Vitamin K is a fat-soluble vitamin that the body uses for blood clotting and bone formation. The “K” in vitamin K comes from the German word koagulation, because the vitamin is essential for the synthesis of proteins that are required for blood coagulation. There are three different forms of vitamin K: vitamin K1 (phylloquinone), which is found in plant foods containing cholorophyll; vitamin K2 (menaquinone), which is found in animal foods and is also synthesized by bacteria in the human gut; and vitamin K3 (menadione), a synthetic form that is not found in nature. Vitamin K1 and K2 both have roles are dietary supplements in recommended amounts, but vitamin K3 is not used as a dietary supplement.
Good food sources of vitamin K include dark leafy greens, such as spinach, broccoli and kale, and vegetable oils, such as canola oil, soybean oil, olive oil and cottonseed oil. Additionally, some fruits, nuts and vegetables contain small amounts. One cup of dark leafy greens provides about 120 micrograms of vitamin K, the recommended daily intake for adult men. Most multivitamins contain the recommended daily amount of vitamin K, and further supplementation is typically not needed. However, vitamin K1 and K2 supplements are available at health food stores and are useful in cases of specific health conditions.
Although vitamin K deficiency is rare in the United States, a true deficiency interferes with blood clotting. Symptoms of deficiency include various types of excessive bleeding, such as blood in the urine, nosebleeds, bleeding gums, heavy menstrual bleeding, or tarry, (black stools). If you suspect you may be suffering from a vitamin K deficiency, please contact your physician for proper diagnosis and treatment.
Infant Hemorrhagic Disease
In 1961, the American Academy of Pediatrics recommended that all newborn babies receive an injection of vitamin K to prevent hemorrhagic disease, a condition that interferes with blood coagulation. Since infants are born with a sterile intestinal tract, and a major source of vitamin K is gut bacteria, it takes some time until infants’ gut bacteria can colonize and produce adequate levels of vitamin K. The practice of vitamin K supplementation at birth ahs dramatically reduced the incidence of hemorrhagic disease among infants in the United States.
Vitamin K and Coagulation
Scientists refer to the process of blood clotting as the coagulation cascade, a series of interdependent events that stop bleeding though the formation of clots. They body utilizes seven different clotting factors, or proteins, in the coagulation cascade, and vitamin K is required to activate these seven factors. If the body lacks adequate amounts of vitamin K to activate the seven clotting factors, blood clots cannot form, leading to life-threatening bleeding disorders.
Vitamin K and Cardiovascular Disease
Preliminary research suggests that inadequate vitamin K intake may be correlated with an increased incidence of aortic calcification, leading to the development of arteriosclerosis. In a population-based study published in 1995 in the journal Atherosclerosis, researchers followed 256 postmenopausal women and found an inverse correlation between long-term intake of vitamin K and arterosclerotic aorta calcification; in other words, the women with lower vitamin-K levels had more aortic calcification than those with higher levels.
In a 2004 study, Dr. J.M Gelejinse and colleagues also found a significant inverse correlation between long-term, inadequate vitamin K2 intake and aortic calcification. While additional research needs to be done, it looks like maintaining adequate vitamin K levels can help prevent arteriosclerosis and the serious cardiovascular events it can precipitate.