Oral anticoagulants that are widely used for the treatment of thrombo-embolic disease exert their effect by blocking the recycling of vitamin K. Vitamin K acts as a co-factor in the posttranslational carboxylation of vitamin K-dependent proteins such as osteocalcin and matrix-gla protein. It is important to quantify the dose-response relationship of the interaction between vitamin K and oral anticoagulants and to investigate at what dosage vitamin K will interfere with oral anticoagulants in a clinically relevant way.