Calcium supplementation and bone loss in middle-aged women

National guidelines on nutrient reference values for the healthy adult population and for pregnant or lactating women are based on heterogeneous sources of evidence: review of guidelines

Many countries provide dietary guidelines for health practitioners and/or the general population. However, there is no general, international guideline serving as a template for national dietary guidelines, and there is little to no consensus regarding reference values for different nutrients. The present review compared 27 national dietary guidelines for healthy adults as well as for pregnant and/or breastfeeding women, and analysed their quality and the evidence behind their recommendations. The guidelines were evaluated for their quality using the instrument Agree II, and found to be heterogeneous (overall quality score 14%-100%) and often insufficient (quality score < 50%) due to missing information about their methodology and sources of evidence. We analysed the evidence (number of studies, study types and publication years) of reference values of a number of nutrients using the five guidelines that provided the highest scores in the Agree II assessment. The reference values varied among guidelines, were rarely based on up-to-date meta-analyses, and were often based on insufficiently reported evidence (22/27 guidelines with quality score < 50%). We recommend systematic reviews of high quality studies to formulate future guidelines, and to use guidelines on how to write guidelines.

[Nutritional advices for postmenopausal woman. Postmenopausal women management: CNGOF and GEMVi clinical practice guidelines]

Menopause is a key period for health due to physiological changes, particularly of body composition (with decrease of lean mass and increase of fat mass) and of body fat distribution, leading to a higher risk for bone and muscular health and cardiometabolic health. Nutritional advices, associated to physical activity advices, may partially prevent these effects. The energy balance will be moderately negative if there is a weight gain, while the protein intake will be preserved and a regular physical activity will be increased. A Mediterranean style diet will be beneficial on cardiovascular health. Dairy products will be preserved, but restrictive and dietary exclusion will be avoided.

Effects of Lemon Beverage Containing Citric Acid with Calcium Supplementation on Bone Metabolism and Mineral Density in Postmenopausal Women: Double-Blind 11-Month Intervention Study

A critical factor for preventing osteoporosis after menopause is attenuation of the accelerated turnover rate of bone metabolism. The present randomized controlled study was conducted to clarify the effects of a lemon beverage with calcium (Ca) supplementation that makes use of the chelating action of citric acid. Comprehensive evaluations of bone were performed by assessments of bone mineral density (BMD) and biomarkers related to bone turnover. Seventy-nine postmenopausal women were enrolled and asked to participate in an 11-month continuous intake of the test beverages. The subjects were divided into three groups: those who consumed a lemon beverage containing citric acid with Ca supplementation (LECA group), those who consumed a lemon beverage containing citric acid without Ca supplementation (LE group), and those who consumed no test beverage (control group). Using a double-blind protocol, subjects in the LECA and LE groups consumed one bottle containing 290 mL of the test beverage each day. The ratio of change in BMD after 11 months was significantly higher in the LECA group as compared to the control and LE groups. The LECA group also showed significant decreases in concentrations of tartrate-resistant acid phosphatase 5b (TRACP-5b), a bone resorption marker, and bone alkaline phosphatase (BAP) as compared to the other groups, as well as a significant decrease in concentration of osteocalcin (OC), a bone formation marker, as compared to the LE group. Based on our findings, we speculated that bone resorption and bone formation in postmenopausal women might be suppressed along with an increase in Ca resorption caused by chelation of citric acid in association with continuous ingestion of a Ca-supplemented lemon beverage containing citric acid, resulting in suppression of high bone metabolic turnover. In addition, the results provide information regarding BMD maintenance in the bones of the trunk, including the lumbar spine and proximal femur.

Associations between Dietary Fiber Intake and Bone Mineral Density in Adult Korean Population: Analysis of National Health and Nutrition Examination Survey in 2011

Background

The correlations between the amount of daily fiber intake and bone mineral densities (BMDs) in Korean adult population were investigated in our study.

Methods

Utilizing the Korean National Health and Nutrition Examination Survey in 2011, multivariable linear regression was performed to explore the association between fiber consumption and BMD of lumbar vertebrae 1 to 4 (L1–4 total), L1, L2, L3, and L4 vertebrae, femur neck, femur total, and trochanter. All models were adjusted for age, body mass index, vitamin D level, smoking, physical activity, alcohol use, contraceptive use, hormonal replacement therapy, consumption of carbohydrate, protein, fat, calcium, phosphate, iron, thiamine, riboflavin, niacin, and vitamin C.

Results

In males aged between 18 and 45, fiber intake significantly increased BMDs of L1 (coefficient β=0.004, P=0.040) and L2 (β=0.004, P=0.038) while daily protein consumption significantly lowered BMDs of femur neck (β=−0.001, P=0.009), femur total (β=−0.001, P=0.008), and trochanter (β=−0.001, P=0.008). In males aged 65 and older, nutrient intake shows no significant correlations with BMDs except fat consumption was inversely associated with BMD of trochanter (β=−0.001, P=0.017). In females aged between 18 and 45, fiber intake shows no significant relationship with BMDs while daily fat consumption significantly increased BMDs of L1 (β=0.001, P=0.028), L2 (β=0.001, P=0.024), L3 (β=0.001, P=0.033), and L1–4 total (β=0.001, P=0.017).

Conclusions

Fiber intake was a protective factor of lumbar spine (L1 and L2) BMD in male aged between 18 and 45 but not in female participants of any age groups.

Regulation of bone mineral density in the grey squirrel, Sciurus carolinensis: Bioavailability of calcium oxalate, and implications for bark stripping

The damage caused when grey squirrels strip the outer bark off trees and ingest the underlying phloem can result in reduced timber quality or tree death. This is extremely costly to the UK forestry industry and can alter woodland composition, hampering conservation efforts. The calcium hypothesis proposes that grey squirrels ingest phloem to ameliorate a seasonal calcium deficiency. Calcium in the phloem predominantly takes the form of calcium oxalate (CaOx), however not all mammals can utilise CaOx as a source of calcium. Here, we present the results of a small-scale study to determine the extent to which grey squirrels can utilise CaOx. One of three custom-made diets containing calcium in varying forms and quantities (CaOx diet, Low-calcium carbonate (CaCO3 ) diet and Control diet) were fed to three treatment groups of six squirrels for 8 weeks. Bone densitometric properties were measured at the end of this time using peripheral quantitative computed tomography and micro-computed tomography. Pyridinoline-a serum marker of bone resorption-was measured regularly throughout the study. Bone mineral density and cortical mineralisation were lower in squirrels fed the CaOx diet compared to the Control group but similar to that of those on the Low-calcium diet, suggesting that calcium from calcium oxalate was not effectively utilised to maintain bone mineralisation. Whilst no differences were observed in serum pyridinoline levels between individuals on different diets, females had on average higher levels than males throughout the study. Future work should seek to determine if this apparent lack of ability to utilise CaOx is common to a large sample of grey squirrels and if so, whether it is consistent across all areas and seasons.

