In addition, peak bone mass, a major determinant of the risk for osteoporosis .. or the density of cortical bone in the femurs in either boys or girls; all correlation in Caucasian females and its implication for the prevention of osteoporosis. Given the knowledge that high peak bone density reduces osteoporosis risk later Women and men older than age 30 can help prevent bone loss with regular. Key words: Peak bone mass Adolescence Vitamin D Calcium Osteoporosis Saudi Arabia .. investigated the inverse relationship between PHT and determined.
Only children in early puberty Tanner stage 2 were enrolled in this study. Measurements of height, weight, and sitting height were obtained, and thereafter body surface area and body mass indices were calculated Skeletal maturation was assessed on the basis of roentgenograms of the left hand and wrist according to the method of Greulich and Pyle 13and those in whom skeletal age differed from chronological age by more than 1 yr were excluded from further evaluation.
On the same day, measurements of bone size and bone density were obtained by CT. Subsequently, participants were given instructions to record their dietary intake over a 3-day period. Using this approach, a total of 50 healthy children 25 girls and 25 boys were enrolled in this study. All participants were asked to return every 6 months for a physical examination, and CT bone measurements were repeated at each change in Tanner stage from baseline Tanner 2 to sexual maturity Tanner 5.
During the course of the study, 10 children were withdrawn [5 due to residence relocation 2 girls and 3 boys2 began taking birth control pills, 1 became pregnant, 1 boy was severely injured in an automobile accident, and another was randomly excluded at completion of the study to facilitate stratification of the results into quartiles]. Thus, we longitudinally studied the changes in bone density and bone size in the axial and appendicular skeletons of 20 girls and 20 boys from the beginning of puberty to sexual maturity.
For determinations in the axial skeleton, the apparent density of cancellous bone and the cross-sectional area were measured at the lumbar vertebrae, and, in the appendicular skeleton, the cross-sectional area, the cortical bone area, and the material density of cortical bone were measured at the midshaft of both femurs, as described previously 14 Because of the relatively small size of the trabeculae when compared with the pixel, CT values for apparent cancellous bone density reflect not only the amount of mineralized bone and osteoid, but also the amount of marrow per pixel These measurements are analogous to in vitro determinations of the volumetric density of trabecular bone, which are obtained by washing the marrow from the pores of a specimen of cancellous bone, weighing it, and dividing the weight by the volume of the specimen, including the pores Because of the thickness and the relative lack of porosity of cortical bone in the femur, CT values reflect the material or true density of the bone the amount of collagen and mineral in a given volume of bone These measurements are analogous to in vitro determinations of the intrinsic mineral density of bone, which are commonly expressed as the ash weight per unit volume of bone The coefficients of variation for repeated CT measurements of vertebral cross-sectional area, cancellous bone density, femoral cross-sectional area, cortical bone area and cortical bone density were calculated to be between 0.
Nutritional analysis Nutritional information was obtained every 6 months from all subjects until they achieved sexual maturity using written, 3-day records of dietary intake. Each participant and their parent s received instructions from a dietetic technician on how to record their food intake. The mean of the three daily determinations was calculated for each nutritional component in all subjects, and the information was entered into a database.
Differences among quartiles were assessed by linear trend analysis using a repeated measures model with unstructured covariance matrix 22 Results The age and anthropometric characteristics of the children studied at different Tanner stages of sexual development are shown in Table 1.
Role of energy intake and muscle mass development. In healthy subjects, the energy intake is adjusted to increased physical activity.
Hence it is difficult to ascribe the additional gain in bone mass to mechanical loading alone. Indeed, nutrients such as calcium and proteins, that are usually consumed in various amounts in relation to physical activity, could substantially contribute to the positive effect on bone mass acquisition.
The independent mechanical contribution can be measured by the differential effect observed according to the skeletal sites solicited. However, the best evidence of the distinct effect of mechanical loading from concomitant increase in nutritional intakes is provided by studies on the use of rackets, as determined by measuring the difference between loaded and unloaded arms.
Peak bone mass and osteoporosis prevention.
It has been suggested that the exercise-induced gain in bone mass, size and strength essentially results from an adaptation secondary to the increase in muscle mass and strength. Impaired bone mass acquisition can occur when intensive physical activity leads to hypogonadism and low body mass. Intake of energy, protein and calcium may be inadequate as athletes go on diets to maintain an idealized physique for their sport. Intensive training during childhood may contribute to a later onset and completion of puberty.
