The UK food data-base for vitamin K and why we need it

Abstract

The need to make accurate assessments of dietary intakes vitamin K has been driven by recent evidence that vitamin K-dependant (Gla) proteins are widely present in the body and have other important physiological functions other than coagulation. Two of these proteins, osteocalcin and matrix Gla protein (MGP), are thought to have a role in maintaining skeletal integrity while MGP acts as an inhibitor of calcification in arteries and cartilage. An added impetus has been the development of functional markers that enable vitamin K status to be assessed from a tissue-specific perspective and evidence that bone Gla-proteins require higher dietary intakes of vitamin K for optimal carboxylation than do hepatic coagulation Gla-proteins. The UK food data-base for vitamin K began on an ad-hoc basis to identify the major individual food contributors but recently has been expanded to include values based on recipe calculations and food similarities. To date the data-base is restricted to the plant form phylloqinone, the major food source of vitamin K. The food items used to calculate values for composite foods have all been analyzed by a validated HPLC procedure, some 170 by our London laboratory. Currently about 2000 food items have been assigned a provisional phylloquinone content. Although this food data-base has enabled the first assessments of dietary intakes of phylloquinone in UK populations, many assigned values are provisional and need to be validated by direct analysis. Further work is needed to assess issues such as inter-sample variability, storage losses and the content of bacterial menaquinones.