Calcium supplementation and bone mineral density in females from childhood to young adulthood: a randomized controlled trial. Calcium supplementation increases stature and bone mineral mass of 16- to 18-year-old boys. Effect of calcium supplementation on bone mineral accretion in gambian children accustomed to a low-calcium diet. Appendicular bone mass in children with a high prevalence of low dietary calcium intakes. [Calcium supplementation and bone absorptiometry in girls]. Parent/Child Training to Increase Preteens' Calcium, Physical Activity, and Bone Density: A Controlled Trial Calcium supplementation and increases in bone mineral density in children. Double-blind, controlled calcium supplementation and bone mineral accretion in children accustomed to a low-calcium diet. Calcium supplementation provides an extended window of opportunity for bone mass accretion after menarche. Cumulative effects of calcium supplementation and physical activity on bone accretion in premenarchal children: a double-blind randomised placebo-controlled trial. Effects of two years' milk supplementation on size-corrected bone mineral density of Chinese girls. Prevention of bone demineralization by calcium supplementation in precocious puberty during gonadotropin-releasing hormone agonist treatment. Reduced rates of skeletal remodeling are associated with increased bone mineral density during the development of peak skeletal mass. Calcium-enriched foods and bone mass growth in prepubertal girls: a randomized, double-blind, placebo-controlled trial. Effect of habitual dietary calcium intake on calcium supplementation in 12-14-y-old girls. Gain in bone mineral mass in prepubertal girls 3–5 years after discontinuation of calcium supplementation: a follow-up study The effect of calcium supplementation on bone density in premenarcheal females: a co-twin approach.
BACKGROUND Short-term studies established that calcium influences bone accretion during growth . Whether long-term supplementation influences bone accretion in young adults is not known . OBJECTIVE This study evaluated the long-term effects of calcium supplementation on bone accretion among females from childhood to young adulthood . DESIGN A 4-y r and omized clinical trial recruited 354 females in pubertal stage 2 and optionally was extended for an additional 3 y. The mean dietary calcium intake of the participants over 7 y was approximately 830 mg/d ;  calcium-supplemented persons received an additional approximately 670 mg/d . Primary outcome variables were distal and proximal radius bone mineral density ( BMD ) , total-body BMD ( TBBMD ) , and metacarpal cortical indexes . RESULTS Multivariate analyses of the primary outcomes indicated that  calcium-supplementation  effects vary over time . Follow-up univariate analyses indicated that all primary outcomes were significantly larger in the supplemented group than in the placebo group at the year 4 endpoint . However , at the year 7 endpoint , this effect vanished for TBBMD and distal radius BMD . Longitudinal models for TBBMD and proximal radius BMD , according to the time since menarche , showed a highly significant effect of supplementation during the pubertal growth spurt and a diminishing effect thereafter . Post hoc stratifications by compliance-adjusted total calcium intake and by final stature or metacarpal total cross-sectional area showed that calcium effects depend on compliance and body frame . CONCLUSIONS Calcium supplementation significantly influenced bone accretion  in young females during the pubertal growth spurt . By young adulthood , significant effects remained at metacarpals and at the forearm of tall persons , which indicated that the calcium requirement for growth is associated with skeletal size . These results may be important for both primary prevention of osteoporosis and prevention of bone fragility fractures during growth The effect of calcium carbonate supplementation on bone growth and mineral accretion was studied in 143 boys aged 16 - 18 yr , r and omized to 1000 mg Ca/d or a matching placebo for 13 months .  