Bone density in young women is associated with body weight and muscle strength but not dietary intakes

GWAS-informed data integration and non-coding CRISPRi screen illuminate genetic etiology of bone mineral density

Over 1,100 independent signals have been identified with genome-wide association studies (GWAS) for bone mineral density (BMD), a key risk factor for mortality-increasing fragility fractures; however, the effector gene(s) for most remain unknown. Informed by a variant-to-gene mapping strategy implicating 89 non-coding elements predicted to regulate osteoblast gene expression at BMD GWAS loci, we executed a single-cell CRISPRi screen in human fetal osteoblast 1.19 cells (hFOBs). The BMD relevance of hFOBs was supported by heritability enrichment from cross-cell type stratified LD-score regression involving 98 cell types grouped into 15 tissues. 24 genes showed perturbation in the screen, with four (ARID5B, CC2D1B, EIF4G2, and NCOA3) exhibiting consistent effects upon siRNA knockdown on three measures of osteoblast maturation and mineralization. Lastly, additional heritability enrichments, genetic correlations, and multi-trait fine-mapping revealed that many BMD GWAS signals are pleiotropic and likely mediate their effects via non-bone tissues that warrant attention in future screens.

The Influences of Macronutrients on Bone Mineral Density, Bone Turnover Markers, and Fracture Risk in Elderly People: A Review of Human Studies

Osteoporosis is a health condition that involves weak bone mass and a deteriorated microstructure, which consequently lead to an increased risk of bone fractures with age. In elderly people, a fracture attributable to osteoporosis elevates mortality. The objective of this review was to examine the effects of macronutrients on bone mineral density (BMD), bone turnover markers (BTMs), and bone fracture in elderly people based on human studies. A systematic search was conducted in the PubMed®/MEDLINE® database. We included human studies published up to April 2023 that investigated the association between macronutrient intake and bone health outcomes. A total of 11 meta-analyses and 127 individual human studies were included after screening the records. Carbohydrate consumption seemed to have neutral effects on bone fracture in limited studies, but human studies on carbohydrates' effects on BMD or/and BTMs are needed. The human studies analyzed herein did not clearly show whether the intake of animal, vegetable, soy, or milk basic proteins has beneficial effects on bone health due to inconsistent results. Moreover, several individual human studies indicated an association between eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and osteocalcin. Further studies are required to draw a clear association between macronutrients and bone health in elderly people.

Adolescent female handball players present greater bone mass content than soccer players: A cross-sectional study

BACKGROUND

Osteoporosis is a systemic disease affecting half of women over the age of 50 years. Considering that almost 90% of peak of bone mass is achieved until the second decade of life, ensuring a maximal bone mineral content acquisition may compensate for age-associated bone loss. Among several other factors, physical activity has been recommended to improve bone mass acquisition. However, it is unknown whether athletes involved with sports with different impact loading characteristics differ in regards to bone mass measurements.

AIM

To compare the bone mass content, bone mass density and lean mass of young female soccer players (odd-impact loading exercise), handball players (high-impact loading exercises) and non-athletes.

METHODS

A total of 115 female handball players (15.5 ± 1.3 years, 165.2 ± 5.6 cm and 61.9 ± 9.3 kg) and 142 soccer players (15.5 ± 1.5 years, 163.7 ± 6.6 cm and 56.5 ± 7.7 kg) were evaluated for body composition using a dual-emission X-ray absorptiometry system, and 136 female non-athletes (data from NHANES) (15.1 ± 1.32 years, 163.5 ± 5.8 cm and 67.2 ± 19.4 kg) were considered as the control.

RESULTS

Handball players presented higher bone mass content values than soccer players for upper limbs (294.8 ± 40.2 g and 270.7 ± 45.7 g, p < 0.001), lower limbs (1011.6 ± 145.5 g and 967.7 ± 144.3 g, p = 0.035), trunk (911.1 ± 182.5 g and 841.6 ± 163.7 g, p = 0.001), ribs (312.4 ± 69.9 g and 272.9 ± 58.0 g, p < 0.001), spine (245.1 ± 46.8 g and 222.0 ± 45.1 g, p < 0.001) and total bone mass (2708.7 ± 384.1 g and 2534.8 ± 386.0 g, p < 0.001). Moreover, non-athletes presented lower bone mass content for lower limbs (740.6 ± 132.3 g, p < 0.001), trunk (539.7 ± 98.6 g, p < 0.001), ribs (138.2 ± 29.9 g, p < 0.001), pelvis (238.9 ± 54.6 g, p < 0.001), spine (152.8 ± 26.4 g, p < 0.001) and total bone mass (1987.5 ± 311.3 g, p < 0.001) than both handball and soccer players. Handball players also presented higher bone mass density values than soccer players for trunk, ribs and spine (p < 0.05) and handball and soccer players presented higher bone mass density than non-athletes for all measurements (p < 0.005). Finally, the non-athletes' lower limb lean mass was lower than soccer and handball players values (p < 0.05).

CONCLUSION

Adolescent females engaged in handball training for at least one year present higher bone mass contents than those who are engaged in soccer training, which, in turn, present higher bone mass contents than non-athletes. These results might be used by physicians and healthcare providers to justify the choice of a particular sport to enhance bone mass gain in female adolescents.

Assessment of total and regional bone mineral density using bioelectrical impedance vector analysis in elderly population

This study aimed to investigate the relationship between bone mineral density (BMD) and height-adjusted resistance (R/H), reactance (Xc/H) and phase angle (PhA). A total of 61 male and 64 female subjects aged over 60 years were recruited from middle Taiwan. The R and Xc were measured using Bodystat Quadscan 4000 at a frequency of 50 kHz. BMD at the whole body, L2–L4 spine, and dual femur neck (DFN), denoted as BMD_Total, BMD_L2–L4, and BMD_DFN, were calculated using a Hologic DXA scanner. The R-Xc graph was used to assess vector shift among different levels of BMD. BMD was positively correlated with Xc/H and negatively correlated with R/H (p < 0.001). The General Linear Model (GLM) regression results were as follows: BMD_Total = 1.473–0.002 R/H + 0.007 Xc/H, r = 0.684; BMD_L2–L4 = 1.526–0.002 R/H + 0.012 Xc/H, r = 0.655; BMD_DFN = 1.304–0.002 R/H + Xc/H, r = 0.680; p < 0.0001. Distribution of vector in the R-Xc graph was significantly different for different levels of BMD_Total, BMD_L2–L4 and BMD_DFN. R/H and Xc/H were correlated with BMD in the elderly. The linear combination of R/H and Xc/H can effectively predict the BMD of the whole body, spine and proximal femur, indicating that BIVA may be used in clinical and home-use monitoring tool for screening BMD in the elderly in the future.

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.

Adolescents and Bone Health

Adolescence is a critical time for the acquisition of peak bone mass. There are modifiable factors that may influence bone health in an adolescent. For those at risk for bone fragility, initial management includes optimization of calcium and vitamin D, weight-bearing exercise, and maintenance of a normal body weight. In certain scenarios, bisphosphonate treatment is indicated, as is reviewed. How hormonal contraceptives affect bone mineral density is unclear, but in patients with risk factors or known bone fragility, prescribers should consider their skeletal effects. Some conditions, including restrictive eating disorders and primary ovarian insufficiency, warrant long-term monitoring of bone health.

