Mineral Accretion Research Articles

Calcium Absorption in Infants and Small Children: Methods of Determination and Recent Findings

Determining calcium bioavailability is important in establishing dietary calcium requirements. In infants and small children, previously conducted mass balance studies have largely been replaced by stable isotope-based studies. The ability to assess calcium absorption using a relatively short 24-hour urine collection without the need for multiple blood samples or fecal collections is a major advantage to this technique. The results of these studies have demonstrated relatively small differences in calcium absorption efficiency between human milk and currently available cow milk-based infant formulas. In older children with a calcium intake typical of Western diets, calcium absorption is adequate to meet bone mineral accretion requirements.

Differential physiological responses of two congeneric scleractinian corals to mineral accretion and an electric field

Despite increasing popularity of ‘electric’ reefs as a means for reef restoration, there is a distinct lack of quantitative evidence supporting the alleged benefits of this method. This study investigated the effects of an electric field versus an electric field in combination with a cathode on coral growth (skeletal extension) rates, coral survival, zooxanthella densities, chlorophyll a (chl a) concentrations, and chlorophyll fluorescence of Acropora pulchra and A. yongei. Coral transplants were grown for 4 months under three treatment conditions: (1) on an iron cathode, (2) on bamboo inside an electric field, or (3) on bamboo in the absence of an electric field. Contrary to predictions, coral growth rates of both species were highest inside the electric field and not on the cathode. Except for chl a concentrations, the cathode had a significant adverse effect on all measured variables for A. yongei but not for A. pulchra. Treatment had no effect on the survival of A. pulchra, while mortality rates of A. yongei were significantly higher in the presence of mineral accretion compared to the electric field and control. A. yongei on the cathode featured low zooxanthella densities, depressed electron transport rates (rETR) and maximum quantum yield (F v/F m), and reduced growth. By contrast, treatment had no effect on the fluorescence characteristics of A. pulchra, and zooxanthella densities were highest for corals on the cathode, coincident with high growth rates relative to the control. Overall, the data indicate that the proposed benefits of the mineral accretion technology to meet important objectives of reef rehabilitation with regard to colony growth and survival should be considered with caution.

Bone disease and hypercalciuria in children

There have been relatively few studies of bone mass in children with idiopathic hypercalciuria (IH). When performed, bone mineral density (BMD) measurements have consistently disclosed decreased Z-scores for children with IH at the lumbar spine and, to a lesser extent, at the femoral neck. Few investigations have delineated the nature of the mechanism(s) that may contribute to the bone loss in these children. Some studies have been consistent, showing increased bone resorption as the probable mechanism of bone loss. To date, there have been no reports regarding the assessment of biochemical markers specific for bone formation in children with IH. However, since most of the children with IH in these reports had demonstrated normal longitudinal growth, it seems less likely that there is an alteration in bone formation. The causes for increased bone resorption also are not firmly established, but genetics, dietary indiscretions, and altered cytokine production have been proposed as being contributory to the decreased BMD observed in these children with IH. Optimal bone mineral accretion during childhood and adolescence is important in attaining peak bone mass and may serve to prevent the development of osteoporosis in adulthood. Thus, a better understanding of bone loss in children with IH is warranted.

Effect of Long-term Corticosteroid Use on Bone Mineral Density in Children: A Prospective Longitudinal Assessment in the Childhood Asthma Management Program (CAMP) Study

Kelly HW, Van Natta ML, Covar RA, et al. Pediatrics . 2008;122(1). Available at: www.pediatrics.org/cgi/content/full/122/1/e53 PURPOSE OF THE STUDY. To evaluate the effects of multiple short courses of oral corticosteroid treatment and longterm inhaled corticosteroid (ICS) treatment on bone mineral accretion over a period of years. STUDY POPULATION. Cohort follow-up study for a median of 7 years with 877 children 5 to 12 years of age who had mild-to-moderate asthma and initially were randomly assigned in the Childhood Asthma Management Program. …

Calcium requirements for bone growth in Canadian boys and girls during adolescence

