The relationship of dietary and lifestyle factors to bone mineral indexes in children

Assessment of Bone Health Using Dual-Energy X-Ray Absorptiometry (DEXA) And Its Association with Dietary Intakes, Serum Vitamin D Levels, and Anthropometric Measures in Healthy Urban Preschool Children

OBJECTIVES

To generate reference data for bone mineral content (BMC) and bone mineral density (BMD) measures among apparently healthy children aged 4-5 y and to study the relationship of BMC and BMD with age, sex, anthropometric measures, dietary intakes, and serum vitamin D levels.

METHODS

This cross-sectional study was conducted among 219 urban preschool children, aged 4.0-5.11 y. Bone health (BMC and BMD) was measured using dual energy X-ray absorptiometry (DEXA). Anthropometric parameters were measured using standard methodology. The 24-h dietary recall method was used to assess the dietary intake of the children. Serum vitamin D levels were assessed using the ELISA kit method. Percentiles for BMC and BMD for each age and sex were constructed using the lambda-mu-sigma (LMS) method.

RESULTS

The mean BMD and BMC among children was 0.75 ± 0.04 g/cm2 and 544.9 ± 87.6 g, respectively, and were significantly different by age and sex category. The BMC and BMD values of boys and girls increased with age, with boys having significantly higher values. A significant positive correlation was observed for BMC and BMD with anthropometric measures and dietary intake of calcium, phosphorous, protein, zinc, and B vitamins.

CONCLUSION

This study developed smoothed percentile curves for BMC and BMD in preschool children, which could be used as reference values for children from India.

Effects of vitamin D and high dairy protein intake on bone mineralization and linear growth in 6- to 8-year-old children: the D-pro randomized trial

BACKGROUND

Vitamin D and dairy protein may stimulate bone mineralization and linear growth in children, but previous studies show inconsistent results and have not examined their combined effects.

OBJECTIVES

To investigate combined and separate effects of vitamin D supplementation and high-protein (HP) compared with normal-protein (NP) yogurt intake on children's bone mineralization and linear growth.

METHODS

In a 2 × 2-factorial trial, 200 healthy, 6- to 8-year-old, Danish, children with light skin (55°N) were randomized to 20 µg/d vitamin D3 or placebo and to substitute 260 g/d dairy with HP (10 g protein/100 g) or NP (3.5 g protein/100 g) yogurt for 24 weeks during an extended winter. Outcomes were total body less head (TBLH) and lumbar spine bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) by dual-energy X-ray absorptiometry, height, and biomarkers of bone turnover and growth. The primary outcome was TBLH BMD.

RESULTS

In total, 184 children (92%) completed the study. The baseline serum 25-hydroxyvitamin D was 80.8 ± 17.2 nmol/L, which increased by 7.2 ± 14.1 nmol/L and decreased by 32.3 ± 17.5 nmol/L with vitamin D and placebo, respectively. The baseline protein intake was 15.4 ± 2.4 energy percentage (E%), which increased to 18.3 ± 3.4 E% with HP. There were no vitamin D-yogurt interactions and no main effects of either intervention on TBLH BMD. However, vitamin D supplementation increased lumbar spine BMD and TBLH BMC compared to placebo, whereas HP groups showed lower increments in lumbar spine BMD, TBLH BMC and BA, and plasma osteocalcin compared to NP groups. Height, growth factors, and parathyroid hormone levels were unaffected.

CONCLUSIONS

Although there were no effects on whole-body BMD, vitamin D increased bone mass and spinal BMD, whereas high compared with normal dairy protein intake had smaller incremental effects on these outcomes. This supports a recommended vitamin D intake of around 20 µg/d during winter but not use of HP dairy products for improved bone mineralization among healthy, well-nourished children. This trial was registered at clinicaltrials.gov as NCT03956732.

Dietary protein and bone health: towards a synthesised view

The present paper reviews published literature on the relationship between dietary protein and bone health. It will include arguments both for and against the anabolic and catabolic effects of dietary protein on bone health. Adequate protein intake provides the amino acids used in building and maintaining bone tissue, as well as stimulating the action of insulin-like growth factor 1, which in turn promotes bone growth and increases calcium absorption. However, the metabolism of dietary sulphur amino acids, mainly from animal protein, can lead to increased physiological acidity, which may be detrimental for bone health in the long term. Similarly, cereal foods contain dietary phytate, which in turn contains phosphate. It is known that phosphate consumption can also lead to increased physiological acidity. Therefore, cereal products may produce as much acid as do animal proteins that contain sulphur amino acids. The overall effect of dietary protein on physiological acidity, and its consequent impact on bone health, is extremely complex and somewhat controversial. The consensus is now moving towards a synthesised approach. Particularly, how anabolic and catabolic mechanisms interact; as well as how the context of the whole diet and the type of protein consumed is important.

Effects of Dairy Product Consumption on Height and Bone Mineral Content in Children: A Systematic Review of Controlled Trials

There is a physiological basis for the roles of selected nutrients, especially proteins, calcium, and vitamin D, in growth and development, which are at a maximum during the pediatric period. Milk and dairy products are particularly rich in this group of nutrients. The present systematic review summarizes the available evidence relating dairy product intake with linear growth and bone mineral content in childhood and adolescence. A search was conducted in the MEDLINE (via PubMed) and SCOPUS databases following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and included intervention-controlled clinical trials with dairy products in children from 1 January, 1926 to 30 June, 2018. The risk of bias for each study was assessed using the Cochrane methodology. The number of study participants, the type of study and doses, the major outcomes, and the key results of the 13 articles included in the review are reported. The present systematic review shows that supplementing the usual diet with dairy products significantly increases bone mineral content during childhood. However, the results regarding a possible relation between dairy product consumption and linear growth are inconclusive.

Dietary protein and bone health across the life-course: an updated systematic review and meta-analysis over 40 years

We undertook a systematic review and meta-analysis of published papers assessing dietary protein and bone health. We found little benefit of increasing protein intake for bone health in healthy adults but no indication of any detrimental effect, at least within the protein intakes of the populations studied. This systematic review and meta-analysis analysed the relationship between dietary protein and bone health across the life-course. The PubMed database was searched for all relevant human studies from the 1st January 1976 to 22nd January 2016, including all bone outcomes except calcium metabolism. The searches identified 127 papers for inclusion, including 74 correlational studies, 23 fracture or osteoporosis risk studies and 30 supplementation trials. Protein intake accounted for 0-4% of areal BMC and areal BMD variance in adults and 0-14% of areal BMC variance in children and adolescents. However, when confounder adjusted (5 studies) adult lumbar spine and femoral neck BMD associations were not statistically significant. There was no association between protein intake and relative risk (RR) of osteoporotic fractures for total (RR_(random) = 0.94; 0.72 to 1.23, I² = 32%), animal (RR _(random) = 0.98; 0.76 to 1.27, I² = 46%) or vegetable protein (RR _(fixed) = 0.97 (0.89 to 1.09, I² = 15%). In total protein supplementation studies, pooled effect sizes were not statistically significant for LSBMD (total n = 255, MD_(fixed) = 0.04 g/cm² (0.00 to 0.08, P = 0.07), I² = 0%) or FNBMD (total n = 435, MD_(random) = 0.01 g/cm² (-0.03 to 0.05, P = 0.59), I² = 68%). There appears to be little benefit of increasing protein intake for bone health in healthy adults but there is also clearly no indication of any detrimental effect, at least within the protein intakes of the populations studied (around 0.8-1.3 g/Kg/day). More studies are urgently required on the association between protein intake and bone health in children and adolescents.