Calcium intake and bone mineral density: systematic review and meta-analysis

OBJECTIVE

To determine whether increasing calcium intake from dietary sources affects bone mineral density (BMD) and, if so, whether the effects are similar to those of calcium supplements.

DESIGN

Random effects meta-analysis of randomised controlled trials.

DATA SOURCES

Ovid Medline, Embase, Pubmed, and references from relevant systematic reviews. Initial searches were undertaken in July 2013 and updated in September 2014.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials of dietary sources of calcium or calcium supplements (with or without vitamin D) in participants aged over 50 with BMD at the lumbar spine, total hip, femoral neck, total body, or forearm as an outcome.

RESULTS

We identified 59 eligible randomised controlled trials: 15 studied dietary sources of calcium (n=1533) and 51 studied calcium supplements (n=12,257). Increasing calcium intake from dietary sources increased BMD by 0.6-1.0% at the total hip and total body at one year and by 0.7-1.8% at these sites and the lumbar spine and femoral neck at two years. There was no effect on BMD in the forearm. Calcium supplements increased BMD by 0.7-1.8% at all five skeletal sites at one, two, and over two and a half years, but the size of the increase in BMD at later time points was similar to the increase at one year. Increases in BMD were similar in trials of dietary sources of calcium and calcium supplements (except at the forearm), in trials of calcium monotherapy versus co-administered calcium and vitamin D, in trials with calcium doses of ≥ 1000 versus <1000 mg/day and ≤ 500 versus >500 mg/day, and in trials where the baseline dietary calcium intake was <800 versus ≥ 800 mg/day.

CONCLUSIONS

Increasing calcium intake from dietary sources or by taking calcium supplements produces small non-progressive increases in BMD, which are unlikely to lead to a clinically significant reduction in risk of fracture.

Calcium supplementation increases blood creatinine concentration in a randomized controlled trial

Background

Calcium supplements are widely used among older adults for osteoporosis prevention and treatment. However, their effect on creatinine levels and kidney function has not been well studied.

Methods

We investigated the effect of calcium supplementation on blood creatinine concentration in a randomized controlled trial of colorectal adenoma chemoprevention conducted between 2004–2013 at 11 clinical centers in the United States. Healthy participants (N = 1,675) aged 45–75 with a history of colorectal adenoma were assigned to daily supplementation with calcium (1200 mg, as carbonate), vitamin D₃ (1000 IU), both, or placebo for three or five years. Changes in blood creatinine and total calcium concentration were measured after one year of treatment and multiple linear regression was used to estimate effects on creatinine concentrations.

Results

After one year of treatment, blood creatinine was 0.013±0.006 mg/dL higher on average among participants randomized to calcium compared to placebo after adjustment for other determinants of creatinine (P = 0.03). However, the effect of calcium treatment appeared to be larger among participants who consumed the most alcohol (2–6 drinks/day) or whose estimated glomerular filtration rate (eGFR) was less than 60 ml/min/1.73 m² at baseline. The effect of calcium treatment on creatinine was only partially mediated by a concomitant increase in blood total calcium concentration and was independent of randomized vitamin D treatment. There did not appear to be further increases in creatinine after the first year of calcium treatment.

Conclusions

Among healthy adults participating in a randomized clinical trial, daily supplementation with 1200 mg of elemental calcium caused a small increase in blood creatinine. If confirmed, this finding may have implications for clinical and public health recommendations for calcium supplementation.

Trial Registration

ClinicalTrials.gov NCT00153816

Calcium supplements and cancer risk: a meta-analysis of randomised controlled trials

Some evidence suggests that Ca and vitamin D supplements affect cancer risk; however, it is uncertain whether the effects are due to Ca, vitamin D or the combination. We investigated the effect of Ca supplements without co-administered vitamin D on cancer risk. Medline, Embase and the Cochrane Central Register of Controlled Trials, reference lists of meta-analyses and two clinical trial registries were searched for randomised, placebo-controlled trials of Ca supplements ( ≥ 500 mg/d), with ≥ 100 participants and duration >1 year. The lead authors of eligible trials supplied data on cancer outcomes. Trial-level data were analysed using random-effects meta-analyses and patient-level data using Cox proportional hazards models. A total of sixteen trials were eligible, six had no data available, ten provided trial-level data (n 10 496, mean duration 3·9 years), and of these, four provided patient-level data (n 7221, median duration 3·5 years). In the meta-analysis of trial-level data, allocation to Ca did not alter the risk of total cancer (relative risk 0·95, 95 % CI 0·76, 1·18, P= 0·63), colorectal cancer (relative risk 1·38, 95 % CI 0·89, 2·15, P= 0·15), breast cancer (relative risk 1·01, 95 % CI 0·64, 1·59, P= 0·97) or cancer-related mortality (relative risk 0·96, 95 % CI 0·74, 1·24, P= 0·75), but reduced the risk of prostate cancer (relative risk 0·54, 95 % CI 0·30, 0·96, P= 0·03), although there were few events. The meta-analysis of patient-level data showed similar results, with no effect of Ca on the risk of total cancer (hazard ratio 1·07, 95 % CI 0·89, 1·28, P= 0·50). Ca supplements without co-administered vitamin D did not alter total cancer risk over 4 years, although the meta-analysis lacked power to detect very small effects, or those with a longer latency.

Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis

OBJECTIVE

To investigate whether calcium supplements increase the risk of cardiovascular events.

DESIGN

Patient level and trial level meta-analyses.

DATA SOURCES

Medline, Embase, and Cochrane Central Register of Controlled Trials (1966-March 2010), reference lists of meta-analyses of calcium supplements, and two clinical trial registries. Initial searches were carried out in November 2007, with electronic database searches repeated in March 2010.

STUDY SELECTION

Eligible studies were randomised, placebo controlled trials of calcium supplements (>or=500 mg/day), with 100 or more participants of mean age more than 40 years and study duration more than one year. The lead authors of eligible trials supplied data. Cardiovascular outcomes were obtained from self reports, hospital admissions, and death certificates.