Muscle-Bone Interactions in Chinese Men and Women Aged 18-35 Years

To characterize bone mineral density (BMD), bone strength, muscle and fat mass, and muscle strength and power in Chinese women (n = 25) and men (n = 28) classified as in the bone accrual phase (18-25 years) or in the peak bone mass phase (26-35 years). Calcium intakes, physical activity levels, and serum vitamin D were measured. Dual-energy X-ray absorptiometry (DXA) assessed body composition, lumbar spine, and hip areal BMD (aBMD) variables and peripheral quantitative computed tomography (pQCT) assessed cortical and trabecular volumetric BMD (vBMD) and bone strength. Muscle strength and power were assessed by grip strength, leg press, and vertical jump tests. Calcium, serum vitamin D, and physical activity levels were similar across age and sex groups. Significant sex differences (p < 0.05) were found for most body composition variables, hip aBMD, tibia variables, and muscle strength and power. Adjusting for height and weight eliminated most of the significant sex differences. Women showed stronger positive correlations between body composition and bone variables (r = 0.44 to 0.78) than men. Also, correlations between muscle strength/power were stronger in women vs. men (r = 0.43 to 0.82). Bone traits were better related to body composition and muscle function in Chinese women compared to Chinese men aged 18 to 35 years, and peak bone mass seems to be achieved by 25 years of age in both Chinese men and women since there were no differences between the two age groups.

Correlation of Bone Mineral Density with Pulmonary Function in Advanced Duchenne Muscular Dystrophy

BACKGROUND

A relationship between bone mineral density (BMD) and physical function has been revealed in the general population and various diseases. However, there is a lack of research investigating the correlation between BMD and respiratory function, one of few measurable physical parameters in patients with advanced Duchenne muscular dystrophy (DMD).

OBJECTIVE

To determine whether pulmonary function parameters, including respiratory muscle strength, are related to BMD.

DESIGN

Retrospective observational study.

SETTING

A tertiary university hospital.

PATIENTS

DMD patients who were over 20 years of age, nonambulatory, and supported by mechanical ventilators.

METHODS

The patients' age, weight, and pulmonary function as well as the BMD of the first and the fourth lumbar vertebra were assessed. Pulmonary function includes forced vital capacity (FVC), unassisted and assisted peak cough flow (UPCF and APCF), maximal expiratory pressure (MEP), and maximal inspiratory pressure (MIP).

MAIN OUTCOME MEASURES

A bivariate correlation for BMD and other pulmonary parameters was calculated, and hierarchical regression analysis was used to determine predictors of spine Z-score.

RESULTS

It was observed that the decrease in the spine BMD was not significantly correlated with age. However, the body mass index (BMI) and all parameters of pulmonary function were correlated with BMD. Partial correlation analysis adjusted by BMI showed that UPCF and APCF were powerful predictors of spine BMD.

CONCLUSIONS

The BMD of the lumbar spine correlated with BMI and PCF in patients with DMD at an advanced stage.

Association between grip strength and bone mineral density in general US population of NHANES 2013-2014

Association between strength of nonadjacent muscles and bone mineral density is unclear. We used data from the National Health and Nutrition Examination Survey to convince the effect of grip strength on femoral neck and lumbar spine mineral density in the general US population. This research can broaden the area of muscle-bone interaction.

INTRODUCTION

Grip test measures the maximum isotonic strength of hand and forearm and is often used as an indicator of general muscle strength. Muscle has been shown to exert positive effects on bone health, and studies are needed to test whether grip strength can be associated with bone mineral density of nonadjacent bones. The aim of this study is to assess whether grip strength is an independent predictor for bone mineral density (BMD) of femoral neck and total lumbar spine in the general US population.

METHODS

We used the data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014, and 1850 participants aged from 40 to 80 years old were included in the analysis. Grip strength was recorded as the largest reading of three efforts of one's dominant hand using a handgrip dynamometer. Femoral neck and lumbar spine BMDs were measured through Dual-energy X-ray absorptiometry (DXA) scan. Univariate and multivariate linear regression analyses were done to examine the association between grip strength and BMDs.

RESULTS

After adjusting for age, ethnicity, body mass index (BMI), use of female hormones, smoking habit, drinking habit, family history of osteoporosis, use of calcium and vitamin D supplements, physical activity, serum calcium, and phosphorus levels, grip strength is associated with increased femoral neck and total lumbar spine BMDs in men (P < 0.001, P = 0.005), premenopausal women (P = 0.040, P = 0.014), and postmenopausal women (P = 0.016, P = 0.012).

CONCLUSIONS

Our results suggest that (1) grip strength can be associated with BMD of nonadjacent bones, and (2) grip strength of dominant hand can be an indicator of BMD in the general US population across genders and menopausal status.

Does Muscular Power Predict Bone Mineral Density in Young Adults?

The aim of this study was to explore the relationships between maximum power and bone variables in a group of young adults. Two hundred and one young adults (53 men and 148 women) whose ages range from 18 to 35 years voluntarily participated in this study. Weight and height were measured, and body mass index was calculated. Body composition, bone mineral content (BMC) and bone mineral density (BMD) were determined for each individual by dual-energy X-ray absorptiometry. Vertical jump was evaluated using a validated field test (Sargent test). The highest vertical jump was selected. Maximum power (P max, in watts) of the lower limbs was calculated accordingly. In young men, maximum power was positively correlated to whole body (WB) BMC (r = 0.65; p < 0.001), WB BMD (r = 0.41; p < 0.01), L1-L4 BMC (r = 0.54; p < 0.001), total hip (TH) BMC (r = 0.50; p < 0.001), femoral neck (FN) BMC (r = 0.35; p < 0.01), FN cross-sectional area (CSA) (r = 0.33; p < 0.05) and FN cross-sectional moment of inertia (CSMI) (r = 0.50; p < 0.001). In young women, maximum power was positively correlated to WB BMC (r = 0.48; p < 0.001), WB BMD (r = 0.28; p < 0.001), L1-L4 BMC (r = 0.34; p < 0.001), TH BMC (r = 0.43; p < 0.001), TH BMD (r = 0.21; p < 0.01), FN BMC (r = 0.42; p < 0.001), FN BMD (r = 0.31; p < 0.001), FN CSA (r = 0.41; p < 0.001), FN CSMI (r = 0.40; p < 0.001) and FN Z (r = 0.41; p < 0.01). The current study suggests that maximum power is a positive determinant of WB BMC, WB BMD, FN CSA, and FN CSMI in young men. It also shows that maximum power is a positive determinant of WB BMC, WB BMD, TH BMD, FN BMD, FN CSA, FN CSMI, and FN Z in young women.

The relationships between bone variables and physical fitness across the BMI spectrum in young adult women

In this cross-sectional study we aimed to evaluate the relationship between physical fitness and bone variables across the body mass index (BMI) spectrum in women aged 20-35 years. The study included 13 underweight women (BMI < 18.5 kg/m²), 24 normal weight women (BMI 18.5-24.9 kg/m²), and 20 overweight/obese women (BMI ≥ 25 kg/m²) aged between 20 and 35 years. Bone mineral density (BMD) and content (BMC) at the whole body, lumbar spine, and femoral neck, lumbar spine trabecular bone score, femoral neck geometry were assessed using dual-energy X-ray absorptiometry. Cardiorespiratory fitness and lower limb muscle power were estimated using the 20-m shuttle run test and the Sargent jump test, respectively. The associations between bone variables and physical fitness were different according to BMI categories. Correlations between physical fitness and bone parameters are particularly significant in normal BMI and less significant in low and high BMI. Multivariate ANCOVA regression models demonstrated that absolute VO_2max (L/min) is a strong determinant of all the bone parameters regardless of BMI. Implementing strategies for increasing VO_2max (L/min) by increasing lean mass and promoting resistance and/or high-intensity interval training could be effective to optimize bone health in underweight and overweight young adult women.

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.

