Factors that influence peak bone mass formation: a study of calcium balance and the inheritance of bone mass in adolescent females

Lifetime milk consumption and bone mineral density in older women

This study examined the relationship between lifetime milk consumption both axial and appendicular bone mineral density in 581 postmenopausal White women. Positive significant, graded associations between milk consumption in adulthood and bone mineral density at the spine, total hip, trochanter, intertrochanter, and midradius, but not the ultradistal wrist or femoral neck, were observed. Adolescent milk consumption showed similar, statistically significant associations (spine and midradius). Associations were independent of age, body mass index, years postmenopausal, thiazide, estrogen and alcohol use, smoking, and exercise. Regular milk consumption in youth and adulthood is associated with better bone mineral density at cortical and trabecular sites in elderly women.

Exercise, smoking, and calcium intake during adolescence and early adulthood as determinants of peak bone mass. Cardiovascular Risk in Young Finns Study Group

OBJECTIVE

To evaluate the contribution to peak bone mass of exercise, smoking, and calcium intake in adolescents and young adults.

DESIGN

Prospective cohort study with end point measurement (bone mineral density) after 11 years' follow up for lifestyle.

SETTING

Five university hospital clinics.

SUBJECTS

264 (153 females, 111 males) subjects aged 9 to 18 years at the beginning of the follow up and 20 to 29 years at the time of measurement of bone mineral density.

MAIN OUTCOME MEASURE

Bone mineral density of lumbar spine and femoral neck by dual energy x ray absorptiometry; measures of physical activity and smoking and estimates of calcium intake repeated three times during follow up.

RESULTS

In the groups with the lowest and highest levels of exercise the femoral bone mineral densities (adjusted for age and weight) were 0.918 and 0.988 g/cm2 for women (P = 0.015, analysis of covariance) and 0.943 and 1.042 g/cm2 for men (P = 0.005), respectively; at the lumbar spine the respective values were 1.045 and 1.131 (P = 0.005) for men. In men the femoral bone mineral densities (adjusted for age, weight, and exercise) were 1.022 and 0.923 g/cm2 for the groups with the lowest and highest values of smoking index (P = 0.054, analysis of covariance). In women the adjusted femoral bone mineral density increased by 4.7% together with increasing calcium intake (P = 0.089, analysis of covariance). In multiple regression analysis on bone mineral density of the femoral neck, weight, exercise, age, and smoking were independent predictors for men; with weight, exercise, and age for women. These predictors together explained 38% of the variance in bone mineral density in women and 46% in men. At the lumbar spine, weight, smoking, and exercise were predictors for men; and only weight for women.

CONCLUSIONS

Regular exercise and not smoking is important in achieving maximal peak bone mass in adolescents and young adults.

Weight-bearing activity during youth is a more important factor for peak bone mass than calcium intake

In a 15 year longitudinal study (Amsterdam Growth and Health Study) is evaluated the effect of daily calcium intake (CAI) during adolescence and young adulthood on the development of peak bone mass at age 27 when the influence of weight-bearing activity (WBA) and body weight was accounted for. A group of 84 males and 98 females were measured longitudinally from age 13 until age 28. Measurements were taken six times of anthropometric characteristics. Lifestyle was also evaluated six times by cross-check interviews of CAI and WBA. Bone mineral density (BMD) of the lumbar spine was determined at age 27 by dual x-ray absorption. Three periods were considered, that is, the adolescent period, the period 13-21 years, and the total period (13-27 years). In multiple linear regression analyses, only WBA and body weight were significant positive contributors to the final model of lumbar BMD at age 27. In all three periods WBA was the best predictor in males and body weight in females. ANOVA was performed on BMD and the highest and lowest quartiles of calcium intake with the significant predictor variables of the linear regression model as covariates. Again calcium intake appeared not a significant predictor of BMD in the three periods in both sexes. Regular weight-bearing exercise and at least a normal age-related body weight in adolescence and young adulthood are of key importance in reaching the highest lumbar peak bone mass at the age of 27 years.

Longitudinal measurement of regional and whole body bone mass in young healthy adults

The so-called peak bone mass (PBM) represents the highest amount of bony tissue achieved during life at a given site of the skeleton. It has been suggested that PBM might be achieved as late as the fourth decade, but recent data have indicated that PBM is already achieved by the end of sexual maturation, namely at the end of the second decade. The solving of this apparent controversy is of interest for a better understanding of bone homeostasis and for defining the cohort of normal subjects to be evaluated in order to establish a PBM reference range--necessary for the diagnosis of osteoporosis and evaluation of the fracture risk. To study bone mass evolution in young healthy adults and to determine whether such a cohort can be used to establish PBM reference values, we measured bone mineral density (BMD) in sixty 20- to 35-year-old young healthy adults by dual-energy X-ray absorptiometry at the levels of the lumbar spine (in both anteroposterior and lateral views), femoral neck, trochanter region, total hip and of Ward's triangle, as well as whole-body BMD and bone mineral content (BMC) in cross-sectional and longitudinal studies. In the cross-sectional analysis, none of the bone mass variables was dependent on age using linear regression analysis. The longitudinal study indicated that the mean changes in lumbar spine, proximal femur and whole body BMD or BMC determined after a 1-year interval were not statistically different from zero in either females or males aged 20-35 years.(ABSTRACT TRUNCATED AT 250 WORDS)

A review of calcium preparations

There are more than a dozen commonly prescribed calcium supplements and hundreds of different formulations commercially available. Numerous factors need to be considered when selecting a calcium preparation. Physical properties such as solubility, interference from coingested medications or foodstuffs, dosage, and timing can all affect the bioavailability of calcium. Medical conditions such as lactose intolerance, impaired gastric acid secretion, and high risk profile for kidney stone formation may impact on selection of a calcium supplement. This article will review the available literature and make general recommendations for the optimal use of calcium preparations.

