Annual skeletal balance and metabolic bone marker changes in healthy early postmenopausal women: results of a prospective study

Roles of Follicle-Stimulating Hormone on Bone Metabolism in Late Postmenopausal Women

BACKGROUND

The effects of elevated follicle-stimulating hormone (FSH) levels on physiological changes in the bone remain unclear. This study aimed to clarify the association between FSH concentrations and bone mineral density (BMD) and bone turnover markers (BTM) in late postmenopausal women.

METHODS

A total of 169 Korean women were enrolled. The participants' ages ranged from 60 to 84 years (mean age, 69.0±5.1) and reported a mean duration of 19.4±6.6 years since menopause (YSM). The participants showed an average body mass index (BMI) of 24.4±2.8 kg/m2. Age, YSM, estradiol, testosterone, and BMI were confounders in the Pearson's partial correlation. A test for trends across the quartiles of FSH levels was performed for each variable.

RESULTS

The mean FSH and estradiol concentrations were 61.5 IU/L and 2.9 pg/mL, respectively. Serum FSH concentration was not significantly associated with BMD (lumbar, r=0.09, P=0.30; total hip, r=0.00, P=0.96; and femoral neck, r=0.05, P=0.62). BTM across the FSH quartiles did not show any trend association (bone-specific alkaline phosphate, P=0.31; crosslinked C-terminal telopeptide of type I collagen, P=0.90). Instead, FSH levels were negatively correlated with BMI (r=-0.34, P=0.00). In the multivariate regression model adjusted for age, testosterone, and estradiol, only BMI showed a negative value across the FSH quartiles (β coefficient -0.11, P=0.00).

CONCLUSIONS

This study identified that high FSH concentrations were not associated with bone loss or high bone turnover in women in the late postmenopausal period.

The Effects of Hormonal Therapy and Exercise on Bone Turnover in Postmenopausal Women: A Randomised Double-Blind Pilot Study

INTRODUCTION

Hormone replacement therapy (HRT) and walking were investigated independently and in combination, to determine which treatment provided most effect on bone turnover in postmenopausal women.

METHODS

Using a randomised double-blind pilot study, 10 subjects received HRT (transdermal estradiol, 50 μg/day and oral MPA 5 mg/day) and 12 received placebo for 20 weeks. Following a baseline period of treatment, both groups undertook a graduated walking regimen, which increased in intensity, duration and frequency parameters from weeks 8-20. Measurements of aerobic capacity, female sex hormones, bone formation markers [osteocalcin (OC) and bone alkaline phosphatase (BAP)] and bone resorption markers [deoxypyridinoline (DPD) and pyridinoline (PYR)] were measured at baseline (T1), week 8 (T2) and week 20 (T3).

RESULTS

Age, time of postmenopause, weight or body mass index were no different between each groups. The HRT group had significantly higher estradiol levels compared with the placebo group at T2 and T3. FSH and LH levels were significantly reduced following HRT. DPD and PYR were significantly reduced from baseline levels at T2 and T3 with HRT. No significant changes occurred in OC or BAP levels with either HRT or walking. Walking did not change bone turnover markers in either the HRT or placebo group.

CONCLUSION

HRT reduces bone resorption, however, walking alone at the intensity and duration prescribed, or the combination of HRT and walking, provided no additional benefit after menopause. Therefore, HRT, but not walking is an effective treatment in reducing bone turnover in postmenopause women.

Association between levels of serum ferritin and bone mineral density in Korean premenopausal and postmenopausal women: KNHANES 2008-2010

BACKGROUND

As women go through menopause, serum estrogen decreases and ferritin increases. Decreased serum estrogen is well known to cause detrimental effects on bone health; however, data on the associations of serum ferritin with BMD before and after menopause are still lacking. Therefore, this study aimed to investigate the association between serum ferritin levels and BMD in premenopausal and postmenopausal Korean women.

METHODS

This study was performed using data from the 2008-2010 Korean National Health and Nutrition Examination Survey, including 7300 women (4229 premenopausal and 3071 postmenopausal). BMD was measured using dual X-ray absorptiometry at the femur and the lumbar spine, and serum ferritin levels were measured by chemiluminescent immunoassay.

