Vitamin K is a fat-soluble vitamin essential for the functioning of several proteins involved in blood clotting. Discovered in 1929 by Danish scientist Henrik Dam, the vitamin received the letter “K” because the initial discoveries were reported in a German journal in which the substance was designated as “Koagulationsvitamin.” Research during the last 30 years has resulted in greater appreciation for vitamin K. For instance, although vitamin K is usually identified as a critical factor in blood coagulation, recent research reveals it is a cofactor in bone metabolism.2-8 Inhibition of cancerous cell growth in vivo and in vitro by vitamin K has also been observed.9-16 Furthermore, recent findings suggest it may be an important cofactor in the treatment and prevention of  therosclerosis and calcified arterial plaque.17,18

The primary dietary source of vitamin K is generally green leafy vegetables. Consequently, high vitamin K intake may serve as a marker for a healthy diet rich in vegetables.