Dietary Approaches for Bone Health: Lessons from the Framingham Osteoporosis Study

Osteoporosis is characterized by systemic impairment of bone mass, strength, and microarchitecture, resulting in increased risk for fragility fracture, disability, loss of independence, and even death. Adequate nutrition is important in achieving and maintaining optimal bone mass, as well as preventing this debilitating disease. It is widely accepted that adequate calcium and vitamin D intake are necessary for good bone health; however, nutritional benefits to bone go beyond these two nutrients. This review article will provide updated information on all nutrients and foods now understood to alter bone health. Specifically, this paper will focus on related research from the Framingham Osteoporosis Study, an ancillary study of the Framingham Heart Study, with data on more than 5000 adult men and women.

Optimizing bone health in children and adolescents

The pediatrician plays a major role in helping optimize bone health in children and adolescents. This clinical report reviews normal bone acquisition in infants, children, and adolescents and discusses factors affecting bone health in this age group. Previous recommended daily allowances for calcium and vitamin D are updated, and clinical guidance is provided regarding weight-bearing activities and recommendations for calcium and vitamin D intake and supplementation. Routine calcium supplementation is not recommended for healthy children and adolescents, but increased dietary intake to meet daily requirements is encouraged. The American Academy of Pediatrics endorses the higher recommended dietary allowances for vitamin D advised by the Institute of Medicine and supports testing for vitamin D deficiency in children and adolescents with conditions associated with increased bone fragility. Universal screening for vitamin D deficiency is not routinely recommended in healthy children or in children with dark skin or obesity because there is insufficient evidence of the cost-benefit of such a practice in reducing fracture risk. The preferred test to assess bone health is dual-energy x-ray absorptiometry, but caution is advised when interpreting results in children and adolescents who may not yet have achieved peak bone mass. For analyses, z scores should be used instead of T scores, and corrections should be made for size. Office-based strategies for the pediatrician to optimize bone health are provided. This clinical report has been endorsed by American Bone Health.

Protein intake and lumbar bone density: the Multi-Ethnic Study of Atherosclerosis (MESA)

Dietary protein has been shown to increase urinary Ca excretion in randomised controlled trials, and diets high in protein may have detrimental effects on bone health; however, studies examining the relationship between dietary protein and bone health have conflicting results. In the present study, we examined the relationship between dietary protein (total, animal and vegetable protein) and lumbar spine trabecular volumetric bone mineral density (vBMD) among participants enrolled in the Multi-Ethnic Study of Atherosclerosis (n 1658). Protein intake was assessed using a FFQ obtained at baseline examination (2000-2). Lumbar spine vBMD was measured using quantitative computed tomography (2002-5), on average 3 years later. Multivariable linear and robust regression techniques were used to examine the associations between dietary protein and vBMD. Sex and race/ethnicity jointly modified the association of dietary protein with vBMD (P for interaction = 0·03). Among white women, higher vegetable protein intake was associated with higher vBMD (P for trend = 0·03), after adjustment for age, BMI, physical activity, alcohol consumption, current smoking, educational level, hormone therapy use, menopause and additional dietary factors. There were no consistently significant associations for total and animal protein intakes among white women or other sex and racial/ethnic groups. In conclusion, data from the present large, multi-ethnic, population-based study suggest that a higher level of protein intake, when substituted for fat, is not associated with poor bone health. Differences in the relationship between protein source and race/ethnicity of study populations may in part explain the inconsistent findings reported previously.

Gene-by-diet interactions influence calcium absorption and bone density in mice

Dietary calcium (Ca) intake is needed to attain peak bone mineral density (BMD). Habitual low Ca intake increases intestinal Ca absorption efficiency to protect bone mass, but the mechanism controlling, and the impact of genetics on, this adaptive response is not clear. We fed 11 genetically diverse inbred mouse lines a normal (0.5%) or low (0.25%) Ca diet from 4 to 12 weeks of age (n = 8 per diet per line) and studied the independent and interacting effects of diet and genetics on Ca and bone metabolism. Significant genetic variation was observed in all bone, renal, and intestinal phenotypes measured including Ca absorption. Also, adaptation of Ca absorption and bone parameters to low dietary Ca was significantly different among the lines. Ca absorption was positively correlated to femur BMD (r = 0.17, p = 0.02), and distal femur bone volume/tissue volume (BV/TV) (r = 0.34, p < 0.0001). Although Ca absorption was correlated to 1,25 dihydroxyvitamin D (1,25(OH)2 D) (r = 0.35, p < 0.0001), the adaptation of Ca absorption to low Ca intake did not correlate to diet-induced adaptation of 1,25(OH)2 D across the 11 lines. Several intestinal proteins have been proposed to mediate Ca absorption: claudins 2 and 12, voltage gated Ca channel v1.3 (Cav1.3), plasma membrane Ca ATPase 1b (PMCA1b), transient receptor potential vanilloid member 6 (TRPV6), and calbindin D9k (CaBPD9k). Only the mRNA levels for TRPV6, CaBPD9k, and PMCA1b were related to Ca absorption (r = 0.42, 0.43, and 0.21, respectively). However, a significant amount of the variation in Ca absorption is not explained by the current model and suggests that novel mechanisms remain to be determined. These observations lay the groundwork for discovery-focused initiatives to identify novel genetic factors controlling gene-by-diet interactions affecting Ca/bone metabolism.

Association of total protein intake with bone mineral density and bone loss in men and women from the Framingham Offspring Study

OBJECTIVE

To examine (i) the association of percentage of total energy intake from protein (protein intake %) with bone mineral density (BMD, g/cm2) and bone loss at the femoral neck, trochanter and lumbar spine (L2-L4) and (ii) Ca as an effect modifier.

SETTING

The Framingham Offspring Study.

SUBJECTS

Men (n 1280) and women (n 1639) completed an FFQ in 1992-1995 or 1995-1998 and underwent baseline BMD measurement by dual-energy X-ray absorptiometry in 1996-2000. Men (n 495) and women (n 680) had follow-up BMD measured in 2002-2005.

DESIGN

Cohort study using multivariable regression to examine the association of protein intake % with each BMD, adjusting for covariates. Statistical interaction between protein intake % and Ca (total, dietary, supplemental) intake was examined.

RESULTS

The mean age at baseline was 61 (sd 9) years. In the cross-sectional analyses, protein intake % was positively associated with all BMD sites (P range: 0·02-0·04) in women but not in men. Significant interactions were observed with total Ca intake (<800 mg/d v. ≥800 mg/d) in women at all bone sites (P range: 0·002-0·02). Upon stratification, protein intake % was positively associated with all BMD sites (P range: 0·04-0·10) in women with low Ca intakes but not in those with high Ca intakes. In the longitudinal analyses, in men, higher protein intake % was associated with more bone loss at the trochanter (P = 0·01) while no associations were seen in women, regardless of Ca intake.

CONCLUSIONS

This suggests that greater protein intake benefits women especially those with lower Ca intakes. However, protein effects are not significant for short-term changes in bone density. Contrastingly, in men, higher protein intakes lead to greater bone loss at the trochanter. Longer follow-up is required to examine the impact of protein on bone loss.

Bone mineral density and body composition of adult premenopausal women with three levels of physical activity

Weight-bearing and resistance physical activities are recommended for osteoporosis prevention, but it is unclear whether an intensity level above current recommendations has a positive effect on adult premenopausal women. Body composition and bone mineral density (BMD) by DXA were compared in three groups of women as follows: Sedentary, Maintenance exercise, and federated Sport Team (n = 16 for each group). Physical activity was estimated from the International Physical Activity Questionnaire (IPAQ). The groups did not differ in age, height, weight, or body mass index. Bone mineral content and non-fat soft tissue mass were higher and fat mass was lower in the Sport Team group than in the other groups. The same was true for BMD of total skeleton, lumbar spine, femoral neck, and total hip. A test for linear trend of body composition and BMD showed significant results when including all three groups. Simple and multiple regression analyses showed significant associations between physical activity level (or alternatively, years of participation in programmed physical activity) and bone mass measures at all sites except for the middle third of radius. It is concluded that a level of physical activity higher than that usually recommended benefits bone health in adult premenopausal women.