Adequate dietary intake during the growth period is critical for bone mineral accretion. In 1997, an adequate intake (AI) of 1300 mg/d Ca was set for North American adolescents aged 9-18 years based on best available data. We determined bone Ca accrual values from age 9 to 18 years taking into account sex and maturity. Furthermore, we used the accrual data to estimate adolescents' Ca requirements. Total body bone mineral content (TBBMC) of eighty-five boys and sixty-seven girls participating in the Saskatchewan Paediatric Bone Mineral Accrual Study were used to determine annual TBBMC accumulation over the pubertal growth period. Using a similar factorial approach as the AI, we estimated Ca requirements of adolescent boys and girls for two age groups: 9-13 and 14-18 years. Between 9 and 18 years, boys accrued 198.8 (SD 74.5) g bone mineral content (BMC) per year, equivalent to 175.4 (SD 65.7) mg Ca per d with the maximum BMC accrual of 335.9 g from age 13 to 14 years. Girls had 138.1 (SD 64.2) g BMC per year, equalling121.8 (SD 56.6) mg Ca per d with the maximum annual BMC accrual of 266.0 g from age 12 to 13 years. Differences were observed between both sex and age groups with respect to Ca needs: boys and girls aged 9-13 years would require 1000-1100 mg/d Ca, and from age 14 to 18 years, the mean Ca requirements would be relatively stable at 1000 mg/d for girls but would rise to 1200 mg/d for boys.

International longitudinal pediatric reference standards for bone mineral content

To render a diagnosis pediatricians rely upon reference standards for bone mineral density or bone mineral content, which are based on cross-sectional data from a relatively small sample of children. These standards are unable to adequately represent growth in a diverse pediatric population. Thus, the goal of this study was to develop sex and site-specific standards for BMC using longitudinal data collected from four international sites in Canada and the United States. Data from four studies were combined; Saskatchewan Paediatric Bone Mineral Accrual Study ( n = 251), UBC Healthy Bones Study ( n = 382); Penn State Young Women's Health Study ( n = 112) and Stanford's Bone Mineral Accretion study ( n = 423). Males and females (8 to 25 years) were measured for whole body (WB), total proximal femur (PF), femoral neck (FN) and lumbar spine (LS) BMC (g). Data were analyzed using random effects models. Bland–Altman was used to investigate agreement between predicted and actual data. Age, height, weight and ethnicity independently predicted BMC accrual across sites ( P < 0.05). Compared to White males, Asian males had 31.8 (6.8) g less WB BMC accrual; Hispanic 75.4 (28.2) g less BMC accrual; Blacks 82.8 (26.3) g more BMC accrual with confounders of age, height and weight controlled. We report similar findings for the PF and FN. Models for females for all sites were similar with age, height and weight as independent significant predictors of BMC accrual ( P < 0.05). We provide a tool to calculate a child's BMC Z-score, accounting for age, size, sex and ethnicity. In conclusion, when interpreting BMC in pediatrics we recommend standards that are sex, age, size and ethnic specific.

Maternal plasma 25‐hydroxyvitamin D concentration and birthweight, growth and bone mineral accretion of Gambian infants

Maternal plasma 25‐hydroxyvitamin D concentration and birthweight, growth and bone mineral accretion of Gambian infants

Do dairy products improve bone density in adolescent girls?

Previous studied have shown that when calcium is supplemented in adolescents who normally consume less than 1000 mg calcium, bone mineral accretion improves between 1 and 5%. This increment in bone accretion is improved up to 10% when dairy products are used as a source of supplemental calcium in adolescent girls. Because the addition of dairy foods is a simple, inexpensive intervention that carries no risk and because it substantially increases bone accretion with potential long-term benefits, adolescents should be encouraged to include dairy products in their diet.

Mineral accretion in nursing piglets in relation to sow performance and mineral source