Milk consumption, dietary calcium intake and nutrient patterns from adolescence to early adulthood and its effect on bone mass: the 1993 Pelotas (Brazil) birth cohort

The objective of this study is to evaluate the effect of milk consumption, dietary calcium intake and nutrient patterns (bone-friendly and unfriendly patterns) from late adolescence to early adulthood, on bone at 22 years of age. Cross-sectional analysis was performed with 3,109 participants from 1993 Pelotas (Brazil) birth cohort in the follow-ups of 18 and 22 years of age. Bone mineral density (BMD) of the lumbar spine, right femur and whole body were assessed at 22 years using a dual-energy X-ray absorptiometry (DXA). The exposure variables (dietary calcium, milk and nutrient patterns) were created by combining the consumption frequencies between the two follow-ups (always low, moderate, high, increase or decrease). Multiple linear regressions were performed, stratified by sex. In the right femur site, men classified into the “always high” (mean = 1.148g/cm²; 95%CI: 1.116; 1.181) and “increased” categories of milk consumption (mean = 1.154g/cm²; 95%CI: 1.135; 1.174) presented a slightly low BMD comparing with low (mean = 1.190g/cm²; 95%CI: 1.165; 1.215) and moderate (mean = 1.191g/cm²; 95%CI: 1.171; 1.210) categories. In addition, men always classified in the highest tertile of the “bone-unfriendly” pattern presented the lowest mean of whole body BMD (mean = 1.25g/cm²; 95%CI: 1.243; 1.266). No associations were observed between the categories of dietary calcium intake and “bone-friendly” pattern and each of the three BMD outcomes. These results point to the fact that diets composed of inhibiting foods/nutrients can contribute negatively to bone health.

Whole egg consumption and cortical bone in healthy children

Eggs contain bioactive compounds thought to benefit pediatric bone. This cross-sectional study shows a positive link between childhood egg intake and radius cortical bone. If randomized trials confirm our findings, incorporating eggs into children's diets could have a significant impact in preventing childhood fractures and reducing the risk of osteoporosis.

INTRODUCTION

This study examined the relationships between egg consumption and cortical bone in children.

METHODS

The cross-sectional study design included 294 9-13-year-old black and white males and females. Three-day diet records determined daily egg consumption. Peripheral quantitative computed tomography measured radius and tibia cortical bone. Body composition and biomarkers of bone turnover were assessed using dual-energy X-ray absorptiometry and ELISA, respectively.

RESULTS

Egg intake was positively correlated with radius and tibia cortical bone mineral content (Ct.BMC), total bone area, cortical area, cortical thickness, periosteal circumference, and polar strength strain index in unadjusted models (r = 0.144-0.224, all P < 0.050). After adjusting for differences in race, sex, maturation, fat-free soft tissue mass (FFST), and protein intakes, tibia relationships were nullified; however, egg intake remained positively correlated with radius Ct.BMC (r = 0.138, P = 0.031). Egg intake positively correlated with total body bone mineral density, BMC, and bone area in the unadjusted models only (r = 0.119-0.224; all P < 0.050). After adjusting for covariates, egg intake was a positive predictor of radius FFST (β = 0.113, P < 0.050) and FFST was a positive predictor of Ct.BMC (β = 0.556, P < 0.050) in path analyses. There was a direct influence of egg on radius Ct.BMC (β = 0.099, P = 0.035), even after adjusting for the mediator, FFST (β = 0.137, P = 0.020). Egg intake was positively correlated with osteocalcin in both the unadjusted (P = 0.005) and adjusted (P = 0.049) models.

CONCLUSION

If the positive influence of eggs on Ct.BMC observed in this study is confirmed through future randomized controlled trials, whole eggs may represent a viable strategy to promote pediatric bone development and prevent fractures.

Sedentary behaviour and bone health in children, adolescents and young adults: a systematic review

Sedentary behaviour (SB) is increasing in Western societies and some studies suggest a deleterious effect of SB on bone. The aim of this systematic review was to examine the association between SB and bone health in children, adolescents and young adults. Electronic databases (PubMed, MEDLINE, PsycINFO and Science Citation Index) were searched for relevant articles up to January 9, 2017. Studies were included when results on bone health (e.g. strength, mass and structure) and either subjectively (questionnaires) or objectively (accelerometry) measured SB were reported in healthy participants ≤24 years. Two reviewers independently screened titles and abstracts for eligibility, rated methodological quality and extracted data. Seventeen observational studies were included. Several studies that used DXA or quantitative ultrasound suggested that objectively measured SB was negatively associated with lower extremity bone outcomes, such as femoral neck bone mineral density. The magnitude of this negative association was small and independent of moderate-to-vigorous physical activity. In contrast to the lower extremities, there was insufficient evidence for an association of lumbar spine bone outcomes with objectively measured SB. In high-quality studies that used DXA, no association was observed between objectively measured SB and total body bone outcomes. In studies using questionnaires, none of these relationships were observed. Well-designed longitudinal studies, objectively measuring SB, are needed to further unravel the effect of SB, physical activity and their interaction on bone health.

Dietary Food-Additive Phosphate and Human Health Outcomes

Dietary intake of phosphorus is required for human health, and dietary reference intakes for phosphorus have been established. Food-grade phosphates are used as additives to provide a wide range of technical functions in food production. Phosphates are often the most efficient ingredients to provide the required functionality in many applications, and in some cases, there are not effective and approved alternatives. However, many investigators have expressed concern about the quantities of phosphorus and food-additive phosphate present in the diets of many populations. This paper presents the outcome of an extensive review of 110 primary research articles focused on identifying evidence that substantiates or refutes associations of total dietary phosphorus and food-additive phosphate intake with health and disease in humans. The lack of conclusive evidence prevented the drawing of firm conclusions about the safety and possible risks of food-additive phosphate in the general population, which is consonant with the overall assessments of authoritative institutions who have concluded that available data are insufficient to make the required determinations. Despite the inadequacy of the evidence currently available, many of the authors of the publications reviewed for this paper expressed concerns about the quantities of phosphorus and food-additive phosphate in the diets of the populations and subpopulations they studied. At the same time, most of these authors offered only qualified conclusions and expressed themselves tentatively. In addition, authors of primary research publications, authors of review articles, and authoritative institutions have called for the conduct of further research.