Chicken soup revisited: calcium content of soup increases with duration of cooking

Because low dietary calcium intake may accelerate bone loss, patients often are advised to increase their dietary intake of calcium. However, some patients may be unable to tolerate good calcium sources such as dairy products. We postulated that the calcium content of soups and stews could be increased by prolonged cooking with a beef bone. Three experiments were done to prove this theory: (1) a bone soup made with a beef bone and distilled water, cooked for 24 hours; (2) a bone-vegetable soup cooked the same way; and (3) a vegetable soup made the same way but without the bone. It was concluded that prolonged cooking of a bone in soup increases the calcium content of the soup when cooked at an acidic, but not at a neutral pH.

Family history of osteoporosis and bone mineral density at the axial skeleton: the Rancho Bernardo Study

To determine whether a family history of osteoporosis identifies individuals with low bone mineral density (BMD), we studied 1477 white elderly (aged 60-89 years), noninstitutionalized ambulatory men (n = 600) and women (n = 877) from the Rancho Bernardo, California cohort. Family history data on biologic parents and full sisters were obtained by questionnaire. BMD of the lumbar spine and hip was measured using dual-energy x-ray absorptiometry. After adjustment for age, body mass index, history of cigarette smoking, thiazide use, and estrogen use, men and women with a family history of osteoporosis had lower BMD than those with a negative family history. In men, a positive family history was associated with lower BMD at the hip (p = 0.01), whereas in women a significant association was observed for the spine (p = 0.02). BMD decreased in a stepwise fashion with an increasing number of family members with a history of osteoporosis. Analysis of the effect of parental history of osteoporosis on BMD showed a significant relation between paternal (but not maternal) history and lumbar spine BMD in both sexes and a significant relation between maternal (but not paternal) history and hip BMD only in men. The relative risk of having categoric osteopenia was highest in those whose fathers had a history of osteoporosis (RR 2.16, 95% CI = 1.38-3.37). A similar association was found for subjects with fractures. These results were not explained by differential awareness of family history in individuals with known osteoporosis, because the prevalence of family history was unrelated to personal history of osteoporosis in men and only weakly related in women.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbonated beverages, dietary calcium, the dietary calcium/phosphorus ratio, and bone fractures in girls and boys

PURPOSE

The aim of this study was to explore the association between carbonated beverage consumption, as well as other nutritional intake, and the occurrence of bone fractures in girls (mean +/- SD) 14.3 yr +/- 1.8 and boys 14.6 yr +/- 1.6.

METHODS

Food-frequency questionnaires and medical histories were obtained from 76 girls and 51 boys. Subjects were recruited from a swimming club and physicians' offices; their physical characteristics are representative of the normal adolescent population.

RESULTS

The data show a strong association between cola beverage consumption and bone fractures in girls [the adjusted odds ratio (OR) = 3.59; 95% confidence interval (CI) 1.21, 10.75; p = 0.022]. High intake of dietary calcium was protective (adjusted OR = 0.284; 95% CI 0.087, 0.920; p = 0.036). No association between the non-cola drinks and bone fractures was found. In boys, only total caloric intake was associated with the risk of bone fractures; the association was inverse.

CONCLUSION

The high consumption of carbonated beverages and the declining consumption of milk are of great public health significance for girls and women because of their proneness to osteoporosis in later life.

Calcium supplementation increases bone density in adolescent girls

In a longitudinal calcium intervention study, bone density was assessed in pubertal girls for 18 months. Significant additional increases in total body bone mineral density (1.3%) and spine bone mineral density (2.9%) and content (4.7%) were noted in the calcium-supplemented group. Increasing bone mass during adolescence with adequate calcium intake, if maintained into adulthood, could decrease the risk of osteoporosis later in life.

The four-compartment models in body composition: data from a study with dual-energy X-ray absorptiometry and near-infrared interactance on 815 normal subjects

With the aim of studying body composition according to a four-compartment model in different age groups of healthy subjects, total body water (TBW), body fat (BF), lean body mass (LBM), and total-body bone mineral content (TBBMC) were estimated with dual-energy x-ray absorptiometry (DEXA) and near-infrared interactance in 308 normal males and 507 normal females aged 15 to 83 years. Subjects were divided into 5-year groups up to the age of 50, and then into 10-year groups. In both sexes, BF showed a positive correlation with age (P < .001) and was higher in females aged 40 to 44 compared with younger groups. LBM decreased with age only among males (P < .05). A similar finding was observed with TBW. TBBMC values did not differ between sexes in the 15- to 19-year-old group, and were greater in males in the remaining age groups. This parameter did not vary among females until menopause, and decreased in the 50- to 59-year-old group (P < .001) and from the age of 60 onward (P < .001). Height decreased (P < .001) and weight increased with age (P < .001). Both in male and female groups height and weight correlated with TBBMC (P < .001). When corrected for weight, TBBMC did not vary except in men older than 50, who showed lower values (P < .005). When corrected for height, TBBMC only changed in women aged 30 to 34 and 35 to 39.(ABSTRACT TRUNCATED AT 250 WORDS)

Associations of social and demographic variables with calcium intakes of high school students

OBJECTIVE

To assess usual calcium intake of urban high school students and to assess the association of social and demographic variables with calcium intake.