Dual-energy X-ray absorptiometry-based body volume measurement for 4-compartment body composition

BACKGROUND

Total body volume (TBV), with the exclusion of internal air voids, is necessary to quantify body composition in Lohman's 4-compartment (4C) model.

OBJECTIVE

This investigation sought to derive a novel, TBV measure with the use of only dual-energy X-ray absorptiometry (DXA) attenuation values for use in Lohman's 4C body composition model.

DESIGN

Pixel-specific masses and volumes were calculated from low- and high-energy attenuation values with the use of first principle conversions of mass attenuation coefficients. Pixel masses and volumes were summed to derive body mass and total body volume. As proof of concept, 11 participants were recruited to have 4C measures taken: DXA, air-displacement plethysmography (ADP), and total body water (TBW). TBV measures with the use of only DXA (DXA-volume) and ADP-volume measures were compared for each participant. To see how body composition estimates were affected by these 2 methods, we used Lohman's 4C model to quantify percentage fat measures for each participant and compared them with conventional DXA measures.

RESULTS

DXA-volume and ADP-volume measures were highly correlated (R(2) = 0.99) and showed no statistically significant bias. Percentage fat by DXA volume was highly correlated with ADP-volume percentage fat measures and DXA software-reported percentage fat measures (R(2) = 0.96 and R(2) = 0.98, respectively) but were slightly biased.

CONCLUSIONS

A novel method to calculate TBV with the use of a clinical DXA system was developed, compared against ADP as proof of principle, and used in Lohman's 4C body composition model. The DXA-volume approach eliminates many of the inherent inaccuracies associated with displacement measures for volume and, if validated in larger groups of participants, would simplify the acquisition of 4C body composition to a single DXA scan and TBW measure.

Protective effect of high protein and calcium intake on the risk of hip fracture in the Framingham offspring cohort

The effect of protein on bone is controversial, and calcium intake may modify protein's effect on bone. We evaluated associations of energy-adjusted tertiles of protein intake (ie, total, animal, plant, animal/plant ratio) with incident hip fracture and whether total calcium intake modified these associations in the Framingham Offspring Study. A total of 1752 men and 1972 women completed a baseline food frequency questionnaire (1991-1995 or 1995-1998) and were followed for hip fracture until 2005. Hazard ratios (HRs) were estimated using Cox proportional hazards regression adjusting for confounders. Baseline mean age was 55 years (SD 9.9 years, range 26 to 86 years). Forty-four hip fractures occurred over 12 years of follow-up. Owing to significant interaction between protein (total, animal, animal/plant ratio) and calcium intake (p interaction range = .03 to .04), stratified results are presented. Among those with calcium intakes less than 800 mg/day, the highest tertile (T3) of animal protein intake had 2.8 times the risk of hip fracture [HR = 2.84, 95% confidence interval (CI) 1.20-6.74, p = .02] versus the lowest tertile (T1, p trend = .02). In the 800 mg/day or more group, T3 of animal protein had an 85% reduced hip fracture risk (HR = 0.15, 95% CI 0.02-0.92, p = .04) versus T1 (p trend = .04). Total protein intake and the animal/plant ratio were not significantly associated with hip fracture (p range = .12 to .65). Our results from middle-aged men and women show that higher animal protein intake coupled with calcium intake of 800 mg/day or more may protect against hip fracture, whereas the effect appears reversed for those with lower calcium intake. Calcium intake modifies the association of protein intake and the risk of hip fracture in this cohort and may explain the lack of concordance seen in previous studies.

Osteoporosis in anorexia nervosa

Anorexia nervosa is a condition associated with reduced bone mass and increased bone fragility, for which there is no known effective treatment. Anorexia nervosa usually has its onset during adolescence, the critical time when peak bone mass is accrued. Low bone mass is caused by reduced bone formation, as well as accelerated bone resorption. The etiology is multifactorial and includes poor nutrition, low bodyweight, sex hormone deficiency and hypercortisolism. Weight gain and resumption of menses is accompanied by some improvement in bone mass, but may not restore it to normal levels. Oral estrogen-replacement therapy is not effective in increasing bone mass in this disorder. The bisphosphonates, used in conjunction with nutritional rehabilitation and weight gain, have shown promise, but concerns about safety have limited their use. The aim of this article is to highlight recent recommendations regarding the assessment of fracture risk in children and adolescents, summarize the evidence for low bone mass and increased fracture risk in anorexia nervosa, and discuss approaches to the management of low bone mass in this disorder.

Compositional breast imaging using a dual-energy mammography protocol

PURPOSE

Mammography has a low sensitivity in dense breasts due to low contrast between malignant and normal tissue confounded by the predominant water density of the breast. Water is found in both adipose and fibroglandular tissue and constitutes most of the mass of a breast. However, significant protein mass is mainly found in the fibroglandular tissue where most cancers originate. If the protein compartment in a mammogram could be imaged without the influence of water, the sensitivity and specificity of the mammogram may be improved. This article describes a novel approach to dual-energy mammography, full-field digital compositional mammography (FFDCM), which can independently image the three compositional components of breast tissue: water, lipid, and protein.

METHODS

Dual-energy attenuation and breast shape measures are used together to solve for the three compositional thicknesses. Dual-energy measurements were performed on breast-mimicking phantoms using a full-field digital mammography unit. The phantoms were made of materials shown to have similar x-ray attenuation properties of the compositional compartments. They were made of two main stacks of thicknesses around 2 and 4 cm. Twenty-six thickness and composition combinations were used to derive the compositional calibration using a least-squares fitting approach.

RESULTS

Very high accuracy was achieved with a simple cubic fitting function with root mean square errors of 0.023, 0.011, and 0.012 cm for the water, lipid, and protein thicknesses, respectively. The repeatability (percent coefficient of variation) of these measures was tested using sequential images and was found to be 0.5%, 0.5%, and 3.3% for water, lipid, and protein, respectively. However, swapping the location of the two stacks of the phantom on the imaging plate introduced further errors showing the need for more complete system uniformity corrections. Finally, a preliminary breast image is presented of each of the compositional compartments separately.

CONCLUSIONS

FFDCM has been derived and exhibited good compositional thickness accuracy on phantoms. Preliminary breast images demonstrated the feasibility of creating individual compositional diagnostic images in a clinical environment.

Dietary protein and bone health: a systematic review and meta-analysis

BACKGROUND

There has been a resurgence of interest in the controversial relation between dietary protein and bone health.

OBJECTIVE

This article reports on the first systematic review and meta-analysis of the relation between protein and bone health in healthy human adults.

DESIGN

The MEDLINE (January 1966 to September 2007) and EMBASE (1974 to July 2008) databases were electronically searched for all relevant studies of healthy adults; studies of calcium excretion or calcium balance were excluded.

RESULTS

In cross-sectional surveys, all pooled r values for the relation between protein intake and bone mineral density (BMD) or bone mineral content at the main clinically relevant sites were significant and positive; protein intake explained 1-2% of BMD. A meta-analysis of randomized placebo-controlled trials indicated a significant positive influence of all protein supplementation on lumbar spine BMD but showed no association with relative risk of hip fractures. No significant effects were identified for soy protein or milk basic protein on lumbar spine BMD.

CONCLUSIONS

A small positive effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials supports the positive association between protein intake and bone health found in cross-sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were small and had 95% CIs that were close to zero. Therefore, there is a small benefit of protein on bone health, but the benefit may not necessarily translate into reduced fracture risk in the long term.