Anthropometry and dual-energy x-ray absorptiometry of the whole body , lumbar spine , hip , and forearm were performed before , during , and after the intervention . The intervention result ed in greater bone mineral content ( BMC ) of the whole body ( + 1.3 % , P = 0.02 ) , lumbar spine ( + 2.5 % , P = 0.004 ) , and hip ( total + 2.3 % , P = 0.01 ; neck + 2.4 % , P = 0.02 ; intertrochanter + 2.7 % , P = 0.01 ) . This was associated with greater height ( + 0.4 % , P = 0.0004 , equivalent to 7 mm ) , lean mass ( + 1.3 % , P = 0.02 ) , and lumbar spine bone area ( + 1.5 % , P = 0.003 ) . The increases in BMC diminished after size adjustment , suggesting that the intervention effect was mediated through an effect on growth . The BMC response at the intertrochanter was greater in subjects with high physical activity ( + 4.4 % , P = 0.05 ) . There were no other significant interactions with physical activity , plasma testosterone , calcium intake , or tablet compliance . We conclude that calcium carbonate supplementation  of adolescent boys increased skeletal growth , result ing in greater stature and bone mineral acquisition . Follow-up studies will determine whether this reflects a change in the tempo of growth or an effect on skeletal size that persists into adulthood BACKGROUND Rural Gambian children have poor growth , delayed puberty , a low bone mineral content , and a low calcium intake . OBJECTIVE We investigated the effect of a calcium supplement on bone mineral accretion in rural Gambian children . DESIGN A r and omized , double-blind , placebo-controlled study was conducted in 160 children ( 80 boys , 80 girls ) aged 8.3 - 11.9 y.  Bone mineral content ( BMC ) , bone mineral density ( BMD ) , and BMC adjusted for bone width , body weight , and height ( size-adjusted BMC ) were measured at the midshaft and distal radius . Each child received either 1000 mg Ca/d ( as calcium carbonate ) or a placebo 5 d/wk for 12 mo . Supplementation increased calcium intake from 342 to 1056 mg/d ( 8.6 to 26.4 mmol/d ) . RESULTS Calcium supplementation result ed in a higher BMC , BMD , and size-adjusted BMC ( & xmacr ; difference + /- SE ) : midshaft radius- BMC ( 3.0 + /- 1.4 % ; P = 0.034 ) , BMD ( 4.5 + /- 0.9 % ; P < /= 0.0001 ) , and size-adjusted BMC ( 4.6 + /- 0.9 % ; P < /= 0.0001 ) ; distal radius- BMC ( 8 . 4 + /- 3.2 % ; P = 0.009 ) , BMD ( 7.0 + /- 2.7 % ; P = 0.011 ) , and size-adjusted BMC ( 5.5 + /- 2.7 % ; P = 0.042 ) . Supplementation had no significant effect on height , weight , or bone width at the midshaft radius or distal radius . At the end of the study , the calcium group had a significantly lower mean plasma osteocalcin concentration than the placebo group after adjustment for baseline concentration , sex , and pubertal status ( -21.9 + /- 6.5 % ; P = 0.001 ) . CONCLUSIONS Increased calcium intake result ed in increased bone mineral status , possibly in association with a decreased bone remodeling space . Further studies are needed to determine whether an increased calcium intake has long-term benefits in Gambian children We have previously documented evidence of dietary calcium deficiency in black children living in a rural community in the eastern part of South Africa . The present study determined the bone mass of the distal one-third of the radius in a r and om sample of children living in the same community and compared their bone mass measurements with those of black children living in a similar rural community but without evidence of dietary calcium deficiency . Further , factors ( weight , height , serum corrected total calcium , phosphorus , and alkaline phosphatase [ ALP ] ) that might influence appendicular bone mass were assessed and correlated with the bone mass measurements . A r and om sample of 306 boys and 345 girls between the ages of 1 and 20 years were included in the study .  Hypocalcemia was found in 6.5 % of the boys and 5 % of the girls , while elevated ALP values were recorded in 20 and 26 % of the boys and girls , respectively . After adjusting for differences in age , weight , and height , bone mineral density ( BMD ) and bone mineral apparent density ( BMAD ) were significantly lower and bone width ( BW ) greater in study than control children . In a stepwise regression analysis , weight and /or height accounted for the majority of the observed variance in BMC , BW , and BMD ; however , a significant effect of serum calcium ( positively ) and ALP ( negatively ) on BMC and BMD was also found . In boys , but not girls , serum ALP also had a positive effect on BW.BMAD was negatively correlated to ALP and positively correlated to serum calcium in both boys and girls . Those children with hypocalcemia or elevated ALP levels had significantly lower BMC , BMD , and BMAD