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

Formula Milk Supplementation and Bone Acquisition in 4-6 Years Chinese Children: A 12-Month Cluster-Randomized Controlled Trial

Dairy foods are crucial for adequate calcium intake in young children, but scarce data are available on the effects of formula milk on bone acquisition. This cluster-randomized controlled trial investigated the effects of the supplementation of formula milk on bone health in rural children accustomed to a low-calcium diet between September 2021 and September 2022. We recruited 196 healthy children aged 4-6 years from two kindergartens in Huining County, Northwest China. A class-based randomization was used to assign them to receive 60 g of formula milk powder containing 720 mg calcium and 4.5 µg vitamin D or 20-30 g of bread per day for 12 months, respectively. Bone mineral density (BMD) and bone mineral content (BMC) at the left forearm and calcaneus, bone biomarkers, bone-related hormones/growth factors, and body measures were determined at baseline, 6, and 12 months. A total of 174 children completed the trial and were included in the analysis. Compared with the control group, formula milk intervention showed significant extra increments in BMD (3.77% and 6.66%) and BMC (4.55% and 5.76%) at the left forearm at 6th and 12th months post-intervention (all p < 0.001), respectively. Similar trends were observed in BMD (2.83%) and BMC (2.38%) in the left calcaneus at 6 months (p < 0.05). The milk intervention (vs. control) also showed significant changes in the serum concentrations of osteocalcin level (-7.59%, p = 0.012), 25-hydroxy-vitamin-D (+5.54%, p = 0.001), parathyroid hormone concentration (-15.22%, p = 0.003), and insulin-like growth factor 1 (+8.36%, p = 0.014). The percentage increases in height were 0.34%, 0.45%, and 0.42% higher in the milk group than in the control group after 3-, 6-, and 9-month intervention, respectively (p < 0.05). In summary, formula milk supplementation enhances bone acquisition at the left forearm in young Chinese children.

The effect of calcium supplementation in people under 35 years old: A systematic review and meta-analysis of randomized controlled trials

Background:

The effect of calcium supplementation on bone mineral accretion in people under 35 years old is inconclusive. To comprehensively summarize the evidence for the effect of calcium supplementation on bone mineral accretion in young populations (≤35 years).

Methods:

This is a systematic review and meta-analysis. The Pubmed, Embase, ProQuest, CENTRAL, WHO Global Index Medicus, Clinical Trials.gov, WHO ICTRP, China National Knowledge Infrastructure (CNKI), and Wanfang Data databases were systematically searched from database inception to April 25, 2021. Randomized clinical trials assessing the effects of calcium supplementation on bone mineral density (BMD) or bone mineral content (BMC) in people under 35 years old.

Results:

This systematic review and meta-analysis identified 43 studies involving 7,382 subjects. Moderate certainty of evidence showed that calcium supplementation was associated with the accretion of BMD and BMC, especially on femoral neck (standardized mean difference [SMD] 0.627, 95% confidence interval [CI] 0.338–0.915; SMD 0.364, 95% CI 0.134–0.595; respectively) and total body (SMD 0.330, 95% CI 0.163–0.496; SMD 0.149, 95% CI 0.006–0.291), also with a slight improvement effect on lumbar spine BMC (SMD 0.163, 95% CI 0.008–0.317), no effects on total hip BMD and BMC and lumbar spine BMD were observed. Very interestingly, subgroup analyses suggested that the improvement of bone at femoral neck was more pronounced in the peripeak bone mass (PBM) population (20–35 years) than the pre-PBM population (<20 years).

Conclusions:

Our findings provided novel insights and evidence in calcium supplementation, which showed that calcium supplementation significantly improves bone mass, implying that preventive calcium supplementation before or around achieving PBM may be a shift in the window of intervention for osteoporosis.

Funding:

This work was supported by Wenzhou Medical University grant [89219029].

Osteoporosis and bone fractures are common problems among older people, particularly older women. These conditions cause disability and reduce quality of life. Progressive loss of bone mineral density is usually the culprit. So far, strategies to prevent bone weakening with age have produced disappointing results. For example, taking calcium supplements in later life only slightly reduces the risk of osteoporosis or fracture. New approaches are needed.

Bone mass increases gradually early in life and peaks and plateaus around 20-35 years of age. After that period, bone mass slowly declines. Some scientists suspect that increasing calcium intake during this period of peak bone mass may reduce osteoporosis or fracture risk later in life.

A meta-analysis by Liu, Le et al. shows that boosting calcium intake in young adulthood strengthens bones. The researchers analyzed data from 43 randomized controlled trials that enrolled 7,382 participants. About half the studies looked at the effects of taking calcium supplements and the other half analyzed the effects of a high calcium diet. Boosting calcium intake in people younger than age 35 improved bone mineral density throughout the body. It also increased bone mineral density at the femoral neck, where most hip fractures occur. Calcium supplementation produced larger effects in individuals between the ages of 20 and 35 than in people younger than 20.

Both high calcium diets and calcium supplements with doses less than 1000 mg/d boosted bone strength. Higher dose calcium supplements did not provide any extra benefits. The analysis suggests people should pay more attention to bone health during early adulthood. Large randomized clinical trials are needed to confirm the long-term benefits of boosting calcium intake during early adulthood. But if the results are validated, taking calcium supplements, or eating more calcium-rich foods between the ages of 20 and 35 may help individuals build healthier bones and prevent fractures and osteoporosis later in life.

Calcium repletion to rats with calcipenic rickets fails to recover bone quality: A calcipenic "memory"

Calcipenic rickets is prevalent in underprivileged children in developing countries. Calcipenic rickets resulting from dietary calcium (Ca) deficiency decreases bone mass and deteriorates bone microstructure in humans. The effect of dietary Ca replenishment (CaR) on rachitic bones in animal models depends on the amount, critical period and duration of replenishment, however, the extent of recovery in various bone parameters including bone quality remains unclear. We investigated the effect of CaR in rat skeleton after inducing calcipenic rickets. Female SD rats (postnatal 28 days/P28) were rendered calcipenic by feeding calcium deficient (CaD) diet (0.1% Ca) till P70 while control SD rats were fed Ca sufficient diet (0.8% Ca). At P70, calcipenic rats were switched to 0.8% Ca diet till P150 for one group and P210 for another group (endpoint). The CaD groups received 0.1% Ca diet throughout the study (P210). In the CaD groups, serum Ca and phosphate, and bone mineral density (BMD) were significantly decreased whereas serum alkaline phosphatase (ALP), iPTH and CTX-1 were increased compared to age-matched controls. Moreover, at the endpoint, the CaD group had reduced bone mass, surface referent bone formation parameters, tissue mineralization and strength accompanied by the increased osteoid thickness and microarchitectural decay (measured by trabecular geometric parameters) with poor crystal packing. The CaR group showed complete recovery in serum Ca, iPTH, ALP and CTX-1, and BMD, however, the bone quality parameters including bone strength, microarchitectural decay, tissue mineralization, and crystallinity were incompletely restored. Decreased surface referent bone formation and increased unmineralized bones (osteoid) indicative of osteomalacia were also observed in the CaR group at P210 compared with control despite prolonged replenishment. We conclude that a prolonged Ca repletion following the induction of calcipenic rickets in rats although shows the recovery of biochemical measures of bone metabolism and bone mass, however, the bone quality remains compromised. This suggests that a "memory" of calcipenia occurring at the early growth stage persists in the skeleton of adult rats despite a prolonged Ca replenishment.