Hypogonadism, as expressed by the occurrence of oligomenorrhea or amenorrhea, can lead to bone loss in females who begin training intensively after menarche. The differential impact of calcium The extent to which variations in the intake of certain nutrients by healthy, apparently well-nourished, children and adolescents affect bone mass accumulation, particularly at sites susceptible to osteoporotic fractures, has received increasing attention over the last 15 years.
Most studies have focused on the intake of calcium. However, other nutrients such as proteins, which are not discussed in this review, should also be considered. In most regions of the world, the supply of calcium is sufficient to avoid the occurrence of clinically manifest bone disorders during growth. Nevertheless, by securing adequate calcium intake, provided the skin and food supply of vitamin D is adequate, it is expected that bone mass gain can be increased during infancy, childhood and adolescence and thereby optimal PBM can be achieved.
The prevention of adult osteoporotic fractures is the main reason for this widespread preoccupation. International and national agencies have adopted recommendations for calcium intake from infancy to the last decades of life. Decisions from these recommending bodies can be based on either calcium balance, allowing estimations to be made regarding maximal retention, or on a factorial method that calculates from available data on calcium accretion and endogenous losses modified by fractional absorption.
Observational and interventional studies are also taken into consideration. The recommendations vary widely among regional agencies56 table I. Thus, for children aged years, the recommended daily calcium intakes are set at,and up to mg, in the United Kingdom, the Nordic European countries, France and the United States of America, respectively. Variability in calcium intake recommendations can be explained partly by the discrepant results obtained in observational and interventional studies.
Retrospective epidemiological data obtained in women aged years, indicated that milk consumption during childhood and adolescence can be positively correlated to bone mineral mass.
Several calcium intervention studies have been carried out in children and adolescents. Nevertheless, the response appears to vary markedly according to several factors including the skeletal sites examined, the stage of pubertal maturation, the basal nutritional conditions, i.
Preventing Osteoporosis | International Osteoporosis Foundation
The benefit of supplemental calcium was usually greater in the appendicular that in the axial skeleton. In agreement with our longitudinal observation in healthy subjects aged 8 to 19 years figure 6the skeleton appears to be more responsive to calcium supplementation before the onset of pubertal maturation than during the peripubertal period. Two co-twin studies strongly suggest that increasing calcium intake after the onset of pubertal maturation above a daily spontaneous intake of about mg does not exert a significant positive effect on bone mineral mass acquisition.
This contrasts to the widespread intuitive belief that the period of pubertal maturation with its acceleration of bone mineral mass accrual would be the most attractive time for enhancing calcium intake well above the prepubertal requirements.
As described above efficient adaptive mechanisms secure an adequate bone mineral economy in response to the increased demand of the peripubertal growth spurt.
As intuitively expected, the benefit observed at the end of intervention is particularly substantial in children with a relatively low calcium intake. In contrast, the additional gain was minimal in those girls with a relatively high calcium intake. According to the "programming" concept, environmental stimuli during critical periods of early development can provoke long-lasting modifications in structure and function of various biological systems.
The possibility that physical activity could modulate the bone response to dietary calcium supplementation during growth has been considered in infants, children and adolescents. Overall, the results suggest an interaction: At moderately low calcium intake, the effect may not be positive. Thus, in a longitudinal study in infants months of age, i. In young children aged years, either calcium supplement or gross motor activity increased bone mass accrual as compared to either placebo or fine motor activity.
This regional specificity suggests that the effect of physical activity alone or combined with relatively high calcium supply is not merely due to an indirect influence on the energy intake, which in turn would positively affect bone mass acquisition.
It has not been established whether the type of calcium salt used to supplement diets may modulate the nature of the bone response. The observation that calcium supplementation can increase bone size, at least transiently, has been observed using either milk extracted calcium-phosphate as well as calcium carbonate salt.
Another uncertainty is the question of whether gains observed by the end of the intervention are maintained or lost after discontinuation of calcium supplementation.
A clear answer to this question requires long term follow up, since sustained gain even on bone mass and size may be transient, possibly resulting from some indirect influence of calcium supplementation on the tempo of pubertal and thereby bone maturation. The observational and interventional studies discussed above illustrate the numerous factors that can modulate the bone response to calcium intake. This foregoing analysis may, at least in part, explain the difficulty to reach a scientifically based worldwide consensus on dietary allowance recommendation for children and adolescents.
Nevertheless, taking into account both the results of all studies as well as our knowledge on the physiology of calcium and bone metabolism, particularly on the adaptive mechanisms operating during the peripubertal period,61 it appears reasonable and safe to recommend food intake that would provide about mg of calcium per day from prepuberty to the end of adolescence. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis.
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Peak Bone Mass: Three Factors Impacting the Risk of Osteoporosis
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