The present study investigated the effect of a moderate substitution of inorganic mineral sources with chelated mineral sources from four weeks prior to parturition throughout lactation on sow and litter performance. In addition, the aims were to determine whether the mineral source and litter performance affect mineral status and accretion in piglets at birth and at weaning. Forty gestating sows in a commercial pig herd were selected and randomly assigned to two experimental groups, with part of the Cu, Mn, Zn and Fe content of the feed added as either an inorganic mineral source or a chelated mineral source. From each sow, one piglet was randomly selected at birth and at weaning for total body mineral analysis. Neither the performance of the sows and the piglets nor the total body mineral concentrations of the piglets at birth and at weaning were significantly different between the two diet groups (&lt;i&gt;P&lt;/i&gt; &gt; 0.05). Fe, Na and P content of piglets at birth were inversely correlated with birth weight (&lt;i&gt;r&lt;/i&gt; = –0.447, &lt;i&gt;P&lt;/i&gt; = 0.004 for Fe; &lt;i&gt;r&lt;/i&gt; = –0.431, &lt;i&gt;P&lt;/i&gt; = 0.005 for Na; &lt;i&gt;r&lt;/i&gt; = –0.340, &lt;i&gt;P&lt;/i&gt; = 0.032 for P). Daily accretion rate of K and Ca of piglets was positively correlated with piglet growth performance during the entire lactation period (&lt;i&gt;r&lt;/i&gt; = 0.469, &lt;i&gt;P&lt;/i&gt; = 0.008 for K; &lt;i&gt;r&lt;/i&gt; = 0.581, &lt;i&gt;P&lt;/i&gt; &lt; 0.001 for Ca), and negatively correlated with number of liveborn piglets (&lt;i&gt;r&lt;/i&gt; = –0.424, &lt;i&gt;P&lt;/i&gt; = 0.014 for K, and &lt;i&gt;r&lt;/i&gt; = –0.405, &lt;i&gt;P&lt;/i&gt; = 0.027 for Ca). In conclusion, the study documented that partial substitution of inorganic minerals with a chelated mineral source failed to exert significant effects on performance and total body mineral concentrations. The importance of the influence of sow milk production on mineral body stores in piglets warrants further investigation.

The recognition and treatment of growth disorders – A 50-year retrospective

The past 50 years have seen great progress in the understanding and treatment of classic growth disorders. Advances such as the recognition of hormone receptor defects, the development of recombinant growth hormone, and the expanding awareness of epigenetic phenomena affecting growth are among these great achievements. Yet growth failure remains a pervasive problem among children with complex health conditions, such as survivors of childhood cancers, premature infants, organ transplant recipients, and children with cystic fibrosis. The significant increases in life expectancy among these groups underscores the potential consequences of poor growth, whether due to the underlying conditions or medical treatments, as they may have long-lasting effects into adulthood. The ongoing contributions of human biologists to the study of human growth remain essential in the recognition and treatment of growth disorders, by defining normal patterns of growth and body composition, the interplay of growth and maturation, the role of environmental, behavioral and genetic factors, and the long-term consequences of growth patterns. Examples will be given based on two common genetic disorders, cystic fibrosis and sickle-cell anemia, to highlight the relationships between growth failure, survival, and malnutrition. Also, a study of bone mineral accretion in children with cystic fibrosis will illustrate the importance of understanding patterns of growth in healthy children, and their application in the diagnosis and management of children with chronic disease. These examples accentuate the need for continued participation of human biologists in the study of growth and development and the care of children.

Stress Fracture and Military Medical Readiness

Military recruits and distance runners share a special risk of stress fracture injury. Recent efforts by US and Israeli military-sponsored researchers have uncovered important mechanisms and practical low-cost interventions. This article summarizes key findings relevant to prevention of stress fracture, including simple strategies to identify and to mitigate risk. Published research supported through the Bone Health and Military Medical Readiness research program and related military bone research was analyzed for contributions to preventing stress fracture in military recruits and optimizing bone health. Thousands of military recruits helped test hypotheses about predictors of risk, safer exercise regimens, and rest, nutrition, gait training, and technology interventions to reduce stress fracture risk. Concurrent cellular, animal, and human laboratory studies were used to systematically investigate mechanisms of mechanical forces acting on bone and interactions through muscle, hormonal and genetic influences, and metabolism. The iterative and sometimes simultaneous process of basic discovery and field testing produced new knowledge that will provide safer science-based physical training. Human training studies evaluating effects on bone require special commitment from investigators and funders due to volunteer compliance and attrition challenges. The findings from multiple studies indicate that measures of bone elasticity, fragility, and geometry are as important as bone mineral density in predicting fracture risk, with applications for new measurement technologies. Risk may be reduced by high intakes of calcium, vitamin D, and possibly protein (e.g., milk products). Prostaglandin E2, insulin-like growth factor 1, and estrogens are important mediators of osteogenesis, indicating reasons to limit the use of certain drugs (e.g., ibuprofen), to avoid excessive food restriction, and to treat hypogonadism. Abnormal gait may be a correctable risk factor. Brief daily vibration may stimulate bone mineral accretion similar to weight-bearing exercise. Genetic factors contribute importantly to bone quality, affecting fracture susceptibility and providing new insights into fracture healing and tissue reengineering.

