Relationship among Nutritional Intake, Duration of Outdoor Activities, Vitamin D Status and Bone Health in High School Girls

This study investigated the interactions of bone health with several variables such as outdoor activity hours, nutritional status including habitual intake of calcium and vitamin D status in 72 high school girls aged 16-17 years attending day classes or night classes [South Korea; date not given]. The subjects consisted of 39 day-class students and 33 night-class students. Dietary nutrient intakes were estimated using the 24-hour recall method. The daily activities of each subject were assessed using an activity questionnaire. Urinary calcium and creatinine excretion were assayed from subjects' 24-hour urine, while 25-OH-vitamin D[25-(OH)-D] and osteocalcin were measured from the subjects' fasting blood. Intake of energy, iron, vitamin A and vitamin C were worse in the night-class students. There was no significant difference in dietary calcium between the subjects in the different class types. Time spent on outdoor activities was significantly less in subjects attending night classes. Urinary calcium excretion of the night-class subjects was significantly higher than that of the day-class subjects (p<0.05). There was no significant difference in serum 25-(OH)-D level according to class type. Serum osteocalcin for night-class subjects was significantly higher than that for day-class subjects (p