Determinants of Vitamin K Metabolism

The purpose of this study is to learn how the body responds to different amounts of vitamin K in the diet in order to understand the roles that vitamin K may have in the body. We also need to determine if older adults need more or less vitamin K in their diet compared to younger adults in order to maintain normal body stores of vitamin K.

Vitamin K has a role in bone health, but little is known about vitamin K metabolism in aging and in maintenance of bone mass. The limited understanding of vitamin K metabolism impedes the establishment of dietary recommendations for vitamin K, and the interpretation of results from clinical trials on vitamin K supplementation and bone health of women in a narrow age group. This study is the first to assess the role of dietary and other factors that influence the response to vitamin K status and bone turnover to vitamin K depletion and repletion in adults. This study also compares the absorption efficiency and body retention of vitamin K relative to current vitamin K status. Men and women [21 younger (18-40y) and 21 older (55+y)] will participate in a 62-d metabolic study, with a 5d run-in period, followed by a 28d dietary vitamin K restriction period (10 ug/d), and ending with a 28d dietary vitamin K supplementation period (500 ug/d). Coagulation times will be monitored during the dietary restriction period. Serial measurements of vitamin K status markers and of bone turnover markers will show the response of vitamin K to dietary manipulation for both age groups under identically controlled dietary conditions. Deuterium-labeled vitamin K in collards will be used to compare the absorption of vitamin K during a vitamin K-deplete state to that of a vitamin K-replete state. Vitamin K is transported in triglyceride-rich lipoproteins, which may vary among individuals due to differences in adiposity and lipid homeostasis. Therefore, measurement of body composition by Dual Energy X-Ray Absorptiometry (DXA) and plasma lipids will provide insight into the role of lipids in absorption and transport of vitamin K. The findings of this study are critical for the interpretation of the epidemiologic and clinical data used to determine the protective role vitamin K may have in chronic disease prevention.

Inclusion Criteria: - Exclusion Criteria: kidney, GI, or liver disease requiring treatment prescribed osteoporosis medications in the previous 3 months use of acid reducers more than twice per week blood clotting disorder and/or abnormal clotting time warfarin or anticoagulant use in the previous 12 months diabetes smoking hormone therapy in the previous 3 months oral contraceptive use in the previous 3 months; pregnancy strict vegetarian diet

Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University

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Ellis JL, Fu X, Al Rajabi A, Grusak MA, Shearer MJ, Naumova EN, Saltzman E, Barger K, Booth SL. Plasma Response to Deuterium-Labeled Vitamin K Intake Varies by TG Response, but Not Age or Vitamin K Status, in Older and Younger Adults. J Nutr. 2019 Jan 1;149(1):18-25. doi: 10.1093/jn/nxy216.