RESULTS

Median serum ferritin levels in postmenopausal women were higher than those in premenopausal women despite the same age ranges. Serum ferritin levels were only significantly correlated with BMD on the lumbar spine (β = -0.189, p-value = 0.005) in premenopausal women after adjusting confounding factors. Additionally, BMD on the lumbar spine had tended to decrease as serum ferritin quartiles increase (P for trend = 0.035) in premenopausal women after adjusting confounding factors. On the other hand, there were no significant associations between serum ferritin levels and BMD on the total femur and, femur neck in premenopausal women, and BMD on the total femur, femur neck, and lumbar spine in postmenopausal women.

CONCLUSION

Increased serum ferritin levels were significantly associated with BMD in premenopausal women, particularly on the lumbar spine, but not in postmenopausal women.

Associations between bone mineral density and subclinical atherosclerosis: a cross-sectional study of a Chinese population

CONTEXT

The significance of associations between bone mineral density (BMD) and atherosclerosis in the Asian population is less clear.

OBJECTIVE

The aim of this study was to explore the population-level associations between BMD and subclinical atherosclerosis.

DESIGN AND SETTING

This was a community-based cross-sectional study conducted in Shenyang, China.

PARTICIPANTS

A total of 385 Chinese women and men aged 37-87 years were studied.

MAIN OUTCOME MEASURES

The BMD was measured at the total hip and lumbar spine using dual-energy x-ray absorptiometry. The ankle-brachial index (ABI), pulse wave velocity (PWV), and carotid intima-media thickness (CIMT) were measured to assess atherosclerosis. Multiple regression analysis was applied to study the associations. Multicolinearity was examined using the variance inflation factor, condition index, and variance proportions. Factor analysis and principal component regression were used to remove the problem of multicolinearity.

RESULTS

The differences of ABI, PWV, and CIMT among the normal BMD, osteopenia, and osteoporosis groups were not found. Total hip BMD was correlated with ABI in women after adjustment for age (r = 0.156). Sex-specific regression models included adjustment for age, body mass index, cigarette smoking, alcohol consumption, menopausal status (women), systolic blood pressure, diastolic blood pressure, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting blood glucose, serum uric acid, estimated glomerular filtration rate, high-sensitivity C-reactive protein, and fibrinogen. Total hip BMD was associated with ABI in women after adjustment for age (per SD decrease in ABI: -0.130 g/cm(2), P = .022), but the association was borderline significant after full adjustment (P = .045). Total hip BMD and lumbar spine BMD were not associated with ABI, PWV, and CIMT after full adjustment in participants without a fracture history. The risk of osteoporosis was not associated with ABI, PWV, and CIMT.

CONCLUSIONS

Low BMD is not associated with subclinical atherosclerosis as assessed by ABI, PWV, and CIMT.

Stimulus in the form of rotation and shaking of a platform and its effect on the formation of trabecular bone in the lumbar vertebrae of mice

BACKGROUND AND AIMS

Elderly individuals who suffer a fracture develop a gait disturbance and require prolonged bedrest. A fracture has a massive impact both physically and mentally and markedly diminishes quality of life. A new form of therapeutic exercise that mitigates the abrupt decrease in bone density in postmenopausal women must soon be developed so that those problems can be avoided.

METHODS

The current study used a model of the decrease in bone density in ovariectomized mice to simulate postmenopausal women. The stimulus was provided by a shaking horizontal platform rotating in a circular motion.

RESULTS

Comparison of the +/+ (ovariectomized/stimulated) group and +/- group indicated a significant decrease in BV/TV (p < 0.01), Tb.Th (p < 0.01), and Tb.N (p < 0.05) in the +/+ group and a significant increase in OV/BV (p < 0.01), OV/OS (p < 0.01), BFR/BV (p < 0.01), dLS/BS (p < 0.05), MS/BS (p < 0.05), BRs.R (p < 0.01), and Tb.Sp (p < 0.01) in the +/+ group. Physical therapy to prevent a decrease in bone density was studied via stimulus in the form of rotation of a platform. Analysis of bone histomorphometry revealed lessening of the decrease in bone density of the lumbar vertebrae, a feat that the stimulus from conventional physical therapy had failed to achieve.

CONCLUSION

The current study delivered a shaking stimulus to mice in a model of postmenopause. Analysis of bone histomorphometry of the lumbar vertebrae suggested lessening of the abrupt decrease in bone density of trabecular bone. If this finding is used clinically, it could lead to physical therapy exercise that would be able to prevent compression fractures of the lumbar vertebrae.