and a trend toward greater BW than children with normal biochemistry . The findings suggest that low dietary calcium intake may have a detrimental effect on appendicular bone density in rural black children . Whether or not these effects are disadvantageous in the long-term is not known BACKGROUND The achievement of a peak bone mass is an important factor in the prevention of osteoporotic fractures . In normal children , the amount of calcium intake could affect bone mineral increment . AIM To assess the effect of a daily 500 mg calcium supplement on bone mineral density , in a group of healthy Chilean girls . PATIENTS AND METHODS Fifty healthy girls were studied and 25 were r and omly assigned to receive a 500 mg calcium supplement during 10 months . Bone mineral density of the distal and ultradistal region of the forearm was measured in all girls by single X ray absorptiometry ( Osteometer DTX-100 ) at the beginning and end of the study . Bone mineral density was expressed as Z values . RESULTS Significant increments in bone mineral density at the distal radioulnar region were obtained in the supplemented girls . No significant changes in bone density were observed in control girls . CONCLUSIONS A daily 500 mg calcium supplement for 10 months increased bone mineral density in healthy girls Purpose . To test effects of  parent/child training design ed to increase calcium intake , bone-loading physical activity ( PA )  , and bone density . Design . Two-group r and omized controlled trial . Setting . Family-based intervention delivered at research center . Subjects . 117 healthy children aged 10–13 years ( 58.1 % female , 42.7 % Hispanic , 40.2 % White ) . Ninety-seven percent of participants had at least one parent graduate from high school and 37.2 % had at least one parent graduate from a 4-year university . Intervention . Children and parents were r and omly assigned to diet and exercise ( experimental ) or injury prevention ( control ) interventions . Children were taught in eight weekly classes how to engage in bone-loading PA and eat calcium-rich foods or avoid injuries . Parents were taught behavior management techniques to modify children 's behaviors . Measures . Measures at baseline and at 3 , 9 , and 12 months included 24-hour diet and PA recalls , and bone mineral density ( BMD ) by dual-energy x-ray absorptiometry . Analysis . Analysis of variance and generalized estimating equations ( GEE ) assessed group by time differences . Comparisons were conducted separately for boys and girls . Results . For boys , cross-sectional differences between experimental and control groups were achieved for 3- and 9-month calcium intake ( 1352 vs. 1052 mg/day , 1298 vs. 970 mg/day , p < .05 ) . For girls , marginal cross-sectional differences were achieved for high-impact PA at 12 months ( p < .10 ) . For calcium intake , a significant group by time interaction was observed from pretest to posttest for the full sample ( p = .008 ) and for girls ( p = .006 ) but not for boys . No significant group by time differences in calcium were observed across the follow-up period . No group by time differences were observed for  high-impact PA  . Among boys , longitudinal group by time differences reached significance for total hip BMD ( p = .045 ) and femoral neck BMD ( p = .033 ) , even after adjusting for skeletal growth . Similar differential increases were observed among boys for bone mineral content ( BMC ) at the hip ( p = .068 ) and total body ( p = .054 ) regions . No significant group by time interaction effects were observed for girls at any bone site for BMD . For BMC , control girls showed a significant increase ( p = .03 ) in spine BMC compared to intervention girls . Conclusion . This study demonstrated that parent/preteen training can increase calcium intake and attenuate the decline in high-impact PA . Results suggest that more powerful interventions are needed to increase activity levels and maximize bone mineral accrual during preadolescent years BACKGROUND Increased dietary intake of calcium during childhood , usually as calcium in milk , is associated with increased bone mass in adulthood ; the increase in mass is important in modifying the later risk of fracture . Whether the increase is due to the calcium content of milk , however , is not certain . METHODS We conducted a three-year , double-blind , placebo-controlled trial of the effect of calcium supplementation ( 1000 mg of calcium citrate malate per day ) on bone mineral density in 70 pairs of identical twins ( mean [ + /- SD ] age , 10 + /- 2 years ; range , 6 to 14 ) . In each pair , one twin served as a control for the other ; 45 pairs completed the study .  