Serum vitamin D status of Korean postmenopausal women during the winter months.

OBJECTIVE: To determine the vitamin D status of Korean postmenopausal women during the winter months according to the intake of vitamin D supplements.
DESIGN: Cross sectional study of serum 25(OH)D levels according to the intake of vitamin D supplements in postmenopausal women.
METHOD: Between November 2006 and February 2007, 254 postmenopausal women who visited our menopausal clinic for hormone therapy or osteoporosis medication were recruited. Serum 25(OH)D levels were measured with a radioimmunoassay kit and the results were compared among groups that were classified according to the intake amount of vitamin D supplements.
RESULTS: The mean serum 25(OH)D level was 83.3 +/- 32.8 nmol/L and it increased as the intake amount of vitamin D supplements increased. The mean serum 25(OH)D level was not significantly different between groups 1 (no vitamin D supplements) and 2 (daily 100-300 IU supplements). However, the mean serum 25(OH)D level was significantly higher in group 3 (daily 400 IU supplements) than in group 1. While the mean value of group 4 (daily 600 IU) was not significantly different from that of group 3, it was significantly lower than that of group 5 (daily 800-900 IU).
CONCLUSION: Vitamin D supplementation is highly effective in improving vitamin D status and the vitamin D status in this study population was improved considerably when compared to previous studies. Therefore, it is concluded that the prevalence of vitamin D insufficiency should be re-evaluated in postmenopausal women in most countries including Korea.