DESIGN

A self-administered survey instrument containing the following elements: a food frequency questionnaire (FFQ) developed to estimate calcium intake; questions to elicit demographic information; and scales to reflect taste enjoyment of dairy products, social reinforcement for consumption of milk, perceptions of others' opinions about milk, and behavioral modeling of milk consumption (ie, the frequency of observing friends' and family members' use of milk). The FFQ was shown to include major sources of calcium in diets of a pretest sample (n = 130).

SETTING

Urban high schools in a metropolitan setting.

SUBJECTS/SAMPLES

Students in one class per grade level in six high schools (approximately 900 students) were asked to participate. Of the 856 questionnaires completed, 785 were usable.

MAIN OUTCOME MEASURES

Total calcium intake, as estimated using the FFQ.

STATISTICAL ANALYSES PERFORMED

Descriptive statistics, t tests, one-way analysis of variance, correlation analysis, and stepwise multiple regression analysis were used to assess relationships of independent variables with calcium intake.

RESULTS

Mean estimated calcium intakes for male and female students were 1,146 +/- 41 mg/day (mean +/- standard error of the mean) and 815 +/- 26 mg/day (P < .001), respectively, 59% of which was obtained from milk. Median intakes were 1,016 mg/day for boys and 676 mg/day for girls, and more than half the students had intakes that were below current recommendations. Multiple regression analysis revealed significant predictors of total calcium intake: gender (boys > girls); taste enjoyment of dairy products; number of meals and snacks per day; age; ethnicity (whites > Asians); behavioral modeling of milk consumption; perceptions of others' opinions, recommendations, and use of milk; and soft drink consumption (total adjusted R2 = .304). With the exception of age, these variables were positively associated with calcium intake. Regression equations developed for boys and girls separately revealed that different variables entered the equations.

APPLICATIONS/CONCLUSIONS

Most of the variability in adolescents calcium intakes remained unexplained by the variables included in this study. Nevertheless, the results suggest that education programs focusing on taste enjoyment of dairy products and building on the influence of peers and family members may have a positive impact on calcium intake.

Dairy products and adolescent nutrition

Adolescence is an intense anabolic period. The requirement for all nutrients is increased, but particularly that for dietary calcium. A balanced intake of the macronutrients (protein, fats and carbohydrates) is recommended to prevent the chronic degenerative disorders of adulthood. The temporal pattern of the calorie intake also deserves attention since it may affect homeostatic regulation. Adolescents often show disorders of dietary behaviour predisposing them to both obesity and anorexia. Dietary intervention in this age-group should promote the regular consumption of breakfast, a balanced intake of animal and vegetable foods and an increased calcium supply to maximize bone density. Dairy products and vegetables (mainly enriched cereals) constitute the basis of a good diet for adolescents, to supply their needs for growth and for subsequent good health.

Familial comparison of bone mineral density at the proximal femur and lumbar spine

Familial resemblance of bone mineral density (BMD) was studied in the lumbar spine and three regions of the proximal femur in 41 biological mother-daughter (M-D), 42 mother-son (M-S), 24 mother-grandmother (M-G) pairs and 18 mother-grandmother-daughter (M-G-D) triads. Children were placed into three maturity categories based on an assessment of secondary sex characteristics and growth velocities. Two sets of standardized BMD Z-scores were derived for the children based on either their chronological age or their maturational status. These scores were compared with maternal Z-scores derived from age-specific norms. Similar comparisons were made between the Z-scores of the mothers and grandmothers. For all three regions of the proximal femur and for the total AP lumbar spine the correlations between Z-score values were similar and significant (P < 0.05) between the M-G and M-D pairs ranging from 0.41 to 0.57. In general, the familial correlations improved when maturity-status based Z-scores were used for comparison. The absolute BMD values measured in the grandmothers and the three maturity groups of the children--expressed as a percentage of the BMD of the mothers--showed that at the neck and the trochanteric regions of the proximal femur the late-pubescent girls and boys had a significantly (P < 0.05) greater bone density than their mothers (115-123%), whereas at the AP spine these groups averaged only 88% of their mothers BMD. This site differential was not apparent when comparing the post-menopausal grandmothers with the pre-menopausal mothers (80% at both sites). Three generation comparisons demonstrated a strong familial resemblance in bone mineral density. The value of incorporating maturity-based versus chronological-based parameters for comparison with adult measures in studies that involve growing children at different stages of development was also demonstrated.

Timing of peak bone mass in Caucasian females and its implication for the prevention of osteoporosis. Inference from a cross-sectional model

To determine the timing of peak bone mass and density, we conducted a cross-sectional study of bone mass measurements in 265 premenopausal Caucasian females, aged 8-50 yr. Bone mass and bone mineral density were measured using dual X-ray absorptiometry and single-photon absorptiometry at the spine (anteroposterior, lateral), proximal femur, radius shaft, distal forearm, and the whole body. Bone mass parameters were analyzed using a quadratic regression model and segmented regression models with quadratic-quadratic or quadratic-linear form. The results show that most of the bone mass at multiple skeletal locations will be accumulated by late adolescence. This is particularly notable for bone mineral density of the proximal femur and the vertebral body. Bone mass of the other regions of interest is either no different in women between the age of 18 yr and the menopause or it is maximal in 50-yr-old women, indicating slow but permanent bone accumulation continuing at some sites up to the time of menopause. This gain in bone mass in premenopausal adult women is probably the result of continuous periosteal expansion with age. Since rapid skeletal mineral acquisition at all sites occurs relatively early in life, the exogenous factors which might optimize peak bone mass need to be more precisely identified and characterized.

