There was no effect of calcium supplementation  on femoral neck or lumbar spine BMD .
There was no evidence of effect modification by baseline calcium intake , sex , ethnicity , physical activity or pubertal stage .
While there is a small effect of calcium supplementation in the upper limb , the increase in BMD which results is unlikely to result in a clinical ly significant decrease in fracture risk .
The results do not support the use of calcium supplementation  in healthy children as a public health intervention .
These results can not be extrapolated to children with medical conditions affecting bone metabolism
BACKGROUND Clinical trials have shown that  calcium supplementation in children can increase  bone mineral density ( BMD ) although this effect may not be maintained .
There has been no quantitative systematic review of this intervention .
To determine the effectiveness of calcium supplementation for improving BMD  in children .
.
To determine if any effect varies by sex , pubertal stage , ethnicity or level of physical activity , and if any effect persists after supplementation is ceased .
A co-twin study of the effect of calcium supplementation on bone density during adolescence
The effect of calcium supplementation on bone mineral density ( BMD ) was evaluated in female twin pairs aged 10–17 years with a mean age of 14 years . Forty-two twin pairs ( 22 monozygotic , 20 dizygotic ; ( including one monozygotic pair from a set of triplets ) completed at least 6 months of the intervention : 37 pairs to 12 months and 28 pairs to 18 months . BMD was measured by dual-energy X-ray absorptiometry ( DXA ) . In a double-blind manner , one twin in each pair was r and omly assigned to receive daily a 1000 mg effervescent calcium tablet ( S and ocal 1000 ) , and the other a placebo tablet similar in taste and appearance to the calcium supplement but containing no calcium .  Compliance ( at least 80 % tablets consumed ) , as measured by tablet count , was 85 % in the placebo group and 83 % in the calcium group over the 18 months of the study , on average increasing dietary calcium to over 1600 mg/day . There was no within-pair difference in the change in height or weight . When the effect of calcium supplementation  on BMD was compared with placebo at approximately 6 , 12 and 18 months , it was found that there was a 0.015±0.007 g/ cm2 greater increase in BMD ( 1.62±0.84 % ) at the spine in those on calcium after 18 months . At the end of the first 6 months there was a significant within-pair difference of 1.53±0.56 % at the spine and 1.27±0.50 % at the hip . However , there were no significant differences in the changes in BMD after the initial effect over the first 6 months . Therefore , we found an increase in BMD at the spine  with calcium supplementation in females with a mean age of 14 years . The greatest effect was seen in the first 6 months ; thereafter the difference was maintained , but there was no accelerated increase in BMD  associated with calcium supplementation . The continuance of the intervention until the attainment of peak bone mass and follow-up after cessation of calcium supplementation will be important in clarifying the optimal timing for increased dietary calcium and the sustained , long-term effects of this intervention
There was no effect of calcium supplementation  on femoral neck or lumbar spine BMD .
There was no evidence of effect modification by baseline calcium intake , sex , ethnicity , physical activity or pubertal stage .
While there is a small effect of calcium supplementation in the upper limb , the increase in BMD which results is unlikely to result in a clinical ly significant decrease in fracture risk .
The results do not support the use of calcium supplementation  in healthy children as a public health intervention .
These results can not be extrapolated to children with medical conditions affecting bone metabolism
BACKGROUND Clinical trials have shown that  calcium supplementation in children can increase  bone mineral density ( BMD ) although this effect may not be maintained .
There has been no quantitative systematic review of this intervention .
To determine the effectiveness of calcium supplementation for improving BMD  in children .
.
To determine if any effect varies by sex , pubertal stage , ethnicity or level of physical activity , and if any effect persists after supplementation is ceased .