Nutritional determinants of bone health

Osteoporosis is a major public health problem. The aging population will require vigilant prevention, education, and treatment to maintain bone density and reduce the risk of fractures and falls. Nutritional requirements of elderly persons can have a profound effect on bone health. Calcium, vitamin D, and protein are vital nutrients for optimal bone health. Adequate calcium is essential for bone maintenance. Vitamin D research shows a link between reduced falls and fractures. Related macro- and micronutrients play an important role in bone mass integrity and quality. Adequate nutrition for older adults needs to be encouraged to promote and maintain bone health.

The effects of dietary protein on bone mineral mass in young adults may be modulated by adolescent calcium intake

The effect of dietary protein on bone mass measures at different life stages is controversial. We investigated the influence of protein intake on bone mass measures in young adults, considering the influence of calcium intake through adolescence. Subjects were 133 young adults (59 males, 74 females) who were participating in the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-1997, 2003-2006). At adulthood, their mean age was 23 y. We assessed dietary intake via serial 24-h recalls carried out at least once yearly. Total body (TB) bone mineral content (BMC) and TB bone mineral density (BMD) were assessed annually using Dual energy X-ray absorptiometry. We determined TB-BMC net gain from the age of peak height velocity (PHV) to early adulthood. We analyzed data from all subjects and subsets based on sex and calcium intake using multiple regression. TB-BMC significantly increased from age at PHV to early adulthood by 41% in males and 37% in females. Height, weight, physical activity, and sex were significant predictors of TB-BMC, TB-BMC net gain, and TB-BMD among all subjects. Protein intake predicted TB-BMC net gain in all subjects (beta = 0.11; P = 0.015). In females at peri-adolescence or early adulthood with adequate calcium intake (>1000 mg/d), protein intake positively predicted TB-BMC, TB-BMC net gain, and TB-BMD (P < 0.05). Our results indicate that when calcium intake is adequate, protein intake has a beneficial effect on the bone mass of young adult females. Protein, in the absence of sufficient calcium, does not confer as much benefit to bone.

Heritability of BMD of femoral neck and lumbar spine: a multivariate twin study of Finnish men

Of the 80% variation in BMD among male twins that is caused by genetics, part was explained by genetic influences on lifting strength and lean body mass/height. Lifting strength was significant in both the femoral and spine BMD and body weight only for lumbar BMD.

INTRODUCTION

The dominant role of heritability in BMD has been shown in twin studies among women. However, the mechanisms of genetic influences are poorly understood. BMD is associated with lean body mass and muscle strength, which both have a genetic component, but the relative effects of muscle strength and lean body mass/height on the total genetic and environmental variations influencing BMD of men are unclear.

MATERIALS AND METHODS

Measurements of BMD from a DXA scanner on a representative sample of 147 monozygotic and 153 dizygotic male twin pairs (age, 35-70 yr) were related to a variety of anthropometric and behavioral covariates and interview data. Data were analyzed with univariate modeling of genetic characteristics, bivariate modeling of covariates that were significant in univariate models, and multivariate modeling of the simultaneous effects of significant covariates from the bivariate models.

RESULTS

Heritability influences were estimated to account for 75% of the variance in femoral BMD and 83% in lumbar BMD. Univariate and bivariate modeling showed that, of the factors studied, only lifting force and lean body mass/height had statistically significant influences. Of the total genetic variation in femoral BMD, lifting force explained 9%, and lean body mass/height 18%; the proportions for lumbar BMD were 9% and 11%, respectively. Of the total environmental variation, the correlation with isokinetic lifting force explained 9% for femoral BMD and 10% for lumbar BMD. The genetic correlations between lifting force and femoral and lumbar BMD were approximately 0.3, as were the environmental correlations of isokinetic lifting force and femoral and lumbar BMD and of lean body mass/height and femoral BMD. The environmental correlation of lean body mass/height and femoral BMD was not significant.

CONCLUSIONS

Lifting force had effects on both femoral and lumbar BMD. Body weight was important, but only for lumbar BMD. Muscle strength may have the best potential for modification among behavioral factors to increase both femoral and lumbar BMD.

Relationships between physical activity and physical capacity in adolescent females and bone mass in adulthood

This study investigates whether physical activity and physical performance in adolescence are positively related to adult bone mineral density (BMD). In 1974, physical activity, endurance, and muscular strength were measured in 204 randomly selected female students, age 16.1 +/- 0.3 year (range 15-17 years). Twenty years later, 36 of the women volunteered to undergo a measurement of their BMD. Women who were members in a sports club in adolescence had significantly higher adult BMD (mean differences of 5% to 17% depending on site) compared with subjects who were not engaged in a sports club. Furthermore, women with persistent weight-bearing activity in adulthood had significantly higher BMD compared with women who had stopped being active or had never been active. The differences ranged between 5% and 19% with the highest difference found in trochanter BMD. Stepwise regression analyses showed that membership in a sports club at baseline was a significant independent predictor of BMD in the total body, lumbar spine, legs, trochanter, and femoral neck, explaining 17-26% of the variation in BMD. Change in body weight was a strong independent predictor of BMD of the total body and arms, explaining 8% of the variation in both sites. In addition, running performance at baseline was an independent predictor of total body BMD, whereas the two-hand lift performance significantly predicted BMD of the total body, legs and trochanter. The hanging leg-lift and handgrip were both significant predictors of arm BMD. In conclusion, membership in a sports club and site-specific physical performance in adolescence together with the change in body weight were significantly associated with adult BMD in premenopausal women.

Decreased activities of daily living and associations with bone loss among aged residents in a rural Japanese community: the Miyama Study

The present study aimed to clarify frequencies of decreased activities of daily living (ADL) and associations with rate of bone loss among inhabitants more than 60 years old in Miyama, a rural community in Japan. A cohort of 1543 inhabitants aged 40-79 years was established according to Miyama resident registrations in 1989. Men (n = 50) and women (n = 50) from each of two age strata between 60 and 79 years (N = 200) were selected from this cohort, and bone mineral density (BMD) of the lumbar spine and proximal femur was measured using dual-energy X-ray absorptiometry in 1990 (initial survey) and again in 1993, 1997, and 2000. Difficulties involving ADL were surveyed at every follow-up study. Of the 200 initial participants, 124 (57 men, 67 women; 62.0%) completed all BMD measurements and answered all items about ADL in the follow-up survey. The following items were investigated as a general indication of changes to ADL: reaching objects on a high shelf or cupboard (reaching); washing and drying the body (washing body); washing hair over a washbasin (washing hair); sitting for 1 h on a hard chair (sitting); raising the torso from a lying position in bed (raising); standing continuously for 30 min (standing); taking socks on and off the feet (taking socks); bending down from a seated position and picking up a small object at the side of the chair (bending); lifting heavy objects (lifting); and running 100 m without stopping (running). Among ADL items, the most frequent difficulties in men involved running (50.0%), followed by raising (30.6%), standing (27.1%), sitting (24.7%), and reaching (16.5%). In women, difficulties involved running (67.0%), followed by lifting (36.3%), standing (33.1%), reaching (30.8%), and sitting (23.6%). To evaluate relationships between decreased ADL and changes in BMD, annual rates of change for BMD at the lumbar spine and femoral neck were compared to changes for each ADL item (2 grade decrease; 1 grade decrease; or no change). Analysis of covariance (ANCOVA) was then performed on decreased ADL and annual bone changes after adjustment for age, concomitant disease (previous fractures, gastrectomy, diabetes mellitus, and renal dialysis at initial survey). In men, annual rates of change in BMD at the femoral neck over 10 years were significantly correlated with decreased abilities in bending (P = 0.046; R2 = 0.10). In women, annual rates of change in BMD at the lumbar spine over 10 years were significantly correlated with decreased abilities in reaching (P = 0.007; R2 = 0.25), and lifting (P = 0.014, R2 = 0.27), and those at the femoral neck were significantly correlated with decreased abilities in lifting (P = 0.001, R2 = 0.33).

