New Perspectives for the Nutritional Value of Vitamin K in Human Health

Carla SB Viegas and Dina C Simes

Vitamin K is an essential micronutrient in the post-translational modification of specific glutamic acid residues (Glu) into γ-carboxyglutamic acid residues (Gla) in target proteins known as vitamin K-dependent proteins (VKDPs). In healthy conditions of sufficient vitamin K status, a vitamin K recycling system maintains sufficient vitamin K levels for proper γ-carboxylation of VKDPs, and vitamin K antagonists (VKAs) widely used as anticoagulants inhibit vitamin K recycling. Besides its well-known function in the maintenance of normal coagulation, vitamin K has been reported to have other diverse physiological functions with impact in human health. In extra-hepatic tissues vitamin K deficiency results in impairment of VKDPs γ-carboxylation with important implications in bone and cardiovascular health. Although most of vitamin K effects have been associated with regulation of mineralization in connective tissues through the action of matrix Gla protein (MGP) and osteocalcin (OC), the discovery of Gla-rich protein (GRP) open new perspectives on the potential therapeutic range of vitamin K.