Effect of calcium supplementation on bone mineral accretion in gambian children accustomed to a low-calcium diet

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 randomized, 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 resulted 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 相似文献   

Bone mineral contents and plasma osteocalcin concentrations of Gambian children 12 and 24 mo after the withdrawal of a calcium supplement

BACKGROUND: Our randomized, placebo-controlled supplementation study of 160 rural Gambian children aged 8.3-11.9 y showed that an increase in calcium intake of 714 mg/d for 12 mo resulted in a 5% increase in forearm bone mineral acquisition and a 22% decrease in plasma osteocalcin concentration, a bone formation marker, but had no effect on height or bone dimensions. OBJECTIVE: We investigated whether these results were sustained after supplement withdrawal. DESIGN: All participants were followed up 12 (FU1) and 24 (FU2) mo after supplementation ended. 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. Plasma osteocalcin concentration was measured at FU1. RESULTS: At follow-up, the calcium group had greater bone mineral status than did the placebo group at the midshaft radius (mean difference +/- SE), FU1: BMC (4.7 +/- 1.6%; P = 0.004), BMD (5.1 +/- 1.1%; P 相似文献   

膳食钙摄入量与青春前期女童骨量关系的研究

目的:研究青春前期女童膳食钙摄入量与骨量的关系,为指导合理钙营养提供科学依据。方法:采用双能X线骨密度测量仪测量年龄在10±1岁的194名青春前期女童全身及多位点骨密度和骨矿物质含量,采用食物频数及3d膳食询问法调查膳食钙摄入量,问卷法调查体力活动。结果:日均钙摄入量与所测各位点骨矿物质含量及骨密度均呈显著正相关;日均钙摄入量平均从257mg增加到759mg,不同位点的骨矿物质含量和骨密度分别增加13%～22%和3.6%～16%。结论:增加青春前期女童膳食钙摄入量有助于获得较高骨量和骨密度。     

补钙16个月对青春期男女生骨量的影响

目的探讨不同钙摄入量对我国青少年骨量的影响。方法对北京郊区337人(平均年龄为13.6岁)开展为期16个月的双盲对照干预研究,每天给予3次不同剂量碳酸钙片,每片含60IU维生素D,用双能X线吸收仪(DXA)测定全身、腰椎和前臂骨量。结果女生全身骨矿物密度的年增长率由低钙摄入组到高钙摄入组逐渐升高,调整混杂因素后差异消失。女生前臂远端1/3处和男生前臂远端1/10处的骨矿物含量年增长率和骨面积年增长率均以每天钙摄入900～1100mg/d的人群(平均钙摄入量984mg/d)最高,其中调整混杂因素后男生差异消失。结论青春期钙摄入量达到1000mg/d以上可促进青少年骨量增长,此结果有性别差异。     

Calcium supplementation and bone mineral accretion in adolescent girls: an 18-mo randomized controlled trial with 2-y follow-up

BACKGROUND: A recent meta-analysis raised doubt as to whether calcium supplementation in children benefits spine and hip bone mineral density (BMD). OBJECTIVE: We used state-of-the-art measures of bone (fan-beam dual-energy X-ray absorptiometry and 4 bone turnover markers) to determine whether girls with low habitual calcium intake benefited from supplementation with a soluble form of calcium (calcium citrate malate dissolved in a fruit drink). DESIGN: The trial was an 18-mo randomized trial of calcium supplementation (792 mg/d) with follow-up 2 y after supplement withdrawal. Subjects were 96 girls (mean age: 12 y) with low calcium intakes (mean: 636 mg/d). The main outcome measure was change in total-body, lumbar spine, and total hip bone mineral content (BMC) during supplementation and 2 y after supplement withdrawal. Changes in BMD and bone turnover markers were secondary outcome measures. RESULTS: The mean additional calcium intake in the supplemented group was 555 mg/d. Compared with the control group, the supplemented group showed significantly (P < 0.05) greater gains in BMC (except at the total hip site) over the 18-mo study. BMD change was significantly (P < 0.05) greater for all skeletal sites, and concentrations of bone resorption markers and parathyroid hormone were significantly (P < 0.01) lower in the supplemented group than in the control group after 18 mo. After 42 mo, gains in BMC and BMD and differences in bone resorption were no longer evident. CONCLUSIONS: Calcium supplementation enhances bone mineral accrual in teenage girls, but the effect is short-lived. The likely mechanism for the effect of the calcium is suppression of bone turnover, which is reversed upon supplement withdrawal.     

