Vitamin K is a generic term for several fat-soluble molecules found in natural and processed foods, playing an important role in human health for blood coagulation and bone metabolism. Although vegetable oils contain only phylloquinone (vitamin K₁), milk and infant formula contain not only a phylloquinone but also menaquinone-4 (vitamin K₂), which has a polarity more similar to that of triglyceride and impurities, therefore requiring silica gel column chromatography before HPLC analysis can be performed. By focusing on silica gel particle size to reduce the required quantity of silica gel and organic solvent, we have reported an efficient analytical procedure for quantification of phylloquinone and menaquinone-4. However, the procedure left room for improvement in terms of the on-duty-hours required for manual pretreatment by the operator. Accordingly, we have now developed a more time-efficient analytical procedure using an automated solid phase extraction system, which frees the operator from the time required for manual chromatography pretreatment. Furthermore, by examining more closely the conditions required for this system, we have developed a better procedure capable of reducing the required quantity of silica gel and organic solvent for vitamin K analysis in milk, powdered infant formula, liquid infant formula and plant oils, thus making it more ecofriendly.

We analyzed dietary data for the general population to examine differences in nutrient intake values calculated using the 2015 (seventh) and 2020 (eighth) editions of the Standard Tables of Food Composition in Japan. The subjects were 7,596 men and 7,566 women who had completed the 3-day dietary record using the weighing method from the first to the seventh wave of the Longitudinal Epidemiological Study of Aging. There was a significant correlation between nutrient intakes estimated using the seventh and eighth editions, but there were differences in the mean percentages of energy (5.1％), carbohydrate (5.8％), and protein (6.0％) calculated as the sum of amino acids, for which the measurement method had been changed; there were also differences in nutrient intake values for which the numbers of components, such as organic acids, had been changed. These results indicate the possibility of systematic errors due to database revision. In addition, our results showed sex-related differences. The degree of influence of the two editions may differ depending on the diet quality of individual subjects. These findings suggest that it is important to revise the nutrition assessment databases carefully. However, in epidemiological studies, such as those in which subjects are ranked by nutrient intake, the impact of database revision might be relatively small.