Longitudinal Measurements of Bone Density in Adolescent Girls and Intervention in Diet

Ca intake raises bone mineral density (BMD) in adolescence. The present study aimed at improving BMD in adolescent girls by increasing Ca intake from foods, and developing a supportive method for keeping this eating habit. In July of 1997 and 1998, BMD of the left os calcis was measured by ultrasound bone densitometry in 55 college girls respectively in the 1st and 2nd grades by calculating levels of stiffness which served as the index for BMD. We told them the analyzed results both times, giving instruction in life-style for preventing osteoporosis in 1997 and explanation about Ca-rich foods in 1998. After the measurement in 1998, we selected 11 girls with low BMD for the following intervention in diet (intervention group): i) kind and amount of Ca-rich foods were daily recorded for 4 weeks; ii) difference between the calculated intake and necessary level was told; and iii) subjects were continually encouraged to take daily necessary level from foods. Then, BMD of the intervention group was measured 12 weeks after. Further, in 1999, we measured BMD for the intervention group and 10 selected students with normal BMD in the 2nd grade (non-intervention group). Mean stiffness was significantly lower (P < 0.01) in the 2nd grade than in the 1st. In the 2nd grade, the intervention group showed a significantly higher mean 12 weeks after than in July. In the 3rd grade, the decrease in stiffness was stopped in both groups. The longitudinal measurements of BMD over a 2-year period made adolescent girls recognize the decreasing tendency of BMD. We conclude that adolescent girls can maintain BMD by utilizing their knowledge of preventing osteoporosis and by taking ample Ca from foods