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

Randomized controlled trial in 354 healthy White girls enrolled at pubertal stage 2 in central Ohio, with 1:1 allocation to calcium citrate-malate or placebo. Participants were followed from childhood through late adolescence into young adulthood, with analyses reported for 4-year and 7-year cohorts.

Oral calcium citrate-malate supplementation at 1000 mg/day, given as 4 pills daily (2 in the morning and 2 in the evening), was compared with placebo. The intervention continued for 4 years and was extended for a total follow-up of 7 years.

Calcium supplementation improved bone mass accrual during the pubertal growth spurt, with some benefits persisting into young adulthood. At 4 years, the supplemented group had significantly higher total-body BMD, proximal and distal radius BMD, and metacarpal cortical area to total area ratio after covariate adjustment, including total-body BMD P = 0.0003 for covariate-adjusted values and P = 0.0006 for gain, distal radius BMD P = 0.0026, and CA:TA P = 0.024. In the 7-year cohort, mean responses remained significant for total-body BMD P = 0.0004, proximal radius BMD P = 0.024, and distal radius BMD P = 0.028, with metacarpal measures still higher at year 7 (CA P = 0.024; CA:TA P = 0.0034). Benefits were most evident at metacarpals and proximal forearm in taller individuals or those with higher compliance, while effects at other sites diminished over time, consistent with catch-up during growth.

Follow-up attrition was substantial, with only 51% completing the 7-year trial. Generalizability is limited because participants were healthy White girls from central Ohio, and the strongest effects were site-specific rather than uniform across the skeleton. Some long-term findings depended on compliance and body size, which may complicate interpretation.