Effect of gender and geographic location on the expression of primary hyperparathyroidism

BACKGROUND

The effect of gender on the expression of primary hyperparathyroidism (PHPT) is not well characterized.

AIM

We therefore evaluated two Caucasian populations (US and Italian) of men and women with PHPT, matched for age and body mass index (BMI), in a cross-sectional retrospective observational study.

METHODS

We studied 74 US (23 men) and 126 Italian (42 men) patients evaluating main biochemical indices of the disease and bone mineral density (BMD) at the spine and proximal femur.

RESULTS

Mean serum calcium levels were higher both in Italian men compared to women (11.7 ± 1.22 mg/dl and 11.1 ± 0.83, p<0.01) and in Italian compared to US patients (11.3 ± 1.01 and 10.8 ± 0.58, p<0.001), with similar results for the serum ionized calcium. Mean serum PTH levels were not different either between the genders or between the countries. After controlling for BMI, the mean BMD at both the femoral neck and total hip in females US patients was significantly higher compared with Italian female patients.

CONCLUSION

Despite similar levels of circulating PTH, Italian patients have more pronounced effects of the disease as assessed by serum calcium and a more significant cortical involvement in women as assessed by BMD.

Screening for specific biomarkers in the serum of postmenopausal osteoporosis patients using proteomic fingerprint techniques

The aim of this study was to detect serum protein biomarkers and establish a diagnostic model for postmenopausal osteoporosis (PMOP) adopting matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) combined with weak cationic exchange (WCX) magnetic beads, and to study the clinical significance of the model in the early diagnosis of PMOP. Serum samples from 45 patients with PMOP, 30 patients with osteopenia and 40 healthy controls were prepared using WCX magnetic beads, and were then analyzed using a PBSII-C mass spectrometer reader. The protein spectra of the serum samples were normalized using the Ciphergen Proteinchip software. The peak labeling was performed using the Biomarker Wizard software. The specific protein biomarkers were screened using the Biomarker Pattern software to construct a diagnostic model for PMOP. A total of 138 discriminative mass-to-charge (m/z) ratios were found to be associated with PMOP. Of these, the m/z peaks at 3167.4, 4071.1, 7771.7 and 8140.5 were used to construct a diagnostic model in a training set. In a test set, the sensitivity and specificity of the model were 91.11 and 92.86%, respectively. Potential protein biomarkers for PMOP were detected in patient serum using MALDI-TOF MS combined with WCX magnetic beads. This model of multiple biomarkers provided a powerful and reliable diagnostic method for PMOP diagnosis with high sensitivity and specificity.

Hospital based preliminary study on osteoporosis in postmenopausal women

The awareness of osteoporosis has grown world wide in recent years. This silently progressing metabolic bone disease is widely prevalent in India, and osteoporotic fractures are a common cause of morbidity and mortality in adult Indian men and women. Rapid bone loss occurs in postmenopausal women due to hormonal factors which lead to increased risk of fractures. Biochemical markers of bone metabolism are used to assess skeletal turnover. A cross-sectional study of 150 pre- and post menopausal women was carried out at S.D.M College of Medical Sciences and Hospital, Dharwad, during the period of May 2005 to September 2005. The study group consisted of 75 Premenopausal women in the age group of 25-45 years and 75 Postmenopausal women in the age group of 46-65 years. Bone formation markers (Total Calcium, lonised calcium, Phosphorus, Alkaline phosphatase), and bone resorption markers (Urinary Hydroxyproline) were analysed in pre and post menopausal women. Bone formation markers, Total and lonised calcium were significantly decreased (p<0.001) and Alkaline phosphatase was significantly increased (p<0.001) in postmenopausal women compared to premenopausal women. Bone resorption markers, Urinary hydroxyproline excretion was significantly increased (p<0.001) in postmenopausal women. The results from this study suggest that simple, easy, common biochemical markers can still be used to assess the bone turnover in postmenopausal women and hence their risk of developing osteoporosis and fractures.

Association between Serum Cholesterol Level and Bone Mineral Density at Lumbar Spine and Femur Neck in Postmenopausal Korean Women

BACKGROUND

Blood lipid profiles have been suggested to be a risk factor for osteoporosis. However, the association between lipid profiles and bone mineral density (BMD) is still unclear. This study aimed to evaluate an association between blood lipid profiles and BMD through both a cross-sectional and a longitudinal study.