Dietary Zinc and Incident Calcium Kidney Stones in Adolescence

PURPOSE

We determined the association between dietary zinc intake and incident calcium kidney stones in adolescents. We also examined the relationship between dietary zinc intake and urinary zinc excretion between cases and controls.

MATERIALS AND METHODS

We conducted a nested case-control study within a large pediatric health care system. Three 24-hour dietary recalls and spot urine chemistry analyses were obtained for 30 participants 12 to 18 years old with a first idiopathic calcium based kidney stone and 30 healthy controls matched for age, sex, race and month of enrollment. Conditional logistic regression models were used to estimate the association between daily zinc intake and incident calcium kidney stones, adjusting for dietary phytate, protein, calcium, sodium and oxalate. Multivariable linear regression was used to estimate the association between dietary and urine zinc, adjusting for urine creatinine and dietary phytate and calcium.

RESULTS

Cases had lower daily zinc intake (8.1 mg) than controls (10 mg, p = 0.029). Daily zinc intake of boys and girls with calcium stones was 2 mg and 1.2 mg less, respectively, than the daily intake recommended by the Institute of Medicine. Odds of incident stones were reduced by 13% for every 1 mg increase in daily zinc intake (OR 0.87, 95% CI 0.75-0.99). There was an estimated 4.5 μg/dl increase in urine zinc for every 1 mg increase in dietary zinc (p = 0.009), with weak evidence of a smaller increase in urine zinc in cases than in controls (interaction p = 0.08).

CONCLUSIONS

Decreased dietary zinc intake was independently associated with incident calcium nephrolithiasis in this population of adolescents.

An evidence-update on the prospective relationship between childhood sedentary behaviour and biomedical health indicators: a systematic review and meta-analysis

Evidence for adverse health effects of excessive sedentary behaviour in children is predominantly based on cross-sectional studies, measuring TV viewing as proxy for sedentary behaviour. This systematic review and meta-analysis summarizes the evidence on the prospective relationship between childhood sedentary behaviour and biomedical health indicators, overall and stratified by type of sedentary behaviour (TV viewing, computer use/games, screen time and objective sedentary time). PubMed, EMBASE, PsycINFO and Cochrane were systematically searched till January 2015. Methodological quality of all included studies was scored, and a best evidence synthesis was applied. We included 109 studies of which 19 were of high quality. We found moderate-to-strong evidence for a relationship of overall sedentary time with some anthropometrics (overweight/obesity, weight-for-height), one cardiometabolic biomarker (HDL-cholesterol) and some fitness indicators (fitness, being unfit). For other health indicators, we found no convincing evidence because of inconsistent or non-significant findings. The evidence varied by type of sedentary behaviour. The meta-analysis indicated that each additional baseline hour of TV viewing (β = 0.01, 95%CI = [-0.002; 0.02]) or computer use (β = 0.00, 95%CI = [-0.004; 0.01]) per day was not significantly related with BMI at follow-up. We conclude that the evidence for a prospective relationship between childhood sedentary behaviour and biomedical health is in general unconvincing.

BMI and BMD: The Potential Interplay between Obesity and Bone Fragility

Recent evidence demonstrating an increased fracture risk among obese individuals suggests that adipose tissue may negatively impact bone health, challenging the traditional paradigm of fat mass playing a protective role towards bone health. White adipose tissue, far from being a mere energy depot, is a dynamic tissue actively implicated in metabolic reactions, and in fact secretes several hormones called adipokines and inflammatory factors that may in turn promote bone resorption. More specifically, Visceral Adipose Tissue (VAT) may potentially prove detrimental. It is widely acknowledged that obesity is positively associated to many chronic disorders such as metabolic syndrome, dyslipidemia and type 2 diabetes, conditions that could themselves affect bone health. Although aging is largely known to decrease bone strength, little is yet known on the mechanisms via which obesity and its comorbidities may contribute to such damage. Given the exponentially growing obesity rate in recent years and the increased life expectancy of western countries it appears of utmost importance to timely focus on this topic.

Dietary magnesium intake, bone mineral density and risk of fracture: a systematic review and meta-analysis

Dietary magnesium intake has been related to osteoporosis and risk of fractures in earlier studies; however, findings were conflicting. This meta-analysis indicated that high magnesium intake was not associated with increased risk of fracture; however, a positive marginally significant correlation was found between magnesium intake and bone mineral density (BMD) in total hip as well as in femoral neck. Although there is some evidence on the association between magnesium intake, BMD and fractures, no previous study has summarized findings in this regard. We aimed to systematically review the current evidence on this association and to perform a meta-analysis of observational studies. We searched MEDLINE, Scopus, EMBASE and Google Scholar up to January 2015 for studies that examined the relationship between magnesium intake and BMD or fracture. Studies that had reported correlation coefficients between magnesium intake and BMD or those that reported odds ratios (ORs) or relative risks (RRs) for risk of fracture in different sites were included. In total, 12 studies were included in the meta-analysis. We found that high intakes of magnesium were not significantly associated with risk of total hip fracture (summary effect size 1.92; 95 % CI 0.81, 4.55) or total fractures (1.01; 0.94-1.07). Combining four effect sizes, a positive marginally significant correlation was observed between magnesium intake and total BMD (pooled r 0.16; 95 % CI 0.001, 032). Based on nine effect sizes, we found a marginally significant association between magnesium intake and femoral neck BMD (0.14; 0.001, 0.28). However, no significant correlation was found between magnesium intake and BMD in lumbar spine (0.09; -0.01, 0.19). We found that high intakes of magnesium were not associated with increased risk of hip and total fractures. There was a positive marginally significant correlation between magnesium intake and BMD in femoral neck and total hip. No significant correlations were observed between magnesium intake and BMD in lumbar spine.

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.

Nutritional aspects of bone health

Bone mass, geometry and microstructure, and bony tissue material level properties determine bone strength, hence the resistance to fracture. At a given age, all these variables are the consequence of the amount accumulated and of the structure developed during growth, up to the so-called peak bone mass, and of the bone loss and microstructure degradation occurring later in life. Genetic factors primarily contribute to the variance of the determinants of bone strength. Nutritional intakes are environmental factors that influence both processes, either directly by modifying modelling and remodelling, or indirectly through changes in calcitropic hormone secretion and action. Some effects of nutrition on the offspring bone could take place during foetal life. There are interplays between genetic factors, nutritional intakes and physical exercise. Among the nutrients, sufficient dietary intakes of calcium and protein are necessary for bone health in childhood and adolescence as well as later in life.