Peak bone mass

Peak bone mass, which can be defined as the amount of bony tissue present at the end of the skeletal maturation, is an important determinant of osteoporotic fracture risk. Measurement of bone mass development. The bone mass of a given part of the skeleton is directly dependent upon both its volume or size and the density of the mineralized tissue contained within the periosteal envelope. The techniques of single-1 and dural-energy photon or X-ray absorptiometry measure the so-called 'areal' or 'surface' bone mineral density (BMD), a variable which has been shown to be directly related to bone strength. Bone mass gain during puberty. During puberty the gender difference in bone mass becomes expressed. This difference appears to be essentially due to a more prolonged bone maturation period in males than in females, with a larger increase in bone size and cortical thickness. Puberty affects bone size much more than the volumetric mineral density. There is no significant sex difference in the volumetric trabecular density at the end of pubertal maturation. During puberty, the accumulation rate in areal BMD at both the lumbar spine and femoral neck levels increases to four- to sixfold over a 3- and 4-year period in females and males, respectively. Change in bone mass accumulation rate is less marked in long bone diaphyses. There is an asynchrony between the gain in statural height and bone mass growth. This phenomenon may be responsible for the occurrence of a transient period of a relative increase in bone fragility that may account for the pattern of fracture incidence during adolescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethnic and genetic differences in susceptibility to osteoporotic fractures

A plethora of investigations in recent years has demonstrated the occurrence of ethnic differences in bone mineral content, bone density and fracture rates. These findings indicate that genetic determinants exist both for bone development during growth and for bone loss during aging. Twin and parent-offspring studies have corroborated the existence of a hereditary component. It is most evident in the greater bone mass and lower fracture rate in blacks than in whites. Differences in bone mass between Asians and whites are less clear than between blacks and whites because of disparities in body size and other confounding factors. Black children and adults excrete less urinary calcium than whites on essentially the same diets and consequently retain more calcium in their skeletons. Better calcium retention is commensurate with the faster rate of bone growth of black children.

The effects of high phosphorus intake on calcium homeostasis

Survey data confirm that the dietary pattern of many American women who are at high risk of developing osteoporosis is typically high in phosphorus and low in calcium. The imbalance between calcium and phosphorus intake may become more pronounced with continued changes in food preferences and the growing use of phosphorus-containing food additives. Recent studies in young women have shown that a high phosphorus diet moderately low in calcium results in a mild secondary hyperparathyroidism that persists over 4 weeks. Plasma levels of calcitriol did not change despite changes in PTH and serum ionized calcium. Studies on men have shown that dietary phosphorus at levels within the normal range of intakes can affect the renal production and serum concentration of calcitriol. High phosphorus intakes for ten days reduced their plasma calcitriol levels; a 70% reduction in phosphate intake significantly increased their plasma calcitriol. Thus, several lines of evidence indicate that prolonged high phosphorus intake may impair the usual homeostatic mechanisms that come into play when dietary calcium is limited. This, in turn, could impair achievement of maximal bone mass or accelerate bone loss. Although no clinical studies have linked high phosphorus intake with lower bone mass or higher rates of bone loss in humans, this relationship has been demonstrated in animal models. For example, young beagles fed high phosphorus, moderately low calcium diets showed a significant reduction in vertebral bone mass. Current dietary patterns of high phosphorus, low calcium consumption result in persistent changes in calcium regulating hormones that are not conducive to maximizing peak bone mass during growth or slowing the rate of aging bone loss. The net effect of the present dietary pattern on bone status, particularly in teenage and young adult women, needs to be determined. Optimal nutrition early in life, which may include higher calcium and lower phosphorus intakes, together with adequate exercise, may be the most cost-effective approach to the prevention of osteoporotic fractures.

A paradigm for skeletal strength homeostasis

This article integrates engineering principles with skeletal biology to describe skeletal strength homeostasis. Skeletal strength revolves around its perceived mechanical usage. Mass, geometric properties, and fatigue damage burden are the principle determinants of structural strength. Bone cells form sensor and effector systems that monitor usage and adjust strength and stiffness by changing mass, geometric properties, and fatigue damage burden. The bone lining cell-osteocyte complex is the sensor; the bone modeling and remodeling systems are the effectors. Deformation and fatigue damage in bone are the signals received by the sensor. Accumulated energy in the sensor's cytoskeleton determines the rate at which the sensor sends messages to the effectors. The activity of both effector systems is proportional to the rate of incoming messages. Modeling raises bone strength and stiffness by improving geometric properties as it adds bone where customary deformation is greatest. Remodeling improves bone strength by replacing fatigue-damaged areas without mass changes. Bone removed during modeling and remodeling comes from sites where the impact on bone strength and stiffness is least. Hormones and agents alter the rigidity of the cytoskeleton and, thus, its capacity to deform and store energy. Osteopenic agents make it more rigid, causing detection of fewer deformations and transmission of fewer loading signals to the effector. Osteotropic agents decrease the rigidity of the cytoskeleton, causing detection of more strain events and transmission of more loading signals to the effector. Agent treatment thus establishes false conditions of disuse or hyperuse.

