Improvement of Vitamin D Status in Japanese Institutionalized Elderly by Supplementation with 800 IU of Vitamin D₃

抄録

To study the adequate intake (AI) for vitamin D in the elderly, we have performed an intervention study with 800 IU/d of vitamin D₃ in the institutionalized elderly. Sixty-two institutionalized elderly were randomly assigned to two groups; receiving either supplements of 200 mg calcium plus 800 IU vitamin D₃/d (Ca+VD group), or supplements of 200 mg calcium/d (Ca group) for 30 d in October. Serum concentrations of 25-hydroxyvitamin D (25OH-D), parathyroid hormone (PTH), and bone turnover markers were measured before and after intervention. Average dietary vitamin D intake during the intervention period was approximately 300 IU/d in both groups, exceeding the AI in Dietary Reference Intakes for Japanese 2005 of 200 IU/d. In both groups, mean serum 25OH-D level at baseline fell into the hypovitaminosis D range (9.7 ng/mL), despite apparently adequate vitamin D intake. Serum PTH level at baseline was within the reference range. Mean serum 25OH-D concentration significantly increased to 19.3 ng/mL in the Ca+VD group and to 11.1 ng/mL in the Ca group. Post intervention serum 25OH-D level was significantly higher in the Ca+VD group than in the Ca group (p<0.001). In 53 subjects (85.5%) who took more than 80% of their supplements for 30 d, serum PTH level in the Ca+VD group was significantly lower than in the Ca groups (p=0.05). Bone turnover markers were not significantly changed after intervention in either group. Daily supplementation of 800 IU vitamin D₃ was considered effective in the institutionalized elderly with minimal chance of sun exposure, but further studies with longer duration are necessary.