Dietary intake and adequacy of vitamin K

Abstract

The current daily recommended dietary allowance for vitamin K is 1 μg/kg. Reliable measurements of vitamin K content in foods are now available, and data from 11 studies of vitamin K intake Indicate that the mean intake of young adults is ~80 μg phylloquinone/d and that older adults consume ~150 μg/d. The vitamin K concentration in most foods is very low (<10 μg/100 g), and the majority of the vitamin is obtained from a few leafy green vegetables and four vegetable oils (soybean, cottonseed, canola and olive) that contain high amounts. Limited data indicate that absorption of phylloquinone from a food matrix is poor. Hydrogenated oils also contain appreciable amounts of 2',3'-dihydrophylloquinone of unknown physiological importance. Menaquinones absorbed from the diet or the gut appear to provide only a minor portion of the human daily requirement. Measures of the extent to which plasma prothrombin or serum osteocalcin lack essential γ- carboxyglutamic acid residues formed by vitamin K action, or the urinary excretion of this amino acid, provide more sensitive measures of vitamin K status than measures of plasma phylloquinone or insensitive clotting assays.