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Vitamin K is a family of structurally similar, fat-soluble vitamers found in foods and marketed as dietary supplements. [1] The human body requires vitamin K for post-synthesis modification of certain proteins that are required for blood coagulation ("K" from Danish koagulation, for "coagulation") or for controlling binding of calcium in bones and other tissues. [2]
Phytomenadione, also known as vitamin K 1 or phylloquinone, is a vitamin found in food and used as a dietary supplement. [6] [7] It is on the World Health Organization's List of Essential Medicines. [8] It is used to treat certain bleeding disorders, [7] including warfarin overdose, vitamin K deficiency, and obstructive jaundice. [7]
There are two primary types of vitamin K: vitamin K1 and vitamin K2. ... Women ages 19 and older need 90 micrograms of vitamin K per day, and men ages 19 and older require 120 micrograms daily.
Vitamin K 1-deficiency may occur by disturbed intestinal uptake (such as would occur in a bile duct obstruction), by therapeutic or accidental intake of a vitamin K 1-antagonist such as warfarin, or, very rarely, by nutritional vitamin K 1 deficiency. As a result, Gla-residues are inadequately formed and the Gla-proteins are insufficiently active.
Menadione is converted to vitamin K 2 (specifically, MK-4) by the prenyltransferase action of vertebrate UBIAD1. [4] This reaction requires the hydroquinone (reduced) form of K 3, menadiol, produced by NQO1. [6] Menadione is also a circulating form of vitamin K, produced in small amounts (1–5%) after intestinal absorption of K 1 and K 2.
Newborn infants are a special case. Plasma vitamin K is low at birth, even if the mother is supplemented during pregnancy, because the vitamin is not transported across the placenta. Vitamin K deficiency bleeding (VKDB) due to physiologically low vitamin K plasma concentrations is a serious risk for premature and term newborn and young infants.
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Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, avidin is a protein in raw egg whites that inhibits the absorption of biotin; it is deactivated by cooking. [50] Pyrithiamine, a synthetic compound, has a molecular structure similar to thiamine, vitamin B 1, and inhibits the enzymes that use ...