Calcium supplementation and bone mineral density in females from childhood to young adulthood: a randomized controlled trial.

BACKGROUND: Short-term studies established that calcium influences bone accretion during growth. Whether long-term supplementation influences bone accretion in young adults is not known. OBJECTIVE: This study evaluated the long-term effects of calcium supplementation on bone accretion among females from childhood to young adulthood. DESIGN: A 4-y randomized clinical trial recruited 354 females in pubertal stage 2 and optionally was extended for an additional 3 y. The mean dietary calcium intake of the participants over 7 y was approximately 830 mg/d; calcium-supplemented persons received an additional approximately 670 mg/d. Primary outcome variables were distal and proximal radius bone mineral density (BMD), total-body BMD (TBBMD), and metacarpal cortical indexes. RESULTS: Multivariate analyses of the primary outcomes indicated that calcium-supplementation effects vary over time. Follow-up univariate analyses indicated that all primary outcomes were significantly larger in the supplemented group than in the placebo group at the year 4 endpoint. However, at the year 7 endpoint, this effect vanished for TBBMD and distal radius BMD. Longitudinal models for TBBMD and proximal radius BMD, according to the time since menarche, showed a highly significant effect of supplementation during the pubertal growth spurt and a diminishing effect thereafter. Post hoc stratifications by compliance-adjusted total calcium intake and by final stature or metacarpal total cross-sectional area showed that calcium effects depend on compliance and body frame. CONCLUSIONS: Calcium supplementation significantly influenced bone accretion in young females during the pubertal growth spurt. By young adulthood, significant effects remained at metacarpals and at the forearm of tall persons, which indicated that the calcium requirement for growth is associated with skeletal size. These results may be important for both primary prevention of osteoporosis and prevention of bone fragility fractures during growth.

Nutrition influences skeletal development from childhood to adulthood: a study of hip, spine, and forearm in adolescent females.

This study evaluated the long-term efficacy of supplemental calcium and dairy products on bone mineral areal density of the hip and spine and on the bone geometry and volumetric bone mineral density of the forearm in young females during late adolescence. The study was conducted among participants of a randomized double-blinded, placebo-controlled clinical trial with calcium supplements and among participants of an observational study with higher consumption of dairy products. Hip and spine measurements by dual-energy X-ray absorptiometry were done every 6 mo (dairy group every 12 mo) during last 3 y of the follow-up while peripheral quantitative computerized tomography of the forearm was done at the last visit. The results of the study show a positive influence of calcium supplementation and dairy products on bone mineral density of the hip and the forearm. Dairy products were also associated with a higher bone mineral density of the spine while calcium supplementation did not have an effect. Calcium exerts its action on bone accretion during growth primarily by influencing volumetric bone mineral density while milk may have an additional impact on bone growth and periosteal bone expansion.

Selenium intakes, absorption, retention, and status in adolescent girls.

OBJECTIVES: To assess selenium intakes, absorption, retention, and status in healthy adolescent girls and the effect of calcium supplementation on selenium parameters. DESIGN: Annual 2-week study conducted each year for 3 consecutive years in which yearly selenium intakes, absorption, and retention and blood selenium status were measured. SETTING: A metabolic unit in a large metropolitan hospital located in Columbus, Ohio--a low selenium region of the United States. SUBJECTS: Healthy white girls aged 11 to 14 years (n=16) enrolled in a calcium balance study and randomly assigned to receive a placebo of methylcellulose (n=9) or a calcium supplement containing 1,000 mg supplemental calcium as calcium citrate malate (n=7). INTERVENTIONS: Each subject consumed a diet with approximately 100 microg selenium/day during the yearly 2-week balance studies. RESULTS: Selenium status measurements (serum and erythrocyte selenium and glutathione peroxidase activity) were all within normal ranges for adults during the study. Apparent selenium absorption averaged 71%, 76%, and 74% for years 1, 2, and 3 of the study, respectively, and did not vary significantly (P>.05). Average daily selenium retention did not differ among the years of the study (P>.05) and indicated that the usual selenium intake was approximately 100 microg daily. Measurements of selenium status and retention did not differ between calcium-supplemented and placebo groups. CONCLUSIONS: An intake of approximately 100 microg selenium/day is the typical intake of the mineral among the subjects and appeared adequate to maintain selenium status in these healthy adolescent girls; in addition, calcium supplementation of 1,000 mg daily does not have a negative impact on selenium parameters.