Calcium supplementation provides an extended window of opportunity for bone mass accretion after menarche

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.     

钙摄入量对青春前期女童骨量增长的影响—两年随机干预实验

目的研究不同钙摄入量对于青春前期女童骨量增长的影响,为该人群钙适宜摄入量的修订提供科学依据。方法以年龄10.0±0.7岁的241名青春前期健康女童为对象,设计普通膳食组、牛奶补充组和钙剂补充组三组,总钙摄入量分别为600、900和1200mg/d,进行2年干预,采用多次称量及3d膳食询问法获得2年间日均膳食钙摄入量,使用双能X线骨密度仪测量干预前后全身、腰椎及近端股骨骨矿物密度和骨矿物含量。结果2年间三组的平均钙摄入量分别为552±61、864±139和1166±207mg/d;日均钙摄入量与全身、多位点骨矿物含量和骨矿物密度显著正相关;当日均钙摄入量达到864mg/d时,全身骨矿物含量增加值显著高于钙摄入量为552mg/d膳食组;当日均钙摄入量达到1166mg/d时,股骨颈骨矿物含量及骨矿物密度和腰椎骨矿物密度的增加值显著高于未达到1166mg/d的干预组。结论9～11.5岁的青春前期女童钙摄入量达到1166mg/d,全身特别是负重部位能获得较高骨矿物含量和骨矿物密度增长,提示青春前期钙适宜摄入量可能为1200mg/d。     

Effects of two years' milk supplementation on size-corrected bone mineral density of Chinese girls

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 randomised, 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.     

Calcium supplementation for 1 y does not reduce body weight or fat mass in young girls

BACKGROUND: Accumulating evidence from observational studies indicates that a high calcium intake may reduce body weight and body fat. However, few randomized trials have been conducted. OBJECTIVE: We examined whether calcium supplementation affects body weight and body fat in young girls and whether a relation exists between habitual calcium intake and body weight and body fat. DESIGN: A randomized, double-blind, placebo-controlled intervention study was conducted in 110 young girls. The subjects were randomly assigned to receive 500 mg Ca/d as calcium carbonate or placebo for 1 y. Two groups of girls were selected according to habitual calcium intake from a large group; one group consumed 1000-1304 mg/d (40th-60th percentile; n = 60) and the other group consumed <713 mg/d (<20th percentile; n = 50). Height, body weight, body fat, and calcium intake were measured at baseline and after 1 y. RESULTS: At baseline a significant negative correlation was observed between habitual dietary calcium intake and percentage of body fat (r = -0.242, P = 0.011). However, calcium supplementation had no effect on height, body weight, or percentage body fat. CONCLUSIONS: Habitual dietary calcium intake was inversely associated with body fat, but a low-dose calcium supplement had no effect on body weight, height, or body fat over 1 y in young girls. It is possible that the effect of calcium on body weight is only exerted if it is ingested as part of a meal, or the effect may be due to other ingredients in dairy products, and calcium may simply be a marker for a high dairy intake.     

Sustained effect of short-term calcium supplementation on bone mass in adolescent girls with low calcium intake