RESULTS

15 trials were eligible for inclusion, five with patient level data (8151 participants, median follow-up 3.6 years, interquartile range 2.7-4.3 years) and 11 with trial level data (11 921 participants, mean duration 4.0 years). In the five studies contributing patient level data, 143 people allocated to calcium had a myocardial infarction compared with 111 allocated to placebo (hazard ratio 1.31, 95% confidence interval 1.02 to 1.67, P=0.035). Non-significant increases occurred in the incidence of stroke (1.20, 0.96 to 1.50, P=0.11), the composite end point of myocardial infarction, stroke, or sudden death (1.18, 1.00 to 1.39, P=0.057), and death (1.09, 0.96 to 1.23, P=0.18). The meta-analysis of trial level data showed similar results: 296 people had a myocardial infarction (166 allocated to calcium, 130 to placebo), with an increased incidence of myocardial infarction in those allocated to calcium (pooled relative risk 1.27, 95% confidence interval 1.01 to 1.59, P=0.038).

CONCLUSIONS

Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction. As calcium supplements are widely used these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.

The effect of calcium supplementation on bone loss in 32 controlled trials in postmenopausal women

SUMMARY

In 32 controlled trials of calcium supplementation (700-2000 mg) in 3,169 postmenopausal women, mean bone loss in the controls was -1.07% p.a. and in the treated subjects -0.27% p.a. (P for difference <0.001). The effect was similar at all measured sites and at all doses of 700 mg or more but became weaker after 4 years.

INTRODUCTION

We have reviewed 32 trials of calcium supplementation in 3,169 postmenopausal women.

METHODS

We found 24 publications reporting 32 controlled trials lasting at least 1 year, which provided annual percentage changes in bone mass or density at one or more sites in the calcium-treated and control subjects.

RESULTS

The median calcium supplement was 1,000 mg, median duration of the trials 2 years and total number of sites measured 79. The average of the mean rates of change in bone mass or density was -1.07% p.a. (P < 0.001) in the controls and -0.27% p.a. (ns) in the treated subjects (P for difference < 0.001). The effect of calcium was much the same at all measured sites (forearm/hand, proximal femur, spine, and total body and others). Supplements of less than 700 mg were not effective, but there was no significant beneficial effect of higher doses. There was significantly faster bone loss at total calcium intakes below 1,150 mg than on intakes over 1,350 mg. The effect of calcium appeared to be lost after 4 years of treatment.

CONCLUSION

Calcium supplementation of about 1,000 mg daily has a significant preventive effect on bone loss in postmenopausal women for at least 4 years.

WITHDRAWN: Calcium supplementation on bone loss in postmenopausal women

BACKGROUND

Although calcium is one the simplest and least expensive strategies for preventing osteoporotic fractures calcium supplementation is nevertheless not without controversy (Kanis 1989; Nordin 1990). The Food and Drug Administration in the US has permitted a bone health claim for calcium-rich foods, and the NIH in its Consensus Development Process approved a statement that high calcium intake reduces the risk of osteoporosis.

OBJECTIVES

To assess the effects of calcium on bone density and fractures in postmenopausal women.

SEARCH STRATEGY

We searched Cochrane Controlled Register, MEDLINE and EMBASE up to 2001, and examined citations of relevant articles and proceedings of international meetings.

SELECTION CRITERIA

Trials that randomized postmenopausal women to calcium supplementation or usual calcium intake in the diet and reported bone mineral density of the total body, vertebral spine, hip, or forearm or recorded the number of fractures, and followed patients for at least one year were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Three independent reviewers assessed the methodologic quality and extracted data for each trial. For each bone density site (lumbar spine, total body, combined hip and combined forearm), we calculated the weighted mean difference in bone density between treatment and control groups using the percentage change from baseline. We constructed regression models in which the independent variables were year and dose, and the dependent variable was the effect size. This regression was used to determine the years across which pooling was appropriate. Heterogeneity was assessed. For each fracture analysis we calculated a risk ratio.

MAIN RESULTS

Fifteen trials, representing 1806 participants, were included. Calcium was more effective than placebo in reducing rates of bone loss after two or more years of treatment. The pooled difference in percentage change from baseline was 2.05% (95% CI 0.24 to 3.86) for total body bone density, 1.66% (95% CI 0.92 to 2.39) for the lumbar spine at 2 years, 1.60% (95% CI 0.78 to 2.41) for the hip, and 1.91% (95% CI 0.33 to 3.50) for the distal radius. The relative risk of fractures of the vertebrae was 0.79 (95% CI 0.54 to 1.09); the relative risk for non-vertebral fractures was 0.86 (95% CI 0.43 to 1.72).

AUTHORS' CONCLUSIONS

Calcium supplementation alone has a small positive effect on bone density. The data show a trend toward reduction in vertebral fractures, but it is unclear if calcium reduces the incidence of non vertebral fractures.

Calcium intake, calcium bioavailability and bone health

Calcium accounts for 1–2 % of adult human body weight. Over 99 % of total body Ca is found in the teeth and bones. Therefore, in addition to the obvious structural role of the skeleton, it also serves as a reservoir for Ca. Dietary Ca intake has an important impact on bone metabolism and bone health. Chronic Ca deficiency resulting from inadequate intake or poor intestinal absorption is one of several important causes of reduced bone mass and osteoporosis. It is vital, therefore, that adequate dietary Ca is consumed at all stages of life — in early life so that the genetically programmed peak bone mass can be reached and in later adulthood so that the skeletal mass can be maintained and age-related bone loss minimised. Unfortunately, there is wide variation in the estimates of daily Ca requirements made by different expert authorities. Furthermore, there is evidence that many individuals are not consuming these recommended levels. The consequence of this for bone health will be discussed in the present review. Besides the amount of Ca in the diet, the absorption of dietary Ca in foods is also a critical factor in determining the availability of Ca for bone development and maintenance. Thus, there is a need to identify food components and/or functional food ingredients that may positively influence Ca absorption in order to ensure that Ca bioavailability from foods can be optimised. This approach may be of particular value in individuals who fail to achieve the dietary recommended level of Ca.

