Background: Calcium supplementation during childhood has been advocated to enhance peak bone mass and reduce the impact of age-related bone loss later in life. Childhood calcium supplementation also has been suggested for potential reduction of childhood fracture risk. Several studies have reported increases in bone mass and other positive outcomes with supplementation, but the long-term effects of calcium supplements are unclear. Winzenberg and colleagues reviewed all available evidence to establish the potential benefits of calcium supplementation in children and to determine whether any subgroups might benefit more than others.
The Study: The reviewers studied electronic databases and information on leading conferences to identify randomized controlled trials (RCTs) of calcium supplementation that included a placebo group and provided treatment for at least three months. Other criteria for studies were selection of healthy children with no significant medical conditions or treatments affecting bone metabolism; follow-up for at least six months; and use of objective measures of bone density such as volumetric bone mineral density, bone mineral content, or ultrasound measurements of bone. Subgroup analyses included age, sex, baseline calcium intake, pubertal stage, ethnicity, physical activity, type of calcium supplement, and duration of treatment.
Results: The meta-analysis incorporated 19 RCTs with 2,859 participants three to 18 years of age. Calcium supplements of 300 to 1,200 mg per day were reported. All eligible studies used tablets or pills as the source of calcium; none used dairy foods. Studies used different body sites and techniques to measure changes in bone mineral density. Overall, a modest increase (1.7 percentage points) was found in the upper limb and in total body bone mineral content, but no effect was found at the femoral neck or lumbar spine. The effect on the upper limb persisted after supplementation ended but was unlikely to be clinically significant. Although girls seemed to benefit more than boys from supplementation, the difference was not statistically significant. None of the subgroup analyses showed any significant findings.
Conclusion: The authors conclude that calcium supplementation had little effect on bone mineral density in healthy children and that the observed slight increase in the upper limb should be interpreted with caution because of design factors in the studies and meta-analysis. They suggest more studies of supplementation with vitamin D are needed and that measures to increase fruit and vegetable intake may be more appropriate nutritional interventions.