BONE MASS AND BODY COMPOSITION CHANGES, AND CALCIUM INTAKE IN FEMALE COLLEGIATE ATHLETES 781

Abstract

As part of longitudinal study, we report bone mineral density (BMD) changes in the lumbar spine (LS), hip and whole body (including arms, legs, trunk and pelvis) at a point in the athletes' training cycle which was 4.90±0.92 months (mean±SD) after baseline BMD measures. The subjects are competitive female track (Tr, n=12), tennis (T, n=5), soccer (S, n=14), volleyball (VB, n=6), and golf (G, n=6) athletes, and controls (C, n=12). BMD and body composition were assessed by dual-energy x-ray absorptiometry (DXA). There were no group differences (p>0.05) for% change BMD at the LS, any hip site, or whole body (legs, trunk, pelvis). The% change for arms BMD was different among groups (p=0.05); VB tended to lose BMD in the arms(-4.1±5.6%), while the other groups either maintained or gained BMD at this site (as compared to zero). VB increased legsBMD (1.2±1.1%, p<0.05). Soccer (-1.6±2.4%, p<0.05) and C (-1.6±1.8%, p=0.01) lost LSBMD. No other group or BMD site changed significantly over this time period. Dietary analyses indicated group differences for calcium intake(p=0.05) and calcium/phosphorus ratio (p<0.01). Calcium was significantly less than the RDA (1200mg) for all groups except VB (984±275 mg). Vitamin D intake was significantly less than the RDA (10μg) for all groups. Group differences were found for changes in weight (p<0.05) and fat(p<0.01); change in bone-free lean mass (BFLM) did not differ among groups, although S lost BFLM (0.6±0.9kg, p<0.05), and VB tended to gain BFLM(0.8±1.3kg). C gained weight (1.1±0.9kg) and fat(1.4±0.8kg) (p<0.001) but maintained BFLM. In conclusion: 1) loss of bone mass may be due, in part, to changes in body composition, i.e., loss of BFLM with (C) or without (S) an increase in weight or fat; 2) gains in BFLM(VB) may enhance BMD at certain sites (i.e., legs) and may be somewhat protective against bone loss at other sites; and 3) dietary calcium may play an interactive role in bone mass changes.