Familial interactions and physical, lifestyle, and dietary factors to affect bone mineral density of children in the KNHANES 2009-2010

We examined familial bone mineral density (BMD) interactions between parents and children and lifestyle factors affecting BMD in the Korean general population of children under 20 and parents under 50 years of age. This cross-sectional study included 2,453 participants (667 daughters, 705 sons, 719 mothers, and 362 fathers) in the 2009-2010 Korean National Health and Nutrition Examination Survey. We calculated prevalence ratios and 95 % confidence intervals for BMD values of whole femur, femur neck, lumbar spine, and whole body excluding the head being in the low tertile in adolescents according to parental BMD tertile after adjusting for physical, lifestyle, and dietary factors. For daughters and sons, there were significant differences in BMD at the four bone sites according to age group, body fat percentage, regular walking and exercise, and milk consumption compared to the reference value for each classification category. Surprisingly, there were no differences in BMD according to serum 25-OH-D levels. Birth order affected BMD of only whole body except head, but its impact was less than that of lifestyle factors. The mean differences in BMD between daughters and sons in the first and third parental BMD tertiles were statistically significant. Notably, the prevalence ratio of whole body without head BMD being in the low tertile increased eight and ten-folds in adolescent daughters and sons, respectively, when parents were in the low BMD tertile. In specific bone regions, parental BMD had a greater effect on total femur in daughters but in the lumbar spine in sons. In conclusion, parental BMD positively influences BMD in daughters and sons after adjustment for environmental parameters. This suggests that the children from parents with low BMD need to make an extra effort to increase BMD through dietary and lifestyle changes.

Magnesium metabolism in 4-year-old to 8-year-old children

Magnesium (Mg) is a key factor in bone health, but few studies have evaluated Mg intake or absorption and their relationship with bone mineral content (BMC) or bone mineral density (BMD) in children. We measured Mg intake, absorption, and urinary excretion in a group of children 4 to 8 years of age. Mg absorption was determined using a dual-tracer stable isotope technique, with (25) Mg given intravenously and (26) Mg given orally. We found a small, but significantly greater Mg absorption efficiency (percentage absorption) in males than females (67% ± 12% versus 60% ± 8%, p = 0.02) but no difference in estimated net Mg retention (average of 37 mg/d in both males and females). Relating dietary Mg intake to estimated Mg retention showed that an intake of 133 mg/d, slightly above the current estimated average requirement (EAR) of 110 mg/d, led to a net average retention of 10 mg/d, the likely minimum growth-related need for this age group. Covariate analysis showed that Mg intake and total Mg absorption, but not calcium intake or total absorption were significantly associated with both total body BMC and BMD. These results suggest that usual Mg intakes in small children in the United States meet dietary requirements in most but not all children. Within the usual range of children's diets in the United States, dietary Mg intake and absorption may be important, relatively unrecognized factors in bone health.

Bone-related complications of transfusion-dependent beta thalassemia among children and adolescents

Thalassemia and the blood transfusion complications associated with it predispose children to poor bone health. This study was conducted to determine the prevalence of bone-related abnormalities and identify the bone health predictors within this population. One hundred and forty transfusion-dependent beta thalassemic subjects 8-18 years old in Mashhad, Iran, participated in this cross-sectional study. Anthropometric measures, dietary intake, bone-related biomarkers and bone densitometry, were assessed. The incidence of underweight and short stature was 33.6 and 41.4 %, respectively, which were indicators of malnutrition among thalassemic subjects in this study. Low bone density was detected in the lumbar spine and femoral region in 82 and 52 % of subjects, respectively. Hypocalcemia and hypophosphatemia were seen in 22 and 18.2 %, whilst vitamin D deficiency was present in more than 85 % of thalassemic children and adolescents. The relationships between weight, height and other anthropometric indices, serum calcium and bone markers, intake of macronutrients, zinc and vitamin E with bone mineral density (BMD) and bone mineral content (BMC) in the lumbar spine and femoral area were positively related, indicating that better nutritional status were associated with higher BMD and BMC values. Puberty, gender and serum osteocalcin were negative predictors for BMD and BMC values, whereas age, weight and height were the positive predictors. High incidence of low bone density and deficit in other aspects of bone health among thalassemia patients makes routine bone health assessment necessary for this vulnerable group. Considering influencing factors, dietary counseling and preventive supplementation therapy for this high risk group of children and adolescents may be necessary, although this should be assessed by intervention studies.

Protein intake from 0 to 18 years of age and its relation to health: a systematic literature review for the 5th Nordic Nutrition Recommendations

The present systematic literature review is a part of the 5th revision of the Nordic Nutrition Recommendations. The aim was to assess the health effects of different levels of protein intake in infancy and childhood in a Nordic setting. The initial literature search resulted in 435 abstracts, and 219 papers were identified as potentially relevant. Full paper selection resulted in 37 quality-assessed papers (4A, 30B, and 3C). A complementary search found four additional papers (all graded B). The evidence was classified as convincing, probable, limited-suggestive, and limited-inconclusive. Higher protein intake in infancy and early childhood is convincingly associated with increased growth and higher body mass index in childhood. The first 2 years of life is likely most sensitive to high protein intake. Protein intake between 15 E% and 20 E% in early childhood has been associated with an increased risk of being overweight later in life, but the exact level of protein intake above which there is an increased risk for being overweight later in life is yet to be established. Increased intake of animal protein in childhood is probably related to earlier puberty. There was limited-suggestive evidence that intake of animal protein, especially from dairy, has a stronger association with growth than vegetable protein. The evidence was limited-suggestive for a positive association between total protein intake and bone mineral content and/or other bone variables in childhood and adolescence. Regarding other outcomes, there were too few published studies to enable any conclusions. In conclusion, the intake of protein among children in the Nordic countries is high and may contribute to increased risk of later obesity. The upper level of a healthy intake is yet to be firmly established. In the meantime, we suggest a mean intake of 15 E% as an upper limit of recommended intake at 12 months, as a higher intake may contribute to increased risk for later obesity.

Human biology at the interface of paediatrics: measuring bone mineral accretion during childhood

BACKGROUND

Professor Tanner established a paradigm for the study of growth and development that demands precise growth measurements, description of normal variability through development to adulthood, consideration of the effects of tempo and the study of factors that influence growth outcomes. The relatively new field of paediatric bone health assessment fits this paradigm and reflects the collaboration of human biologists and paediatricians in understanding the growth of the human skeleton.

REVIEW

This review describes the reasons for clinical assessment of bone density in children, the technological developments in bone health assessment in children, the development of reference curves and the effects of growth, body composition, pubertal timing, genetics and lifestyle on bone health outcomes.