Bone mineral density was measured by photon absorptiometry at two sites in the radius ( at base line , six months , and one , two , and three years ) and at three sites in the hip and in the spine ( at base line and three years ) . RESULTS The mean daily calcium intake of the twins given placebo was 908 mg , and that of the twins given calcium supplements was 1612 mg ( 894 mg from the diet and 718 mg from the supplement ) . Among the 22 twin pairs who were prepubertal throughout the study , the twins given supplements had significantly greater increases in bone mineral density at both radial sites ( mean difference in the increase in bone mineral density : midshaft radius , 5.1 percent [ 95 percent confidence interval , 1.5 to 8.7 percent ] ; distal radius , 3.8 percent [ 95 percent confidence interval , 1.4 to 6.2 percent ] ) and in the lumbar spine ( increase , 2.8 percent [ 95 percent confidence interval , 1.1 to 4.5 percent ] ) after three years ; the differences in the increases at two of three femoral sites approached significance ( Ward 's triangle in the femoral neck , 2.9 percent ; greater trochanter , 3.5 percent ) . Among the 23 pairs who went through puberty or were postpubertal , the twins given supplements received no benefit . CONCLUSIONS In prepubertal children whose average dietary intake of calcium approximated the recommended dietary allowance , calcium supplementation increased the rate of increase in bone mineral density . If the gain persists , peak bone density should be increased and the risk of fracture reduced A r and omized , double-blind , controlled calcium supplementation trial was conducted for 18 mo to determine its effects on bone acquisition and height increment in 162 7-y-old Chinese children ( 87 boys and 75 girls ) with habitually low calcium intakes ( 280 mg/d ) . Distal one-third radial bone mineral content ( BMC ) , area bone density ( BMC /bone width ) , and height were evaluated every 6 mo . Baseline dietary intakes , serum 25-hydroxycholecalciferol , and physical activity  were determined . The study group received 300 mg Ca/d as calcium carbonate ; control subjects received placebo tablets . After 18 mo the study group had significantly greater gains in BMC ( 16.5 % vs 13.97 % ; P = 0.02 ) and BMC /bone width ( 9.45 % vs 6.31 % ; P = 0.0008 ) than the control subjects . The findings confirm a positive effect of calcium intake on bone acquisition but no effect on height increment . Whether a higher bone mass attained at age 8 - 9 y would be maintained and beneficial to future peak bone mass requires longitudinal investigation . Further study is warranted to determine calcium requirements for Chinese children BACKGROUND High calcium intakes during adolescence may increase bone acquisition . The magnitude of the effect of dietary calcium supplementation and the timing of its administration to achieve significant effects on bone health are still incompletely defined . OBJECTIVE The objective of this study was to assess the effect of calcium supplementation on bone mass accretion in postmenarcheal adolescent girls with low calcium intakes . DESIGN A double-blind , placebo-controlled calcium supplementation study was implemented . One hundred girls with a mean ( + /- SD ) age of 14 + /- 0.5 y with habitual calcium intakes < 800 mg/d completed a 12-mo protocol . The treatment group received a daily supplement containing 1000 mg elemental calcium .  Bone mineral density ( BMD ) and bone mineral content ( BMC ) of the total body , lumbar spine , and femoral neck were determined at inclusion , 6 mo , and 12 mo . Also measured were serum concentrations of biochemical markers of bone turnover ( osteocalcin and deoxypyridinoline ) , parathyroid hormone , and vitamin D. RESULTS The calcium-supplemented group had greater accretion of total-body BMD and lumbar spine BMD but not BMC than did the control group . Calcium supplementation appeared selectively beneficial for girls who were 2 y postmenarcheal . Calcium supplementation significantly decreased bone turnover and decreased serum parathyroid hormone concentrations . CONCLUSION Calcium supplementation of postmenarcheal girls with