BACKGROUND: The effect of short-term calcium supplementation on peak bone mass in adolescent girls is not completely defined. In our previous double-blind, placebo-controlled, calcium-supplementation study (1000 mg calcium carbonate/d), we showed that calcium supplementation of postmenarcheal girls with low calcium intakes enhances bone mineral acquisition. OBJECTIVE: The objective of this follow-up study, conducted 3.5 y after the end of calcium supplementation, was to investigate the sustained effect of calcium supplementation on bone mineral mass. DESIGN: Anthropometric data, nutrient intakes, and bone variables were reassessed in 96 of the 100 adolescent girls whose data had been studied at the end of the supplementation period. Bone mineral content and bone mineral density (BMD) of the total body, lumbar spine, and femoral neck were determined by dual-energy X-ray absorptiometry. RESULTS: The calcium-supplemented group tended to have a greater accretion of total-body BMD (TBBMD) than did the control group 3.5 y after the end of supplementation. The finding was statistically significant in the active-treatment cohort (n = 17 in the calcium-supplemented group and 28 in the placebo group), who had a compliance rate of > or =75% during the intervention study. In a multivariate linear-regression analysis, TBBMD accretion from the beginning of the intervention study to the follow-up study in the active-treatment cohort was attributed to calcium supplementation and to the time since inclusion in the initial study. CONCLUSION: Calcium supplementation for 1 y in postmenarcheal girls with low calcium intakes may provide a sustained effect on the basis of TBBMD measurements in participants with compliance rates of > or =75%.     

甲状旁腺激素基因多态性与钙摄入量对青春期女童骨量增长的交互作用

目的:探讨甲状旁腺激素(PTH)基因多态性与钙摄入量对青春期女童骨量增长的交互作用。方法:选择228名9～11.5岁未月经初潮的健康女童进行2年追踪,用双能X线骨密度仪(DEXA)检测对象追踪前后全身、左侧近端股骨(包括股骨颈、大转子、粗隆间和华氏三角区)、L1～L4腰椎骨矿含量和骨密度,采用PCR-RFLP技术检测PTH基因BstBⅠ位点多态性。结果:BB基因型女童L1～L4腰椎骨矿含量增长率、左侧近端股骨、粗隆间和L1-L4腰椎骨密度增长率均高于含b等位基因女童(P=0.022～0.047)。BB基因型女童在高钙摄入(>950mg/d)时,粗隆间骨矿含量(ITBMC)增长率较中等和低钙摄入时分别高29.4%和35.0%,股骨颈骨密度(FNBMD)增长率分别高66.7%和46.2%。而含b等位基因女童的ITBMC和FNBMD增长率在不同钙摄入量之间没有显著性差异。结论:PTH基因BstBⅠ多态性与钙摄入量对青春期女童骨量增长存在交互作用,BB基因型女童高钙摄入可促进其骨量增长。     

Bone mass in Chinese premenarcheal girls: the roles of body composition, calcium intake and physical activity

The association of growth and anthropometric characteristics and lifestyle factors with bone mass and second metacarpal radiogrammetry parameters was evaluated in 373 healthy Chinese premenarcheal girls aged 9-11 years. Bone mineral content (BMC) and density (BMD) and bone area (BA) of distal forearm, proximal forearm and total body, bone mineral-free lean (BMFL) mass and fat mass were measured by dual-energy X-ray absorptiometry. Metacarpal bone periosteal and medullary diameters were measured. Dietary intakes were assessed by 7 d food record and physical activity (PA) by questionnaire. BMFL and fat mass together explained 6.3 and 51.6% of the variation in total body BMC and BMD, respectively. BMFL mass contributed to a substantial proportion of the variation in forearm BMC and BMD and periosteal diameter (10.4-41.0%). The corresponding BA explained 14.8-80.4% of the variation in BMC. Other minor but significant predictors of total body bone mass were Ca intake, height, age and PA score (BMD only), and of forearm bone mass were PA score, bone age, height and fat mass. Nevertheless, after adjusting for bone and body size and for age or bone age, subjects with Ca intake above the median (417 mg/d) had 1.8% greater total body BMC (P<0.001), and subjects with PA scores above the median had 2.4-2.5% greater distal and proximal forearm BMC (P<0.05) than those below. Vitamin D intake negatively associated with medullary diameter (partial R2 1.7%). The results indicate that premenarcheal girls should be encouraged to optimise nutrition and Ca intake and exercise regularly to achieve maximum peak bone mass.     