Nutrition, mild hyperparathyroidism, and bone mineral density in young Japanese women

BACKGROUND

The adverse effects of poor nutrition on the bones of young Asian women have not been fully elucidated.

OBJECTIVE

The purpose of this study was to investigate possible associations of vitamin D nutrition, calcium intake, and other nutrients with bone metabolism and bone mass in young Japanese women.

DESIGN

The subjects were 108 female college students aged 19-25 y. Dietary nutrients were measured by using the duplicate sampling method on 3 weekdays. Serum 25-hydroxyvitamin D [25(OH)D], intact parathyroid hormone, and bone turnover markers were also measured. Bone mineral density (BMD) of the spine and femur was measured by dual-energy X-ray absorptiometry.

RESULTS

The proportions of the subjects with low 25(OH)D (< 30 nmol/L) and high intact parathyroid hormone (> or = 6.9 pmol/L) concentrations were 32.4% and 15.7%, respectively. Serum 25(OH)D concentrations (P = 0.0265) and calcium intake (P = 0.0103) were inversely associated with serum intact parathyroid hormone. In addition to weight and physical activity, the presence of mild hyperparathyroidism was associated with a low BMD of the lumbar spine (P = 0.0062) and the femoral neck (P = 0.0250), and a low calcium intake was associated with a low BMD of the femoral neck (P = 0.0044).

CONCLUSIONS

Low calcium intake (based on low BMD of the femoral neck only) and mild hyperparathyroidism (based on low BMD of both the femoral neck and lumbar spine), partly explained by low vitamin D nutrition and a low calcium intake, are important predictors of low BMD in young Japanese women. Effects of poor nutrition and mild hyperparathyroidism on bone peak bone mass in young women should be further investigated in longitudinal studies.

Protein consumption is an important predictor of lower limb bone mass in elderly women

BACKGROUND

The effect of protein intake on bone density is uncertain, and evidence exists for beneficial effects of both low and high protein intakes.

OBJECTIVE

The objective was to study the relation between protein consumption and bone mass in elderly women with allowance for other lifestyle factors affecting bone metabolism.

DESIGN

We conducted a cross-sectional and longitudinal study of a population-based sample of 1077 women aged 75 +/- 3 y. At baseline, protein consumption was measured with a food-frequency questionnaire, and bone mass and structure were measured by using quantitative ultrasound of the heel. One year later, hip bone mineral density (BMD) was measured by using dual-energy X-ray absorptiometry.

RESULTS

Subjects consumed a mean (+/-SD) of 80.5 +/- 27.8 g protein/d (1.19 +/- 0.44 g protein/kg body wt). Regression analysis showed a positive correlation between protein intake and qualitative ultrasound of the heel and BMD after adjustment for age, body mass index, and other nutrients. The dose-response effect was best characterized by protein consumption expressed in tertiles, such that subjects in the lowest tertile (<66 g protein/d) had significantly lower qualitative ultrasound of the heel (1.3%) and hip BMD (2.6%) than did the subjects in the higher tertiles (>87 g protein/d).

CONCLUSION

These data suggest that protein intakes for elderly women above current recommendations may be necessary to optimize bone mass.

Bone mineral density changes over two years in first-time users of depot medroxyprogesterone acetate

OBJECTIVE

To compare longitudinal changes in bone mineral density (BMD) among first-time depot medroxyprogesterone acetate (DMPA) users to women using no hormonal contraception, and evaluate user characteristics associated with that BMD change.

DESIGN

Prospective longitudinal study.

SETTING

Healthy volunteers in an academic research environment.

PATIENT(S)

Women, aged 18 to 35, choosing DMPA for contraception (n = 178) and women using no hormonal contraception (n = 145).

MAIN OUTCOME MEASURE(S)

Hip and spine BMD measured, at three-month intervals for 24 months, by dual energy x-ray absorptiometry.

RESULT(S)

Mean hip BMD declined 2.8% (SE = 0.034) 12 months following DMPA initiation and 5.8% (SE = 0.096) after 24 months. Mean spine (L1-L3) BMD declined 3.5% (SE = 0.022) and 5.7% (SE = 0.034), respectively, after one and two years of DMPA use. Mean hip and spine BMD of control participants changed less than 0.9% over the same period. Among DMPA users, body mass index (BMI) change was inversely associated with BMD change at the hip, but not at the spine. Calcium intake, physical activity, and smoking did not influence BMD change in either group.

CONCLUSION(S)

Hip and spine BMD declined after one DMPA injection and this decline continued with each subsequent injection for 24 months. With the exception of increasing BMI among DMPA users, no user characteristics offered protection against DMPA-related BMD loss.

Effects of pubertal development, height, weight, and grip strength on the bone mineral density of the lumbar spine and hip in peripubertal Japanese children: Kyoto kids increase density in the skeleton study (Kyoto KIDS study)

The effects of growth and pubertal development on the bone mineral density (BMD) of the lumbar spine and hip in peripubertal Japanese children were studied as a basis for evaluating the effects of modifiable factors on bone mass gain. The study comprised bone mass measurements in the lumbar spine (L2-4), femoral neck, and total hip using dual-energy X-ray absorptiometry as well as body size measurements and detailed interviews on medical history and pubertal status. The subjects were 404 first-grade students in three junior high schools (129 boys and 275 girls, mean age 12.8 +/- 0.3 years) with no diseases or medication that would affect bone metabolism. BMD at each site showed an increasing trend with physical growth and sexual maturity. Significant positive correlations were observed between BMD at every skeletal site and height, weight, and grip strength in pre- and postpubertal boys and girls. In multiple regression analyses, pubertal development had a significant positive independent effect on BMD at every skeletal site in girls, but not in boys. Physical and pubertal development showed major effects on BMD, but the magnitude of these effects differed in boys and girls, even if they were of the same age. We conclude that confounding factors due to physical and pubertal development should be taken into consideration in different ways for boys and girls in investigations on the effects of environmental or behavioral factors on bone mass acquisition in peripubertal children.

Positive, site-specific associations between bone mineral status, fitness, and time spent at high-impact activities in 16- to 18-year-old boys

The incidence of hip and forearm fracture in elderly men in the United Kingdom is a public health issue, but there is limited knowledge on lifestyle factors affecting male bone health. The aim of this cross-sectional study was to evaluate the relationships between whole body and regional bone mineral status and self-reported participation time in no-, low-, moderate-, and high-impact activities and fitness measurements in 16- to 18-year-old boys. One hundred twenty-eight boys underwent absorptiometry (DXA) measurements (Hologic QDR 1000W) of bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the whole body, hip, spine, and forearm. They also completed the EPIC (European Prospective Investigation of Cancer) physical activity questionnaire, which allowed categorization of activities according to impact and aerobic intensity. Fitness and strength were assessed in each subject using estimated VO2 max, grip strength, and back strength. Significant positive relationships were found between BMC, BA, and BMD and the fitness and strength measurements and participation time in high-impact sports at most skeletal sites. The relationships were further examined after adjustment of BMC for height, weight, and bone area, thereby minimizing the influence of body and bone size on these relationships. VO2 max was a significant positive determinant of size-adjusted BMC at the whole body, the ultradistal and one-third radius, and all the hip sites, except the trochanter. Size-adjusted BMC at the forearm sites and trochanter was significantly positively associated with grip strength. Size-adjusted BMC at the whole body and all the hip sites was significantly positively associated with time spent at high-impact activities. Differences in size-adjusted BMC across thirds of time spent at high-impact activities were also examined. Boys in the highest third of high-impact activity had significantly greater size-adjusted whole body BMC and total hip BMC compared to subjects in the lowest third [+3.4 (1.2)% for whole body and +8.5 (2.2)% for hip, both P = 0.001]. Boys in the highest third of high-impact activity spent most activity time jogging, playing tennis, football and rugby, basketball, and exercising with weights. Back strength and lean mass were significantly greater in subjects in the highest third compared to those in the middle (P = 0.02) and lowest third (P = 0.03). No significant differences were found between subjects in each third of high-impact activity for potential confounders including TV viewing, calcium intake, body fat, and height. These findings indicate that participation of male adolescents in a range of high-impact activities for 1 h or more a day is associated with greater bone size and mineral content, especially at the hip.