low calcium intakes enhances bone mineral acquisition , especially in girls > 2 y past the onset of menarche High calcium intake combined with physical activity during childhood have been shown to improve bone mass accrual and bone mineral density . Our aim was to study the combined effect of calcium and exercise on  bone gain in children . Two milk-powder products containing either 800 mg of calcium phosphate ( calcium ) or not ( placebo ) were r and omly allocated to 113 healthy premenarchal girls on a daily basis for 1 year . The group was composed of 63 exercise ( 7.2 + /- 4 hours of exercise/week ) and 50 sedentary ( 1.2 + /- 0.8 hours of exercise/week ) children . The final experiment had 4 groups : exercise/calcium ( n = 12 ) , exercise/placebo ( n = 42 ) , sedentary/calcium ( n = 10 ) , and sedentary/placebo ( n = 21 ) . Bone mineral density ( BMD ) at 6 skeletal sites and body composition were determined by DXA . Bone age was calculated and the daily spontaneous calcium intake was assessed by a frequency question naire . All the tests were performed at baseline and 1 year by the same observer . BMD gains were significantly greater in the exercise/calcium group than in other groups at the total body ( increase of 6.3 % , p < 0.05 ) , lumbar spine ( 11 % , p < 0.05 ) , femoral neck ( 8.2 % , p < 0.02 ) , and Ward 's triangle ( 9.3 % , p < 0.01 ) . There was no difference between the other groups . These data suggest that calcium supplementation increases the effect of physical exercise on bone mineral acquisition in the period preceding puberty , and that calcium supplementation without physical activity does not improve the BMD acquisition during this period . Physical exercise that stimulates bone accretion needs a high calcium intake to be completely effective Much existing data on the effects of calcium or milk products on bone mineral accretion are based on bone mineral content ( BMC ) or areal bone mineral density ( aBMD ) , neither of which accounts for changing bone size during the growing period . The aim of this study was to investigate the effects of 2-year milk supplementation on total body size-corrected BMD in Chinese girls with low habitual dietary calcium intake . Chinese girls aged 10 years were r and omised , according to their school , to receive calcium fortified milk ( Ca milk ) , or calcium and vitamin D fortified milk ( CaD milk ) for two years or act as unsupplemented controls . Dual-energy X-ray absorptiometry  total body bone measures were obtained from 345 girls at baseline and 2 years . Size-corrected total body and regional BMD was calculated as : BMDsc = BMC /BApc , where pc was the regression coefficient of the natural logarithm transformed total body BMC and bone area . After 2 years , both supplemented groups had significantly greater gain in BMDsc of total body ( 3.5 - 5.8 % , p < 0.05 ) and legs ( 3.0 - 5.9 % , p < 0.05 ) than did the control group . Milk supplementation showed positive effects on bone mineral accretion when accounting for the changing skeletal size during growth . The effects were mainly on the lower limbs We have previously demonstrated a negative impact on peak bone mass in girls with precocious puberty treated with GnRH agonist ( GnRHa ) .  Several studies have shown that a high calcium intake positively influences bone mass in prepubertal girls and leads to a higher peak bone mass . The aim of this study was to evaluate the effect of calcium supplementation in girls with precocious puberty during GnRHa treatment .  Forty girls affected by true central precocious puberty and treated with the GnRHa triptorelin were studied for 2 yr . After diagnosis , the patients were r and omly assigned to three groups : group A , treated only with GnRHa ; group B , treated for 12 months solely with GnRHa and then supplemented with calcium gluconolactate/carbonate ( 1 g calcium/day in two doses ) for 12 months ; and group C , treated from the beginning with combined GnRHa and calcium .  