1a. Objectives (from AD-416)
1. Determine the amounts of individual dietary forms of vitamin K in nationally representative samples of frequently consumed U.S. foods and dietary supplements. 2. Characterize the effects of dietary and non-dietary factors, such as age, lipid profile and body fat, on the bioavailability and utilization of different forms of vitamin K in humans. 3. Identify mechanisms of action for vitamin K, other than its classic role as an enzyme cofactor, using cellular and animal models.
1b. Approach (from AD-416)
Laboratory analysis of different forms of vitamin K will be conducted in selected foods obtained through collaboration with the USDA Nutrient and Data Laboratory (NDL), as part of the Food and Nutrient Analysis Program. Priorities for food analysis will include dietary supplements, food purchased in family style restaurants, foods common to the Hispanic/Latino diet, and foods associated with high calorie diets. Food composition data will be transferred to the NDL for entry into national food composition databases. To identify dietary and non-dietary factors that determine how much vitamin K obtained from foods is utilized, we will apply stable isotope techniques to measures of vitamin K metabolism. Data obtained from ongoing metabolic studies in men and women, in addition to pilot feasibility studies, will be used to refine the study design to test the response of these measures to intake of different vitamin K-rich food sources. Animal models will be used to identify tissue-specific effects of interactions between vitamin K and other fat-soluble vitamins, with an emphasis on vitamins A and D. To identify mechanisms of action for vitamin K other than its classic role as an enzyme cofactor, urinary and serum levels of vitamin K metabolites will be measured in response to vitamin K supplementation using archived samples from human and animal studies. We will then focus on the role of different forms of vitamin K in inflammation through the inactivation of nuclear receptors in macrophages.
3. Progress Report
To conduct studies for guidance on the health benefits of vitamin K, accurate and up-to-date food composition information is required. Foods obtained from restaurants and markets from various locations were analyzed for vitamin K. The vitamin K food composition data were transferred to the Nutrient Data Laboratory at Beltsville Human Nutrition Research Center for entry into the USDA National Nutrient Database for Standard Reference, Release 24. These data will be used in research and for nutrition monitoring. 1C. Provide U.S. Food Composition Data. Although green vegetables have high concentrations of vitamin K, the amount that is absorbed is low. Therefore there is interest in identifying other food sources that may have greater absorption and biological activity of vitamin K. Spirulina, which is a cyanobacteria, has been identified as a potentially rich source of vitamin K. We measured samples obtained from a human feeding study which examined the uptake of different nutrients from a single meal containing spirulina. Although spirulina contained vitamin K, it was not well absorbed. Therefore spirulina will not be considered for future human feeding studies of vitamin K nutrition. 2A. Identify Roles of Food, Nutrients, Food Components, and Physical Activity in Promoting Health and Preventing Disease. Vitamin K is a nutrient that may contribute to cardiovascular health. A new biological marker of a vitamin K-dependent protein present in the vascular system was recently developed, but the extent to which this marker reflect vitamin K’s role in vascular calcification among healthy adults was unknown. We determined that this biological marker was associated with vitamin K status and responded in the expected direction with vitamin K supplementation. However, the biomarker did not appear to reflect coronary artery calcification in healthy older adults. We concluded that this was not a robust marker of vitamin K in the vascular system. 2A. Identify Roles of Food, Nutrients, Food Components, and Physical Activity in Promoting Health and Preventing Disease.
1. Importance of dietary intake of vitamin K in younger and older adults Vitamin K is a nutrient that is essential for health, yet is consumed in low amounts by the elderly. To understand the benefits of an increased consumption of vitamin K on human health, ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, studied the effects of dietary and non-dietary factors, including age, sex, blood lipids and body fat, on the utilization of vitamin K. Dietary restriction of vitamin K caused a decline in vitamin K status, which was rapidly reversed by high vitamin K intake. The vitamin K status of elderly men and women benefited from vitamin K intake as well as young men and women. These data suggest that individuals with low vitamin K intake will benefit from increased consumption, regardless of their age or sex.