Inulin-type fructans and bone health: state of the art and perspectives in the management of osteoporosis

If the primary role of diet is to provide sufficient nutrients to meet the metabolic requirements of an individual, there is an emerging rationale to support the hypothesis that, by modulating specific target functions in the body, it can help achieve optimal health. Regarding osteoporosis prevention, since Ca is most likely to be inadequate in terms of dietary intake, every strategy targeting an improvement in Ca absorption is very interesting. Actually, this process may be susceptible to manipulation by fermentable substrates. In this light, inulin-type fructans are very interesting, even if we need to gather more data targeting bone metabolism before health professionals can actively advocate their consumption to prevent senile osteoporosis. Besides targeting the prevention of postmenopausal osteoporosis, inulin-type fructans still remain a source for putative innovative dietary health intervention. Indeed, given in combination with isoflavones, they may have a potential for maintaining or improving the bone mass of human subjects, by modulating the bioavailability of phyto-oestrogens.

Trabecular bone status in ultradistal tibia under habitual gait loading: a pQCT study in postmenopausal women

This study investigated regional volumetric trabecular bone mineral density (tBMD) and bone area at the ultradistal tibia in Chinese women using peripheral quantitative computed tomography. Fifty-six postmenopausal women aged 47-62 yr participated in BMD measurements at baseline and 22 of them were followed at both 1-yr and 3-yr follow-up scans. Regional baseline tBMD, rate of annual bone loss, and trabecular bone area were determined. Baseline measurements showed that the tBMD of both the posterior (252.9+/-63.4 mg/cm(3)) and medial (226.6+/-68.9 mg/cm(3)) regions was significantly higher than that of the anterior (126.3+/-61.9 mg/cm(3)) and lateral regions (149.8+/-50.6 mg/cm(3)), respectively (p<0.001). Both the 1-yr and 3-yr follow-up measurements showed that there was significant physiological annual tBMD loss on an average of 1.61%, at the four regions. Inter-slice regional tBMD and trabecular bone area measurements demonstrated a significant linear decrease from the distal to proximal aspects (p<0.001). Findings suggest that dynamic compressive loading during the heel strike and the body weight vector shifting toward the medial aspect during the stance phase in a normal gait might account for the regional tBMD differences. Increased tBMD and bone area toward the distal tibial endplate may adapt to withstand the axial impact loading. However, the low-impact weight-bearing nature of a normal gait may not be osteogenic to prevent regional bone loss. An exercise program specific to the women at risk should be contemplated.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

A controlled trial of the effect of milk basic protein (MBP) supplementation on bone metabolism in healthy menopausal women

Milk has more beneficial effects on bone health than other food sources. Recent in vitro and in vivo studies have shown that milk whey protein, especially its basic protein fraction (milk basic protein, MBP), contains several components capable of promoting bone formation and inhibiting bone resorption. The object of this study was to examine the effect of MBP on the bone metabolism of healthy menopausal women. Thirty-two healthy menopausal women were randomly assigned to treatment with either placebo or MBP (40 mg per day) for 6 months. The bone mineral density (BMD) of the lumbar vertebrae L2-L4 of each subject was measured by dual-energy X-ray absorptiometry (DXA) at 0 and 6 months of treatment. Serum and urine indices of bone metabolism were measured at 0, 3 and 6 months. Twenty-seven subjects who completed the study in accordance with the protocol were included in the analysis. The mean rate of gain of lumbar BMD in the MBP group (1.21%) was significantly higher than in the placebo group (-0.66%, P=0.046). When compared with the placebo group, urinary cross-linked N-telopeptides of type-I collagen (NTx) were significantly decreased in the MBP group at 6 months, but no significant difference in serum osteocalcin was observed between the two groups. The urinary NTx excretion was found to be related to serum osteocalcin in the MBP group at 3 and 6 months, indicating that MBP maintained the balance of bone remodeling. These results suggested that MBP supplementation was effective in preventing bone loss in menopausal women and that this improvement in BMD may be primarily mediated through the inhibition of bone resorption while maintaining the balance of bone remodeling by MBP supplementation.

Calcium supplementation on bone loss in postmenopausal women

BACKGROUND

Although calcium is one the simplest and least expensive strategies for preventing osteoporotic fractures calcium supplementation is nevertheless not without controversy (Kanis 1989; Nordin 1990). The Food and Drug Administration in the US has permitted a bone health claim for calcium-rich foods, and the NIH in its Consensus Development Process approved a statement that high calcium intake reduces the risk of osteoporosis.

OBJECTIVES

To assess the effects of calcium on bone density and fractures in postmenopausal women.

SEARCH STRATEGY

We searched Cochrane Controlled Register, MEDLINE and EMBASE up to 2001, and examined citations of relevant articles and proceedings of international meetings.

SELECTION CRITERIA

Trials that randomized postmenopausal women to calcium supplementation or usual calcium intake in the diet and reported bone mineral density of the total body, vertebral spine, hip, or forearm or recorded the number of fractures, and followed patients for at least one year were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Three independent reviewers assessed the methodologic quality and extracted data for each trial. For each bone density site (lumbar spine, total body, combined hip and combined forearm), we calculated the weighted mean difference in bone density between treatment and control groups using the percentage change from baseline. We constructed regression models in which the independent variables were year and dose, and the dependent variable was the effect size. This regression was used to determine the years across which pooling was appropriate. Heterogeneity was assessed. For each fracture analysis we calculated a risk ratio.

MAIN RESULTS

Fifteen trials, representing 1806 participants, were included. Calcium was more effective than placebo in reducing rates of bone loss after two or more years of treatment. The pooled difference in percentage change from baseline was 2.05% (95% CI 0.24 to 3.86) for total body bone density, 1.66% (95% CI 0.92 to 2.39) for the lumbar spine at 2 years, 1.60% (95% CI 0.78 to 2.41) for the hip, and 1.91% (95% CI 0.33 to 3.50) for the distal radius. The relative risk of fractures of the vertebrae was 0.79 (95% CI 0.54 to 1.09); the relative risk for non-vertebral fractures was 0.86 (95% CI 0.43 to 1.72).

REVIEWER'S CONCLUSIONS

Calcium supplementation alone has a small positive effect on bone density. The data show a trend toward reduction in vertebral fractures, but it is unclear if calcium reduces the incidence of non vertebral fractures.

Determinants of osteoporosis prevention in low-income Mexican-American women

BACKGROUND

Prevention is the most cost-effective means of managing osteoporosis. However, little is known about osteoporosis-related preventive practices in Mexican-American women. We examined factors that might influence women's decision to start preventive measures for osteoporosis.

METHODS

Information was gathered through a cross-sectional survey of low-income Mexican-American women who were seen at two clinics in southern Texas.

