Determination of fat-soluble vitamins in human plasma, breast milk and food samples: Application in nutrition survey for establishment of "Dietary Reference Intakes for Japanese"

Dietary habits are an important risk factor for lifestyle-related diseases. To carry out a nutrition survey of fat-soluble vitamins, we developed determination methods of fat-soluble vitamins using liquid chromatographyatmospheric pressure chemical ionization/tandem mass spectrometry or high-performance liquid chromatography with fluorescence detection. In these methods, stable isotope-labeled compounds or vitamin K analogs with a saturated side-chain were used as internal standards. These methods have high sensitivity and sufficient accuracy, and we applied them in a nutrition survey about the status of fat-soluble vitamins in Japanese women. Plasma concentrations of 25-hydroxyvitamin D₃ [25(OH)D₃] and 25-hydroxyvitamin D₂ [25(OH)D₂] in healthy postmenopausal women (n = 98) were 20.5 ± 7.9 and 0.4 ± 1.4 ng/ml, respectively. A significant negative correlation in plasma levels between 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone was observed. For vitamin K homologs, plasma levels of phylloquinone (PK), menaquinone-4 (MK-4) and menaquinone-7 (MK-7) in Japanese women of various ages (n = 1409) were 1.03 ± 0.90, 0.12 ± 0.28 and 6.71 ± 13.6 ng/ml, respectively. The mean total vitamin K intake of Japanese young women was about 230 μg/day, and 94% of participants met the Adequate Intake of vitamin K for women aged 18-29 years in Japan, 60 μg/day. Moreover, we determined fat-soluble vitamins in breast milk collected from Japanese lactating women and revealed that the contents of all-trans-retinol, vitamin D₃, 25(OH)D₃, α-tocopherol, PK and MK-4 in breast milk were 0.39 ± 0.14 μg/ml, 0.10 ± 0.15 ng/ml, 0.08 ± 0.04 ng/ml, 3.96 ± 1.84 μg/ml, 3.56 ± 2.19 and 1.77 ± 0.68 ng/ml, respectively.