Vitamin K2 contributes to bone and cardiovascular health. Therefore, two vitamin K2 homologues, menaquinone-4 (MK-4) and menaquinone-7 (MK-7), have been used as nutrients by the food industry and as nutritional supplements to support bone and cardiovascular health. However, little is known about the bioavailability of nutritional MK-4. To investigate MK-4 and MK-7 bioavailability, nutritional doses were administered to healthy Japanese women.

There have been no simple methods to estimate dietary nutrient intakes for the prevention and management of osteoporosis. The aim of this study was to develop and validate a new, simple food frequency questionnaire (FFQ) for dietary intake of calcium and other nutrients relevant to the bone health of adult Japanese women. We developed a 28-item FFQ. To validate this, 208 and 72 adult women aged between 18 and 69 y were recruited for testing reliability and reproducibility, respectively. In the 208 women, moderate-to-high Spearman's correlation coefficients between our FFQ and the conventional diet record method were found in intakes of calcium (r=0.668), sodium chloride (NaCl) (r=0.475), vitamin A (r=0.501), vitamin D (r=0.413), vitamin K (r=0.649), and energy (r=0.471). In the 72 women, coefficients of variance of the four repeated measurements of intakes throughout a year were 14.1% for calcium, 7.3% for NaCl, 21.2% for vitamin A, 13.6% for vitamin D, 36.8% for vitamin K, and 9.6% for energy. In conclusion, the FFQ we developed is a useful tool to evaluate the intake of dietary calcium of adult Japanese women. Although it can also measure intakes of dietary vitamin A, vitamin D, vitamin K, NaCl, and energy, further improvement is needed to measure intakes of these nutrients and energy.

Background: The association between dietary total antioxidant capacity (TAC) from different assays and serum C-reactive protein (CRP) has not been assessed in non-Western populations. We examined the association between dietary TAC and serum CRP concentration in young Japanese women using different four TAC assays. Methods: The subjects were 443 young Japanese women aged 18–22 years. Dietary TAC was assessed with a self-administered diet history questionnaire and the TAC value of each food using the following four assays: ferric reducing ability of plasma (FRAP); oxygen radical absorbance capacity (ORAC); Trolox equivalent antioxidant capacity (TEAC); and total radical-trapping antioxidant parameter (TRAP). Serum CRP concentrations were measured by highly sensitive nephelometry. Results: The major contributor to dietary TAC was green, barley, and oolong tea (FRAP: 53%, ORAC: 45%, TEAC: 36%, and TRAP: 44%). The prevalence of elevated CRP concentrations (≥ 1 mg/L) was 5.6%. TAC from FRAP was inversely associated with serum CRP concentrations (adjusted odds ratio [OR] for elevated CRP concentration in high [compared with low] dietary TAC group: 0.39 [95% confidence interval (CI): 0.16-0.98]; P = 0.04). TAC from ORAC was inversely associated with CRP, although the association was not significant (OR: 0.48 [95% CI: 0.20-1.14]; P = 0.10). TAC from TEAC was inversely associated with CRP (OR: 0.32 [95% CI: 0.12-0.82]; P = 0.02), as was TAC from TRAP (OR: 0.31 [95% CI: 0.12-0.81]; P = 0.02). Conclusions: Dietary TAC was inversely associated with serum CRP concentration in young Japanese women regardless of assay. Further studies are needed in other populations to confirm these results.

Summary Intestinal fractional calcium absorption (FCA) was assessed before and after vitamin D3 treatment. Serum 1,25(OH)₂D concentration was significantly increased by plain vitamin D3 and reduced by eldecalcitol. The 1α hydroxyl calcidiol and eldecalcitol treatments increased FCA, which may be induced through direct stimulation of vitamin D receptors in the intestine. Introduction To assess the effects of vitamin D3 compounds on intestinal FCA and calcium-regulating hormones in post-menopausal osteoporosis, a randomized open-label prospective study was conducted. Methods Forty eligible patients were allocated randomly into four groups: eldecalcitol (ELD; 0.75 μg/day), 1α hydroxyl calcidiol (ALF; 1 μg/day), plain vitamin D3 (800 IU/day), and control. Before and after the 4-week treatment, intestinal FCA was estimated by using a double isotope method, and serum concentrations of calcium-regulating hormones and a bone turnover marker were measured. Results The baseline FCA value of the participants was 21.5 ± 7.9% (mean ± SD) and was significantly correlated with serum 1,25(OH)₂D (calcitriol) concentration. After the treatment, the FCA significantly increased by 59.5% (95% CI, 41.6 to 77.4%) in the ELD group and by 45.9% (27.9 to 63.8%) in the ALF group, whereas no significant change in the plain vitamin D3 group was found. Unlike the baseline FCA, post-treatment FCA exhibited no significant correlation with serum calcitriol concentration. Parathyroid hormone levels were suppressed by ALF and plain vitamin D3 but were sustained in the ELD and control groups. Serum calcitriol tended to be suppressed by ELD, whereas plain vitamin D3 treatment increased both serum 25(OH)D and calcitriol concentrations. Conclusion These findings suggest that oral administration of vitamin D3 analogues (ALF and ELD) stimulates FCA but plain vitamin D3 does not. Those effects of vitamin D3 compounds on FCA were independent of serum calcitriol concentration, suggesting that ALF and ELD may directly stimulate intestinal vitamin D receptors.