Bone mineral density ( BMD ) at the lumbar spine was measured by dual energy x-ray absorptiometry at the beginning of the study and after 12 and 24 months and was expressed as the calculated true volumetric density ( BMDv ) in milligrams per cm3 . Group A showed a decrease in absolute BMDv levels , in SD score for chronological age ( CA ) , and even more in SD score for bone age ( BA ) . Group B showed the same behavior during the first year , but this trend was reversed in the second year , when calcium supplementation was added to GnRHa treatment . Group C showed an increase in absolute BMDv levels and in SD score for CA and BA . BMDv variations ( expressed as absolute values , SD score for CA , and SD score for BA ) became statistically significant at 24 months between groups C and A ( P = 0.036 , P = 0.032 , and P = 0.025 , respectively ) . The behavior of the lumbar spine BMDv in the three groups is consistent with a positive effect of calcium supplementation during GnRHa treatment . In calcium-supplemented patients , the normal process of bone mass accretion at puberty is preserved despite GnRHa treatment . Therefore , the reduction in BMD during GnRHa treatment in girls with precocious puberty is at least completely reversible and preventable if calcium supplementation is associated from the beginning Two related studies were conducted to assess the associations between markers of skeletal modeling and remodeling in healthy children . Members of monozygotic twin pairs , aged 6 - 14 , enrolled in a clinical trial of calcium supplementation  , were studied at the end of the period of supplementation and for 3 years thereafter . Supplemented children had significantly higher rates of gain in bone mineral density ( BMD ) ( + 3 % on average ) during the period of supplementation accompanied by significantly lower concentrations of serum osteocalcin ( OC , -15 % ) . During postsupplement follow-up , both differences in BMD and OC disappeared . Black females , age matched to the baseline ages of the white children , had significantly lower serum concentrations of both OC and tartrate-resistant acid phosphatase ( TRAP ) at all ages and higher BMDs . When stratified on serum TRAP concentrations , regardless of race , children with lower concentrations had significantly higher BMDs , and no racial differences were apparent . In regression models accounting for 70 - 80 % of the variability in BMD in children , body size and TRAP , but not race , remained significantly associated with BMD . The skeletal advantages seen with calcium supplementation and black race appear to be associated with reduced rates of skeletal turnover . Given that markers of turnover during growth reflect both skeletal modeling and remodeling , and there is no apparent advantage to reduced skeletal modeling , it seems probable that reduced remodeling is the factor that accounts for the increases in bone mass High calcium intake during childhood has been suggested to increase bone mass accrual , potentially result ing in a greater peak bone mass . Whether the effects of calcium supplementation on bone mass accrual vary from one skeletal region to another , and to what extent the level of spontaneous calcium intake may affect the magnitude of the response has , however , not yet been clearly established . In a double-blind , placebo-controlled study , 149 healthy prepubertal girls aged 7.9+/-0.1 yr ( mean+/-SEM ) were either allocated two food products containing 850 mg of calcium ( Ca-suppl . ) or not ( placebo ) on a daily basis for 1 yr . Areal bone mineral density ( BMD ) , bone mineral content ( BMC ) , and bone size were determined at six sites by dual-energy x-ray absorptiometry . The difference in BMD gain between calcium-supplemented ( Ca-suppl . ) and placebo was greater at radial ( metaphysis and diaphysis ) and femoral ( neck , trochanter , and diaphyses ) sites ( 7 - 12 mg/cm2 per yr ) than in the lumbar spine ( 2 mg/cm2 per yr ) . The difference in BMD gains between Ca-suppl . and placebo was greatest in girls with a spontaneous calcium intake below the median of 880 mg/d . The increase in mean BMD of the 6 sites in the low-calcium consumers was accompanied by increased gains in mean BMC , bone size , and statural height . These results suggest a possible positive effect of calcium supplementation on skeletal growth at that age . In conclusion , calcium-enriched foods significantly increased bone mass accrual in prepubertal girls , with a preferential effect in the appendicular skeleton , and greater benefit at lower spontaneous calcium intake BACKGROUND There is no agreement on how much calcium young girls need for optimal bone mineralization . OBJECTIVE We evaluated whether the effect of calcium supplementation on whole-body bone mineral accretion depends on habitual calcium intake . DESIGN This was a r and omized , double-blind , placebo-controlled , 1-y calcium intervention study of girls aged 12 - 14 y selected from a larger group according to habitual calcium intake : subgroup A ( n = 60 ) habitually consumed 1000 - 1307 mg/d ( 40th-60th percentile ) , and subgroup B ( n = 53 ) habitually consumed < 713 mg/d ( < 20th percentile ) . The girls from each subgroup were r and omly assigned to receive either 500 mg Ca/d or placebo .  