Bone mineral density changes in young women: a two year study

Achievement of a high peak bone mass is considered a pivotal preventive strategy against future osteoporotic fractures. The ostensible interaction between physiology and lifestylefor the development of bone mass over time is sparsely outlined among young women. The aim of this study was to follow bone density and bone resorption over time among healthy young women in relation to lifestyle factors and to evaluate the perceived influence of other factors. Data were collected in 1999 and in 2001. Healthy young women (n=152) were given a structured questionnaire, a heel bone scanner (dual X-ray absorptiometry) performed bone mineral density measurements and deoxypyridinoline was measured in urine. Data were analyzed by linear, multiple and logistic regression analysis. Mean bone mineral density (BMD) was 0.562 g/cm2 (+/-0.090). Bone density at baseline was the best predictorfor the bone density atfollow-up. Bone density at baseline together with smoking and alcohol (dichotomized) accounted for 86.5% of the variation in bone density 2 years later. Of the participants 62% had decreased/unchanged bone density and 38% had increased their bone density from 1999 to 2001. Use of oral contraceptives or alcohol at baseline was associated with an increased risk of belonging to the group who decreased their bone density. Deoxypyridinoline was not a strongpredictor to bone density and all potential predictors of deoxypyridinoline had a minor influence (<10%). In conclusion, lifestyle behaviors such as use of oral contraceptives, smoking and alcohol consumption seem to have a negative influence on BMD development among young women and warrant further scrutiny.

Influence of soft tissues on mandibular gray scale levels

The purpose of this study was to analyze the gray levels, expressed in pixels, of the mandibular retromolar region, with regard to the influence of muscular and fat soft tissues near this region. Fifteen dry mandibles were X-rayed with the presence of soft tissue simulators. The radiographs were digitized and evaluated by Digora software. A one cm thick layer of wax was used as a simulator of the muscular soft tissue. Animal fat samples of different thicknesses - 0.5, 1.0, 1.5 and 2.0 cm - were used as a simulator of the fat soft tissue. Results showed that the fat soft tissue simulator influenced the gray level values in pixels of the mandibular retromolar region when analyzed in different thicknesses using the Digora digitized image software.

A DXA study of muscle-bone relationships in the whole body and limbs of 2512 normal men and pre- and post-menopausal women

A whole-body DXA study of 1450 healthy Caucasian individuals [Bone 22 (1998) 683] found that mineral mass, either crude (BMC) or statistically adjusted to fat mass (FM-adjusted BMC), correlated linearly with lean mass (LM, proportional to muscle mass). The results showed similar slopes but decreasing intercepts (ordinate values) in the order: pre-MP women > men > post-MP women > children. This supports the hypothesis that sex hormones influence the control of bone status by muscle strength in all species. Now we further study those relationships in 2512 healthy Hispanic adults (307 men, 753 pre-MP women, 1452 post-MP women), including separate determinations in their upper and lower limbs. The slopes of the BMC or FM-adjusted BMC vs. LM relationships were parallel in all the studied regions. However, region-related differences were found between the ordinates of the curves. In the whole body, the crude-BMC/LM relationships showed the same ordinate differences as previously observed. In the lower limbs, those differences were smaller in magnitude but highly significant, showing the order: pre-MP women > men = post-MP women. In the upper limbs, the decreasing ordinate order was: men > pre-MP women > post-MP women. After fat adjustment of the BMC, order in both limbs was: men > pre-MP women > post-MP women. Parallelism of the curves was maintained in all cases. LM had a larger independent influence on these results than FM, body weight, or age. The parallelism of the curves supports the idea that a common biomechanical control of bones by muscles occurs in humans. Results suggest that sex-hormone-associated differences in DXA-assessed muscle-bone proportionality in humans could vary according to the region studied. This could be related to the different weight-bearing nature of the musculoskeletal structures studied. Besides the obvious anthropometric associations, FM would exert a mechanical effect as a component of body weight, evident in the lower limbs, while muscle contractions would induce a more significant, dynamical effect in both lower and upper limbs. Muscles seem to exert a larger influence than FM, body weight, and age on BMC in the whole body and lower limbs, regardless of the gender and reproductive status of the individual. The muscle-bone relationships studied may provide a rationale for a future differential diagnosis between disuse-related and other types of osteopenia.

Lifestyle influences on 9-year changes in BMD in young women

The effects of dietary calcium intake and physical activity on longitudinal changes in BMD over a mean of 9.4 years were examined in 62 healthy young women. Proximal femur BMD declined, lumbar spine BMD increased, and physical activity was associated with BMD change at intertrochanter and total hip sites.

INTRODUCTION

Maximizing premenopausal BMD is an important strategy for the prevention of osteoporosis and resultant fractures later in life.

MATERIALS AND METHODS

Young women who previously participated in a placebo-controlled 2-year calcium intervention study at a mean age of 18.5 +/- 0.3 years were remeasured at 27.8 +/- 1.0 years of age. DXA (Hologic QDR 1000W) was used to measure changes in BMD, and lifestyle factors were ascertained by questionnaire.

RESULTS AND CONCLUSIONS

Early decline in BMD at the neck of femur (-3.3%/decade) and the converse gain in BMD at the lumbar spine (+4.3%/decade) and intertrochanter (+1.9%/decade) suggest site-specific changes in BMD in young premenopausal women. No effect of previous calcium supplementation was seen on current BMD or changes in BMD (p > 0.10). Lifestyle predictors of change in BMD were determined using hierarchical regression analysis after forced correction for the covariates baseline BMD and previous calcium supplementation. Physical activity was positively associated with change in BMD at total hip and intertrochanter sites (beta-coefficients, beta = 0.26 and 0.26 respectively; p < 0.05). Calcium intake was negatively associated with change in BMD at the lumbar spine (beta = -0.27, p < 0.05). Parity was negatively associated with change in BMD at all sites (beta = -0.40 to -0.26, p < 0.05). These data show that BMD is already declining at the proximal femur in these healthy young women. Physical activity assists in maintenance of BMD at some sites and thus may contribute to lifelong fracture prevention. There was no positive association between calcium intake and change in BMD.

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

BACKGROUND

High calcium intakes during adolescence may increase bone acquisition. The magnitude of the effect of dietary calcium supplementation and the timing of its administration to achieve significant effects on bone health are still incompletely defined.

OBJECTIVE

The objective of this study was to assess the effect of calcium supplementation on bone mass accretion in postmenarcheal adolescent girls with low calcium intakes.

DESIGN

A double-blind, placebo-controlled calcium supplementation study was implemented. One hundred girls with a mean (+/- SD) age of 14 +/- 0.5 y with habitual calcium intakes < 800 mg/d completed a 12-mo protocol. The treatment group received a daily supplement containing 1000 mg elemental calcium. Bone mineral density (BMD) and bone mineral content (BMC) of the total body, lumbar spine, and femoral neck were determined at inclusion, 6 mo, and 12 mo. Also measured were serum concentrations of biochemical markers of bone turnover (osteocalcin and deoxypyridinoline), parathyroid hormone, and vitamin D.

