Vitamin K is essential for many types of normal biological processes, one of which is blood clotting. The "K" of vitamin K was taken from the German word "koagulation," the English translation of which is "coagulation." Coagulation is the clinical term for blood clotting, which is mediated in part by the activation of platelets. If you have a deficiency in vitamin K or a low platelet count, your blood may clot abnormally slowly or not at all, putting you at risk for severe and uncontrolled bleeding.
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The most common type of blood clot you may be familiar with is a scab, which occurs when blood clots on the outer surface of the skin. Blood can also clot underneath the skin, which may be visible as a bruise. Clots can also form inside blood vessels; if these clots block the flow of blood, they may cause a heart attack or stroke.
Platelets are cell fragments that are necessary for normal blood clotting. Thromboycytopenia is the clinical term for very low levels of platelets in the blood. Normally, you have between 150,000 and 450,000 platelets in each microliter of blood. If the number of platelets drops very low, such as below 10,000 per microliter of blood, you are at risk for thrombocytopenia and uncontrollable bleeding due to abnormal blood clotting.
Roles of Vitamin K and Platelets in Blood Clotting
Clots form as a result of platelets and the vitamin K dependent coagulation cascade, in which each protein activates another in a chain of protein signaling. The cascade ultimately results in the activation of fibrinogen. Upon contact with air, such as when a cut exposes blood to air, platelets being to disintegrate and react with fibrinogen to form thread-like fibers called fibrin. Fibrin ultimately forms a mesh-like patch that traps blood cells and stems the flow of blood.
Vitamin K Deficiency
A deficiency in vitamin K results in slow or absent blood clotting. If you suspect your blood is not clotting normally, your doctor can perform tests to measure blood clotting time. Slow blood clotting puts you at risk for excessive and uncontrollable bleeding, even though your platelet numbers may be normal. The symptoms of a vitamin K deficiency include frequent or heavy nosebleeds; gums that bleed abnormally; blood-laced stool; abnormally heavy menstrual bleeding in woman; and skin that bruises very easily. If you are experiencing these symptoms, the cause may be a vitamin K deficiency or a low platelet count, or both.
Sources of Vitamin K
The recommended daily allowance, or RDA, for vitamin K is 80 mcg per day for adult women and 65 mcg for adult men. Dark leafy greens are a great source of vitamin K: 1 cup of swiss chard contains 299 mcg, 1 cup of raw kale contains 547 mcg, and 1 cup of cooked broccoli contains 220 mcg. Several types of oil also provide vitamin K, including soybean, canola and olive oils, each of which contains 25.0 mcg, 26.6 mcg, and 8.1 mcg of this vitamin in 1 tbsp. of oil, respectively.