METHODS

Study subjects were 958 postmenopausal Korean women who have repeatedly undertaken laboratory tests and BMD measurements at lumbar spine and femur neck with an interval of 7.1 years. The associations between lipid profiles and BMD were examined using Spearman correlation analysis with an adjustment for age, smoking, alcohol drinking, physical activity, body mass index, and follow-up duration.

RESULTS

Lumbar spine BMD was not associated with total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and high density lipoprotein cholesterol (HLD-C) regardless of when the measurement was performed. In an analysis using data measured at the beginning of the study, femur neck BMD was not associated with TC and LDL-C. However, femur neck BMD showed weak but significantly positive correlation with HDL-C (correlation coefficient, 0.077; 95% confidence interval, 0.005 to 0.149). When the analysis was repeated with data measured at the end of the follow-up, there was no significant correlation between femur neck BMD and any lipid profile. In addition, change in femur neck BMD during follow-up was not associated with the change in lipid profiles.

CONCLUSION

Although further study with a consideration of calcium intake and osteoporosis medication seems necessary, this study found no association between serum lipid profiles and BMD in postmenopausal Korean women.

The relationship between bone turnover markers and BMD decreasing rates in Chinese middle-aged women

BACKGROUND

The relationship between bone turnover markers (BTMs) and BMD decreasing rate (BDR) in Chinese women is unclear. Wu investigated the relationship between (BTMs) and BDR at various skeletal sites in Chinese middle-aged women.

METHODS

A cross-section study of 555 healthy Chinese women over 35-60years of age. BMD at posteroanterior spine, the left hip, and the left forearm were measured with a DXA. Levels of serum osteocalcin (OC), bone-specific alkaline phosphatase (BAP), cross-linked N-terminal telopeptides of type I collagen (sNTX) and total urinary deoxypyridinoline (uDPD) were determined.

RESULTS

BDR at various skeletal sites had significant negative correlation with serum OC(r=-0.395 to -0.530), BAP(r=-0.297 to -0.486), and sNTX(r=-0.207 to -0.272). After adjustment of age and weight, serum OC, BAP, and sNTX rather than total uDPD still exhibited significant correlations with BDR. Stepwise regression analyses showed that, serum OC and BAP were the significantly negative determinants of BDR. Between 4.7-27.7% and 1.2-16.1% of the changes in BDR were determined by serum OC and BAP, respectively. However, sNTX and total uDPD had no significant effect on BDR at various skeletal sites.

CONCLUSIONS

This study indicated the correlation between BTMs and early-stage BDR in Chinese middle-aged women and suggested that serum OC and BAP, rather than sNTX and total uDPD, are the key determining factors of early BMD decreases.

Cyclical changes of vertebral body heights and bone loss in healthy women after menopause

Annual changes in vertebral body heights (VHs) and lumbar bone mineral density (LBMD) were evaluated in 120 healthy pre- and post-menopausal women aged 45-74 years. Subjects were divided into groups according to menstrual status and years since menopause (YSM). Vertebral heights were evaluated, using radiological morphometry as the sum of anterior vertebral body heights (AVHs) from T4 to L5 at baseline and exactly 12 months later. Results indicate that the sum of VHs is inversely correlated with advancing age, and the decrease in VHs is not a constant process over time but rather exhibits cyclical damping oscillations. When log-linear trend of VH decrease was transformed into a constant considering annual percentage changes, the presence of a cyclical component of 7 years was evident. Employing a harmonic regression model, the cyclical component was also statistically significant on baseline data. The cyclical decrease of VHs corresponds to an analogous cyclical behavior of LBMD values. These results suggest that a lack of estrogen acts as a synchronizer on bone remodeling, triggering a latent cyclical rhythm of bone loss, accompanied by cyclical bone microarchitecture deterioration and consequent vertebral body deformities, which after menopause persists throughout life. The existence of a chronobiological rhythm of bone loss and trabecular bone strength reduction at vertebral level after menopause, if confirmed, could have important clinical implications.