RESULTS

Of the 270 participants, 37% reported calcium supplementation, and 41% reported regular weight-bearing exercise to prevent osteoporosis. Fifty (41%) of the postmenopausal women were currently using hormone replacement therapy. Only 15% of the premenopausal and 13% of the postmenopausal women recalled that their health care provider had counseled them about prevention. Multivariate analysis showed that public education, bone densitometry evaluation, knowledge of osteoporosis, and counseling were determinants of prevention.

CONCLUSION

Although osteoporosis is a preventable condition, our findings suggest that the majority of Mexican-American women do not receive adequate preventive measures or counseling about osteoporosis. Furthermore, we found that their health care provider's counseling about osteoporosis was a major determinant of osteoporosis prevention in these women.

A longitudinal study of bone density in midlife women

A longitudinal study of 386 healthy Black and White women aged 35-60 years was conducted to determine the effects of physical activity and other related factors on lumbar bone mineral density over 24 months. Bone mineral density of the lumbar spine, L2-L4, was measured using dual energy x-ray (Hologic 1000). Physical activity levels in three dimensions (leisure, household, and occupational) from both a lifelong and current perspective were obtained by questionnaire. Body mass index was calculated from measured weight in kilograms divided by measured height in meters squared. Calcium, caffeine, and alcohol intake was estimated using a food frequency questionnaire. Age, race, and smoking were determined by self-report. Radioimmunoassays of follicle stimulating hormone (FSH) and estradiol were used to validate self-reports of menopausal status. Multiple regression analysis revealed that race, age, weight, FSH, calcium, and years of tobacco intake formed the best model at baseline (r(2) = 0.32) and at 24 months (r(2) = 0.303). Physical activity was not a significant predictor for bone mineral density at either time point. There were cross-sectional changes of bone mineral density with race, age, and menopausal status. Black women had significantly higher bone mineral density than White women. However, an age-related decline in bone mineral density was exhibited in both Black and White women. Perimenopausal women had significantly lower bone mineral density as compared with premenopausal women. Furthermore 37 (9.6%) women at baseline and 34 (11%) at 24 months were designated at risk for fracture.

Meta-analyses of therapies for postmenopausal osteoporosis. VII. Meta-analysis of calcium supplementation for the prevention of postmenopausal osteoporosis

OBJECTIVE

To summarize controlled trials examining the effect of calcium on bone density and fractures in postmenopausal women.

DATA SOURCE

We searched MEDLINE and EMBASE up to 1998 and the Cochrane Controlled Register up to 2000, and we examined citations of relevant articles and proceedings of international meetings. We contacted osteoporosis investigators to identify additional studies, and primary authors for unpublished data.

STUDY SELECTION

We included 15 trials (1806 patients) that randomized postmenopausal women to calcium supplementation or usual calcium intake in the diet and reported bone mineral density of the total body, vertebral spine, hip, or forearm, or recorded the number of fractures, and followed patients for at least 1 yr.

DATA EXTRACTION

For each trial, three independent reviewers assessed the methodological quality and extracted data.

DATA SYNTHESIS

We found calcium to be more effective than placebo in reducing rates of bone loss after two or more years of treatment. The pooled difference in percentage change from baseline was 2.05% [95% confidence interval (CI) 0.24-3.86] for total body bone density, 1.66% (95% CI 0.92-2.39) for the lumbar spine, 1.64% (95% CI 0.70-2.57) for the hip, and 1.91% (95% CI 0.33-3.50) for the distal radius. The relative risk (RR) of fractures of the vertebrae was 0.77, with a wide CI (95% CI 0.54-1.09); the RR for nonvertebral fractures was 0.86 (95% CI 0.43-1.72).

CONCLUSIONS

Calcium supplementation alone has a small positive effect on bone density. The data show a trend toward reduction in vertebral fractures, but do not meaningfully address the possible effect of calcium on reducing the incidence of nonvertebral fractures.

Postmenopausal survivors of breast cancer at risk for osteoporosis: nutritional intake and body size

Postmenopausal survivors of breast cancer for whom hormone replacement therapy is contraindicated are at risk for development of osteoporosis. The primary purpose of this article is to describe, in a sample of 30 postmenopausal survivors of breast cancer, their calcium and vitamin D intake compared with recommended dietary guidelines for those nutrients for postmenopausal women not taking hormone replacement therapy and the body mass index of these women as nutritional status risk factors for development of osteoporosis. Bone health and presence of osteoporosis were determined by bone mineral density testing of the spine, hip, and forearm. To obtain calcium and vitamin D intake, including supplements, 3-day diet records were completed; height and weight measures were used to calculate body mass index. The sample participants ranged in age from 42 to 65 years; the majority (56%) had been menopausal or off hormone replacement therapy for 5 years or less, and 70% had completed breast cancer treatment for 5 years or less (except tamoxifen). The majority (63%) were of medium body frame size; 30% were of small frame size. The mean body mass index (27.3) and mean weight (160 lbs) indicate that these women, as a group, were over-weight. Although a large percent (63%) were taking calcium supplements, the mean daily intake (diet and supplements) of calcium (1,353 mg) and vitamin D (403 IU) was less than the recommended dietary guidelines for these nutrients in this population. At study entry, 80% of the women were osteopenic (60%) or osteoporotic (20%) and none was receiving treatment/prevention for osteoporosis; only 1 had a previous known osteoporosis diagnosis. This is a special group of women for whom screening and preventive strategies for osteoporosis are imperative.

Milk supplementation of the diet of postmenopausal Chinese women on a low calcium intake retards bone loss

The Chinese diet is low in calcium (less than 500 mg/day on average), and previous observational studies have suggested an association between a low calcium intake and risk of hip and vertebral fracture. In this study, we randomly assigned 200 postmenopausal Chinese women (age range, 55-59 years) to receive 50 g of milk powder containing 800 mg of calcium per day or to a control group. The following are the mean percentage changes (and SEs) in height and bone mineral density (BMD) over 24 months: for height, -0.1 +/- 0.2 cm in the milk supplementation group and -0.2 +/- 0.1 cm in the control group; for BMD at the total hip, -0.06 +/- 0.22% in the milk supplementation group and -0.88 +/- 0.26% in the control group; for BMD at the spine (L1-L4), -0.56 +/- 0.29% in the milk supplementation group and -1.5 +/- 0.29% in the control group; for total body BMD, -0.32 +/- 0.16% in the milk supplementation group and -1.2 +/- 0.19% in the control group (p < 0.05 by analysis of covariance [ANCOVA] for repeated measures for height and BMD at all sites). The milk supplementation group had less loss in terms of both height and BMD than the control group (p < 0.05 by ANCOVA for repeated measures). Serum parathyroid hormone (PTH) concentration was lower and serum 25-hyroxyvitamin D [25(OH)D] level was higher in the milk supplementation group than the control group at 12 months (p < 0.05 by paired t-test). We conclude that supplementing the diet of postmenopausal Chinese women with high calcium milk powder retards bone loss.