Calcium and vitamin D and bone strength ‐ Scientific substantiation of a health claim related to calcium and vitamin D and bone strength pursuant to Article 14 of Regulation (EC) No 1924/2006 ‐ Scientific Opinion of the Panel on Dietetic Products, Nutrition and Allergies

Calcium and vitamin D and bone strength ‐ Scientific substantiation of a health claim related to calcium and vitamin D and bone strength pursuant to Article 14 of Regulation (EC) No 1924/2006 ‐ Scientific Opinion of the Panel on Dietetic Products, Nutrition and Allergies

Effect of long-term corticosteroid use on bone mineral density in children: a prospective longitudinal assessment in the childhood Asthma Management Program (CAMP) study.

Systemic corticosteroids are known to induce osteoporosis and increase the risk for fractures in adults and children. Inhaled corticosteroids have been shown to increase the risk for osteoporosis and fractures in adults at risk; however, long-term prospective studies of children to assess risks of multiple short courses of oral corticosteroids and chronic inhaled corticosteroids have not been performed. Thus, we assessed the effects of multiple short courses of oral corticosteroids and long-term inhaled corticosteroids on bone mineral accretion over a period of years. This was a cohort follow-up study for a median of 7 years of children who had mild-to-moderate asthma and initially were randomly assigned into the Childhood Asthma Management Program trial. Serial dual-energy radiograph absorptiometry scans of the lumbar spine for bone mineral density were performed for all patients. Annual bone mineral accretion was calculated for 531 boys and 346 girls who had asthma and were aged 5 to 12 years at baseline (84% of the initial cohort). Oral corticosteroid bursts produced a dosage-dependent reduction in bone mineral accretion (0.052, 0.049, and 0.046 g/cm(2) per year) and an increase in risk for osteopenia (10%, 14%, and 21%) for 0, 1 to 4, and >or=5 courses, respectively, in boys but not girls. Cumulative inhaled corticosteroid use was associated with a small decrease in bone mineral accretion in boys but not girls but no increased risk for osteopenia. Multiple oral corticosteroid bursts over a period of years can produce a dosage-dependent reduction in bone mineral accretion and increased risk for osteopenia in children with asthma. Inhaled corticosteroid use has the potential for reducing bone mineral accretion in male children progressing through puberty, but this risk is likely to be outweighed by the ability to reduce the amount of oral corticosteroids used in these children.

Eating Disorders and Menstrual Dysfunction in Adolescents

Menstrual dysfunction is a common feature of all eating disorders and results in significant medical complications. The etiology of menstrual dysfunction is multifaceted and the result of a complex interplay of many factors including weight loss, decreased body fat, hypoleptinemia, abnormal eating attitudes and behaviors, exercise, and psychological stressors. This chapter will review the prevalence of menstrual dysfunction in adolescents with eating disorders, its multifactorial etiology, the evidence-based pathophysiology, and the resulting complications to linear growth, pubertal development, bone mineral accretion, and cognitive function. Future research directions are identified that suggest opportunities to gain new insights into our understanding of the mechanisms and treatment of menstrual dysfunction in adolescents with eating disorders.

Whole-Body Dual-Energy X-Ray Absorptiometry Comes of Age: Bone Structural Measures and Their Physiological Determinants in Anorexia Nervosa