Effects of vitamin K on the morphometric and material properties of bone in the tibiae of growing rats

Suboptimal vitamin K nutriture is evident during rapid growth. We aimed to determine whether vitamin K(2) (menaquinone-4 [MK-4]) supplementation is beneficial to bone structure and intrinsic bone tissue properties in growing rats. Male Wistar rats (5 weeks old) were assigned to either a control diet (n = 8) or an MK-4-supplemented diet (22 mg d(-1) kg(-1) body weight, n = 8). After a 9-week feeding period, we determined the serum concentration ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin and the urinary deoxypyridinoline level. All rats were then euthanized, and their tibiae were analyzed by micro-computed tomography for trabecular architecture and synchrotron radiation micro-computed tomography for cortical pore structure and mineralization. Fourier transform infrared microspectroscopy and a nanoindentation test were performed on the cortical midlayers of the anterior and posterior cortices to assess bone tissue properties. Neither body weight nor tibia length differed significantly between the 2 groups. Dietary MK-4 supplementation decreased the ratio of undercarboxylated osteocalcin to γ-carboxylated osteocalcin but did not affect deoxypyridinoline, indicating a positive effect on bone formation but not bone resorption. Trabecular volume fraction and thickness were increased by MK-4 (P < .05). Neither the cortical pore structure nor mineralization was affected by MK-4. On the other hand, MK-4 increased mineral crystallinity, collagen maturity, and hardness in both the anterior and posterior cortices (P < .05). These data indicate the potential benefit of MK-4 supplementation during growth in terms of enhancing bone quality.

Relationship between young peoples' sedentary behaviour and biomedical health indicators: a systematic review of prospective studies

The aim of this systematic review was to describe the prospective relationship between childhood sedentary behaviour and health indicators. We identified prospective studies from searches in PubMed, EMBASE, PsycInfo and Cochrane, from January 1989 through April 2010. Two reviewers independently screened the titles and abstracts for eligibility, rated the methodological quality of the studies, and extracted data. We identified 31 papers, examining 27 different cohorts. The quality score of the studies ranged from 38 to 88%. Nine studies were scored as high quality. According to the best evidence synthesis we found insufficient evidence for a longitudinal positive relationship between 'sedentary time'- mainly TV viewing - and body mass index (BMI) and more specific indicators of fat mass. One high quality and two low quality studies found a significant inverse relationship between sedentary time - mainly TV viewing - and aerobic fitness, leading to moderate evidence for this inverse relationship. There was insufficient evidence for a longitudinal relationship between sedentary time and blood pressure, blood lipids or bone mass. Our systematic review suggests that there is moderate evidence for a longitudinal inverse relationship between screen time and aerobic fitness during childhood. Thus there is evidence to limit screen time in young people in order to prevent low levels of fitness. The possible detrimental health effects of prolonged or excessive sitting on other health indicators needs further study.

Determinants of bone mineral content and bone area in Indian preschool children

The objective of this study was to examine the lifestyle factors that influence total body bone mineral content (TB BMC) and total body bone area (TB BA) in Indian preschool children. TB BMC and TB BA were measured by dual-energy X-ray absorptiometry (Lunar DPX PRO) in 71 apparently healthy children aged 2-3 years. A fasting blood sample was analyzed for serum concentrations of ionized calcium (iCa), intact parathyroid hormone (iPTH), phosphorus (iP) and 25-hydroxyvitamin D(3) (25 OHD). Dietary intake of energy, protein, calcium and phosphorus was estimated from a 3-day diet recall. The daily physical activity and sunlight exposure were recorded by a questionnaire. The study children were shorter than their age-gender matched WHO counterparts with a mean height for age Z score of -1.3 ± 1.5. The mean dietary intake of calcium was 46% of the Indian recommended dietary intakes (RDI). Seventy-three percent of children had low iCa concentrations, and 57% were deficient in vitamin D. Generalized linear model analysis revealed that height, lean body mass, weight, activity, sunlight exposure in minutes and dietary intakes of calcium, zinc and iron were the significantly influencing factors (p < 0.05) of TB BMC and TB BA. In conclusion, attaining optimal height for age, achieving the goals of overall nutrition with adequate calcium, iron and zinc intakes as well as adequate physical activity and sunlight exposure play an important role in achieving better TB BMC and TB BA in preschool children.

A nutritional intervention study with hydrolyzed collagen in pre-pubertal spanish children: influence on bone modeling biomarkers

AIM

The aim of the study was to investigate the influence of dietary intake of commercial hydrolyzed collagen (Gelatine Royal) on bone remodeling in pre-pubertal children.

METHODS

A randomized double-blind study was carried out in 60 children (9.42 +/- 1.31 years) divided into three groups according to the amount of partially hydrolyzed collagen taken daily for 4 months: placebo (G-I, n=18), collagen (G-II, n=20) and collagen+calcium (G-III, n=22) groups. Analyses of the following biochemical markers were carried out: total and bone alkaline phosphatase (tALP and bALP), osteocalcin, tartrate-resistant acid phosphatase (TRAP), type I collagen carboxy-terminal telopeptide, lipids, calcium, 25-hydroxyvitamin D, insulin-like growth factor-1 (IGF-1), thyroid-stimulating hormone, free thyroxin and intact parathormone.

RESULTS

There was a significantly greater increase in serum IGF-1 in G-III than in G-II (p < 0.01) or G-I (p < 0.05) during the study period, and a significantly greater increase in plasma tALP in G-III than in G-I (p < 0.05). Serum bALP behavior significantly (p < 0.05) differed between G-II (increase) and G-I (decrease). Plasma TRAP behavior significantly differed between G-II and G-I (p < 0.01) and between G-III and G-II (p < 0.05).

CONCLUSION

Daily dietary intake of hydrolyzed collagen seems to have a potential role in enhancing bone remodeling at key stages of growth and development.

Nutritional factors that influence change in bone density and stress fracture risk among young female cross-country runners

OBJECTIVE

To identify nutrients, foods, and dietary patterns associated with stress fracture risk and changes in bone density among young female distance runners.

DESIGN AND SETTING

Two-year, prospective cohort study. Observational data were collected in the course of a multicenter randomized trial of the effect of oral contraceptives on bone health.

PARTICIPANTS

One hundred and twenty-five female competitive distance runners ages 18-26 years.

ASSESSMENT OF RISK FACTORS

Dietary variables were assessed with a food frequency questionnaire.

MAIN OUTCOME MEASUREMENTS

Bone mineral density and content (BMD/BMC) of the spine, hip, and total body were measured annually by dual x-ray absorptiometry (DEXA). Stress fractures were recorded on monthly calendars, and had to be confirmed by radiograph, bone scan, or magnetic resonance imaging.

RESULTS

Seventeen participants had at least one stress fracture during follow-up. Higher intakes of calcium, skim milk, and dairy products were associated with lower rates of stress fracture. Each additional cup of skim milk consumed per day was associated with a 62% reduction in stress fracture incidence (P < .05); and a dietary pattern of high dairy and low fat intake was associated with a 68% reduction (P < .05). Higher intakes of skim milk, dairy foods, calcium, animal protein, and potassium were associated with significant (P < .05) gains in whole-body BMD and BMC. Higher intakes of calcium, vitamin D, skim milk, dairy foods, potassium, and a dietary pattern of high dairy and low fat were associated with significant gains in hip BMD.