Resistance Training and Milk-Substitution Enhance Body Composition and Bone Health in Adolescent Girls

Background: Increased soft-drink consumption has contributed to poor calcium intake with 90% of adolescent girls consuming less than the RDA for calcium.Purpose/objectives: The purpose of this investigation was to determine the independent and additive effects of two interventions (milk and resistance training) on nutrient adequacy, body composition, and bone health in adolescent girls.Methods: The experimental design consisted of four experimental groups of adolescent girls 14-17 years of age: (1) Milk + resistance training [MRT]; n = 15; (2) Resistance training only [RT]; n = 15; (3) Milk only [M] n = 20; (4) Control [C] n = 16. A few significant differences were observed at baseline between the groups for subject characteristics. Testing was performed pre and post-12 week training period for all groups. Milk was provided (3, 8 oz servings) for both the MRT and the M groups. The MRT group and the RT groups performed a supervised periodized resistance training program consisting of supervised one-hour exercise sessions 3 d/wk (M, W, F) for 12 wk. Baseline dietary data was collected utilizing the NUT-P-FFQ and/or a 120 item FFQ developed by the Fred Hutchinson Cancer Research Center (Seattle, Washington). Body composition was measured in the morning after an overnight fast using dual-energy X-ray absorptiometry (DXA) with a total body scanner (Prodigy^TM, Lunar Corporation, Madison, WI). A whole body scan for bone density and lumbar spine scans were performed on all subjects. Maximal strength of the upper and lower body was assessed via a one-repetition maximum (1-RM) squat and bench press exercise protocols. Significance was set at P ≤ 0.05.Results: Significant differences in nutrient intakes between groups generally reflected the nutrient composition of milk with greater intakes of protein and improved nutrient adequacy for several B vitamins, vitamin A, vitamin D, calcium, magnesium, phosphorus, potassium, and zinc. Mean calcium intake was 758 and 1581 mg/d, in the non-milk and milk groups, respectively, with 100% of girls in the milk groups consuming > RDA of 1300 mg/d. There were no effects of milk on body composition or muscle performance, but resistance training had a main effect and significantly increased body mass, lean body mass, muscle strength, and muscle endurance. There was a main effect of milk and resistance training on several measures of bone mineral density (BMD). Changes in whole body BMD in the M, RT, MRT, and CON were 0.45, 0.52, 1.32, and -0.19%, respectively (P < 0.01).Conclusions: Over the course of 12 weeks the effects of 1300 mg/d of calcium in the form of fluid milk combined with a heavy resistance training program resulted in the additive effects of greater nutrient adequacy and BMD in adolescent girls. While further studies are needed, combining increased milk consumption with resistance training appears to optimize bone health in adolescent girls.

The National Osteoporosis Foundation's position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations

Lifestyle choices influence 20-40 % of adult peak bone mass. Therefore, optimization of lifestyle factors known to influence peak bone mass and strength is an important strategy aimed at reducing risk of osteoporosis or low bone mass later in life. The National Osteoporosis Foundation has issued this scientific statement to provide evidence-based guidance and a national implementation strategy for the purpose of helping individuals achieve maximal peak bone mass early in life. In this scientific statement, we (1) report the results of an evidence-based review of the literature since 2000 on factors that influence achieving the full genetic potential for skeletal mass; (2) recommend lifestyle choices that promote maximal bone health throughout the lifespan; (3) outline a research agenda to address current gaps; and (4) identify implementation strategies. We conducted a systematic review of the role of individual nutrients, food patterns, special issues, contraceptives, and physical activity on bone mass and strength development in youth. An evidence grading system was applied to describe the strength of available evidence on these individual modifiable lifestyle factors that may (or may not) influence the development of peak bone mass (Table 1). A summary of the grades for each of these factors is given below. We describe the underpinning biology of these relationships as well as other factors for which a systematic review approach was not possible. Articles published since 2000, all of which followed the report by Heaney et al. [1] published in that year, were considered for this scientific statement. This current review is a systematic update of the previous review conducted by the National Osteoporosis Foundation [1]. [Table: see text] Considering the evidence-based literature review, we recommend lifestyle choices that promote maximal bone health from childhood through young to late adolescence and outline a research agenda to address current gaps in knowledge. The best evidence (grade A) is available for positive effects of calcium intake and physical activity, especially during the late childhood and peripubertal years-a critical period for bone accretion. Good evidence is also available for a role of vitamin D and dairy consumption and a detriment of DMPA injections. However, more rigorous trial data on many other lifestyle choices are needed and this need is outlined in our research agenda. Implementation strategies for lifestyle modifications to promote development of peak bone mass and strength within one's genetic potential require a multisectored (i.e., family, schools, healthcare systems) approach.

Peak bone strength is influenced by calcium intake in growing rats

In this study we investigated the effect of supplementing the diet of the growing male rat with different levels of calcium (from low to higher than recommended intakes at constant Ca/P ratio), on multiple factors (bone mass, strength, size, geometry, material properties, turnover) influencing bone strength during the bone accrual period. Rats, age 28days were supplemented for 4weeks with high Ca (1.2%), adequate Ca (0.5%) or low Ca level (0.2%). Bone metabolism and structural parameters were measured. No changes in body weight or food intake were observed among the groups. As anticipated, compared to the adequate Ca intake, low-Ca intake had a detrimental impact on bone growth (33.63 vs. 33.68mm), bone strength (-19.7% for failure load), bone architecture (-58% for BV/TV) and peak bone mass accrual (-29% for BMD) due to the hormonal disruption implied in Ca metabolism. In contrast, novel, surprising results were observed in that higher than adequate Ca intake resulted in improved peak bone strength (106 vs. 184N/mm for the stiffness and 61 vs. 89N for the failure load) and bone material properties (467 vs. 514mPa for tissue hardness) but these effects were not accompanied by changes in bone mass, size, microarchitecture or bone turnover. Hormonal factors, IGF-I and bone modeling were also evaluated. Compared to the adequate level of Ca, IGF-I level was significantly lower in the low-Ca intake group and significantly higher in the high-Ca intake group. No detrimental effects of high Ca were observed on bone modeling (assessed by histomorphometry and bone markers), at least in this short-term intervention. In conclusion, the decrease in failure load in the low calcium group can be explained by the change in bone geometry and bone mass parameters. Thus, improvements in mechanical properties can be explained by the improved quality of intrinsic bone tissue as shown by nanoindentation. These results suggest that supplemental Ca may be beneficial for the attainment of peak bone strength and that multiple factors linked to bone mass and strength should be taken into account when setting dietary levels of adequate mineral intake to support optimal peak bone mass acquisition.

