulting your health care practitioner. If you have a tendency to clotting, K-2 could aggravate this since something is activating the clotting process when it isn’t desirable instead of just having the clotting factors sitting around on stand-by. If you take any prescription blood-thinners like Warfarin, Coumadin, Plavix, etc you certainly wouldn’t want to take either Nattokinase or K-2 without consulting health care practitioner.