Sex steroids and bone

Sex steroids are essential for skeletal development and the maintenance of bone health throughout adult life, and estrogen deficiency at menopause is a major pathogenetic factor in the development of osteoporosis in postmenopausal women. The mechanisms by which the skeletal effects of sex steroids are mediated remain incompletely understood, but in recent years there have been considerable advances in our knowledge of how estrogens and, to a lesser extent androgens, influence bone modeling and remodeling in health and disease. New insights into estrogen receptor structure and function, recent discoveries about the development and activity of osteoclasts, and lessons learned from human and animal genetic mutations have all contributed to increased understanding of the skeletal effects of estrogen, both in males and females. Studies of untreated and treated osteoporosis in postmenopausal women have also contributed to this knowledge and have provided unequivocal evidence for the potential of high-dose estrogen therapy to have anabolic skeletal effects. The development of selective estrogen receptor modulators has provided a new approach to the prevention of osteoporosis and other major diseases of menopause and has implications for the therapeutic use of other steroid hormones, including androgens. Further elucidation of the mechanisms by which sex steroids affect bone thus has the potential to improve the clinical management not only of osteoporosis, both in men and women, but also of a number of other diseases related to sex hormone status.

An overview of group sequential methods in longitudinal clinical trials

During the last decade, several papers have been published on group sequential methods in general and on sequential longitudinal clinical trials in particular. This paper gives an overview of the proposed methods, emphasizing longitudinal clinical trials. Furthermore, it tries to answer some practical questions that may arise during the conduct of interim analyses in longitudinal trials. Simulations have been carried out to obtain insight in these practical considerations.

A prospective study on the effects of depot medroxyprogesterone acetate on trabecular and cortical bone after attainment of peak bone mass

OBJECTIVE

To study the annual change of bone mass in women aged 30-45 years being treated with depot medroxyprogesterone acetate (DMPA) in order to evaluate whether the bone mass depends on the duration of DMPA use or the oestradiol level.

DESIGN

Prospective longitudinal study over an interval of 12 months.

SETTING

A family planning centre of a university hospital.

PATIENTS

Thirty-six current users of DMPA.

INTERVENTIONS

Injection of 150 mg DMPA every 12 weeks.

MEASUREMENTS

Bone mass was measured at the distal radius by peripheral quantitative computed tomography (reproducibility 0.3%).

RESULTS

Mean annual changes (SD) in trabecular and cortical bone mass were 0.06 (1.6%) [P = 0.8] and -0.26% (0.6) [P < 0.04]. The decrease in cortical bone mass was not significant because the changes were within the precision error of the method used for the measurements. Duration of DMPA use and oestradiol levels were not associated to the bone parameters.

CONCLUSION

We did not find a negative impact of DMPA on the bone mass of premenopausal women aged 30-45 years.

[Treatment of osteoporosis with calcium and vitamin D. Systematic review]

BACKGROUND

Systematic review of the efficacy of calcium and vitamin D for the treatment of osteoporosis.

MATERIAL AND METHOD

Review of the database MEDLINE between 1996 and may 1998, by the key words: osteoporosis, calcium, vitamin D (and related terms) and randomized clinical trial. Review of the electronic versions of Best Evidence, The Cochrane Library, congress abstracts and references from two main textbooks. Ascending review of the literature. All the reviews were performed independently by two of the authors. Design parameters and main results of the primary publications of the identified trials were tabulated. Two independent observers carried out methodological scoring of the studies. Results were tabulated and a judgement made for the results.

RESULTS

Eleven studies on calcium, 8 of vitamin D and 12 about calcitriol and other hormone derivatives were included. Studies with calcium were mainly performed on non-clinical populations and in three anti-fracture efficacy was analyzed. Results were positive in population with low baseline intake and substantial supplementation. Trials on vitamin D were done in non-clinical and on institutionalized populations. Trials with calcitriol were developed mainly in osteoporotic fracture populations and reached poorer methodological validity scores. Heterogeneity of the studies precluded a meta-analysis of the different treatments. Studies on calcium showed clinical efficacy in a more consistent way. Inter-observer score was good (kappa = 0.81) and there were no significant correlations between sample size and effect in the different studies.

CONCLUSIONS

Calcium treatment is efficacious in populations with low intake receiving substantial supplementation. Vitamin D is efficacious associated with calcium mainly in deficient populations. Efficacy of calcitriol and other derivatives is more controversial.

The bioavailability of dietary calcium

This update focuses on the bioavailability of dietary calcium for humans. Fundamentals of calcium metabolism, intestinal absorption, urinary excretion and balance are recalled. Dietary factors, especially lactose and other milk components, influencing calcium bioavailability at intestinal and renal levels are reviewed. A critical examination of all the methods used for evaluating calcium bioavailability is made. This includes in vitro assays, classical and isotopic balances, urinary excretion, isotope labeling in the urine, plasma and bones, long term evaluation of bone mineralization and the use of biological bone markers. Importance and advantages of animal models are discussed. The state of the art in the comparative bioavailability of calcium in foods is detailed including a comparison of sources of calcium (dairy products and calcium salts) in human studies and in some animal studies, casein phosphopeptides, proteins, lactose and lactase and their relation with calcium bioavailability (in humans and rats). An update on the consumption of dairy products and bone mass is presented. Emphasis on peculiarities and advantages of calcium in milk and dairy products is given.

The effects of an educational intervention on calcium intake and bone mineral content in young women with low calcium intake

PURPOSE

This study evaluated whether a combined behavioral and dietary intervention would affect young women's calcium intake and bone mineral content (BMC).

DESIGN

The design was a two by three mixed design with one between-subjects factor (treatment vs. control) and one within-subjects factor (time--baseline, 3-month, and 6-month).

SETTING

The study was conducted in a university setting in Memphis, Tennessee.

PARTICIPANTS

A total of 80 premenopausal women (ages 18 to 30) with low baseline calcium intake (< 700 mg/d) were included in the analyses. There were 40 women in the treatment group and 40 women in the control group.