Life Course Perspective: evidence for the role of nutrition

The "Life Course Perspective" proposes that environmental exposures, including biological, physical, social, and behavioral factors, as well as life experiences, throughout the entire life span, influence health outcomes in current and future generations. Nutrition, from preconception to adulthood, encompasses all of these factors and has the potential to positively or negatively shape the individual or population health trajectories and their intergenerational differences. This paper applies the T2E2 model (timing, timeline, equity and environment), developed by Fine and Kotelchuck, as an overlay to examine advances in nutritional science, as well as the complex associations between life stages, nutrients, nutrigenomics, and access to healthy foods, that support the life course perspective. Examples of the application of nutrition to each of the four constructs are provided, as well as a strong recommendation for inclusion of nutrition as a key focal point for all health professionals as they address solutions to optimize health outcomes, both domestically and internationally. The science of nutrition provides strong evidence to support the concepts of the life course perspective. These findings lend urgency to the need to improve population health across the life span and over generations by ensuring ready access to micronutrient-dense foods, opportunities to balance energy intake with adequate physical activity and the need for biological, social, physical, and macro-level environments that support critical phases of human development. Recommendations for the application of the life course perspective, with a focus on the emerging knowledge of nutritional science, are offered in an effort to improve current maternal and child health programs, policies, and service delivery.

Bone mineral density in Nigerian children after discontinuation of calcium supplementation

BACKGROUND

Nigerian toddlers with low dietary calcium intakes increased forearm bone mineral density (BMD) after 18 months of calcium supplementation compared with placebo. However, it is not known if this bone mineral accretion is sustained after calcium supplement withdrawal. We therefore investigated the influence of prior calcium supplementation on forearm BMD 12 months after withdrawal of the supplement.

METHODS

Nigerian toddlers aged 12-18 months from three urban communities were enrolled in a controlled trial of calcium supplementation. Two communities received daily calcium supplements, one as calcium carbonate (400mg), and the other as ground fish (529±109 mg), for a duration of 18 months, and all three communities received vitamin A (2500 IU daily) as placebo. Forearm BMD was measured 5 times during 18 months of calcium supplementation and at 12 months after supplement withdrawal.

RESULTS

Of 647 children enrolled, 390 completed the trial of calcium supplementation and 261 of these returned for the final follow-up 12 months after discontinuation of supplementation. During the 18 months of supplementation, an adjusted model demonstrated that the increase in both distal and proximal forearm BMD over time was significantly greater in the calcium supplemented groups than in the placebo group (P<0.04). However, after supplement withdrawal, the increase in BMD over time was largely attenuated and only remained significant at the proximal forearm in the ground fish group (P=0.03).

CONCLUSION

The benefit of calcium supplementation on forearm BMD in young Nigerian children is not sustained after supplement withdrawal.

Calcium and bone

OBJECTIVE

Evaluate the role of calcium on bone health.

METHODS

Review of literatures on calcium and bone development during childhood and bone health in adulthood and older age.

RESULTS

Calcium intake influences skeletal calcium retention during growth and thus affects peak bone mass achieved in early adulthood. Increased calcium intake is associated with increased bone mineral accretion rate up to a threshold level in all ethnic groups. The minimum intake to achieve maximal retention is 1140 mg/day for white boys and 1300 mg/day for white girls. Calcium also plays a role in preventing bone loss and osteoporotic fractures in later life. Meta-analyses report that calcium supplementation reduce bone loss by 0.5-1.2% and the risk of fracture of all types by at least 10% in older people. Low calcium intake is a widespread problem across countries and age groups.

CONCLUSION

Adequate calcium intake throughout lifetime is important for bone health and the prevention of osteoporosis and related fractures.

Bone health and the female athlete triad in adolescent athletes

Peak bone mass (PBM) is a negative predictor of osteoporosis and lifelong fracture risk. Because osteoporosis is such a prevalent disease with life-threatening consequences, it is important to try to maximize PBM. Adolescence is a critical period for bone acquisition. This article discusses some of the differences in male and female skeletal development and modifiable factors that enhance bone accrual in this age group, particularly in athletes. Hormonal influences, effects of physical activity, and nutritional contributions are included, with a focus on the adolescent athlete. Emphasis is placed on the importance of appropriate energy availability in this age group. We also review prevention and treatment strategies for the female athlete triad (ie, the inter-relationship of decreased energy availability, menstrual irregularity, and low bone density) in adolescents and athletic women. Recommendations for maximizing bone density in both male and female adolescents are discussed.

Nutritional requirements during lactation. Towards European alignment of reference values: the EURRECA network

There is considerable variation in reference values for micronutrient intake during lactation across Europe. The European Micronutrients Recommendations Aligned project aims to harmonize dietary recommendations throughout Europe. Recommended nutrient intakes during lactation are based on limited data and are often extrapolated from known secretion of the nutrient in milk with adjustments for bioavailability, so that differences between values can be partly ascribed to differences in methodological approaches and how these approaches were applied. Few studies have considered the impact of lactation on the mother's nutritional status. Rather, focus has been placed on the influence of maternal nutritional status on the composition of her breast milk. Most common nutritional deficits in breast milk are the result of maternal deficiencies of the water-soluble vitamins, thiamine, riboflavin and vitamins B6 and B12. Other than maternal vitamin A status, which to some extent is reflected in breast milk, concentrations of fat-soluble vitamins and most minerals in breast milk are less affected by maternal status. Factors relating to suboptimal maternal nutritional status during lactation include maternal age, diet and lifestyle factors and spacing of consecutive births. Recent research is providing new knowledge on the micronutrient requirements of lactating women. Identifying needs for research and improving understanding of the differences in values that have been derived by various committees and groups across Europe will enhance transparency and facilitate the application of dietary recommendations in policy-making decision and their translation into recommendations for lactating women. Given the wide variation in breastfeeding practices across Europe, making nutritional recommendations for lactating women is complex and challenging. Thus, it is crucial to first examine the cultural practices within and across European populations and to assess its relevance before making recommendations.