Effect of a calcium and exercise intervention on the bone mineral status of 16-18-y-old adolescent girls

BACKGROUND: Osteoporosis may be prevented or delayed by maximizing peak bone mass through diet modification and physical activity during adolescence. OBJECTIVE: We studied whether increases in calcium intake and physical activity effectively increase the bone mineral status of adolescent girls aged 16-18 y. DESIGN: We conducted a 15.5-mo study of calcium supplementation (1000 mg Ca/d as carbonate) in 144 adolescent girls aged 17.3 +/- 0.3 y ( +/- SD). The subjects were randomly allocated to an exercise (three 45-min exercise-to-music classes/wk during term time) or nonexercise group. Dual-energy X-ray absorptiometry of the whole body, spine, forearm, and hip was performed before and after intervention. RESULTS: The mean (+/- SD) percentage of subjects compliant with supplement taking was 70 +/- 27% and with exercise class attendance was 36 +/- 25%. Baseline calcium intake was 938 +/- 411 mg/d. Calcium supplementation significantly increased size-adjusted bone mineral content. The effect was stronger in subjects with good compliance (percentage difference +/- SE): whole body, 0.8 +/- 0.3% (P < or = 0.01); lumbar spine, 1.9 +/- 0.5% (P < or = 0.001); ultradistal radius, 1.3 +/- 0.6% (P < or = 0.05); total hip, 2.7 +/- 0.6% (P < or = 0.001); femoral neck, 2.2 +/- 0.7% (P < or = 0.001); trochanter, 4.8 +/- 0.9% (P < or = 0.001). Attendance at > 50% of the exercise sessions was significant at the total hip (1.4 +/- 0.7%; P < or = 0.05) and trochanter (2.6 +/- 1.2%; P < or = 0.05). CONCLUSIONS: Calcium supplementation and exercise enhanced bone mineral status in adolescent girls. Whether this is a lasting benefit, leading to the optimization of peak bone mass and a reduction in fracture risk, needs to be determined.     

The effects of a high calcium dairy food on bone health in pre-pubertal children in New Zealand

Childhood and adolescence is the period of most rapid skeletal growth in an individual's lifetime. A greater peak bone mass achieved in the first 2-3 decades of life, may protect against the risk of osteoporotic fracture in later life. The aim of this randomized, controlled study was to assess in pre-pubertal boys and girls (aged 8-10 years) the effect of 18 months of a calcium enriched, cocoa flavoured product on bone density, bone growth and bone size in New Zealand children. One hundred and fifty four pre-pubertal boys and girls (aged 8-10 years) were randomized to receive a high calcium dairy drink or a control drink reconstituted with water for 18 months. They were assessed at baseline and then every 6 months for the first 18 months, while they were having the supplement; they were then followed up 12 months after supplementation had finished. Bone mineral density and bone mineral content were assessed at the total body, hip and spine. Indicators of bone size (vertebral width and height) were also measured at the spine. Anthropometric data was collected, medical history questionnaires were administered (including the Tanner or pubertal stage questionnaire), dietary calcium intake was assessed with a calcium food frequency questionnaire and calcium supplement compliance was determined. There was no significant difference between the 2 groups for bone mineral density or bone mineral content at any time point. There was no difference in vertebral height or width at any stage of the study, indicating no additional influence on bone size at the lumbar vertebrae. There were no significant differences between height, weight, lean mass or fat mass at any time point. Both groups had higher habitual calcium intakes than recommended for this age group going into the study and throughout the study. In this 2(1/2) year study (18 months supplementation, 1 year follow-up) we did not observe a difference in bone mineral density in pre-pubertal children. This was probably due to their high habitual dietary calcium intake whereby minimal addition of calcium to the diet reached the threshold level where no further benefit was seen. There were no significant differences between the two groups in body composition. Growth and the mean height and weight remained between the 50th and 75th percentile for their age. We have shown calcium supplementation in children with high habitual dietary calcium intake appears not to have additional effects on bone mass. Calcium supplementation needs to be targeted in those children with low habitual dietary calcium intake.     

