Vitamin K: A practical guide to the dietary management of patients on warfarin

Warfarin has been successfully used in the medical management of thromboemb olic disease for nearly six decades. It is widely assumed that a dietary vi tamin K-warfarin interaction exists. To avoid this potential interference w ith the efficacy of warfarin in stable anticoagulation, patients typically receive instructions to consume a constant dietary intake of Vitamin K. Whi le dark, green vegetables are primary sources of dietary vitamin K, these f oods are not commonly consumed on a daily basis in the United States. Howev er, there still exists dietary resistance to warfarin that is attributable to vitamin K. Based on food analysis studies on vitamin K, it is now known that dietary Vitamin K is found in certain plant oils and prepared foods co ntaining these plant oils, such as baked goods, margarines, and salad dress ings. The preparation of foods with vitamin K-rich oils may also contribute to a diet-warfarin interaction, although this has yet to be confirmed in a clinical trial. A dose-response of vitamin K on the effect of warfarin ant icoagulation has not yet been established. However, there are sufficient da ta to suggest that a constant dietary intake of vitamin K that meets curren t dietary recommendations of 65-80 mu g/day is the most acceptable practice for patients on warfarin therapy. Vitamin K composition data for commonly consumed foods are now available and may facilitate successful anticoagulat ion for patients being treated with warfarin.