Maximizing bone mineral mass gain during growth for the prevention of fractures in the adolescents and the elderly

Bone mass is a key determinant of fracture risk. Maximizing bone mineral mass during childhood and adolescence may contribute to fracture risk reduction during adolescence and possibly in the elderly. Although more than 60% of the variance of peak bone mass (PBM), the amount of bone present in the skeleton at the end of its maturation process, is genetically determined, the remainder is likely influenced by factors amenable to positive intervention, such as adequate dietary intake of dairy products as a natural source of calcium and proteins, vitamin D, and regular weight-bearing physical activity. Low calcium and vitamin D intakes are associated with negative effects on bone, including suboptimal PBM acquisition. As suggested by intervention studies, regular intake of dairy products may have positive and possibly sustained effects on bone mineral mass gain, contributing thereby to fracture risk reduction. Further evidence from intervention studies suggests that weight-bearing physical activities, such as jumping, may contribute to bone mineral mass gain in children. Optimizing PBM acquisition through dietary and physical exercise measures may represent a valuable primary method for the prevention of fractures.

Racial difference in the correlates of bone mineral content/density and age at peak among reproductive-aged women

SUMMARY

Racial/ethnic differences were observed in age at peak bone density and their correlates, with whites peaking at least 5 years earlier at the femoral neck than black and Hispanic women. Race-specific standards generated in this study could be useful when interpreting bone densitometry data in young women.

INTRODUCTION

The influence of race/ethnicity on bone measurements has not been widely examined. This study identifies age and amount of bone accumulated at peak density and their correlates by race/ethnicity.

METHODS

Bone mineral content (BMC) and bone mineral density (BMD) of the spine and femoral neck were measured by dual X-ray absorptiometry in 708 white, black, and Hispanic reproductive-aged women. Race-specific nonlinear models were used to describe the relationship between age and bone measurements, after adjusting for body weight and height. Log-transformed bone measurements were used to determine predictors based on multiple linear regression.

RESULTS

Predictors, which were race and site specific, included age, age at menarche, body weight, height, months of depot medroxyprogesterone acetate use, weight-bearing exercise, and alcohol use. Women of all races gained BMC and BMD at the spine up to 30-33 years of age. BMC and BMD of the femoral neck peaked among white women earlier (<or=16 years) than among blacks (BMC 22 years; BMD 21 years) and Hispanics (BMC 29 years; BMD 20 years).

CONCLUSION

Age at peak bone mass and its correlates differ by race/ethnicity. Race-specific standards generated in this study could be useful when interpreting bone densitometry data in young women.

Metabolismo do cálcio na fenilcetonúria

A Fenilcetonúria é um erro inato do metabolismo do aminoácido fenilalanina. O tratamento é essencialmente dietético e envolve uma restrição severa no consumo de alimentos contendo aminoácido fenilalanina. Embora a alimentação seja complementada com fórmulas a fim de suprir as necessidades de vitaminas, minerais e aminoácidos essenciais, carências nutricionais ainda ocorrem. Isto se deve, principalmente, à restrição de fontes protéicas, que acarreta deficiência na ingestão de diversos nutrientes, dentre eles o cálcio. O cálcio possui importante relação com a formação mineral óssea. Estudos recentes demonstram que portadores de fenilcetonúria apresentam freqüentemente osteopenia e fraturas, sendo a maior incidência em crianças acima de 8 anos de idade. O rápido aumento da estatura, a dieta deficiente em cálcio e níveis de aminoácido fenilalanina elevados têm sido descritos como os principais fatores para a aquisição de massa óssea inadequada. A suplementação de cálcio em crianças saudáveis mostrou um efeito positivo sobre a aquisição de massa óssea na fase da pré-puberdade. Assim, torna-se relevante compreender a necessidade da suplementação de cálcio em pacientes fenilcetonúria, a fim de favorecer o desenvolvimento ósseo esperado.

Milk, rather than other foods, is associated with vertebral bone mass and circulating IGF-1 in female adolescents

SUMMARY

Low calcium intake hampers bone mineral acquisition in adolescent girls. This study explores dietary calcium sources and nutrients possibly associated with vertebral mass. Milk intake is not influenced by genetic variants of the lactase gene and is positively associated with serum IGF-1 and with lumbar vertebrae mineral content and density.

INTRODUCTION

Low calcium intake hampers bone mineral acquisition during adolescence. We identified calcium sources and nutrients possibly associated with lumbar bone mineralization and calcium metabolism in adolescent girls and evaluated the possible influence of a genetic polymorphic trait associated with adult-type hypolactasia.

METHODS

Lumbar bone mineral content (BMC), bone mineral density (BMD), and area, circulating IGF-1, markers of bone metabolism, and -13910 LCT (lactase gene) polymorphism; and intakes of milk, dairy products, calcium, phosphorus, magnesium, proteins, and energy were evaluated in 192 healthy adolescent girls.

RESULTS

After menarche, BMC, BMD, serum IGF-1, and serum PTH were tightly associated with milk consumption, but not with other calcium sources. All four parameters were also associated with phosphorus, magnesium, protein, and energy from milk, but not from other sources. Girls with milk intakes below 55 mL/day have significantly lower BMD, BMC, and IGF-1 and higher PTH compared to girls consuming over 260 mL/day. Neither BMC, BMD, calcium intakes, nor milk consumption were associated with -13910 LCT polymorphism.

CONCLUSIONS

Milk consumption, preferably to other calcium sources, is associated with lumbar BMC and BMD in postmenarcheal girls. Aside from being a major source of calcium, milk provides phosphates, magnesium, proteins, and as yet unidentified nutrients likely to favor bone health.

Validation of a food frequency questionnaire for determining calcium and vitamin D intake by adolescent girls with anorexia nervosa

Assessing calcium and vitamin D intake becomes important in conditions associated with low bone density such as anorexia nervosa. Food records that assess intake over a representative time period are used in research and sometimes clinical settings. However, compliance in adolescents can be suboptimal. This study was undertaken to determine the validity of a food frequency questionnaire (FFQ) for assessing calcium and vitamin D intake in adolescent girls with anorexia nervosa and healthy girls compared to validated food records assessing intake during a 4-day period, the hypothesis being that intake would be adequately predicted by the FFQ. Thirty-six girls with anorexia nervosa and 39 healthy girls aged 12 to 18 years completed both the food record and the FFQ. An additional 31 subjects (20 with anorexia nervosa, 11 controls) completed the FFQ, but not the food record, and one girl with anorexia nervosa completed the food record, but not the FFQ. Subjects demonstrated greater compliance with the FFQ (99%) than the food record (71%). Daily calcium and vitamin D intake calculated using the food record and FFQ did not differ, although the FFQ tended to under-report vitamin D intake corrected for energy intake. Using quartile analysis, no gross misclassification was noted of calcium or vitamin D intake calculated using the food record or FFQ in girls with anorexia nervosa. Strong correlations were observed for daily vitamin D intake derived from the FFQ vs the food record, particularly in girls with anorexia nervosa (r=0.78, P<0.0001). Less robust correlations were observed for calcium intake (r=0.65, P<0.0001). The FFQ used in this study can be effectively used to assess daily calcium and vitamin D intake in adolescent girls with anorexia nervosa.