RESULTS

The calcium-supplemented group had greater accretion of total-body BMD and lumbar spine BMD but not BMC than did the control group. Calcium supplementation appeared selectively beneficial for girls who were 2 y postmenarcheal. Calcium supplementation significantly decreased bone turnover and decreased serum parathyroid hormone concentrations.

CONCLUSION

Calcium supplementation of postmenarcheal girls with low calcium intakes enhances bone mineral acquisition, especially in girls > 2 y past the onset of menarche.

Dietary protein, calcium metabolism, and skeletal homeostasis revisited

High dietary protein intakes are known to increase urinary calcium excretion and, if maintained, will result in sustained hypercalciuria. To date, the majority of calcium balance studies in humans have not detected an effect of dietary protein on intestinal calcium absorption or serum parathyroid hormone. Therefore, it is commonly concluded that the source of the excess urinary calcium is increased bone resorption. Recent studies from our laboratory indicate that alterations in dietary protein can, in fact, profoundly affect intestinal calcium absorption. In short-term dietary trials in healthy adults, we fixed calcium intake at 20 mmol/d while dietary protein was increased from 0.7 to 2.1 g/kg. Increasing dietary protein induced hypercalciuria in 20 women [from 3.4 +/- 0.3 ( +/- SE) during the low-protein to 5.4 +/- 0.4 mmol/d during the high-protein diet]. The increased dietary protein was accompanied by a significant increase in intestinal calcium absorption from 18.4 +/- 1.3% to 26.3 +/- 1.5% (as determined by dual stable isotopic methodology). Dietary protein intakes at and below 0.8 g/kg were associated with a probable reduction in intestinal calcium absorption sufficient to cause secondary hyperparathyroidism. The long-term consequences of these low-protein diet-induced changes in mineral metabolism are not known, but the diet could be detrimental to skeletal health. Of concern are several recent epidemiologic studies that demonstrate reduced bone density and increased rates of bone loss in individuals habitually consuming low-protein diets. Studies are needed to determine whether low protein intakes directly affect rates of bone resorption, bone formation, or both.

Chemotherapy decreases epiphyseal strength and increases bone fracture risk

To establish the effect of three frequently used chemotherapeutic agents in childhood cancer on the skeleton, growing male Wistar rats were studied. Treatment with doxorubicin, methotrexate, and cisplatin reduces the proximal tibial growth plate shear strength because of a decreased surface area and maximum shear stress. After treatment the bone fracture risk of the tibia and femur is increased because of decreased bending resistance. Doxorubicin and cisplatin reduce the maximum shear stress of the proximal tibial growth plate, none of the chemotherapeutic agents inhibit bone mineralization. These effects are caused by treatment-induced malnutrition and the accompanying weight reduction and a direct effect of the chemotherapeutic agents on the skeleton. The current study confirmed the importance of preventing malnutrition during chemotherapeutic treatment in view of possible skeletal complications. During followup of children treated with chemotherapy, attention should be given to signs and symptoms suggestive of such complications.

Low protein intake: the impact on calcium and bone homeostasis in humans

Increasing dietary protein results in an increase in urinary calcium. Despite over 80 y of research, the source of the additional urinary calcium remains unclear. Because most calcium balance studies found little effect of dietary protein on intestinal calcium absorption, it was assumed that the skeleton was the source of the calcium. The hypothesis was that the high endogenous acid load generated by a protein-rich diet would increase bone resorption and skeletal fracture. However, there are no definitive nutrition intervention studies that show a detrimental effect of a high protein diet on the skeleton and the hypothesis remains unproven. Recent studies from our laboratory demonstrate that dietary protein affects intestinal calcium absorption. We conducted a series of short-term nutrition intervention trials in healthy adults where dietary protein was adjusted to either low, medium or high. The highest protein diet resulted in hypercalciuria with no change in serum parathyroid hormone. Surprisingly, within 4 d, the low protein diet induced secondary hyperparathyroidism that persisted for 2 wk. The secondary hyperparathyroidism induced by the low protein diet was attributed to a reduction in intestinal calcium absorption (as assessed by dual stable calcium isotopes). The long-term consequences of these low protein-induced changes in calcium metabolism are not known, but they could be detrimental to skeletal health. Several recent epidemiological studies demonstrate reduced bone density and increased rates of bone loss in individuals habitually consuming low protein diets. Therefore, studies are needed to determine whether low protein intakes directly affect rates of bone resorption, bone formation or both.

Impact of the analysis of a bone density reference range on determination of the T-score

There are uncertainties concerning the optimal threshold value of bone mineral density (BMD) for the diagnosis of osteoporosis using dual-energy X-ray absorptiometry (DXA). The most widely accepted clinical criteria are based on T- and Z-scores, derived statistically from an age-dependent BMD reference range that includes healthy young adults. This study has compared different analyses of BMD data of healthy, nonfractured, adult white females aged 18-90 years, consisting of 953 studied with DXA in the L1-L4 spine and 1018 measured at the hip. Four regression curves were applied to each reference data set; mean peak BMD (PBMD(R)) and the age-independent standard deviation (SD(R)) were calculated. These data, plus derived T-score thresholds, were compared with equivalent values (PBMD(YN), SD(YN)) determined from BMDs of a subgroup of young normals. Choice of regression curve caused a variation of 0.044 g/cm(2) in spinal PBMD(R) and 0.015-0.022 g/cm(2) in the hip. The variation in calculated SD(R) between the regressions was minimal (maximum variation, 0.03 SD unit in the spine). A split-linear model was chosen as the best overall fit for both the spine and the hip on the basis of goodness-of-fit and biological plausibility. PBMD(R) and PBMD(YN) varied by less than 1% at the spine or hip. Although the difference between SD(R) and SD(YN) was < or =7% for the hip sites, SD(R) was 0.022 g/cm(2) > SD(YN) for the spine (17% difference). At each hip site, BMD T-score thresholds, derived from regression analysis of the entire reference range (T(R)) or from young normals only (T(YN)), were not significantly different; however, equivalent spinal values differed by 0.062 g/cm(2) for T = -2.5. The percentage of the Australian female population (AFP) aged 50 yr or older and classified as osteoporotic, using population census data and the split-line-based T-score threshold of T(R) = -2.5, was 23% for spinal BMD and 17% for the total hip. For T(YN) = -2.5, the values were 36% (spine) and 17% (total hip). The hip BMDs of this study were greater than those of NHANES III in the third, seventh and eighth decades by as much as 0.6 SD. This produced a difference of 0.049-0.077 g/cm(2) for T(YN) = -2.5 between the two reference ranges.

Femur bone mineral density is independently associated with functional recovery after hip fracture in elderly women

OBJECTIVE

To evaluate the association between femur bone mineral density (BMD) and functional recovery after hip fracture.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation hospital in Italy.

PARTICIPANTS

A total of 233 of 263 white women with hip fracture consecutively admitted to a rehabilitation hospital.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Patients underwent BMD assessment by dual-energy x-ray absorptiometry (DXA) at the proximal femur (5 sites) on admission. Functional recovery was evaluated by using Barthel Index scores.

RESULTS

A positive correlation was found between BMD and Barthel Index scores assessed on both admission and discharge (r range,.16-.24, depending on the site of BMD measurement). Linear multiple regression showed that the association between BMD and Barthel Index score was independent of 10 confounding variables: age, body mass index, fracture type, pressure ulcers, cognitive impairment, neurologic diseases, total lymphocyte count as a nutritional index, time between fracture occurrence and DXA assessment, comorbidity, and surgical procedure. Conversely, no significant associations were found between BMD and the change in Barthel Index score attributable to rehabilitation.

CONCLUSIONS

In the study population, femur BMD was an independent predictor of the functional recovery assessed by Barthel Index score after hip fracture, but not of the change in the functional score resulting from rehabilitation.