Bone mineral content of two populations of Chinese children with different calcium intakes

Bone mineral content (BMC) of 5-year-old Chinese children (115 children in Jiangmen, China and 128 children in Hong Kong) was evaluated by single-photon absorptiometry at the distal 1/3 radius. The mean (S.D.) calcium intakes of children of Jiangmen and Hong Kong were 244 (46) and 542 (332) mg/day, respectively. The mean BMC, weight and height of Jiangmen children were significantly less than Hong Kong children by 14%, 10% and 4%, respectively (P < 0.001). Multiple regression analysis showed that 62% of the variance in BMC was explained by bone width (BW), weight and regional location (P < 0.0001). A regional difference in BMC of 0.0303 g/cm (P < 0.0001) still remained after adjusting for BW and weight by multiple regression analysis. When comparing sub-groups of children in the two regions with comparable low current calcium intake at 5 years, the BMC of Jiangmen children was still significantly lower than Hong Kong children even when potential confounders were adjusted (P < 0.003). The study suggests that the regional discrepancy in BMC might be explained by long-term habitual calcium intake and physical activity.

Development of bone mass and bone density of the spine and femoral neck--a prospective study of 65 children and adolescents

The bone mineral density (BMD, g/cm2) of the lumbar spine (L2-L4) and femoral neck was measured twice with a 1-year interval by dual energy X-ray absorptiometry (DEXA) in 65 healthy children and adolescents aged 7-20 years. In addition, the BMD values were corrected for the size of bones to obtain the bone volumetric density (BMDvol, g/cm3) using a method developed previously. The annual increases of BMD and BMDvol in both spine and femoral neck were most marked in females at the time of menarche (during the age of 11-13 years), and in males between the ages of 13 and 17 years. The males showed significantly higher values in their mean annual increment rates of femoral bone mineral content (BMC) and femoral neck width, whereas no differences in spinal parameters were found. The acquisition of bone mass and bone density stopped or markedly diminished before the age of 20 years, supporting the theory that the major portion of the peak bone mass is attained in late adolescence. We could not find any significant relationship between the increment rate of bone density, and physical activity or calcium intake. This study emphasizes the significant effect of puberty and genetic factors on the development of bone mass and density.

Putting osteoporosis in perspective

Osteoporosis is characterized by a reduction in bone mineral density (BMD). Dietary patterns that encourage adequate calcium intake are essential to maximal development and later maintenance of bone mass. The majority of white women are at risk for osteoporosis-related fractures, especially in the wrist, spine, and hip. The degree of fracture risk at a specific bone site is best assessed by measuring BMD with single- or x-ray-photon absorptiometry. BMD in adults of any age is quite variable. Numerous diet and lifestyle factors influence BMD and, in turn, fracture risk. Sufficient evidence exists for a relationship between BMD and diet, particularly calcium and vitamin D; amenorrhea; body weight; alcoholism; smoking; and physical inactivity. Less convincing evidence exists for a relationship with dietary protein, dietary phosphorus, and caffeine intake. To minimize fracture risk, young women should have regular menses, consume a nutritionally adequate diet (according to the principles of the Food Guide Pyramid), perform regular physical activity, only consume a moderate intake of alcohol (if any), and not smoke. Postmenopausal women should follow those same guidelines and should seriously consider estrogen replacement therapy. Elderly persons especially should ensure adequate calcium and vitamin D nutriture. Currently, osteoporosis is the rule, rather than the exception, in old age for many white women. Dietitians can help reduce the prevalence of this disorder.

Body composition in children and Tanner's stages: a study with dual-energy x-ray absorptiometry

Total body bone mineral content (TBBM), body fat content (BF), and fat-free mass (FFM) were measured in 154 children using dual-energy x-ray absorptiometry (DEXA). Total body calcium level (TBCa) was calculated from TBBM. Children were divided into groups according to Tanner's stages 1, 2, 4, and 5. Children in stage 3 were not included in the study in order to better differentiate between prepubertal and postpubertal individuals. We did not find differences in TBBM, TBCa, BF, and FFM between Tanner's stages 1 and 2 or between sexes. TBBM and TBCa in stages 4 and 5 were lower in girls than in boys (P < .001 and P < .01, respectively); no differences were observed between girls of both groups, although boys showed significant differences (P < .05). FFM for both sexes was lower in stages 1 and 2 than in stages 4 and 5. Girls showed lower FFM (P < .001) than boys in stages 4 and 5; FFM was higher in boys in stage 5 than in those in stage 4 (P < .005), and the same was true for girls (P < .002). Boys in stage 4 had less BF than girls (P < .005), and the same was true for stage 5 (P < .001). Girls in stages 4 and 5 had greater BF than those in stages 1 and 2 (P < .001). These differences suggest that as boys go through puberty, both TBBM and FFM continue to increase, while in girls only BF and FFM increase. These data indicate clear sex differences in somatic postpubertal development.