Importance of calcium, vitamin D and vitamin K for osteoporosis prevention and treatment

Throughout the life cycle the skeleton requires optimum development and maintenance of its integrity to prevent fracture. Bones break because the loads placed on them exceed the ability of the bone to absorb the energy involved. It is now estimated that one in three women and one in twelve men aged >55 years will suffer from osteoporosis in their lifetime and at a cost in the UK of > 1.7 pounds x 10(9) per year. The pathogenesis of osteoporosis is multifactorial. Both the development of peak bone mass and the rate of bone loss are determined by key endogenous and exogenous factors. Ca supplements appear to be effective in reducing bone loss in women late post menopause (>5 years post menopause), particularly in those with low habitual Ca intake (<400 mg/d). In women early post menopause (<5 years post menopause) who are not vitamin D deficient, Ca supplementation has little effect on bone mineral density. However, supplementation with vitamin D and Ca has been shown to reduce fracture rates in the institutionalised elderly, but there remains controversy as to whether supplementation is effective in reducing fracture in free-living populations. Re-defining vitamin D requirements in the UK is needed since there is evidence of extensive hypovitaminosis D in the UK. Low vitamin D status is associated with an increased risk of falling and a variety of other health outcomes and is an area that requires urgent attention. The role of other micronutrients on bone remains to be fully defined, although there are promising data in the literature for a clear link between vitamin K nutrition and skeletal integrity, including fracture reduction.

Impact of dairy products and dietary calcium on bone-mineral content in children: results of a meta-analysis

OBJECTIVE

Although calcium is essential for maintaining bone health in children, the optimum dietary intake of calcium in this age group, particularly in the form of dairy foods, is not well defined. A meta-analysis was conducted to examine the impact of dietary calcium/dairy supplementation on bone mineral content in this age group.

METHODS

Data were pooled from randomized controlled intervention trials and observational studies using previously described methods. The outcome of interest was a summary mean difference bone mineral content. Sensitivity analyses were employed to evaluate any observed statistical heterogeneity and to examine the influence of specific study characteristics on the summary estimate of effect.

RESULTS

Initially combining data from twenty-one randomized controlled trials (RCTs) using total body bone mineral content (TB-BMC) as the outcome of interest, yielded a non-statistically significant increase in TB-BMC of 2 g (supplemented versus controls). These data demonstrated substantial statistical heterogeneity with sensitivity analyses revealing that among study subjects with normal or near normal baseline dietary calcium/dairy intakes, supplemental dairy/calcium showed little impact on bone mineral content. Sensitivity analyses suggested that baseline calcium intake could potentially account for the statistical heterogeneity. Pooling the three reports utilizing low intake subjects yielded a statistically significant summary mean BMC of 49 g (24.0-76-6). Pooling two RCTs using calcium/dairy supplement plus vitamin D was also associated with an increase in lumbar spine BMC of, on average, 35 g (-6.8-41.8). The lack of data using BMC measurements at other anatomic sites as well as sparse data from non-randomized studies, precluded further statistical pooling.

CONCLUSION

Increased dietary calcium/dairy products, with and without vitamin D, significantly increases total body and lumbar spine BMC in children with low base-line intakes.

Bone mass and breast milk calcium concentration are associated with vitamin D receptor gene polymorphisms in adolescent mothers

Lactation-associated bone loss has been reported in adolescent mothers. Polymorphisms in the vitamin D receptor (VDR) gene may contribute to differences in the physiologic skeletal response to lactation in these mothers. We evaluated the influence of VDR gene polymorphisms ApaI, BsmI, and TaqI on bone mass, bone and calcium-related hormones, and breast milk calcium of lactating adolescents with habitually low calcium intake. Total body bone mineral content (TBMC), total body bone mineral density (TBMD), lumbar spine BMD (LSBMD), serum hormones [intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, insulin-like growth factor-I (IGF1), prolactin, and estradiol), and breast milk calcium were measured in 40 lactating Brazilian adolescents (15-18 y), and compared by VDR genotype subgroups after adjustment for calcium intake and postmenarcheal and lactational periods. TBMD and LSBMD Z scores were -0.55 +/- 1.01 and -1.15 +/- 1.48, respectively. LSBMD was higher (21%; P < 0.05) in adolescents with the aa genotype (n = 5) compared with those with the AA genotype (n = 7). TBMC and IGF1 were higher (23 and 50%, respectively; P < 0.05) in adolescents with tt (n = 4) than those with TT (n = 29) and Tt (n = 7) genotypes. Breast milk calcium and serum iPTH were higher (24 and 80%, respectively; P < 0.05) in adolescents with bb (n = 8) compared with those with BB (n = 21) genotype. These results indicate that bone mass and breast milk calcium are significantly associated with VDR genotypes in lactating Brazilian adolescents. Those with aa and tt genotypes had a better bone status and those with bb genotype had greater breast milk calcium.

Calcium supplements in healthy children do not affect weight gain, height, or body composition

OBJECTIVE

Calcium intake is a potential factor influencing weight gain and may reduce body weight, but the evidence for this in children is conflicting. The aim of this study was to use data from randomized controlled trials to determine whether calcium supplementation in healthy children affects weight or body composition.

RESEARCH METHODS AND PROCEDURES

This study is a systematic review. We identified potential studies by searching the following electronic bibliographic databases: CENTRAL, MEDLINE, EMBASE, CINAHL, AMED, MANTIS, ISI Web of Science, Food Science and Technology Abstracts, and Human Nutrition up until April 1, 2005 and hand-searched relevant conference abstracts. Studies were included if they were placebo-controlled randomized controlled trials of calcium supplementation, with at least 3 months of supplementation, in healthy children and with outcome measures including weight. Meta-analyses were performed using fixed effects models and weighted mean differences for weight and height and standardized mean differences (SMDs) for body composition measures.

RESULTS

There were no statistically significant effects of calcium supplementation on weight [+0.14 kg; 95% confidence interval (CI), -0.28, +0.57 kg], height (+0.22 cm; 95% CI, -0.30, +0.74 cm), body fat (SMD, +0.04; 95% CI, -0.08, +0.15), or lean mass (SMD, +0.14; 95% CI, -0.03, +0.31).

DISCUSSION

There is no evidence to support the use of calcium supplementation as a public health intervention to reduce weight gain or body fat in healthy children. Although our results do not rule out an effect of dietary supplementation with dairy products on weight gain or body composition, there is little evidence to support this hypothesis.

Calcium and body fat in peripubertal girls: cross-sectional and longitudinal observations

OBJECTIVE

The objective was to investigate whether calcium intake is independently associated with body fat in peripubertal girls.