CONCLUSIONS

In young female runners, low-fat dairy products and the major nutrients in milk (calcium, vitamin D, and protein) were associated with greater bone gains and a lower stress fracture rate. Potassium intake was also associated with greater gains in hip and whole-body BMD.

Assessment of bone mineral density and risk factors in children completing treatment for acute lymphoblastic leukemia

BACKGROUND

Reduced bone mineral density and increased fracture risk have been reported in children with cancer. In this study, we aimed to determine the growth and bone mineral density (BMD) of the children off chemotherapy for acute lymphoblastic leukemia, and the probable risk factors.

PROCEDURE

The age, anthropometric measurements, lumbar spine BMDs were recorded in 70 children. The risk factors on BMD; daily calcium intake, the time interval from the completion of the chemotherapy, cranial radiotherapy, cumulative steroid dose, decrease in physical activity were investigated. Serum calcium, phosphate, alkaline phosphates, magnesium, insulin-like growth factor-1 (IGF-1) and 25 (OH) vitamin D levels were determined.

RESULTS

The mean height percentile at the time of diagnosis was decreased from the value of 53 to a value of 47 at the beginning of the study (P=0.071). Of them; 44% had osteoporosis, 41% had osteopenia, and the rest had normal BMD. BMD z-scores were decreased during the first 2 years from the completion of the treatment. There was a positive correlation between BMD z-scores and daily calcium intake (CC=0.366, P=0.0015). A negative correlation was determined between the time spent on TV and computers and BMD z-scores (CC=-0.464, P=0.0019). Serum IGF-1 and 25 (OH) vitamin D levels of patients were significantly lower than controls (P=0.033).

CONCLUSIONS

Our data revealed that 85% of the survivors had bone mineralization defect. BMDs and z scores were decreased during the first 2 years from the completion of the treatment and then gradually began to increase. The most important risk factor for decreased BMD was low daily calcium intake. Therefore, patients and their families should be encouraged to take sufficient amount of calcium. Prophylactic vitamin D may also be supplemented.

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.

The association between dietary protein intake and bone mass accretion in pubertal girls with low calcium intakes

To assess the association between protein intakes and bone mass accrual in girls, data were analysed for 757 pre-pubertal girls (mean age 10.1 years) in urban Beijing, China, who participated in a 5-year study including 2 years of milk supplementation (intervention groups only) and 3 years of follow-up study. At 0, 12, 24, 48 and 60 months from the baseline, bone mass of the proximal or distal forearm (PF or DF) and total body (TB) was measured with dual energy X-ray absorptiometry; dietary intakes were assessed by a 3-d food record (including two weekdays and one weekend day). Linear mixed models were used and continuous variables were logarithm transformed. The mean longitudinal Ca intake (432-675 mg/d on average) positively influenced bone mineral content (BMC) at TB, PF and DF after controlling for baseline bone mass and other possible confounders. However, negative associations were observed between protein intake (55.9-61.0 g/d on average) and BMC accrual at TB, PF or DF (beta = - 1.92, - 10.2 or - 4.82, respectively, P < 0.01) after adjustment. When protein intake was considered according to animal or plant food sources, protein from animal foods, particularly meat, had significant negative effects on BMC accrual at DF or PF after adjustment. It was concluded that higher protein intake, especially from animal foods, appeared to have a negative effect on bone mass accrual in Chinese pubertal girls with low Ca intakes.

Influence of maternal genetic and lifestyle factors on bone mineral density in adolescent daughters: a cohort study in 387 Japanese daughter-mother pairs

We conducted a cross-sectional study in a cohort of Japanese adolescent schoolgirls (12-18 years of age) and their mothers (387 pairs). Age, lumbar bone mineral density (BMD), birth and menarche-related status, height, body weight and lifestyles were surveyed in the participants. The values of BMD, height and body weight were converted to standard deviation (SD) by age. There were 49 (12.7%) pre-menarche and 338 (87.3%) post-menarche daughters. BMD-SD, height-SD, vitamin D intake and vitamin K intake were significantly correlated between the pre-menarche daughters and mothers (P < 0.05), while BMD-SD, birth weight, age at menarche and all lifestyle-related factors were significantly correlated between the post-menarche daughters and mothers (P < 0.05). BMD-SD in the pre-menarche daughters was affected by BMD-SD in mothers (R (2) = 0.069, P = 0.033) and their own height-SD (R (2) = 0.199, P = 0.001) (model R (2) = 0.340), independently. BMD-SD in the post-menarche daughters was affected by BMD-SD in mothers (R (2) = 0.073, P < 0.001) as well as by their own age at menarche (R (2) = 0.020, P = 0.001), height-SD (R (2) = 0.022, P < 0.001), body weight-SD (R (2) = 0.081, P < 0.001) and intensity of exercise (R (2) = 0.015, P = 0.045) (model R (2) = 0.372), independently. The results suggest that BMD is strongly correlated between daughters and mothers and that a greater age at menarche leads to lower peak bone mass. It was also suggested that maintaining high-intensity physical activity and adequate body weight is important in achieving maximum BMD as factors amenable to intervention in post-menarche daughters.

Bone development in children living on house-boats on a river in Vietnam

Background

With the rapid urbanization of Vietnam, living on boats has come to be associated with underprivileged socioeconomic status, and there are major concerns regarding the health of children living under such conditions. Bone development is a critical concern in children because the foundation for skeletal health is established early in life. We evaluated the bone properties of children living under underprivileged conditions on boats in Hue City, Vietnam, with respect to a number of household factors.

Methods

One hundred and twenty children aged 7-11 years selected randomly from households living on boats in Hue were included in this study. Tibial and radial speed of sound (SOS) were measured by non-invasive quantitative ultrasonometry. Socioeconomic profiles, health promotion proficiency, and nutritional intake of households were assessed by structured interview. The bone properties of 60 children aged 7-11 living on land were also assessed as controls.

Results

The Z-scores of tibial and radial SOS of boat children were -0.16 ± 0.89 and -0.24 ± 0.75 (mean ± SD), respectively. Tibial SOS exhibited a significant correlation with radial SOS (r = 0.39, P < 0.01). Among the household factors examined, the educational level of fathers (P < 0.05) and the health promotion proficiency (P < 0.05) of households exhibited positive associations with the tibial bone properties of the children. The tibial and radial SOS of boat children were lower than those of children living on land (P = 0.001 and P = 0.086, respectively).

Conclusion

The results of the present study revealed the underdevelopment of bone properties in children living on houseboats, which was correlated with their living conditions.