Anorexia nervosa (AN) warrants study by all endocrinologists for a variety of reasons, not the least being the devastating endocrine and structural effects of this disorder of appetite on its unfortunate victims. This is all the more poignant because those of us with more normal satiety regulation lack comprehension of the disorder. If the impact and epidemiology of AN in Westernized societies is not sufficient reason for a detailedunderstandingoftheeffectsofthedisorder,thenitsroleas a physiological model for adolescent and early adulthood starvation the world over should interest both humanitarians and physiologists, involving as it does the regulation of growth and fuel metabolism. In this great tapestry, it could be argued that the skeletal impact of the disorder is of low importance. There are two reasons why this argument is invalid. The first is that the skeleton accuratelyreflectsthephysiologicaleffectsofthediseasewritten in its shape, size, and function, and second, the majority who survive the ravages of the adolescent phase of the disorder are oftenleftwithapermanentlydamagedskeletonasaresultoflack of attainment of their genetically programmed optimal peak bone mass with consequent increased fracture risk (1). Anatomy of Skeletal Growth It is a truism to state that our shape is determined by our bone structure. The huge variety of shape and size of our species, evident to us all every day, is a result of the huge variation in skeletal structure determined in part during the few short years ofouradolescentgrowthspurt.Assessmentofadolescentgrowth bythemeasurementofheightisapartofthephysicalassessment ofteenagersandisausefulpointertoavarietyofdisordersofthe activityofthephyses,thedeterminantsofheight.However,bone enlargement is determined not only by an increase in length but alsobyanincreaseinwidthanddepth,togetherwithanincrease in the bone within the bone. Cohort studies show that peak height velocity occurs 2–3 yr before menarche and peak bone mineral accretion in the 2 yr around menarche (2, 3). Eight percent of adult height and 22% of adult total-body bone mineral are gained in the 2 yr surrounding peak height velocity (4). Because peak bone mineral accretion occurred 1 yr later than peak heightvelocity,thereisadecreaseinsize-correctedbonemineral density(BMD;thebonewithinthebone)beforemenarche(3,5), reflecting a disassociation between linear skeletal growth and bone mineral accretion during the rapid lengthening of bones occurring at this time. Careful examination of the femoral neck site confirms that the periosteal expansion reaches its maximum about 2 yr after the attainment of peak height (6). This latter growth cannot be assessed by physical examinationbutratherneedsanimagingtechniquebestsuppliedbydual

Modulation of extracellular matrix protein phosphorylation alters mineralization in differentiating chick limb-bud mesenchymal cell micromass cultures

Protein phosphorylation and dephosphorylation are important regulators of cellular and extracellular events. The purpose of this study was to define how these events regulate cartilage matrix calcification in a cell culture system that mimics endochondral ossification. The presence of casein kinase II (CK2), an enzyme known to phosphorylate matrix proteins, was confirmed by immunohistochemistry. The importance of phosphoprotein phosphorylation and dephosphorylation was examined by comparing effects of inhibiting CK2 or phosphoprotein phosphatases on mineral accretion relative to untreated mineralizing controls. Specific inhibitors were added to differentiating chick limb-bud mesenchymal cell micromass cultures during the development of a mineralized matrix at the times of cell differentiation, proliferation, formation of the mineralized matrix, or proliferation of the mineral crystals. The mineralizing media for these cultures contained 4 mM inorganic phosphate and no organic-phosphate esters; control cultures had 1 mM inorganic phosphate. Mineralization was monitored based on 45Ca uptake and infrared characterization of the mineral; cell viability was assessed by three independent methods. Treatments that caused cell toxicity were excluded from the analysis. Inhibition of CK2 activity with apigenin or CK2 inhibitor II reduced the rate of mineral deposition, but did not block mineral accretion. Effects were greatest during the time of mineralized matrix formation. Inhibition of phosphoprotein phosphatase activities with okadaic acid, calyculin A, and microcystin-LR, at early time points also markedly inhibited mineral accretion. Inhibition after mineralization had commenced increased the mineral yield. Levamisole, an alkaline phosphatase inhibitor, had no effect on mineral accretion in this system, suggesting the involvement of other phosphatases. Adding additional inorganic phosphate to the inhibited cultures after mineralization had started, but not earlier, reversed the inhibition indicating that the phosphatases were, in part, providing a source of inorganic phosphate. To characterize the roles of specific phosphoproteins blocking studies were performed. Blocking with anti-osteopontin antibody confirmed osteopontin's previously reported role as a mineralization inhibitor. Blocking antibodies to bone sialoprotein added from day 9 or on days 9 and 11 retarded mineralization, supporting its role as a mineralization nucleator. Antibodies to osteonectin slightly stimulated early mineralization, but had no effect after the time that initial mineral deposition occurs. Taken together, the results of this study demonstrate the importance of the phosphorylation state of extracellular matrix proteins in regulating mineralization in this culture system.