Sodium and calcium intakes and bone mass in rats revisited

OBJECTIVE: High sodium intake accompanied by insufficient dietary calcium may have detrimental effects on bone mass. Our study evaluated the effects of increased sodium and decreased calcium intakes on bone mineral density (BMD) and bone mineral content (BMC) in rats. METHODS: Four-month-old female Wistar rats were given deionized water or 1.8% solution of sodium chloride in deionized water and fed normal (1.2%) or marginal (0.33%) calcium in the diet for 2 mo. At the end of the experiment, BMD and BMC of the whole body and urinary sodium and calcium excretion were evaluated. All rats were killed and right femurs were removed to assess dry and ash weights. Two-way analysis of variance was used to evaluate effect of salt intake and effect of dietary calcium on these parameters. RESULTS: Salt-loaded animals had greater water consumption during the entire 2-mo period and significantly lower body weight from week 5 of the experiment. High salt intake increased urine volume and urinary excretion of sodium and calcium. Urinary calcium was about five times higher in salt-loaded animals than in rats on deionized water irrespective of dietary calcium content. Calcium in diet itself had no significant effect on these parameters. High salt intake slightly, but not significantly, decreased BMD, BMC, and femur weights. Lower calcium in diet significantly decreased BMD, and its effect on femur ash weight almost reached a level of significance. CONCLUSION: We confirmed the benefit of adequate calcium intake to BMD. Under our experimental condition, high salt intake in rats for 2 mo had no statistically significant effect on femur weights, BMD, or BMC even with marginal calcium in the diet.     

膳食钙不足对香港青少年先天性脊柱侧凸全身骨质密度偏低的影响(英文)

青少年先天性脊柱侧凸 (AIS)是一种主要影响女孩的脊柱严重三维畸形病。在香港有 3 %～ 4%的发病率 ,AIS的病人同时发现患有全身性的骨密度偏低现象。本文试图研究是否低骨矿物质密度 (BMD)与AIS病人钙摄入量有关。以 11～ 16岁 582名AIS患者和 2 0 6名健康对照人群为研究对象。面积骨矿物质密度 (aBMD)和体积骨矿物质密度 (vBMD)分别用DXA(Norland XR 3 6)和PQCT(Densiscan 10 0 0 )检测。钙和其它营养素摄入量用食物频率法评价。受试者钙绝对摄入量低 (<50 0mg d)。患AIS少女平均钙摄入量显著高于对照组少女 [(441± 3 4 4 )mg dvs.(3 90± 2 81)mg d ,P =0 0 15] ,11～ 16岁AIS患者大多数骨骼测定点BMD显著低于同龄对照组 (P≤ 0 0 5)。AIS患者与对照组BMD的差异程度随着年龄的增长而增加。 15～ 16岁年龄组AIS患者中钙摄入量与在大多数骨骼测定点测得的BMD有显著相关性 ,而在对照组中没有发现这种相关性。经多因素分析 ,在控制干扰变量的情况下 ,预测BMD的变化 ,钙摄入量是一个非依从性决定因素。结果提示 ,AIS患者绝对钙摄入量低 ,在各年龄组青少年中各个骨骼测定点测得的BMD ,AIS患者组均低于对照组。只有在AIS患者中钙摄入量与BMD有相关性 ,而健康的对照中没有相关性。这表明钙摄入量对AIS患者     

补充强化钙-维生素D牛奶中止两年后中学女生骨量的随访研究

目的:随访研究补充强化钙、维生素D牛奶中止2年后北京城区中学女生骨量的变化。方法:从完成1999-2001年补充强化钙和维生素D牛奶实验的698名女生(10.1岁)中随机抽取294名2年后进行随访,其中对照组未补充强化奶,实验1组强化钙奶,实验2组强化钙-维生素D奶。采用问卷调查法收集一般情况、膳食营养摄入、体力活动状况等指标,并检查其体格发育和第二性征发育状况。采用双能X线吸收仪(DEXA)测量全身、桡骨和前臂的骨量。结果:干预后两个实验组的桡骨远端1/3处、前臂远端1/3处和前臂远端1/10处的骨矿含量绝对增长值均显著高于对照组。但是,在干预中止两年后随访时三组间三个部位的骨矿含量增长值没有显著差异。结论:补充钙、维生素D强化牛奶后对女生骨量增长的促进作用均在中止两年后消失。     

