Vitamin K was found to be essential when its role in the synthesis of several blood coagulation factors was determined. In fact, the "K" in vitamin K came from the Danish word "koagulation," which means "blood clotting". Vitamin K is actually 3 different compounds, all of which are fat soluble. It is absorbed from the upper small intestine with the help of bile (or bile salts) and pancreatic secretions, and then carried to the liver.

Several proteins involved in blood clotting require vitamin K. When there isn’t enough K, blood takes longer to clot, increasing the amount of blood lost. Vitamin K is also necessary for the synthesis of a protein that may help regulate blood calcium levels. Calcium, usually associated with keeping bones strong, is also necessary for blood clotting.

Accumulating evidence supports an active role for vitamin K in bone health. High intakes of vitamin K are associated with a lower risk of hip fracture in women; and conversely, low intakes of vitamin K are associated with low bone mineral density and increased risk of bone fractures.

Vitamin K has a key role in the synthesis of at least two proteins involved in calcium and bone metabolism. One of these proteins has been shown to be a strong inhibitor of vascular calcification. Thus vitamin K appears to have a role in maintaining vascular health.

In addition, vitamin K may influence bone metabolism through its effect on urinary calcium excretion or by inhibiting the production of bone resorbing agents.

Vitamin K is made by bacteria, including beneficial flora found in the human GI tract. However, a newborn’s gastrointestinal tract is typically sterile for a few days after birth. The production of vitamin K and, therefore, clotting factors, begins by the fourth day of life, giving babies their ability to clot blood. To help the protect them, newborns are typically given vitamin K injections shortly after birth.

People who are at risk of having problems related to abnormal blood clotting, such as those with a history of stroke or heart disease, are often put on anti-coagulation therapy. These medications reduce blood clotting by competing with vitamin K. Anyone on anticoagulant medicine (blood thinners) should know that the amount of vitamin K in the diet may affect how well the medications work.

Deficiency of vitamin K is rare. Deficiency is more common in sprue or celiac disease (intestinal malabsorption disorders), in colitis, in ileitis, or after bowel surgery. Lack of Vitamin K can result in problems with blood clotting and increased bleeding.

Food Sources of Vitamin K

Vitamin K is found in varied foods including green leafy vegetables, meat and dairy products. Little vitamin K is lost from foods with ordinary cooking.