Factors Associated with Changes in Bone Mineral Content among Girls in Early Pubertal Age

ABSTRACT

The study was conducted to investigate the factors associated with bone mineral content ( BMC) changes among early pubertal aged girls. Two hundred and thirty girls between 9 to 11 years of age participated in four surveys over 2 year period. During each survey, dietary intakes were collected with 3-day food records, BMC of left leg's calcaneus were measured by PIXI ( Lunar Ltd.) and body composition was measured by bioimpedance method ( Inbody 3.0 Biospace Co. Ltd, Seoul, Korea) . Mean values of BMC increased in consecutive measurements - 1.48 g, 1.54 g, 1.61 g and 1.66 g. The change of BMC between the first and last measurements was significantly positively correlated with % body fat, negatively correlated with BMC at the baseline ( p < 0.05) . Change of BMC was also significantly positively correlated with % change of lean mass and mineral mass between the first and last measurements. Nutrient intakes during the study period were calculated as mean daily intakes from all surveys. Mean daily intakes of Vit. C and Vit. B6 were positively and isoflavone intake was negatively correlated with changes of BMC ( p < 0.05) . In stepwise regression of BMC change with body composition and nutrient intakes, baseline values of BMC, weight, BMI and age, % change of mineral mass during the study period, mean intakes of isoflavone, Vit. B6, protein, carotene and zinc were significant explanatory variables ( R 2 = 0.38, p < .001, F = 32.39) . The results imply that the change of BMC among early pubertal aged girls are associated with some body composition and intakes of certain nutrients.