ABSTRACT
Objective: Serum 25−hydroxyvitamin D [25(OH)D] is a vitamin D metabolite and a good indicator of vitamin D nutritional status. Low 25(OH)D levels accelerate age−related bone loss in women. The aim of this study was to assess 25(OH)D levels using population−based samples from women in a community in Japan. Subjects and Methods: Of all 187 adult women living on a solitary island (Niigata, Japan), 150 (80.2%) were enrolled in a cross−sectional study in early June 1998. After excluding 6 subjects who were undergoing treatment for osteoporosis, 144 female subjects were analyzed. Serum 25(OH)D2 and 25(OH)D3 were determined by high−performance liquid chromatography. The sum of 25(OH)D2 and 25(OH)D3 was calculated, yielding 25(OH)D, for which a concentration of less than 30 nmol/L was defined as vitamin D insufficiency. Demographic data such as age, height, weight, and body mass index (BMI) were also recorded. Results: The average age of the subjects was 61.3 years (SD 12.8), ranging from 21 to 87. The average concentrations of 25(OH)D2 and 25(OH)D3 were 0.5nmol/L (SD 3.2) and 64.6nmol/L (SD 17.6), respectively. The number of subjects with 25(OH)D concentration less than 30nmol/L was 4 of 149(2.7%). Serum 25(OH)D concentrations were not significantly correlated with age (r=−0.065, p=0.441) or BMI (r=0.086, p=0.310). Conclusion: The present population−based study confirms adequate levels of 25(OH)D and low prevalence of vitamin D insufficiency in Japanese women. Further research should be directed toward clarifying which dietary factors determine vitamin D nutrition.