A pilot intervention to increase calcium intake in female collegiate athletes

Calcium intake in adolescent and young adult female athletes often is inadequate to optimize peak bone mass, an important determinant of osteoporosis risk. The purpose of this study was to determine if calcium supplementation in eumenorrheic female collegiate athletes increases intake to recommended levels and promotes increases in bone mineral density (BMD). Forty-eight eumenorrheic female athletes from several college teams (15 soccer, 7 cross-country, 8 indoor track, and 18 basketball) were randomized at the beginning of a competitive season to receive either an oral calcium supplement (1000 mg calcium citrate/400 I.U. Vitamin D) or placebo daily throughout the training season (16 weeks). Self-reported daily pill intake was obtained every 2 weeks to assess adherence. Calcium intake was evaluated using the Rapid Assessment Method, and total body and leg BMD was measured at pre-, mid-, and postseason using dual energy x-ray absorptiometry (DEXA; Hologic QDR-2000). Pre-season calcium intake was lower than national recommendations for this age group (12), averaging 842 mg/d (SD = 719) and was lower in the placebo group compared to the supplemented group (649 +/- 268 vs. 1071 +/- 986 mg/d, respectively; p = .064). Adherence to supplementation was good, averaging 70% across the training season. Supplementation boosted total calcium intake to a mean of 1397 +/- 411 mg/d, which is consistent with recommended levels for this group (37). Supplementation did not influence BMD change during this 16-week intervention. Across teams, a small increase of 0.8% was observed in leg BMD. Change in total body BMD was modified by team, with a significant increase of 1.5% observed in basketball players. These results indicate that providing calcium supplements of 1000 mg/d is adequate to boost total intake to recommended levels during athletic training. Longer intervention trials are required to determine whether calcium supplementation has a positive effect on BMD.     

补充钙剂对青春期骨矿含量的影响

为研究补充钙剂对青少年骨矿含量以及体格发育的影响 ,选取 1 61例 9～ 2 0岁健康青少年 ,按性别和性发育程度分为补钙组和对照组。实验前后评价两组膳食钙摄入量、运动量水平、性发育程度 ,并测定两组青少年身高、体重和桡骨远端 1 3处骨矿含量、骨宽和血清总碱性磷酸酶水平。结果表明本组青少年膳食钙摄入量低于每日膳食钙参考摄入量的适宜摄入量水平 ,补充钙剂对青少年身高、体重无明显影响 ;骨矿含量增长除女性青春期后期有显著性差异外 ,其余各组增长与对照组比较无显著性。结果提示 ,青春期存在体格快速发育和骨量迅速积累的特点 ,补充钙剂对骨矿含量的增长作用有限 ,对体格发育也无明显影响 ;在女性骨量增长较少阶段补充钙剂则可能有助于骨矿含量的增加 ,且这种作用可能通过降低骨代谢率实现     

Dairy intakes affect bone density in the elderly

BACKGROUND: Race and sex differences in the effect of diet on bone mineral density (BMD) at the hip in the elderly are unknown. OBJECTIVES: This study related cross-sectional nutrient and dairy product consumption to hip BMD in white and black men and women aged >60 y and evaluated the influence of nutrient and dairy product consumption on changes in BMD in a white cohort participating in a calcium, vitamin D, or placebo trial. DESIGN: The Health Habits and History Questionnaire was used in 289 white women and 116 white men who participated in the trial and in 265 black women and 75 black men to predict total hip and femoral neck BMD or changes in BMD. RESULTS: Blacks had higher calcium intakes than did whites (700 and 654 mg/d, respectively; P = 0.0094), and men had higher calcium intakes than did women (735 and 655 mg/d, respectively; P = 0.0007). For men, the correlation between total hip BMD and dairy calcium intake after adjustment for age, race, and weight was 0.23 (P < 0.005); this relation was not significant in women (r = 0.02, P = 0.12). Similar results were found for femoral neck BMD. In the longitudinal study, calcium supplementation reduced bone loss from the total hip and femoral neck in those who consumed <1.5 servings of dairy products/d and were <72 y old. CONCLUSIONS: Cross-sectional results indicated that higher dairy product consumption is associated with greater hip BMD in men, but not in women. Calcium supplementation protected both men and women from bone loss in the longitudinal study of whites.