Whole-body bone mineral content ( BMC ) , bone area ( BA ) , bone mineral density ( BMD ) , and BMC adjusted for BA , height , and weight ( size-adjusted BMC ) were measured at baseline and after 1 y. RESULTS There was no significant effect modification of baseline habitual calcium intake on the relation between calcium supplementation and height , weight , BMC , size-adjusted BMC , BA , BMD , or alkaline phosphatase .  Calcium supplementation had an effect on BMD ( 0.8 % ; P = 0.049 ) and tended to show signs of an effect on size-adjusted BMC ( 0.5 % ; P = 0.08 ) . CONCLUSION A modest effect of calcium supplementation on BMD was shown . However , the effect was independent of habitual calcium intake BACKGROUND Calcium supplementation  during childhood and adolescence increases bone-mass accrual . Whether or not this benefit persists after discontinuation of supplementation is not known . We previously showed a favourable effect of milk-extracted calcium phosphate incorporated in various foods on accumulation of bone mineral mass in 8-year-old girls . We now report the results of a follow-up study undertaken more than 3 years after the end of calcium supplementation . METHODS Anthropometric and bone variables were measured in 116 of the 144 girls whose data had been studied at the end of the supplementation period . The mean time elapsed between the end of the intervention period and this follow-up measurement was 3.5 years . Areal bone mineral density was measured by dual-energy X-ray absorptiometry at the same six skeletal sites as those studied during the intervention phase . FINDINGS We were able to remeasure 62 and 54 girls of the calcium-supplemented and placebo groups , respectively . The increase from baseline in the overall mean bone mineral density of the six skeletal sites was still highly significant ( calcium-supplemented group 179 mg/cm(2 ) [ SE 8 ] vs placebo group 151 mg/cm(2 ) [ 7 ] , p=0.012 ) . A significant difference in favour of the supplemented group was also seen with respect to mean bone mineral content ( p=0.031 ) and mean bone area ( p=0.04 ) . Difference in pubertal maturation did not seem to account for the recorded differences . INTERPRETATION Our results suggest that this form of milk-extracted calcium phosphate taken during the prepubertal period can modify the trajectory of bone mass growth and cause a long-st and ing increase in bone mass accrual , which lasts beyond the end of supplementation The age and developmental stage at which calcium supplementation produces the greatest bone effects remain controversial . We tested the hypothesis that calcium supplementation may improve bone accrual in premenarcheal females . Fifty-one pairs of premenarcheal female twins ( 27 monozygotic and 24 dizygotic ; mean + /- sd age , 10.3 + /- 1.5 yr ) participated in a r and omized , single-blind , placebo-controlled trial with one twin of each pair receiving a 1200-mg calcium carbonate ( Caltrate ) supplement .  Areal bone mineral density ( aBMD ) was measured at baseline and 6 , 12 , 18 and 24 months . There were no within-pair differences in height , weight , or calcium intake at baseline .  Calcium supplementation was associated ( P < 0.05 ) with increased aBMD compared with placebo , adjusted for age , height , and weight at the following time points from baseline : total hip , 6 months ( 1.9 % ) , 12 months ( 1.6 % ) , and 18 months ( 2.4 % ) ; lumbar spine , 12 months ( 1.0 % ) ; femoral neck , 6 months ( 1.9 % ) . Adjusted total body bone mineral content was higher in the calcium group at 6 months ( 2.0 % ) , 12 months ( 2.5 % ) , 18 months ( 4.6 % ) , and 24 months ( 3.7 % ) , respectively ( all P < 0.001 ) . Calcium supplementation was effective in increasing aBMD at regional sites over the first 12 - 18 months , but these gains were not maintained to 24 months
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 .
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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 .