The fat-soluble Vitamin K plays a role in bone and skin health as well as blood clotting. Vitamin K is naturally available as two compounds that have biological activity: phylloquinone, from dietary sources, and menaquinones, which intestinal bacteria generate. Each form functions as an enzyme that assists in chemically altering proteins involved in the blood clotting. Specifically, this process allows for the binding of prothrombin; factors VII, IX and X; and proteins C and S to damaged membranes.
Sources, Metabolism and Excretion
Dietary sources of vitamin K include leafy green vegetables such as spinach, kale, broccoli, parsley and Swiss chard. The body absorbs dietary vitamin K through the small intestine. Intestinal bacteria, such as E. coli, found in the large intestine produce a significant amount of the body's vitamin K reserve. The body excretes most vitamin K in urine and feces.
Vitamin K Deficiency
Individuals with vitamin K deficiency may complain of bleeding after minimal trauma, nose bleeds, easy bruising, heavy menstrual bleeding, bleeding with urination, gum bleeding or oozing from blood draw sites. Factors that contribute to vitamin K deficiency include celiac disease, inflammatory bowel disease, pancreatitis, biliary disease and short bowel syndrome; liver disease that decreases the production of vitamin K-dependent proteins; drugs, including blood thinners, that prevent the biological activity of the vitamin; and antibiotic overuse, which can eliminate vitamin K producing bacteria. The lack of vitamin K prevents the formation of blood clots, leading to these bleeding disorders.
Vitamin K Toxicity
The overuse of synthetic vitamin K in supplements may cause the rare vitamin K toxicity. Excess vitamin K can interfere with the function of blood-thinning therapy, causing clotting symptoms. Symptoms include rashes, nausea, vomiting, anemia and diarrhea.
Caution
Whether or not you take blood-thinning medication such as warfarin, consult a physician before taking vitamin K in supplement form to address possible drug interactions.
References
- "Harrison's Principles of Internal Medicine"; A.S. Fauci, et al.; 2008
- "Tintinalli's Emergency Medicine: A Comprehensive Study Guide"; J.E. Tintinalli, et al.; 2010
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics"; L.L. Brunton, et al.; 2010
- Linus Pauling Institute at Oregon State University; Vitamin K; Jane Higdon