Drug delivery systems for hormone therapy

Various types of formulations and delivery devices have been developed for hormone therapy (HT) and their modes of hormone action and patient responses have been evaluated. Although the Women's Health Initiative (WHI) reported the controversial results on estrogen/progestin combination therapy, HT still remains a primary therapeutic option for the treatment of menopausal symptoms and osteoporosis. As a novel alternative to HT may not be probable in clinical use for the next decade, the currently available formulations containing estrogen and progestogen should be properly optimized for HT. The extensive reviews and comparisons on the characteristics of various types of HT could lead to the development of an efficient delivery formulation which maximizes patient compliance and minimizes adverse effects for individual users.

Effect of temperature on the longitudinal variability of quantitative ultrasound variables

It is unclear whether longitudinal change in phantom measurements bears any relation to the long-term in vivo instrument performance of quantitative ultrasound devices. Longitudinal quantitative ultrasound phantom data were obtained by measuring the manufacturer-provided phantom at ambient temperature and two different sets of Leeds phantoms at either ambient temperature or following a phantom temperature-control protocol. Measurements were performed using the Achilles Plus bone densitometer. Changes in longitudinal phantom data were compared to in vivo quantitative ultrasound data obtained from seven healthy, young volunteers. A cosinor model with linear trend and Hotelling's T2-test were used to quantify seasonal rhythms and long-term drift in quantitative ultrasound variables. Temperature effects and marked seasonal rhythms on quantitative ultrasound phantom measurements were evident but were far less apparent in vivo. Longitudinal precision of quantitative ultrasound variables was poorer for the manufacturer-provided phantom than for phantoms that were subjected to a temperature-control protocol or for healthy volunteers. This study has shown that longitudinal precision and longitudinal change differs between in vivo and phantom data. Longitudinal quantitative ultrasound measurements for monitoring change in skeletal status cannot, as yet, be properly controlled.

A simulation model at trabecular level to predict effects of antiresorptive treatment after menopause

Antiresorptive drugs are widely used to prevent osteoporotic fractures in men and women. Large clinical trials have shown vertebral fracture risk reductions up to 50%, resulting from relatively small increases of 3-8% in bone mineral density (BMD). We developed a computer model that mimics bone turnover in human vertebral cancellous bone during menopause and antiresorptive treatment. This model links cell activity in trabeculae to changes in bone volume and mechanical properties. We asked whether treatment started shortly after menopause is better than treatment started late after menopause. In order to answer this question we used the model to simulate menopause and 5 years of anti-resorptive treatment with two different agents: one incorporated in the tissue, one not incorporated. We found that late treatment can result in almost the same bone mass as early treatment, but early treatment is much better in conserving the strength and stiffness of the cancellous bone. The effect of the incorporation of drugs in the tissue (giving the drugs a long half-life) was small. After discontinuation of treatment, bone was lost slower, but after 20 years the difference between the incorporated and the not incorporated drug in stiffness and bone volume was below 3%. This kind of simulation model may be used to preclinically test new pharmaceuticals and treatment protocols and to predict long-term effects of treatment before patient data become available.

Investigating the role of natural phyto-oestrogens on bone health in postmenopausal women

Research on the bone effects of natural phyto-oestrogens after menopause is at a relatively early stage. Published studies are few, difficult to compare and often inconclusive, due in part to design weaknesses. Currently, many questions remain to be answered including to what extent a safe daily intake may prevent postmenopausal bone loss. These questions can only be addressed by conducting well-planned, randomised clinical trials that take into consideration present knowledge in the oestrogen, phyto-oestrogen and bone fields. This review is intended to provide hints for critical decision-making about the selection of subjects, type of intervention, suitable outcome measures and variables that need to be controlled.

Influences of hormone replacement therapy on postmenopausal women's health perceptions

OBJECTIVE

To assess the beliefs of climacteric women regarding their health, menopause, and hormone replacement therapy (HRT).

DESIGN

Medical students asked to interview 526 healthy women, ranging from 40 to 64 years of age, between January and February of 2002. Of that number, 26 (4.9%) declined to participate in the interview. Thus, 500 women were interviewed about their beliefs and perceptions regarding their quality of life and health risks, as well as their opinions on menopause and HRT.

