|Vitamin K is a fat-soluble vitamin that plays an important role in blood clotting. Vitamin K is known as the clotting vitamin, because without it blood would not clot. The recommended dietary allowance (RDA) for vitamin K is 80 mg/day for the adult man, 65 mg/day for the adult woman, and 5 mg/day for the newborn infant. Vitamin K is involved as a cofactor in the posttranslational
gamma-carboxylation of glutamic acid residues of certain proteins in the body. Vitamin K deficiency exists when chronic failure to eat sufficient amounts of vitamin K results in a tendency for spontaneous bleeding or in prolonged and excessive bleeding with trauma or injury.
Vitamin K deficiency is very rare and occurs when there is an inability to absorb the vitamin from the intestinal tract. Vitamin K deficiency can also occur after prolonged treatment with oral antibiotics. Individuals with vitamin K deficiency usually have an increased propensity to bruising and bleeding. Deficiency can occur in persons of any age but neonates are at risk of developing haemorrhagic disease of the newborn. This is because of a lack of vitamin K reaching the foetus across the placenta, the low level of vitamin K in breast milk and low colonic bacterial synthesis. In adults, vitamin K deficiency is uncommon. In infants, vitamin K deficiency without bleeding may occur in as many as 50% of infants younger than 5 days old. The classic haemorrhagic disease occurs in 0.25-1.7% of infants. The prevalence of late haemorrhagic disease in breast-fed infants is about 20 per 100,000 live births with no prior prophylaxis with Vitamin K.
Vitamin K deficiency is often the result of impaired absorption rather than not getting enough in the diet. Newborns are at risk for vitamin K deficiency. This is because their digestive tracts contain no vitamin K-producing bacteria. For this reason, doctors often give injections of vitamin K to newborns. The main symptom of vitamin K deficiency is blood that's slow to clot. Prolonged use of antibiotics can also cause a low level of this vitamin because they destroy some of the bacteria in the gut that help to produce vitamin K. Vitamin K deficiency can occur under certain conditions including inadequate dietary intake, malabsorption syndromes (cystic fibrosis, Crohn's disease, ulcerative colitis, Whipple's disease, celiac sprue, short bowel syndrome) and loss of storage sites due to hepatocellular disease. Vitamin K deficiency frequently occurs in those with chronic liver disease, such as primary biliary cirrhosis.
Vitamin K deficiency occurs also in newborn infants, as well as in people treated with certain antibiotics. The protein in the body most affected by vitamin K deficiency is a blood-clotting protein called prothrombin. Newborns are especially prone to vitamin K deficiency. A nursing-mother's milk is low in the vitamin; breast milk can supply only about 20% of the infant's requirement. Infants are born with low levels of vitamin K in their body; they do not have any vitamin K-producing bacteria in their intestines. Their digestive tracts are sterile. As a result, a form of vitamin K deficiency, called hemorrhagic disease of the newborn, may develop. This disease involves spontaneous bleeding beneath the skin or elsewhere in the infant's body, and occurs in about 1% of all infants. In rare cases, it causes death due to spontaneous bleeding in the brain. Vitamin K deficiency in adults is rare. When it occurs, it is found in people with diseases that prevent the absorption of fat. These diseases include cystic fibrosis, celiac disease, and cholestasis. Vitamin K deficiency can exist in adults treated with antibiotics that kill the bacteria that normally live in the digestive tract. As mentioned, the intestine-bacteria supply part of our daily requirement of vitamin K. Vitamin K deficiency can result in bleeding gums, and in skin that is easily bruised.
Many of the popular rodenticides act by inducing a vitamin K deficiency which, if severe, leads to death by bleeding. Coumarin derivatives such as Warfarin and dicumarol interfere with recycling of vitamin K (see above) and thereby lead to vitamin K deficiency. The liver synthesizes bile acids and secretes them into the small intestine where they play a critical role in absorption of lipids. Vitamin K, as a fat-soluble vitamin, requires proper lipid absorption for its own absorption. Liver disease that results in decreased bile salt synthesis leads to impaired vitamin K absorption and deficiency. Vitamin K is a nutrient found in the small intestine where it combines with protein to produce clotting of the blood. Certain cases of vitamin K deficiency have resulted in a failure of the clotting process and in hemorrhages. In particular, there is a danger that hemorrhages may occur in the brains of newborns who lack sufficient vitamin K. Symptoms of vitamin K deficiency include easy bruisability, epistaxis, gastrointestinal bleeding, menorrhagia and hematuria. Chronic vitamin K deficiency may also result in osteoporosis and increased risk of fractures. There is some evidence that chronic warfarin use may also cause osteoporosis.