RESEARCH METHODS AND PROCEDURES

A total of 45 healthy premenarcheal girls (initially 10.5 +/- 0.6 years of age) completed a 2-year prospective observational study. Percent body fat and trunk fat (by DXA), height, weight, maturational stage, and eating attitudes (children's Eating Attitudes Test [EAT]) were measured at baseline and at 1 and 2 years. Physical activity (by questionnaire) and calcium intake (by calcium-specific food frequency questionnaire and 3-day food records) were assessed at 6-month intervals.

RESULTS

Girls with 2-year mean calcium intake below and above the median had similar age, height, lean mass, and maturational stage at baseline, but girls below the median had significantly higher baseline percentage body fat (29.3 +/- 10.3% vs. 22.0 +/- 6.8%, p < 0.01) and trunk fat (24.2 +/- 10.6% vs. 15.8 +/- 6.8%, p < 0.01). However, differences were no longer significant when covariates (most notably children's EAT dieting score) were considered. Regression analysis revealed that dieting score was a consistent positive predictor of percentage body and trunk fat at all cross-sectional time-points, accounting for >20% of the variance, but did not predict 2-year change in percentage fat. Calcium intake did not enter longitudinal regression equations for 2-year change in percentage fat.

DISCUSSION

In this group of girls, an inverse cross-sectional association between calcium intake and body fat appeared to result from avoidance of foods high in calcium by girls who were concerned about their body weight or shape. Calcium intake was not associated with change in fat over time.

Effect of calcium fortified milk supplementation with or without vitamin K on biochemical markers of bone turnover in premenopausal women

OBJECTIVE

We compared the effect of supplementation with a fortified skimmed milk product (high calcium skim milk) with or without added phylloquinone (vitamin K(1)) on markers of bone formation and resorption in premenopausal women.

METHODS

Eighty-two women 20 to 35 y of age were randomly allocated to three groups. Two groups received two daily servings of high calcium skim milk (1000 mg/d of extra calcium) with or without added phylloquinone (80 microg/d) for 16 wk, and a third control group received no supplementation. Bone density was assessed at baseline and the bone markers, total osteocalcin, type I N-terminal procollagen peptide, and cross-linked C-telopeptide of type I collagen were measured at baseline and at weeks 2, 12, and 16. Serum phylloquinone and undercarboxylated osteocalcin were measured in the control and vitamin K-supplemented groups at weeks 0 and 16.

RESULTS

Baseline values for age, body mass index, and bone density did not differ across groups. In vitamin K-supplemented women, mean serum phylloquinone concentrations increased from 0.27 to 0.76 microg/L (P < 0.05) and undercarboxylated osteocalcin concentrations decreased from 9.68 to 4.46 microg/L (P < 0.05) over 16 wk. Plasma cross-linked C-telopeptide of type I collagen, total osteocalcin, and type I N-terminal procollagen peptide levels decreased significantly in both supplemented groups compared with the control group over 16 wk (cross-linked C-telopeptide of type I collagen >30%, total osteocalcin and type I N-terminal procollagen peptide >15%).

CONCLUSION

Fortified milk supplementation in premenopausal women reduced bone turnover significantly. Phylloquinone fortification substantially improved vitamin K status but had no demonstrable additive effect on bone turnover in this short-term study.

How much calcium is in your drinking water? A survey of calcium concentrations in bottled and tap water and their significance for medical treatment and drug administration

INTRODUCTION

Different forms of water vary in calcium content. High divalent ion (i.e., Ca(2+), Mg(2+), etc.) concentration is deleterious to the absorption and efficacy of the bisphosphonate group of drugs in osteoporosis treatment. Water with high calcium concentration may also present an alternate pathway of calcium administration. In either case, knowing the actual concentration is critical.

HYPOTHESIS

The current paper is a surveillance study. We hypothesize that there is considerable variation in the calcium concentrations in the various water sources: tap water from US and Canadian cities of different regions and purified, spring, and mineral bottled waters. In addition, we hypothesize that the water filter removes a significant amount of minerals including calcium from the water.

METHODOLOGY

Calcium concentrations in various city tap waters, as well as an assorted number of bottled waters, were determined through the direct inspection of scientific data. The effect of filtering was also determined by mineral analysis of mineral water directly before and after filtration.

RESULT

The calcium concentration of water varies from 1 to 135 mg/L across the USA and Canada. Most spring waters were found to have a relatively low calcium concentration, with an average of 21.8 mg/L. Purified waters contain a negligible calcium concentration. Mineral waters, on the other hand, were generally found to contain higher calcium concentrations, an average of 208 mg/L of calcium. Filtration was found to remove a considerable amount of calcium from the water, removing 89% on average.

CONCLUSION

Calcium concentration in water varied substantially from different sources in the USA and Canada. Bottled waters presented with concentrations of calcium covering a very large range. Certain tap and bottled waters present with concentrations of calcium sufficient to exhibit a deleterious effect on bisphosphonate treatment. Alternatively, certain waters may be used as a source of calcium that may provide over 40% of the recommended daily intake for calcium.

Calcium supplementation for improving bone mineral density in children

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.

OBJECTIVES

. 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.

SEARCH STRATEGY

We searched CENTRAL, (Cochrane Central Register of Controlled Trials) (Issue 3, 2005), MEDLINE (1966 to 1 April 2005), EMBASE (1980 to 1 April 2005), CINAHL (1982 to 1 April 2005), AMED (1985 to 1 April 2005), MANTIS (1880 to 1 April 2005) ISI Web of Science (1945 to 1 April 2005), Food Science and Technology Abstracts (1969 to 1 April 2005) and Human Nutrition (1982 to 1 April 2005). Conference abstract books (Osteoporosis International, Journal of Bone and Mineral Research) were hand-searched.

SELECTION CRITERIA

Randomised controlled trials of calcium supplementation (including by food sources) compared with placebo, with a treatment period of at least 3 months in children without co-existent medical conditions affecting bone metabolism. Outcomes had to include areal or volumetric BMD, bone mineral content (BMC), or in the case of studies using quantitative ultrasound, broadband ultrasound attenuation and ultrasonic speed of sound, measured after at least 6 months of follow-up.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data including adverse events. We contacted study authors for additional information.

MAIN RESULTS

The 19 trials included 2859 participants, of which 1367 were randomised to supplementation and 1426 to placebo. There was no heterogeneity in the results of the main effects analyses to suggest that the studies were not comparable. There was no effect of calcium supplementation on femoral neck or lumbar spine BMD. There was a small effect on total body BMC (standardised mean difference (SMD) +0.14, 95% CI+0.01, +0.27) and upper limb BMD (SMD +0.14, 95%CI +0.04, +0.24). Only the effect in the upper limb persisted after supplementation ceased (SMD+0.14, 95%CI+0.01, +0.28). This effect is approximately equivalent to a 1.7% greater increase in supplemented groups, which at best would reduce absolute fracture risk in children by 0.1-0.2%per annum. There was no evidence of effect modification by baseline calcium intake, sex, ethnicity, physical activity or pubertal stage. Adverse events were reported infrequently and were minor.