Contributions of dietary calcium and physical activity to primary prevention of osteoporosis in females

In the United States and many Western nations, increasing prevalence of osteoporotic fracture is contributing to the health care system burden, and costs and needs for medical services are predicted to increase significantly by the beginning of the 21st century. Recent reports investigating developmental changes in skeletal mass of adolescent girls and young women under different experimental or ecological conditions support the contention that modification of environmental factors, especially dietary calcium and physical activity, can favorably modulate bone mass and bone density compared to controls. The peripubertal period, starting as early as 10 years of age, seems to be most responsive to modification of environmental/lifestyle factors, whereas potential gains of bone mass during late adolescence and early adulthood, although smaller, may be more readily achieved through improved dietary calcium intakes and regular exercise programs. Scientific evidence in support of these beneficial effects on bone is presented as part of the rationale for prevention of osteoporotic fractures. Also discussed is the need for a national policy to prevent osteoporosis through primary prevention strategies focused at young girls prior to puberty. The goal would be for every prepubertal girl, over the next decade, to achieve peak bone mass (and density) of the spine, hips and other bones by age 20, i.e., early adulthood. A second target group for national policy should be women in their 20s. Attainment of the goal to gain 3-5% additional bone mass during this decade would prolong the time before the fracture threshold range (low bone mass) is reached in the postmenopausal decades.

Reproductive correlates of bone mass in elderly women. Study of Osteoporotic Fractures Research Group

Results from previous studies of reproductive factors and bone density have been conflicting; some demonstrate a beneficial effect, but others show a detrimental effect on bone density. The present study investigates the association of parity, lactation, and menstruation with radial bone density in 2230 white women, 65 years of age and older. Bone density was assessed by single-photon absorptiometry. Linear multiple regression was utilized to determine if reproductive factors were associated with radial bone density. The number of births, duration of menstrual bleeding, age at menarche, and years menstruating were significant independent predictors of postmenopausal bone density of the radius. A 1.4% increase in distal radius bone density was observed with each additional birth. Women who began menstruation at age 9 had 6.3% higher bone density than women who began at age 16. Women who menstruated for 3 days during each menstrual cycle had 2.8% less distal radius bone density than women who bled for 7 days. Each decade of menstruation was associated with a 2% greater distal radius bone density. No difference in bone density was demonstrated for women who breast-fed and women who did not. Length of the menstrual cycle, amount of menstrual flow, and irregularity of the menstrual cycle were not significantly associated with radial bone mineral density. In conclusion, pregnancy and menstruation are associated with postmenopausal bone density of the radius.

Relationship between long-term calcium intake and bone mineral content of children aged from birth to 5 years

This study evaluated Ca intake in Hong Kong Chinese children and examined the association between long-term Ca intake and bone mineral content (BMC) in children. Longitudinal dietary intake from birth to 5 years was obtained in 128 children (sixty-seven boys, sixty-one girls). Ca intakes were evaluated by dietary history and cross-checked with food frequency and 24 h recall. At age 5 years BMC was determined at the one-third distal radius of the right arm using single-photon absorptiometry. The mean Ca intake of 133 children at 5 years was 546 (SD 325) mg/d. Milk was the chief source of Ca (43.5%). From birth to 5 years, 90% of the children had been taking milk regularly. The mean BMC and bone width (BW) of these children were 0.317 (SD 0.042) g/cm and 0.756 (SD 0.074) cm respectively. BMC was not correlated with current intakes of Ca, energy and protein but was positively correlated with weight (r 0.57), height (r 0.47) and BW (r 0.66). However, cumulative Ca intake throughout the past 5 years showed significant correlation with BMC (r 0.235, P = 0.0133). The significant correlation remained even after weight, height, BW, sex, and cumulative intakes of energy and protein were adjusted in multiple regression analysis (r 0.248, P = 0.0107). Moreover, using principal component analysis, Ca intake during the 2nd year of life had the strongest correlation with BMC at 5 years (r 0.240, P = 0.02). Ca intake of Hong Kong Chinese children was higher than the RDA of the Food and Agriculture Organization/World Health Organization (1962) and achieved 66% of the current US recommendation (National Research Council, 1989). The increased regular milk consumption reflects a significant change in dietary habits of the younger generation. Children with a habitually higher Ca intake throughout the past 5 years, particularly in the 2nd year, were found to have higher BMC.

Calcium requirements for growth: are current recommendations adequate?

Peak adult bone mass is determined in each individual by a combination of endogenous and environmental factors. Insufficient accumulation of skeletal mass by the time young adulthood is reached appears to enhance the likelihood of fractures later in life. It is speculated that environment (nutrition and exercise) contributes to about 20% of the variance in bone mass. Although much is yet to be learned about how diet contributes to skeletal growth and development, it now appears that calcium intake may be an important factor in the attainment of peak bone mass. A review of the scientific literature suggests that the current recommended dietary allowance (RDA) for calcium may not be high enough to optimize the genetically programmed peak bone mass in a substantial number of growing individuals. New standards for dietary calcium intakes during growth may be indicated.

Age-related differences in total and regional bone mass: a cross-sectional study with DXA in 429 normal women

Total body bone mineral content (TBBMC), total body bone mineral density (TBBMD) and regional bone mineral content (BMC) and density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA) in 429 normal women aged 15-83 years, of whom 242 were premenopausal and 187 postmenopausal. The population was divided into 5-year age groups. In the premenopausal women no changes in TBBMC, TBBMD or regional BMC and BMD were observed with age, and TBBMC and TBBMD values correlated well with body weight (p < 0.001). Postmenopausal women showed an overall reduction in bone mass (p < 0.001), more marked at the axial level than peripherally (1.6% vs. 0.8%/year). The values of TBBMC and TBBMD correlated well with chronological age, time since the onset of menopause and body weight (p < 0.001). In these women age did not correlate with body weight, which suggests that postmenopausal bone mass loss depends more on chronological age and time since the onset of menopause than on other variables. The stability observed in bone mass values from ages 15-19 to menopause highlights the importance of stimulating the acquisition of an appropriate peak bone mass in women before adolescence begins.

