Optimal vitamin D intake for preventing serum 25-hydroxyvitamin D insufficiency in young Japanese women.

Populations of East Asian countries have been known to have low calcium intakes and low serum 25(OH)D concentrations, suggesting that Ca and vitamin D (VitD)-deficiencies are commonly observed. These nutritional imbalances may lead to low peak bone mass (PBM). The low PBM seen in Ca/VitD-deficient individuals may lead to osteoporosis, as well as an increased risk of fracture. A survey was conducted in young Japanese women (n = 296, 21.2 ± 2.3 years old) on their Ca/VitD intakes and serum 25(OH)D levels, which demonstrated a significant positive correlation between VitD intake and serum 25(OH)D levels (R  = 0.020, P = 0.016), and the proportion with serum 25(OH)D over 20 ng/mL was significantly increased with VitD intake (P = 0.013). Serum 25(OH)D was negatively correlated to serum intact parathyroid hormone (R  = 0.053, P < 0.001). On receiver operating characteristic curve analysis, the VitD intake threshold for maintaining 25(OH)D levels at 20 ng/mL or higher was 11.6 μg/day or greater. It was suggested that the recommended VitD intake allowance, defined in the Adequate Intakes as 5.5 μg/day, may not be sufficient to maintain serum 25(OH)D levels for bone health.