AUTHORS' CONCLUSIONS

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 clinically 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 cannot be extrapolated to children with medical conditions affecting bone metabolism.

Fractional calcium absorption is increased in girls with Rett syndrome

BACKGROUND

Rett syndrome (RTT), an X-linked neurodevelopmental disorder primarilyaffecting girls, is characterized in part by osteopenia and increased risk of skeletal fractures. We hypothesized that decreased intestinal calcium (Ca) absorption relative to dietary Ca intake and increased renal Ca excretion might cause these problems in RTT.

OBJECTIVE

We measured fractional Ca absorption, urinary Ca loss, dietary Ca intake, and the hormonal factors regulating Ca metabolism to determine whether abnormalities in Ca balance might relate to poor bone mineralization in RTT girls and to evaluate the contribution of these factors to the overall dietary Ca needs of RTT girls.

STUDY DESIGN

Ten RTT girls and 10 controls, matched for age, sex, and pubertal status, were given a 3 day constant Ca diet that mimicked their habitual intakes. At the end of each dietary period, girls received single doses of Ca (intravenous) and Ca (oral). Fractional urinary excretion of Ca, Ca, 24 hour urinary Ca, and urinary cortisol excretion were determined. Serum Ca, phosphorous, alkaline phosphatase, vitamin D metabolites, parathyroid hormone (PTH), and osteocalcin were measured in the postabsorptive state. Bone mineral content (BMC) was measured by dual-energy x-ray absorptiometry.

RESULTS

Fractional Ca absorption was significantly higher in RTT than in control girls (mean +/- SDp, 52 vs. 33 +/- 13%). Dietary Ca intake (mean +/- SDp, 1,100 vs. 1,446 +/- 440 g/d) and net Ca absorption (mean +/- SDp, 513 vs. 362 +/- 306 mg/d) did not differ significantly between RTT and controls, respectively. Although urinary Ca excretion did not differ between groups, the increased urinary Ca:creatinine ratio (mean +/- SDp, 0.39 vs. 0.23 +/- 0.38) was consistent with clinical hypercalcuria and paralleled the significantly increased urinary cortisol excretion (mean +/- SDp, 3.1 vs. 1.7 +/- 1.1 mg/kg lean body mass per day) in the RTT girls. BMC was significantly lower in RTT than in controls (mean +/- SDp, 527 vs. 860 +/- 275 g). Serum Ca, P, alkaline phosphatase, vitamin D metabolites, PTH, and osteocalcin concentrations did not differ between the groups.

CONCLUSION

Fractional Ca absorption showed a compensatory increase in the presence of adequate dietary Ca intakes, mild hypercalcuria, and pronounced bone mineral deficits in RTT girls. Whether supplemental dietary Ca could enhance fractional Ca absorption and improve bone mineralization in RTT girls is unknown.

Calcium Supplementation Trials and Bone Mass Development in Children, Adolescents, and Young Adults

The development of bone mass during childhood through young adulthood is an important determinant of bone health later in life, and calcium is the major building block. Most randomized, double-blind, placebo-controlled trials of calcium supplementation have been done in girls; however, calcium supplementation in boys has been investigated in recent studies. Positive short-term effects on bone measures during growth has been shown in boys and girls, particularly in weight-bearing appendicular bone, although the lifelong effect is not certain.

Growth, bone mass, and vitamin D status of Chinese adolescent girls 3 y after withdrawal of milk supplementation

BACKGROUND

A 2-y school milk intervention trial showed that 330 mL of a dietary milk supplement (fortified with calcium alone or with both calcium and vitamin D) enhanced the growth and bone mineral accretion of Chinese girls aged 10 y at baseline. Girls who received milk fortified with both calcium and vitamin D also had better vitamin D status than did girls who received nothing or girls who received milk fortified only with calcium.

OBJECTIVE

The aim was to evaluate whether these effects were sustained 3 y after supplement withdrawal.

DESIGN

Anthropometric measures and dietary intake were reassessed in 501 of the 698 girls whose data had been studied at the end of the intervention. As in the intervention phase, total-body bone mineral content and bone mineral density and serum 25-hydroxyvitamin D concentrations were measured in half of these subjects.

RESULTS

At follow-up, 99% of girls had reached menarche, at a mean (+/-SD) menarcheal age of 12.1 +/- 1.1 y. No significant differences in the timing of menarche were observed between the 3 groups (P = 0.6). No significant differences in the changes of total-body bone mineral content and bone mineral density since baseline were observed between the groups. The group receiving calcium-fortified milk had significantly greater gains in sitting height (0.9 +/- 0.3%; P = 0.02) than did the control group. The group that received calcium- and vitamin D-fortified milk had 17.1 +/- 6.7% lower serum 25-hydroxyvitamin D concentrations than did the control group (P = 0.04), but the difference was attenuated by additional adjustment for physical activity level (14.2 +/- 6.7%; P = 0.08).

CONCLUSION

Milk supplementation during early puberty does not have long-lasting effects on bone mineral accretion.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

Effects of calcium, dairy product, and vitamin D supplementation on bone mass accrual and body composition in 10-12-y-old girls: a 2-y randomized trial

BACKGROUND

Little is known about the relative effectiveness of calcium supplementation from food or pills with or without vitamin D supplementation for bone mass accrual during the rapid growth period.

OBJECTIVE

The purpose was to examine the effects of both food-based and pill supplements of calcium and vitamin D on bone mass and body composition in girls aged 10-12 y.

DESIGN

This placebo-controlled intervention trial randomly assigned 195 healthy girls at Tanner stage I-II, aged 10-12 y, with dietary calcium intakes <900 mg/d to 1 of 4 groups: calcium (1000 mg) + vitamin D3 (200 IU), calcium (1000 mg), cheese (1000 mg calcium), and placebo. Primary outcomes were bone indexes of the hip, spine, and whole body by dual-energy X-ray absorptiometry and of the radius and tibia by peripheral quantitative computed tomography.

RESULTS

With the use of intention-to-treat or efficacy analysis, calcium supplementation with cheese resulted in a higher percentage change in cortical thickness of the tibia than did placebo, calcium, or calcium + vitamin D treatment (P = 0.01, 0.038, and 0.004, respectively) and in higher whole-body bone mineral density than did placebo treatment (P = 0.044) when compliance was >50%. With the use of a hierarchical linear model with random effects to control for growth velocity, these differences disappeared.

CONCLUSIONS

Increasing calcium intake by consuming cheese appears to be more beneficial for cortical bone mass accrual than the consumption of tablets containing a similar amount of calcium. Diverse patterns of growth velocity may mask the efficacy of supplementation in a short-term trial of children transiting through puberty.

