Calcium supplementation and bone fragility fractures during growth: A fracture risk assessment in a randomized controlled trial

It is known from short-term studies that calcium supplementation influences bone accretion during growth, but whether this has any implication with regard to fracture risk reduction is unknown. To address this issue, we have, therefore, evaluated the long-term effects of calcium supplementation (calcium citrate malate 1000 mg/day) on the prevalence of fractures in a cohort of young females, participants of a 7-year clinical trial. A total of 354 females were recruited to participate in a 4-year, randomized, double-blind, placebo-controlled clinical trial covering pubertal growth spurt, with subsequent extension for 3 years into late adolescence. Participants were accustomed to dietary calcium intake of ∼ 830 mg/day/7 years; supplemented individuals received additional ∼ 670 mg of calcium per day/7 years. Participants were asked to report on the fracture history at the end of the study, followed by the subsequent verification of the fracture data. Out of 26 verified fracture cases, 9 fracture cases were documented among the calcium-supplemented individuals, and 17 fractures were confirmed among the placebo individuals. Most fractures were at the forearm (50%) and occurred around the time of menarche. The Kaplan–Meier survival analysis showed a consistently lower rate of fractures among the calcium supplemented individuals, however, this was not statistically significant. The results of this study may be important for the design of a larger intervention trial with calcium supplementation with fracture as the main outcome. The results may have the ultimate implication with regard to the prevention of bone fragility during growth.