title: Vitamin K: dietary intake and requirements in different clinical conditions.
abstract: OBJECTIVE
  Vitamin K is an enzyme cofactor for the carboxylation of vitamin K-dependent proteins. Functions include coagulation and regulation of calcification. Different clinical conditions may alter vitamin K requirements by affecting vitamin K status and vitamin K-dependent proteins carboxylation that are reviewed here.
  
  
  RESULTS
  Vitamin K consumption greater than the current usual daily requirement to maintain health is indicated for prevention of vitamin K-deficient bleeding in infants and for rescue of over-anticoagulation in patients on vitamin K-dependent oral anticoagulants. Additional vitamin K intake may be required in malabsorptive conditions such as cystic fibrosis and following bariatric surgery. Carboxylation of vitamin K-dependent proteins occurs in multiple extrahepatic tissues and has been implicated in soft tissue calcification and insulin resistance, although the exact mechanisms have yet to be determined. Contribution of colonic flora to vitamin K requirements remains controversial.
  
  
  CONCLUSIONS
  With the increased incidence of vitamin K-deficient bleeding and weight-loss surgical procedures, healthcare professionals need to monitor vitamin K status in certain patient populations. Future research on the roles of vitamin K in extrahepatic tissues as they pertain to chronic disease will provide insight into the therapeutic potential of vitamin K and lead to the development of recommendations for specific clinical populations.
authors.affiliation: Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA.
authors.forename: Stephanie G
authors.initials: SG
authors.lastname: Harshman
authors.forename: Edward
authors.initials: E
authors.lastname: Saltzman
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Booth
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage / Q000097:blood; D002908:Chronic Disease / Q000188:drug therapy / Q000517:prevention & control; D019587:Dietary Supplements; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D009751:Nutritional Requirements; D015675:Osteocalcin / Q000378:metabolism; D014812:Vitamin K / Q000008:administration & dosage* / Q000097:blood*
chemical_list: D000925:Anticoagulants; D015675:Osteocalcin; D014812:Vitamin K