Vitamin K plays a role in your blood clot formation and bone health. Many types of food contain vitamin K, and it is rare to have a deficiency. Vitamin K is an essential cofactor in the activation of certain proteins within your body. Without the activation step, certain biochemical reactions cannot be completed. A vitamin K deficiency will predispose you to bleeding, and blocking vitamin K prevents inappropriate clotting.
Vitamin K is a fat-soluble vitamin stored in your fat and liver tissue. Green leafy vegetables, such as kale and spinach, contain the largest amounts of vitamin K. Do not eat large amounts of these foods if you take anticoagulant medications; high vitamin K may disrupt the medication's efficacy. Men need about 19 mcg per day, while women only need 90 mcg. Children need more as they get older.
The Clotting Cascade
The clotting cascade is a pathway containing many biochemical steps in the formation of blood clots during tissue injury. Vitamin K is important in the steps involving protein factor II, VII, IX and X. Factor II is alternatively named prothrombin. Also, anticoagulation proteins C, S and Z, as well as osteocalcin and the matrix-Gla protein depend on vitamin K. Prothrombin alone needs vitamin K to modify 10 different regions within the protein for functionality.
Blood clotting has several phases. The first phase contains several prothrombin activators, including vitamin K. Activation of prothrombin, or factor II, further activates fibrinogen, which activates fibrin. The fibrin begins to physically repair damaged tissue. It forms a physical barrier to prevent further blood loss. If vitamin K is deficient, prothrombin cannot activate and blood clots cannot form.
When cells are damaged, they increase a protein on their surface called tissue factor, or TF. The tissue factor needs to bind to factor VII in the clotting cascade. Factor VII cannot be bound until it is activated with the assistance of vitamin K. Tissue factor bound to factor VII becomes a protease for factors IX and X in the cascade. Proteases cleave molecules off of proteins to activate them.
"F9" is the genetic symbol for the gene that makes clotting factor IX. Factor IX is made in the liver. If your liver has decreased functioning capability, clotting factor IX may be diminished. Hemophilia B results from deficiencies in factor IX. Clotting times can be severely, moderately or mildly decreased. Low levels of vitamin K can exacerbate problems associated with hemophilia B, but any changes in your diet should be discussed with your doctor.
Factor X is also known as the Stuart-Prower factor. It was named after the first two individuals discovered to have a genetic deficiency in factor X. Factor X is an enzyme activated on the surface of your blood platelets with the help of tissue factor, calcium and vitamin K. Once the enzyme is activated it becomes factor Xa, which is responsible for the conversion of prothrombin to thrombin within your clotting cascade.
- The University of Maryland Medical Center; Vitamin K; Steven Ehrlich; June 2009
- Colorado State University; Vitamin K; R. Bowen; July 1999
- Kimballs's Biology Pages; Blood Clotting; John Kimball; January 2011
- National Institutes of Health; F9; May 2010
- The Medical Biochemistry Page; Blood Coagulation—Homostasis; Michael King; February 2011