MEASURES

Hertzler and Frary's rapid assessment questionnaire was employed to evaluate calcium intake, and dual-energy x-ray absorptiometry (DEXA) was employed to assess BMC.

RESULTS

Repeated measures analysis of variance (RM ANOVA) was employed to analyze results. Results indicated that women in the treatment group made greater increases in total calcium intake and supplemental calcium than women in the control group and that all women made significant increases in dietary calcium intake. Additionally, analyses of BMC revealed that women in the treatment group did not experience significant changes in total BMC, and women in the control group experienced significant losses in total BMC.

CONCLUSIONS

In the current study, women were losing BMC, and the women who made the largest increases in calcium intake were able to retard this bone loss. There is increasing evidence that dietary calcium intake in young people is extremely low, and the results of the current study highlight the need for much more intensive evaluations investigating the factors that are positively associated with premenopausal bone mineral change.

The reproducibility of ultrasound bone measures in a triethnic population of pregnant adolescents and adult women

We used bone ultrasound technology with its measurement of attenuation (broadband ultrasound attenuation [BUA] as dB/MHz) and sound velocity (speed of sound as m/s) for assessing the quantitative ultrasound index (QUI) summary measure in a triethnic population of 280 pregnant women. The study purpose was to describe the reproducibility of the ultrasound technology and determine if the correlations of age, weight, and ethnicity with the bone status measures in this population are consistent with the correlations of age, weight, and ethnicity that have been reported with other technologies that measure bone mass. We evaluated the first 280 women enrolled in our longitudinal study of lead turnover from maternal bone during pregnancy and lactation. Enrollees were pregnant, aged 12-29 years, and self-classified as black, white, or Hispanic. Bone ultrasound was measured twice at entry to prenatal care, which, on average, was at 14 weeks gestation. Reproducibility was described with intraclass correlations and the standard error of measurement. Age, weight, and ethnicity were associated with bone status measures using Spearman correlations and generalized linear models. The reproducibility of the summary bone measure, QUI, was high (96-97%). Variation in age and ethnicity did not alter reproducibility; however, the reproducibility of the attenuation measure (BUA as dB/MHz) lessened with increasing weight, declining from 95% to 89%. Since this attenuation is included in the summary QUI measure, there was a slight, and nonsignificant, decline in QUI reproducibility (from 97% to 96%) as women increased in size. There were no statistically significant differences in mean bone ultrasound measures according to age, where ages ranged from 12-29 years. Women who categorized themselves as black had, on average, an 8.5% greater QUI than did women who classified themselves as Hispanic or white. There were no significant pair-wise differences in mean ultrasound measures of bone between women classifying themselves as Hispanic or white. The use of ultrasound is a highly reproducible measure to assess bone characteristics in a population of pregnant adolescent and young adult women and its summary measure of bone mass is correlated with ethnic as well as body size characteristics.

First- and second-year effects in trials of calcium supplementation on the loss of bone density in postmenopausal women

The analysis of clinical trials investigating the effect of calcium on the loss of bone mass or density has been based on the assumption that the effects are the same for all years of follow-up. Hence the average annual rate of loss is calculated and compared in the calcium and control groups. In this metaanalysis, we investigated this assumption and found that it is not tenable in the groups randomized to calcium for most sites that have been measured. The rate of bone loss was significantly less in the first year after randomization than in the second year. By contrast, the rate of loss in the control groups was less in the second year than the first, although this was not significant. At the spine, femoral neck, trochanter, intertrochanter, midtibia, and ultratibia, the effect of calcium in reducing bone loss was statistically significant compared with control only in the first year after randomization; there was no difference in rates between the groups in the second year. The effect of calcium compared to control in two arm sites and Ward's triangle was of a similar magnitude but was not statistically significant. We recommend that analysis and metaanalysis of trials should always consider the effects on a year-by-year basis.

Calcium and osteoporosis

Calcium is an essential nutrient that is involved in most metabolic processes and the phosphate salts of which provide mechanical rigidity to the bones and teeth, where 99% of the body's calcium resides. The calcium in the skeleton has the additional role of acting as a reserve supply of calcium to meet the body's metabolic needs in states of calcium deficiency. Calcium deficiency is easily induced because of the obligatory losses of calcium via the bowel, kidneys, and skin. In growing animals, it may impair growth, delay consolidation of the skeleton, and in certain circumstances give rise to rickets but the latter is more often due to deficiency of vitamin D. In adult animals, calcium deficiency causes mobilization of bone and leads sooner or later to osteoporosis, i.e., a reduction in the "amount of bone in the bone" or apparent bone density. The effects of calcium deficiency and oophorectomy (ovariectomy) are additive. In humans, osteoporosis is a common feature of aging. Loss of bone starts in women at the time of the menopause and in men at about age 55 and leads to an increase in fracture rates in both sexes. Individual fracture risk is inversely related to bone density, which in turn is determined by the density achieved at maturity (peak bone density) and the subsequent rate of bone loss. At issue is whether either or both of these variables is related to calcium intake. The calcium requirement of adults may be defined as the mean calcium intake needed to preserve calcium balance, i.e., to meet the significant obligatory losses of calcium through the gastrointestinal tract, kidneys, and skin. The calcium allowance is the higher intake recommended for a population to allow for individual variation in the requirement. The mean requirement defined in this way, calculated from balance studies, is about 20 mmol (800 mg) a day on Western diets, implying an allowance of 25 mmol (1000 mg) or more. Corresponding requirements and allowances have been calculated for pregnancy and lactation and for children and adolescents, taking into account the additional needs of the fetus, of milk production, and of growth. There is a rise in obligatory calcium excretion at menopause, which increases the theoretical calcium requirement in postmenopausal women to about 25 mmol (1000 mg) and implies an allowance of perhaps 30 mmol (1200 mg) or even more if calcium absorption declines at the same time. At issue here, however, is whether menopausal changes in calcium metabolism are the cause or the result of postmenopausal bone loss. The first interpretation relies on evidence of a positive action of estrogen on the gastrointestinal absorption and renal tubular reabsorption of calcium; the latter interpretation relies on evidence of a direct inhibitory effect of estrogen on bone resorption. The calcium model for postmenopausal bone loss tends to be supported by the effect of calcium therapy. An analysis of the 20 major calcium trials in postmenopausal women reported in the last 20 years yielded a mean rate of bone loss of 1.00% per annum (p.a.) in the controls and 0.014% p.a. (NS) in the treated subjects (P < 0.001). However, trials in which calcium and estrogen have been directly compared have shown that the latter is generally more effective than calcium in that it produces a small, but often significant bone gain. This superiority of estrogen over calcium could be due to the former's dual action on calcium absorption and excretion or to a direct action of estrogen on bone itself. In older women, the importance of calcium intake is overshadowed by the strong association between vitamin D insufficiency and hip fracture. Whether this insufficiency arises primarily from lack of exposure to sunlight or to a progressive failure to activate the vitamin D precursor in the skin or both is uncertain but it is compounded by a general decline in dietary vitamin D intake with age. The biological effect is probably an impairment of calcium absorption and c

Milk, dietary calcium, and bone fractures in women: a 12-year prospective study

OBJECTIVES

This study examined whether higher intakes of milk and other calcium-rich foods during adult years can reduce the risk of osteoporotic fractures.