Vitamin K status is associated with childhood bone mineral content

In adult bone, vitamin K contributes to bone health, probably through its role as co-factor in the carboxylation of osteocalcin. In children, the significance of vitamin K in bone-mass acquisition is less well known. The objective of this longitudinal study was to determine whether biochemical indicators of vitamin K status are related to (gains in) bone mineral content (BMC) and markers of bone metabolism in peripubertal children. In 307 healthy children (mean age 11·2 years), BMC of the total body, lumbar spine and femoral neck was determined at baseline and 2 years later. Vitamin K status (ratio of undercarboxylated (ucOC) to carboxylated (cOC) fractions of osteocalcin; UCR) was also measured at both time points. Markers of bone metabolism, sex steroids, vitamin D status and growth hormones were measured at baseline only. Large variations in the levels of the UCR were found at both time-points, indicating a substantial interindividual difference in vitamin K status. Improvement of vitamin K status over 2 years (n281 children) was associated with a marked increase in total body BMC (r− 49·1,P < 0·001). The UCR was associated with pubertal stage, markers of bone metabolism, sex hormones and vitamin D status. A better vitamin K status was associated with more pronounced increase in bone mass in healthy peripubertal children. In order to determine the significance of these findings for childhood bone health, additional paediatric studies are needed.

Nutrition: its role in bone health

At a given age, bone mass is determined by the amount of bone accumulated at the end of skeletal growth (the so-called peak bone mass), and by the amount of bone lost subsequently. Nutritional intake is an environmental factor that influences both bone capital accumulation, which is fully achieved by the end of the second decade of life, and bone loss, which occurs during the second half of existence. Nutrients may act directly by modifying bone turnover, or indirectly via changes in calciotropic hormone secretion. The study of the association between nutrition and a bone phenotypic expression may provide inconsistent results, in part because of the low accuracy and reproducibility of the various tools used to assess dietary intakes. Sufficient dietary calcium and protein are necessary for bone health during growth as well as in the elderly.

Early life and current determinants of bone in South African children of mixed ancestral origin

BACKGROUND

The influence of early life factors on the bone mineral density of children has been identified, however the contribution of these determinants may vary.

AIM

The study investigated determinants of bone mineral content (BMC) in South African children of mixed ancestral origin.

SUBJECTS AND METHODS

Early life data including birth weight, maternal alcohol consumption and smoking during pregnancy were collected on 9-year-old children of mixed ancestral origin (n = 64). Grip strength was measured, and physical activity, housing density and dietary data were collected. Whole body BMC (WB BMC), fat-free soft tissue and fat tissue were measured using dual energy X-ray absorptiometry.

RESULTS

Maternal alcohol consumption during pregnancy was associated with WB BMC, however after adjusting for possible confounders, this was no longer significant. When combined with gender, gestational age and maternal BMC in a multiple regression, maternal alcohol consumption during pregnancy could explain 20% of the variance in the WB BMC, however when current height was included in the model, the contribution of the other factors was insignificant. There was however a significant correlation between current height and birth weight (r = 0.34; p < 0.01) and alcohol consumption during pregnancy (r = 0.34; p < 0.05). A model consisting of current factors such as age, weight, gender, grip strength and calcium intake was able to explain 81.5% of the variance. Housing density was negatively correlated with WB BMC (r =-0.11; p = 0.05).

CONCLUSION

These data suggest that although early life factors may contribute indirectly to the bone mass of children of mixed ancestral origin, the contribution of current factors is greater. In addition, environmental factors such as housing density have a direct effect on bone mass, independent of body size.

Independent and combined effect of nutrition and exercise on bone mass development

Food intake provides the necessary components for adequate metabolic functions in bone. Calcium, phosphorus, vitamin D, magnesium, proteins, and fluoride are some of the most important nutrients in this regard. These have different effects on bone mass. Additionally, exercise has been shown to elicit osteogenic responses in bone development; indeed, it seems to potentiate, for example, the effect of calcium supplementation on bone mass. However, the nutrition-exercise-bone mass relationship is complex and needs further in-depth investigation. As a first step, therefore, we reviewed current knowledge about the role of nutrition on the development of bone tissue and how physical activity affects the nutrient-bone relationship.

High-protein intake enhances the positive impact of physical activity on BMC in prepubertal boys

In 232 healthy prepubertal boys, increased physical activity was associated with greater BMC at both axial and appendicular sites under high-protein intake.

INTRODUCTION

Physical activity is an important lifestyle determinant of bone mineral mass acquisition. Its impact during childhood can be modulated by nutrition, particularly by protein and calcium intakes. We analyzed the relationship between physical activity levels and protein compared with calcium intake on BMC.

MATERIALS AND METHODS

In 232 healthy prepubertal boys (age: 7.4 +/- 0.4 [SD] yr; standing height: 125.7 +/- 5.9 cm; body weight: 25.3 +/- 4.6 kg), physical activity and protein and calcium intakes were recorded. BMC was measured by DXA at the radial metaphysis, radial diaphysis, total radius, femoral neck, total hip, femoral diaphysis, and L(2)-L(4) vertebrae.

RESULTS

In univariate analysis, the correlation coefficients r with BMC of the various skeletal sites were as follows: physical activity, from 0.26 (p = 0.0001) to 0.40 (p = 0.0001); protein intake, from 0.18 (p = 0.005) to 0.27 (p = 0.0001); calcium intake, from 0.09 (p = 0.181) to 0.17 (p = 0.007). By multiple regression analysis, the beta-adjusted values remained correlated with BMC, ranging as follows: physical activity, from 0.219 (p = 0.0007) to 0.340 (p < 0.0001); protein intake, from 0.120 (p = 0.146) to 0.217 (p = 0.009). In contrast, it was not correlated for calcium intake: from -0.069 (p = 0.410) to 0.001 (p = 0.986). With protein intake (mean = 2.0 g/kg body weight/d) above the median, increased physical activity from 168 to 321 kcal/d was associated with greater mean BMC Z-score (+0.6, p = 0.0005). In contrast with protein intake (mean = 1.5 g/kg body weight/d) below the median, increased physical activity from 167 to 312 kcal/d was not associated with a significantly greater mean BMC Z-score (+0.2, p = 0.371). The interaction between physical activity and protein intake was close to statistical significance for mean BMC Z-score (p = 0.055) and significant for femoral neck BMC (p = 0.012). In keeping with the results derived from multiple regression analysis, the increased physical activity on mean BMC Z-score was not influenced by difference in calcium intake above (mean = 945 mg/d) and below (mean = 555 mg/d) the median.

CONCLUSION

In healthy prepubertal boys, the impact in increased physical activity on BMC seems to be enhanced by protein intake within limits above the usual recommended allowance.

Dietary protein intake and bone mineral content in adolescents-The Copenhagen Cohort Study

Data indicate that various protein sources may exhibit a differential effect on bone metabolism. We investigated associations of milk and meat protein intake with bone mineral content (BMC) in adolescents. Milk, but not meat, protein intake was positively associated with size-adjusted BMC. Milk-derived protein may be beneficial for bone mineralization.