Growth and Bone Mineral Accretion During Puberty in Chinese Girls: A Five-Year Longitudinal Study

There are few longitudinal data on bone development during puberty in children with low calcium intake. This 5-yr longitudinal study showed that, in Chinese girls, the mean apparent calcium retention efficiency during puberty was 40.9%, PHV occurred at 3-0 yr before menarche, and peak bone mineral accretion occurred 1 yr later than PHV. Chinese girls have high calcium retention efficiency during puberty. There are few longitudinal data on bone development during puberty in children with low dietary calcium intake. The aim of this study was to examine the rate of growth and bone mineral accretion and study the predictors of total body BMC during puberty in a 5-yr longitudinal study with Chinese girls. Ninety-two girls, 9.5-10.5 yr of age at baseline, from the unsupplemented control group of a school milk intervention trial were included in this analysis. Data on anthropometric measurements, total body BMC as assessed by DXA, and calcium intake as assessed by a 3-day food record were obtained at baseline and 1, 2, 4, and 5 yr. The mean age of menarche was 12.1 +/- 1.0 yr. The mean annual rate of bone mineral accretion was 197.4 g/yr during the follow-up period, representing a calcium accretion rate of 162.3 mg/d. This calcium retention rate and the average dietary calcium intake of 444.1 mg/d gave an apparent calcium retention efficiency of 40.9%. Peak height velocity (PHV) occurred at 3-0 yr before menarche. Peak bone mineral accretion occurred 1 yr later than PHV. There was a decrease in size-corrected BMD in the year before menarche. In the linear mixed-effects model analysis containing body size and lifestyle factors, we found that height, body weight, and calcium intake were significant independent predictors of total body BMC. Chinese girls with low habitual dietary calcium intake have high calcium retention efficiency during puberty. Because calcium intake is a significant predictor of total body BMC, increasing dietary calcium intake may have beneficial effects on bone mineral accretion in these girls.

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.

Fetal and postnatal bone development: reviewing the role of mechanical stimuli and nutrition

Fetal and postnatal bone development is by tradition viewed as a process of bone mineral accretion or an increase in bone mass. Accordingly, previous approaches to bone development in neonatology and early childhood have emphasized the determinants of peak bone mass and their relationship to osteopenia, osteoporosis and fractures in later life. This suggests that the neonatal period and early childhood is an important period for bone mineral accrual, and that peak bone mass may be correlated with subsequent skeletal health. Nevertheless, describing fetal and postnatal bone development just in terms of changes in mass or density means looking at bones as if they were amorphous heaps of calcium and phosphorus. In reality, of course, bones are complex three-dimensional structures. It is therefore important to create conditions that stimulate bones to become more stable. We suggest that functional bone physiology can be used to explain fetal and postnatal bone development and to devise strategies for improved bone development in both premature infants and neonates.

Calcium requirements for Asian children and adolescents.

Calcium is important for bone health. Over the last 15 years, reference calcium intakes in Western countries have been revised upwards for maximizing bone mass at skeletal maturity and for prevention of osteoporotic fractures. Some of these reference figures have also been adopted for use in Asian countries. However, the scientific data based on for revising reference calcium intakes in the West was largely based on Caucasians. Limited human studies relating to calcium requirements and bone mineralization have been conducted in Asians in Asia. In children and adolescents, a trial has confirmed no effects of calcium supplementation on bone gains in adolescent girls after 7 years. A meta-analysis has also revealed that calcium supplementation has little beneficial effects on bone gain. Given that genetic factors, hormonal status, body size, bone structure, diets, physical activity, vitamin D status and adaptation could modify calcium retention and bone integrity, these factors need to be considered collectively to promote bone health in Asian populations. Furthermore, studies to identify indigenous foods rich in calcium and high in bioavailability are needed to widen sources of dietary calcium. Ethnic differences in calcium retention, hormonal status, bone structure, bone mineral accretion and peak bone mass are evident among Asians, Caucasians and Blacks in USA. Hence, reference calcium intakes for Asians are likely to be unique and different from those of Caucasians. More research has to be conducted in Asian populations in order to develop appropriate reference calcium intakes for the region.