METHODS

This was a 12-year prospective study among 77761 women, aged 34 through 59 years in 1980, who had never used calcium supplements. Dietary intake was assessed with a food-frequency questionnaire in 1980, 1984, and 1986. Fractures of the proximal femur (n = 133) and distal radius (n = 1046) from low or moderate trauma were self-reported on biennial questionnaires.

RESULTS

We found no evidence that higher intakes of milk or calcium from food sources reduce fracture incidence. Women who drank two or more glasses of milk per day had relative risks of 1.45 for hip fracture (95% confidence interval [CI] = 0.87, 2.43) and 1.05 for forearm fracture (95% CI = 0.88, 1.25) when compared with women consuming one glass or less per week. Likewise, higher intakes of total dietary calcium or calcium from dairy foods were not associated with decreased risk of hip or forearm fracture.

CONCLUSIONS

These data do not support the hypothesis that higher consumption of milk or other food sources of calcium by adult women protects against hip or forearm fractures.

A 4-year follow-up study of the effects of calcium supplementation on bone density in elderly postmenopausal women

To determine the long-term effect of calcium supplementation on bone density, 84 elderly women (54-74 years) more than 10 years past the menopause were studied for 4 years as part of a follow-up study of a randomized, double-masked, placebo-controlled trial. The placebo group who did not take calcium supplements at all during the 4-year study (control group, n = 21) served as a comparison with the treated group who took calcium supplements for 4 years (calcium supplement group, n = 14). We also studied subjects who were treated for 2 years with calcium supplements and then ceased taking them (non-compliant group, n = 49). The changes in bone density at the lumbar spine, hip and ankle sites, current calcium intake and activity were monitored. Over the 4 years the calcium supplement group (mean calcium intake 1988 +/- 90 mg/day) did not lose bone at the hip and ankle site. The control group (mean calcium intake 952 +/- 109 mg/day) lost significantly more bone than the calcium supplement group at all sites of the hip and ankle. No overall bone loss was seen at the spine, in either group, over the 4 years of this study. Between years 2 and 4 the non-compliant group (mean calcium intake 981 +/- 75 mg/day) lost significantly more bone at all sites of the ankle than the calcium supplement group. Therefore, calcium supplementation produces a sustained reduction in the rate of loss of bone density at the ankle and hip sites in elderly postmenopausal women. Increasing dietary calcium intake in women should be the aim of a public health campaign.

Therapy of osteoporosis: calcium, vitamin D, and exercise

Calcium supplementation has long been regarded as a fundamental part of the prevention and treatment of postmenopausal osteoporosis, but it is only in recent years that clear evidence has emerged demonstrating its impact on bone mass. Calcium supplementation does not completely arrest postmenopausal bone loss but slows the rate of decline by 30 to 50%. The effect of calcium supplementation on fracture incidence in postmenopausal women has not been established. Vitamin D deficiency is common in the frail elderly, particularly in countries where fortification or food with this vitamin is not practiced. Treatment of vitamin D deficiency has been associated with significant reductions in the number of hip fractures. The role of the potent vitamin D metabolites, calcitriol and alphacalcidol, in the management of postmenopausal osteoporosis is not clear. Although some studies show substantial benefits in bone density or fracture rate from the use of these compounds, the published data are inconsistent. In general, hormone replacement therapy and the potent bisphosphonates produce greater effects on bone density and there is a greater consistency among the results of the published studies of these other interventions. Controlled trials of exercise interventions in postmenopausal women show that exercise can positively influence bone density by a few percent. Exercise interventions in the elderly have been reported to decrease fall frequency by 10%. This latter effect may have a greater impact on fracture frequency than the modest benefits of exercise on bone-density.

Age considerations in nutrient needs for bone health

Age exerts a major influence on the nutritional needs for bone health. Age influences the nutrient requirements for bone health by influencing: the growth and development of bone; the deposition of minerals leading to peak bone mass; the rate of bone loss; the levels of hormones which influence bone; the absorption and retention of nutrients required for optimal bone health, physical activity, food intake, and the level of sun exposure. Adequate calcium intake benefits bones at any age. However, dietary calcium needs vary at different ages. In June 1994, a National Institutes of Health expert panel recommended higher calcium intakes than current Recommended Dietary Allowance for several age groups. Many population groups in the United States, including young girls and women, continue to consume significantly less calcium than current recommended levels. In addition, diets low in calcium are often low in many other essential nutrients important for good bone health, including vitamin D, vitamin B6, and magnesium. Dietary recommendations for bone health should be placed in the full context of the total diet rather than a singular emphasis on calcium. To truly benefit consumers, dietary recommendations for bone health should emphasize consumption of foods high in calcium as part of a healthy diet and a healthy lifestyle.

Peak bone mass development of females: can young adult women improve their peak bone mass?

The purpose of this review is to summarize the effects of calcium intake on peak bone mass (PBM) accrual by premenopausal females during their 20s and possibly 30s. Prospective studies are highlighted because of the value of investigating the same subjects for one or more years. Results of cross-sectional studies are also summarized. Findings from both prospective and cross-sectional investigations suggest a positive benefit of adequate or supplemented calcium intakes on bone mineral content (BMC) in females during the third (20s) and fourth (30s) decades of life. PBM of subjects was found to be increased or maintained in comparison to PBM of controls in the five intervention studies that used calcium supplementation or the addition of calcium-rich foods. The results of cross-sectional studies, including a meta-analysis of approximately 20 such studies, also support the benefit to PBM of adequate calcium intakes. In summary, sufficient consumption of calcium during the various stages of the early life cycle, when combined with overall sound nutrition, regular physical activity, and possibly pregnancy, lactation, and child-rearing, may contribute to PBM accrual of women during the early adult decades.