Calcium and vitamin D status in the adolescent: key roles for bone, body weight, glucose tolerance, and estrogen biosynthesis

This review paper highlights a number of important public health issues related to calcium and vitamin D status in adolescents. Dietary calcium intake has declined dramatically over the past several decades among adolescents, and inadequate serum vitamin D levels have been documented in up to 54% of teens. A recent trend of decreasing consumption of dairy foods, especially milk, has contributed to this problem. Calcium and vitamin D are critically important for bone mineral accrual during adolescence, and altered calcium homeostasis can impact optimal bone acquisition. Serum and cellular calcium concentrations are controlled, in part, by the actions of vitamin D. Newer research seeks to clarify the potential functions of calcium and vitamin D in the regulation of body weight, glucose tolerance, and ovarian function. Numerous observational studies have noted an inverse association between body weight, percent body fat, and dietary calcium intake; however, clinical trials evaluating the affect of increased calcium on weight loss have been mixed. There is a reduced incidence of insulin resistance syndrome with increasing dairy intake in overweight individuals, and serum 25 hydroxyvitamin D levels are positively correlated with insulin sensitivity. Vitamin D receptor is expressed in all calcium-regulated tissues, including the ovary; thus, calcium and vitamin D appear to be necessary for full ovarian function. This review paper will examine the important role of vitamin D and calcium in the regulation of bone, weight, glucose tolerance, and estrogen biosynthesis.

Osteoporosis: the role of micronutrients

Osteoporosis and low bone mass are currently estimated to be a major public health threat. Adequate nutrition plays a major role in the prevention and treatment of osteoporosis; the micronutrients of greatest importance are calcium and vitamin D. Calcium has been shown to have beneficial effects on bone mass at all ages, although the results are not always consistent. Higher doses than the current US recommendation (600 IU) of vitamin D in the elderly (age > or = 65 y) may actually be required for optimal bone health (800-1000 IU/d). The elderly can clearly benefit from increased vitamin D intakes; however, the potential importance of vitamin D in peak bone mass is just being investigated. Vitamin D has been related to falls, with supplementation reducing the number of falls. There are clear fracture benefits demonstrated in randomized clinical trials of calcium and vitamin D supplementation. The other micronutrient needs for optimizing bone health can be easily met by a healthy diet that is high in fruits and vegetables to ensure adequate intakes for magnesium, potassium, vitamin C, vitamin K, and other potentially important nutrients. Healthcare professionals need to be aware of the importance of adequate calcium and vitamin D intakes (easily monitored by serum 25(OH)D) for optimal bone health, as well as the prevention of falls and fractures. In addition, a healthy diet that includes 5 servings a day of fruits and vegetables should optimize the intake of micronutrients required for bone health.

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%.

Bone mass is recovered from lactation to postweaning in adolescent mothers with low calcium intakes

BACKGROUND

Adolescent mothers may be at increased risk of irreversible bone loss during pregnancy and lactation, particularly when calcium intake is low.

OBJECTIVE

Longitudinal changes in bone mass from lactation to postweaning were evaluated in 10 adolescent mothers aged 15-18 y who habitually consumed <500 mg Ca/d.

DESIGN

Total-body bone mineral content (TBBMC), total-body bone mineral density (TBBMD), and lumbar spine bone mineral density (LSBMD) were measured at lactation (6-24 wk postpartum) and after weaning (12-30 mo postpartum). Serum hormones (intact parathyroid hormone, estradiol, and prolactin), serum calcium, and markers of bone turnover [urinary N-telopeptide cross-linking region of type I collagen (NTx) and plasma activity of bone alkaline phosphatase] were measured at lactation.

RESULTS

TBBMC, total calcium content, TBBMD, and LSBMD increased from lactation to postweaning (P < 0.01). TBBMD and LSBMD were, respectively, 3.6% and 9.7% lower than predicted at lactation and 0.3% and 4.8% lower than predicted in the postweaning period. The increase in age-matched TBBMD adequacy was correlated with the time after resumption of menses (r = 0.86, P < 0.01). Calcium accretion from lactation to postweaning correlated negatively with estradiol (r = -0.86) and prolactin (r = -0.69) and positively with intact parathyroid hormone (r = 0.72) and NTx (r = 0.84) measured at lactation (P < 0.05).

CONCLUSIONS

It appears that adolescent mothers with habitually low calcium intakes recover from lactation-associated bone loss after weaning. The rate of bone accretion, however, may not be sufficient to attain peak bone mass at maturity. Hormones regulating bone turnover during lactation may influence bone recovery in adolescent mothers.

Current advances in bone health of disabled children

PURPOSE OF REVIEW

Bone health is now recognized to contribute to overall lifetime management of children, adolescents, and adults with disabling conditions including physical and intellectual disability and with many chronic disease processes. Such disorders have multiple components, with aspects of care covering a wide number of specialist practices. This review will highlight advances in understanding the nature of bone mass accumulation through childhood and adolescence, the impingement of a spectrum of chronic and disabling diseases and their treatments on bone, and will address current approaches to interpretation of bone mass in the growing skeleton and interventional strategies for improving outcomes for this group.

RECENT FINDINGS

Increased skeletal fragility in the disabled child is well recognized. Insights into the contributions of skeletal size and bone strength in males and females have altered interpretation of data, allowing a new focus on determinants of future bone health, particularly with regard to the contributions of growth and puberty. Strategies to address bone health including public and medical education concerning consumption of calcium, appropriate selection of vitamin D preparations, pubertal contribution to phases of growth and possible specialist use of newer drugs, such as bisphosphonates where indicated, are changing the outlook for this large group.

SUMMARY

Implications of these changed understandings provide a new focus on maximizing bone mass accumulation by the end of adolescence within the constraints of what is possible to achieve for an individual and for provision of an holistic approach to bone health.

Comparison of narrow-angle fan-beam and pencil-beam densitometers: in vivo and phantom study of the effect of bone density, scan mode, and tissue depth on spine measurements

This study compared the in vivo and in vitro performances of the Lunar MD and Prodigy dual-energy X-ray absorptiometers (DXAs). Ten volunteers and three different spine phantoms were studied to determine the effect of scan mode, tissue depth, and bone density on measures of spine bone area (BA), bone mineral content (BMC), and areal bone mineral density (BMD). These studies demonstrated that the choice of scan mode was most important for the Prodigy and for subjects who were thin, obese, or had low BMD. Increase in tissue depth caused an increase in measured BMC and BMD for the MD but had a small effect on Prodigy results if the appropriate scan mode was selected. BA was dependent on the BMD for both DXA systems. Results using a hydroxyapatite phantom demonstrated that after correcting for the calibration of Lunar systems, the BMC measured by the MD and Prodigy was similar to the calculated hydroxyapatite content of the phantom. In vivo studies confirmed the in vitro findings and demonstrated that even when the appropriate scan mode was selected, the BMC, BMD, and T-scores were significantly higher on the Prodigy than MD.