Vitamin K
Clotting Factor
Vitamin K was discovered based mostly in part to its important role in blood clotting. A Danish researcher discovered that chicks who had fat extracted from their diet developed hemorrhages. He named this fat-soluble vitamin K after koagulation the Danish spelling for coagulation.
There are two types of this compound, k1 (from plants) and k2 (from fish oils and meats). Vitamin k2 is also synthesized in the human colon by bacteria. K1 is the most biologically active form.
Around 10% of our vitamin K absorption comes from bacterial synthesis in the colon, the rest comes from our diet. Good sources of vitamin K can be found in leafy greens (kale, spinach, turnip greens, cabbage and lettuce), broccoli, green beans and peas. Soy and canola oil are also good sources. Vitamin K is quite heat stable but it is easily destroyed by light exposure. Men need 120 mcg/day and women need 90 mcg/day. Just half a cup of broccoli provides nearly 100 mcg.
Vitamin K is essential in the body as it is required for the synthesis of blood clotting factors. People taking drugs such as warfarin (Coumadin) have this process strongly inhibited as it acts as an anticoagulant. They should should maintain consistent vitamin K consumption and avoid supplementation. Bone metabolism is also affected by vitamin k.
Deficiency can occur in newborns since their stores are so low and their intestinal tracts don’t yet have the bacteria to synthesize vitamin K. In North America, newborns are given a vitamin k injection within 6 hours of birth. Deficiency in others is rare but it can happen with prolonged use of antibiotics and impaired fat absorption. Because hemorrhaging is a risk, all patients should be tested for vitamin K status prior to surgery. Excessive intakes of vitamin A & E can negatively affect the way vitamin K works in the body.
No upper level for vitamin K has been set. Even though it can be stored in the liver and bone, storage is limited and it is more readily excreted than other fat-soluble vitamins.