Osteoporosis: assessment of bone loss and remodeling

Osteoporosis, the most common metabolic bone disorder, is a major health problem in older individuals, and especially in postmenopausal women throughout the world. It is characterized by low bone mass, structural deterioration, and an increased risk of fracture. The expected growth in the percentage of the world population over 65 years of age suggests that control of the chronic diseases of the elderly must be a major international priority. In order to design and implement appropriate prevention and treatment strategies for osteoporosis, it is necessary to assess the extent of the disease or condition in populations, and in individuals in a clinical setting. This review focuses on available and emerging techniques to measure bone mass or density, and on the role of biochemical markers of bone remodeling in the prediction of future bone loss. In order to prevent a disease that progresses without any obvious symptoms, it is important to determine not only the current status of bone mass and remodeling but also to develop methods to predict future bone loss. Different information is derived from each of the assessment approaches, and a combination of measures may be necessary to develop accurate predictive models.

The effect of dietary calcium intake in weanling rats on the efficiency of calcium absorption

Rats were weaned onto high (HCa, 14.6 g/kg)- or low (LCa, 3.88 g/kg)-Ca diets for 12 d and the efficiency of absorption of Ca measured from 20 mg Ca (as CaCl2, labelled with 47Ca) by means of whole-body counting. The LCa group absorbed 74% of the test dose and the HCa group 60% of the test dose (P < 0.001). All animals were then given the LCa diet for 6 weeks and the absorption test repeated. This time there was no difference in efficiency of absorption (HCa 54%, LCa 57%). The femur dry weight was significantly lower in the group initially fed on the LCa diet, but the Ca concentration was similar to that of the HCa group. The results do not lend support to the suggestion that early dietary exposure to Ca manifests itself as a difference in Ca metabolism in later life. They do, however, highlight the importance of adequate Ca intake during critical periods of growth.

Heritable and life-style determinants of bone mineral density

Familial resemblance in bone mineral density at five skeletal sites was measured among 160 adult members of 40 families. Each family included a postmenopausal mother, one premenopausal daughter, one son, and the children's father. Similarities in selected life-style factors thought to influence bone density, such as physical activity, smoking, alcohol use, and diet, were also evaluated. Bone density was measured by dual-energy (total body, femoral neck, and lumbar spine) or single-photon (radius and os calcis) absorptiometry. Correlation coefficients between the midparent Z score and offspring Z scores of bone mineral density ranged from 0.22 to 0.52 among daughters and from 0.27 to 0.58 among sons. Adjustment of bone density for age, height, weight, and significant life-style or environmental factors yielded heritability estimates for the five skeletal sites between 0.46 and 0.62. That is, 46-62% of variance in bone density was attributable to heredity. Most estimates derived from the group of daughters were similar to those from the sons. These observations provide support for a significant contribution of heredity to bone density. However, an individual's life-style may account for a potentially large proportion of the nonheritable variance in bone density.

Hip fracture mortality and morbidity in Switzerland and Japan: a cross-cultural comparison

Based on national mortality data, the frequency of hip fractures in elderly people was compared between Switzerland and Japan. Age-adjusted annual incidence rates per 100,000 population estimated for Swiss persons over 60 years were around 150 and 200 in males and around 450 in females, while for the Japanese they were only 132 in males and 285 in females. Age-adjusted death rates from hip fracture for the Swiss over 60 were 20.0 in males and 28.9 in females, while for the Japanese they were only 1.6 in males and 2.7 in females. The inclination of the age-dependent slope in hip fracture mortality rates was substantially the same in both countries, but there was a "lag time" of approximately 10 years in Japan. Remarkably, the proportion of deaths due to falls among all accidental deaths was several times greater in both sexes for the Swiss than for the Japanese. This differential might be an important underlying reason for the observed difference between death rates of hip fracture in Switzerland and Japan. Other known behavioral risk factors for hip fracture such as diet, exercise, estrogen use etc. are unlikely to explain the observed difference in hip fracture mortality and morbidity between Switzerland and Japan. However, given the doubts on the reliability and thus comparability of the available data on mortality and morbidity, the present findings should be regarded as preliminary. In conclusion, we believe that the unexplained and large difference in the burden of hip fracture between Switzerland and Japan merits further studies, including new aetiological hypotheses.

