Effect of calcium supplementation on bone mineral density in female athletes

Females engaged in athletic activities frequently select to follow severe dietary restrictions, depriving their bodies of essential nutrients such as calcium in an effort to achieve some idealized body shape. Calcium poor diets are associated with stress fractures in the athlete and a rising prevalence in osteoporosis. The purpose of this study was to determine if calcium supplementation would enhance bone mineral density (BMD) in young (18-22 year old) female athletes. In this double blind study, thirty athletes from Division I and Division IU teams were randomized to calcium supplementation (N = 17) and placebo (N = 13) groups. Treatment subjects were given tablets containing 1000 mg. elemental calcium for one year. Six BMD sites (lumbar spine, total hip, femoral neck, trochanter, Ward's Triangle and radius) were assessed at baseline and 6 and 12 months utilizing the Hologic QDR 1000W scanner. Treatment groups were compared with respect to BMD and changes in BMD at baseline and 6 and 12 month intervals utilizing two way ANOVAs. The relationship between primary and secondary efficacy variables were investigated using Pearson and Spearman Rank Correlation's. The impact of calcium supplementation on BMD was investigated using ANCOVA with average calcium intake serving as the covariate. No significant differences in BMD or changes in BMD between treatment groups were observed at baseline, 6 and 12 months. Mean reported compliance was 64 +/- 4.8% for the calcium supplementation (CS) group and 73 +/- 6.3% for the placebo group. Compliance data suggest that the CS group failed to consume the prescribed 1000 mg. daily intake of calcium. Furthermore, subjects in the placebo group reported a higher intake of calcium when compared with the CS group. Lumbar spine BMD increased in the CS group and remained stable in the placebo group. While significant differences in BMD were not achieved with calcium supplementation in these young athletes, study results reflect some benefit to BMD from higher calcium intakes. The potential cost-benefit of decreasing the prevalence of low bone mass in American women supports the need for further calcium supplementation studies in young females. (C) 1998 Elsevier Science Inc.