Vitamin K is a group of structurally similar, fat-soluble
vitamins the human body requires for
complete synthesis of certain proteins that are prerequisites for blood
coagulation that the body needs for controlling binding of calcium in bones and other tissues. The vitamin K-related modification of the proteins allows them to bind
calcium ions, which they cannot do otherwise. Without vitamin K, blood coagulation is seriously impaired, and uncontrolled bleeding occurs. Low levels of vitamin K also weaken bones and promote calcification of arteries and other soft tissues.