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 .
The ratio of animal protein intake to potassium intake is a predictor of bone resorption in space flight analogues and in ambulatory subjects.
BACKGROUND Bone loss is a critical concern for space travelers , and a dietary countermeasure would be of great benefit . Dietary protein and potassium-associated bicarbonate precursors may have opposing effects on the acid-base balance in the body and therefore on bone loss . OBJECTIVE In 2 studies , we examined the ability of dietary protein and potassium to predict markers of bone metabolism . DESIGN In the first study , 8 pairs of male identical twins were assigned to 1 of 2 groups : bed rest ( sedentary , or SED , group ) or bed rest with supine treadmill exercise in a lower-body negative pressure chamber ( EX group ) . In a second study , groups of 4 subjects lived in a closed chamber for 60 or 91 d , and dietary data were collected for two or three 5-d sessions . Urinary calcium , N-telopeptide , and pyridinium cross-links were measured before bed rest ; on bed rest days 5 - 6 , 12 - 13 , 19 - 20 , and 26 - 27 ; and daily during the chamber studies . Data were analyzed by Pearson 's correlation ( P < 0.05 ) . RESULTS The ratio of animal protein intake to potassium intake was significantly correlated with N-telopeptide in the SED group during bed rest weeks 3 and 4 ( r = 0.77 and 0.80 ) and during the 91-d chamber study ( r = 0.75 ) . The ratio of animal protein intake to potassium intake was positively correlated with pyridinium cross-links before bed rest in the EX group ( r = 0.83 ) , in the EX group during bed rest week 1 ( r = 0.84 ) , and in the SED group during bed rest week 2 ( r = 0.72 ) but not during either chamber study . In both studies , these relations were not significant with the ratio of vegetable protein intake to potassium intake . CONCLUSIONS The ratio of animal protein intake to potassium intake may affect bone in ambulatory and bed-rest subjects . Changing this ratio may help to prevent bone loss on Earth and during space flight
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 .