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 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.
Allocation: Non-Randomized, Control: Dose Comparison, Endpoint Classification: Bio-availability Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Basic Science
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University
Active, not recruiting
Results (where available)
- Source: http://clinicaltrials.gov/show/NCT00336232
- Information obtained from ClinicalTrials.gov on July 15, 2010
Medical and Biotech [MESH] Definitions
A lipid cofactor that is required for normal blood clotting. Several forms of vitamin K have been identified: VITAMIN K 1 (phytomenadione) derived from plants, VITAMIN K 2 (menaquinone) from bacteria, and synthetic naphthoquinone provitamins, VITAMIN K 3 (menadione). Vitamin K 3 provitamins, after being alkylated in vivo, exhibit the antifibrinolytic activity of vitamin K. Green leafy vegetables, liver, cheese, butter, and egg yolk are good sources of vitamin K.
The process of aging due to changes in the structure and elasticity of the skin over time. It may be a part of physiological aging or it may be due to the effects of ultraviolet radiation, usually through exposure to sunlight.
Vitamin D Deficiency
A nutritional condition produced by a deficiency of VITAMIN D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as RICKETS in children and OSTEOMALACIA in adults. (From Cecil Textbook of Medicine, 19th ed, p1406)
Vitamin K 1
A family of phylloquinones that contains a ring of 2-methyl-1,4-naphthoquinone and an isoprenoid side chain. Members of this group of vitamin K 1 have only one double bond on the proximal isoprene unit. Rich sources of vitamin K 1 include green plants, algae, and photosynthetic bacteria. Vitamin K1 has antihemorrhagic and prothrombogenic activity.
Vitamin E Deficiency
A nutritional condition produced by a deficiency of VITAMIN E in the diet, characterized by posterior column and spinocerebellar tract abnormalities, areflexia, ophthalmoplegia, and disturbances of gait, proprioception, and vibration. In premature infants vitamin E deficiency is associated with hemolytic anemia, thrombocytosis, edema, intraventricular hemorrhage, and increasing risk of retrolental fibroplasia and bronchopulmonary dysplasia. An apparent inborn error of vitamin E metabolism, named familial isolated vitamin E deficiency, has recently been identified. (Cecil Textbook of Medicine, 19th ed, p1181)
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