Estrogen status and heredity are major determinants of premenopausal bone mass

To analyze their relative effects on premenopausal bone mass, we have studied the impact of lifelong estrogen exposure, assessed by an estrogen score (ES; computed on age at menarche, average length of menstrual cycles since menarche, and use of birth control pills), heredity, and some environmental factors on vertebral bone density (VBD), of 63 premenopausal women (age, 19-40 yr). Compared with women with normal bone density (Z score > -1), subjects with low VBD (Z score < -1) had significantly lower ES (15.1 +/- 3.9 vs. 18.7 +/- 2.4, P = 0.001), higher age at menarche (13.8 +/- 1.7 vs. 12.6 +/- 1.4 yr, P = 0.005), and lower serum estradiol (46.9 +/- 37 vs. 86.6 +/- 57 pg/ml, P = 0.023) and estrone levels (107.4 +/- 60 vs. 178.8 +/- 9.0 pg/ml, P = 0.05). Likewise, women in the lowest quartile for VBD had significantly lower ES (15.3 +/- 4.5 vs. 18.1 +/- 2.7, P = 0.006) and higher age at menarche (13.9 +/- 1.9 vs. 12.8 +/- .4, P = 0.02) than those in the upper three quartiles. A higher proportion of subjects with irregular menses (52 vs. 23%, P = 0.03) and a positive family history of osteoporosis (86 vs. 61%, P = 0.04) was found in the low VBD group compared with subjects with normal VBD. VBD correlated positively with ES (r = 0.44, P = < 0.001) and negatively with age at menarche (r = -0.30, P = 0.03) by simple linear regression, whereas no correlation was found between VBD and age, body mass index, parity, lactation, physical activity, sunlight exposure, and dietary calcium and vitamin D intakes. The correlation between VBD and ES improved after correcting for the effect of all the other variables by partial correlation analysis (Pearson partial r = 0.57, P = < 0.01), which also disclosed a significant contribution of dietary calcium to VBD. However, ES was the only significant independent determinant of VBD, by stepwise multiple regression analysis (R2 = 0.24). Therefore, premenopausal estrogen exposure, and possibly genetic predisposition, rather than environmental factors, are the major determinants for the development of peak bone mass before menopause.

Nutritional intake, height and weight of 11-12-year-old Northumbrian children in 1990 compared with information obtained in 1980

There is little age-specific information on changes in dietary intake over time in this country, yet this is valuable in assessing the effectiveness of health education programmes particularly in vulnerable groups such as adolescents. In 1990, 379 children aged 12 years completed two 3 d dietary records. They were interviewed by one dietitian on the day after completion of each diary to verify and enlarge on the information provided and, with the aid of food models, obtain a quantitative record of food intake. Nutrient intake was calculated using computerized food tables. These children attended the same seven Middle schools in Northumberland as 405 children of the same age who recorded their diet using the same method, 10 years previously. Heights and weights were also recorded in both studies in the same manner. Comparing the nutrient intakes in 1990 with 1980, energy intake fell in the boys (to 8.6 MJ) but not in the girls (8.3 MJ). The contribution of fat to energy intake was unchanged at about 40% (about 90 g/d). Likewise, intake of sugars was unchanged at about 22% of energy (about 118 g/d). Calcium intake remained the same in the girls (763 mg/d in 1990) but fell in the boys (786 mg/d in 1990). Iron, vitamin C and unavailable carbohydrate intakes increased in both sexes, and the nutrient density of the diet improved in all sex and social-class groups. However, a social trend evident in 1980 still existed in 1990 with low social groups having the poorest-quality diet. It is concluded that there is little evidence of substantial progress towards improving the diet of adolescents in this country.

Maximizing peak bone mass: calcium supplementation increases bone mineral density in children

Attaining peak skeletal bone mass during childhood may reduce the incidence of osteoporosis in later life. A recent study in six- to 14-year-old identical twins showed that calcium supplementation increased bone mineral density. The effects of supplementation were especially pronounced in prepubertal children.

Bone mineral density during puberty in western Canadian children

To assess the influence of puberty and its associated changes in body weight and height on bone mineral density (BMD), lumbar spine (L2-L4) and femoral neck BMD were measured in 74 healthy, active children (9-16 years) using dual-photon absorptiometry. Competitive swimmers were recruited to minimize the potential effect variability in mechanical loading regime may have on bone density of the lumbar spine. Tanner staging was used to assess stage of puberty. Current dietary calcium intake was assessed by analysis of 6-day dietary records. Significant differences in spinal and femoral neck BMD occurred between early (Tanner 1 and 2) and late stages of puberty (Tanner 4 and 5), P < 0.05. A significant correlation was found between bone density and dietary calcium intake. However stepwise regression analyses demonstrated stage of puberty or body weight were the only factors which significantly affected spinal BMD, accounting for 77% and 68% of the variability respectively; while at the femoral neck, body weight accounted for 52% of the variability. These results demonstrate that when potential interacting factors are controlled for through regression analyses, differences in BMD occur mainly as a function of puberty and the associated gains in body weight.

Sex differences in the acquisition of total bone mineral mass peak assessed through dual-energy X-ray absorptiometry

Dual energy X-ray absorptiometry evaluation of total body bone mineral content (TBBM), total bone mineral density (TBMD), and regional bone mineral content (BMC) (head, trunk, arms, and legs) was carried out in order to assess sex differences of bone in 120 women and 121 men aged 15-29 years. Subjects from both sexes were divided into 5-year groups (15 through 19, 20 through 24, and 25 through 29 years old, respectively). Significantly higher values for TBBM, TBMD, and regional BMC were observed in males compared with females in the 20 to 24 and 25 to 29-year-old groups (P less than 0.001), but not in the group aged 15-19. After adjusting TBBM for lean body mass (LBM), we observed significantly lower values of TBBM/LBM in the males compared with females in all the age groups. A positive and significant correlation was observed between TBBM and age in the males of all the groups (r = 0.624, P less than 0.001), but not in the females. These data suggest that total bone mass peak acquisition takes place earlier in women than in men, leading to more reduced bone mass value, which in turn may be an osteoporosis predisposing factor.