INTRODUCTION

Milk and meat protein intake has been reported to exhibit a differential effect on serum insulin-like growth factor-I (IGF-I). IGF-I plays a key role in bone metabolism. Therefore, we investigated associations of different protein sources with BMC and bone area (BA) in adolescents.

METHODS

This was a cross-sectional study of 17-year-old girls (n = 63) and boys (n = 46) participating in the second follow-up of The Copenhagen Cohort Study. We measured dietary intake (7-day food record), BMC and BA (dual-energy X-ray absorptiometry), serum markers for bone turnover and serum IGF-I (immunoassays).

RESULTS

The mean total protein intake ( approximately 1.2 g/kg) was modestly higher than that recommended. Total and milk ( approximately 0.3 g/kg) protein intake, but not meat protein intake ( approximately 0.4 g/kg), was positively associated with size-adjusted BMC (P <or= 0.05). The positive association between milk protein intake and size-adjusted BMC remained significant after correction for energy, calcium, and physical activity (P <or= 0.01) and did not seem to be mediated via current serum IGF-I. None of the analyzed protein sources was significantly associated with size-adjusted BA.

CONCLUSIONS

Our results suggest that some components of milk protein may promote bone mineralization. Further studies are needed to elucidate this phenomenon.

Associations of total, dairy, and meat protein with markers for bone turnover in healthy, prepubertal boys

We previously reported that high intake of milk, but not meat, equal in protein content, increased serum insulin-like growth factor-I (sIGF-I) in prepubertal boys. sIGF-I plays a key role in bone metabolism. Therefore, the aim of this cross-sectional study was to investigate associations of total, dairy, and meat protein intake with markers for bone turnover and sIGF-I in prepubertal, healthy boys (n = 81). We measured bone turnover (enzyme-linked immunoassay) in serum osteocalcin (sOC), bone-specific alkaline phosphatase (sBAP), and C-terminal telopeptide of collagen type-I (sCTX); dietary intake was estimated from a 3-d weighed food record. sIGF-I and its binding protein-3 were assessed (immunoassay) in a subgroup of 56 boys. All statistical models included effects of age, BMI, and energy intake. Dairy protein was negatively associated with sOC (P = 0.05) but not significantly associated with sBAP and sCTX. Further analyses showed that dairy protein decreased (P = 0.05) sOC at a high meat protein intake (>0.8 g/kg), whereas meat protein increased (P = 0.03) sOC at a low dairy protein intake (<0.4 g/kg). Total and meat protein intake was positively associated with sBAP (P < or = 0.04) but not significantly associated with sOC and sCTX. Free sIGF-I was positively associated with total (P < 0.01) and dairy (P = 0.06) protein but not with meat protein. Our results indicate that dairy and meat protein may exhibit a distinct regulatory effect on different markers for bone turnover. Future studies should focus on differential effects of dairy and meat protein on bone health during growth.

High intake of milk, but not meat, decreases bone turnover in prepubertal boys after 7 days

OBJECTIVE

To compare the short-term effect of a high milk and a high meat intake, identical in protein amount, on bone turnover during prepuberty.

SETTING

A University department.

DESIGN AND SUBJECTS

From 28, randomly recruited, 8-year-old boys, first 14 were assigned to the milk group and next 14 to the meat group. In each group, 12 boys finished the dietary intervention.

INTERVENTION

Milk (1.5 l/day) and meat (250 g/d), both containing approximately 53 g of protein, were given together with the habitual diet for 7 days. At baseline and day-7, serum osteocalcin (s-OC), bone-specific alkaline phosphatase (s-BAP) and C-terminal telopeptides of type I collagen (s-CTX) were measured (immunoassay) and dietary intake was estimated (a 3-day weighted food record).

RESULTS

Baseline s-OC, s-BAP and s-CTX were not significantly different between the groups. After 7 days, the average protein intake increased in both groups by 47.5 g; the milk group had higher (P<0.0001) calcium intake; s-OC and s-CTX decreased (P< or =0.04) in the milk group (-30.9%; -18.7%, respectively) compared with the meat group (+6.4%; -1.0%, respectively) and s-BAP decreased (P=0.06) both in the milk (-3.9%) and the meat group (-7.5%).

CONCLUSIONS

At the equal protein intake, milk, but not meat, decreased bone turnover in prepubertal boys after 7 days. This effect was probably due to some milk-derived compounds, rather than to the total protein intake. Future studies should elucidate the mechanism(s) of milk-related decline of bone turnover and its relevance for peak bone mass during growth.

SPONSORSHIP

University PhD scholarships.

Bone mineral density in children with chronic renal failure

Bone mineral density (BMD) is important in children and adolescents because of its relationship to long-term skeletal health, and because, in adults with chronic renal failure (CRF), a relationship between low BMD and vascular calcification has been suggested. To investigate the relationship between BMD and manipulable factors that might affect it, i.e. plasma calcium, phosphate and parathyroid hormone (PTH), 64 patients with a median glomerular filtration rate (GFR) of 31 (range 7-60) ml min(-1) 1.73 m(-2) and median age of 10.0 (4.1-16.9) years were followed over 1.3 (0.7-1.7) years at an average of 5 (3-14) clinic visits. At one visit, BMD of the lumbar spine was measured by dual energy X-ray absorptiometry. The mean BMD Z-score was normal (=0.0). Overall mean calcium, phosphate and PTH levels were in their respective normal ranges. The majority of the patients (72%) were treated with calcium carbonate, mean dose 65 mg kg(-1) day(-1); prescription was positively related to serum calcium levels and calcium-phosphate product (P=0.012 and P<0.01 respectively). Almost all patients (98%) were treated with alfacalcidol, mean dose 12 ng kg(-1) day(-1); prescription was not related to investigated factors. Patients grew well; there was no change in height standard deviation score (DeltaHtSDS=0.0). Normal BMD Z-score for age and sex can be achieved in children with CRF managed with the aim of maintaining normal PTH levels by dietary phosphate restriction, calcium-based phosphate binders and small doses of alfacalcidol. Further investigation of the underlying bone by the use of biopsy and histomorphometry is required to determine actual bone health.

Nutrition therapy of organic acidaemias with amino acid-based formulas: emphasis on methylmalonic and propionic acidaemia

Failure to thrive has been described in patients with organic acidaemias due to a variety of causes, both organic and inorganic. Failure to thrive in patients with methylmalonic acidaemia (MMA) and propionic acidaemia (PA) may be related to inadequate protein and energy intake rather than pathology of disease. Inadequate protein intake can also result in decreased resting energy expenditure, clinical signs and symptoms of amino acid deficiency, increased risk of infection, and developmental delay. Amino acid-based formulas (also referred to as 'medical foods') provide a key source of nitrogen, energy, vitamins and minerals which, when prescribed appropriately, can promote anabolism and growth. Although protein requirements in patients with organic acidaemias have not been elucidated, providing an adequate balance of protein, energy and other nutrients will help promote growth.