RESULTS

The mean age of the sample was 53.3 +/- 6.2 years; 83.4% were postmenopausal, and 18.8% were HRT users. Of the women interviewed, 38.6% believed that their health was good. Although 78.8% thought that cancer is the main cause of death, 64% of them considered themselves to be at high risk for cardiovascular disease and osteoporosis. Most (64%) believed that menopause deteriorates the quality of life and that it increases cardiovascular risk (52.4%) and osteoporosis (72.0%). The HRT users perceived that they had better health status (48.9% v 36.2%, P < 0.02) and smaller cardiovascular risk (54.3% v 66.3%, P < 0.04) than did the nonusers; however, they ignored the preventive effect of estrogens in osteoporosis.

CONCLUSIONS

Women believe that menopause deteriorates their health. The HRT users perceived themselves to be healthier and to have a smaller risk for cardiovascular disease.

Cyclical behavior of bone remodeling and bone loss in healthy women after menopause: results of a prospective study

Annual changes in lumbar bone mineral density (LBMD) and bone remodeling markers were measured in 238 healthy pre- and postmenopausal women, aged 45-74 years. The subjects were divided into groups according to their menstrual status and years since menopause. The results obtained indicate that bone loss is not a constant process over time but rather exhibits cyclical damping oscillations. When the log-linear trend of LBMD decrement was transformed into a constant by considering annual percentage changes, the presence of a cyclical component of 7 years was evident. By employing a harmonic regression model, the cyclical component was also statistically significant on baseline data. The cyclical behavior of LBMD decrement corresponded to an analogous behavior of the bone remodeling markers. These results suggest that a lack of estrogen acts as a synchronizer on bone remodeling by triggering a latent cyclical rhythm of bone loss that persists throughout life after menopause. The existence of a chronobiological rhythm of bone loss starting after menopause, if confirmed, could have important clinical implications.

Collagen and bone viscoelasticity: a dynamic mechanical analysis

The purpose of this study was to explore the effects of changes in Type I collagen on the viscoelasticity of bone. Bone coupons were heated at either 100 or 200 degrees C to induce the thermal denaturation of Type I collagen. Half of these specimens were rehydrated after heat treatment; the other half were tested in a dry condition. The degree of denatured collagen (DC%) was analyzed by a selective digestion technique with the use of alpha-chymotrypsin. Isothermal (37 degrees C) and variable temperature tests (scans from 35 to 200 degrees C) were performed with the use of a dynamic mechanical analyzer to evaluate changes in bone viscoelastic properties as a function of collagen damage, specifically, changes in the loss factor (tan delta) and storage modulus (E') were assessed. Significant collagen denaturation occurred only when bone was heated at 200 degrees C irrespective of the hydration condition. Also, DC% did not show a significant effect on tan delta. However, higher values of tan delta were observed in wet samples compared to dry specimens. The temperature-scan tests revealed that the hydration condition, but not DC%, significantly affected the behavior of tan delta. However, E' was not strongly influenced either by DC% or by water content. These results suggest that at a constant frequency the denaturation of collagen triple-helical molecules may have few effects on the viscoelasticity of bone, but moisture may play a prominent role in determining this property.

Calcium, physical activity and bone health--building bones for a stronger future

Adequate provision of nutrients composing the bone matrix and regulating bone metabolism should be provided from birth in order to achieve maximal bone mass, compatible with individual genetic background, and to prevent osteoporosis later in life. Low calcium intake (<250 mg day(-1)) in children is associated with both a reduced bone mineral content and hyperparathyroidism. Optimal calcium intake is, however, still a matter of controversy. The minimisation of fracture risk would be the ideal functional outcome on which to evaluate lifetime calcium intakes, but proxy indicators, such as bone mass measurements or maximal calcium retention, are used instead. Calcium recommendations in Europe and the United States are based on different concepts as to requirements, leading to somewhat different interpretations of dietary adequacy. Minerals and trace elements other than calcium are involved in skeletal growth, some of them as matrix constituents, such as magnesium and fluoride, others as components of enzymatic systems involved in matrix turnover, such as zinc, copper and manganese. Vitamins also play a role in calcium metabolism (e.g. vitamin D) or as co-factors of key enzymes for skeletal metabolism (e.g. vitamins C and K). Physical activity has different effects on bone depending on its intensity, frequency, duration and the age at which it is started. The anabolic effect on bone is greater in adolescence and as a result of weight-bearing exercise. Adequate intakes of calcium appear necessary for exercise to have its bone stimulating action.