A follow-up study on the effects of calcium-supplement withdrawal and puberty on bone acquisition of children

Recent calcium supplementation trials in children have confirmed a positive but moderate effect of calcium intake on bone mineral accretion. However, the lasting effect of a higher bone mineral mass after calcium-supplement withdrawal is not known. This is an 18-mo follow-up study conducted after an 18-mo controlled calcium supplementation trial to study the persistent effect of higher bone mineral mass in children. Radial bone mineral mass was determined by single-photon absorptiometry; lumbar spine and femoral neck bone mineral mass were evaluated by dual-energy X-ray absorptiometry in 84 healthy Hong Kong children at age 8.5 y and these evaluations were repeated at age 10 y. Pubertal status was determined by Tanner staging. At the end of the follow-up, the differences in percentage gains in lumbar spine bone mineral content (12.1 +/- 8.2% compared with 14.9 +/- 10.05%, P = 0.24) and lumbar spine area (8.6 +/- 5.1% compared with 9.4 +/- 5.5%, P = 0.47) between the study and control groups disappeared. Dietary calcium intakes during follow-up were similar for the two groups (555 and 640 mg/d, P = 0.23). In multiple regression analyses, pubertal status was the strongest correlate of bone acquisition and linear growth in the study period. In conclusion, higher percentage gains in bone mineral mass in childhood by calcium supplementation for 18 mo were reversible. Our study showed that the benefits of calcium supplementation disappear after treatment is withdrawn. Longer-term calcium trials are necessary to determine whether peak bone mass can be modified through sustained supplementation so that appropriate calcium intakes can be determined.