Ageing: biology and nutritionDietary vitamin K intake and anticoagulation in elderly patientsRohde, Luis Eduardo; de Assis, Michelli Cristina Silva; Rabelo, Eneida RejaneAuthor Information Cardiovascular Division of Hospital de Clínicas de Porto Alegre, Post-Graduation Program in Cardiovascular Sciences and Cardiology, Federal University of Rio Grande do Sul, Brazil Correspondence to Luis E. Rohde, MD, Cardiovascular Division, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcelos 2350, Sala 2061, Porto Alegre, RS, Brazil 90035-903 Tel: +55 51 21018344; e-mail: [email protected] Supported in part by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo a Pesquisa do Rio Grande do Sul (FAPERGS) and Fundo de Incentivo a Pesquisa (FIPE-HCPA). Current Opinion in Clinical Nutrition and Metabolic Care: January 2007 - Volume 10 - Issue 1 - p 1-5 doi: 10.1097/MCO.0b013e328011c46c Buy Metrics Abstract Purpose of review Vitamin K is an essential co-factor for the synthesis of several coagulation factors. Oral anticoagulants competitively inhibit enzymes that participate in vitamin K metabolism. The purpose of this review is to evaluate the potential interaction of dietary vitamin K and coagulation stability, particularly in the elderly patient. Recent findings Recent prospective evidences suggest that dietary vitamin K plays an essential role in anticoagulation stability. Vitamin K intake of more than 250 μg/day was shown to decrease warfarin sensitivity in anticoagulated patients consuming regular diets. In a randomized crossover study, brief periods of changes on vitamin K intake also had significant effects on coagulation parameters. Patients that were allocated to an 80% decrease of intake increased International Normalized Ratio (INR) by almost 30% 7 days after the intervention. Similarly, it was estimated by dietary records that for each increase in 100 μg of vitamin K intake, the INR would be reduced by 0.2. A recent study also demonstrated that over-the-counter multivitamin supplements contain enough vitamin K1 to significantly alter coagulation parameters. Summary Contemporary data strengthen the concept that the interaction between dietary vitamin K and coumarin derivatives is clinically relevant and plays a major role in INR fluctuations in chronic anticoagulated patients. © 2007 Lippincott Williams & Wilkins, Inc.