Habitual dietary calcium intake and cortical bone loss in perimenopausal women: a longitudinal study

Dietary calcium intake and change in bone mineral density in older adults: a systematic review of longitudinal cohort studies

Many older adults do not achieve recommended intakes of calcium and there is some concern over the potential impact of this on bone health. The objective of this review was to examine evidence from cohort studies on the relationship between calcium intake and change in bone mineral density (BMD) in older adults, something not undertaken in the last two decades. Data sources included Ovid Medline, Embase, and PubMed and references from retrieved reviews and articles. The final search was performed in February 2021. We included cohort studies of calcium intake in participants aged >50 years with change in BMD over ≥1 year as an outcome. We identified 23 studies of women and 7 of men. Most studies found no association between calcium intake and change in BMD in women (71%) or men (71%). Among women, five studies reported high rates (>30% of participants) of hormone treatment or osteoporosis therapy (HT/OT) use; 80% of these studies reported a positive association between calcium intake and change in BMD, compared with 10% of studies in which HT/OT use was low. No study in women in which the mean age was >60 years reported a positive association between calcium intake and change in BMD. We conclude that calcium intake across the ranges consumed in these studies (mean intake in all but one study >500 mg/day) is not an important determinant of bone loss, particularly among women >60 years. The positive findings in studies with high rates of HT/OT use are likely to arise from confounding as a result of co-administration of calcium supplements with these medications.

Calcium and Bone

The maintenance of extracellular calcium levels within a narrow range is necessary for normal function of the nervous system, muscle, and coagulation, to maintain mineralization of the skeleton but to avoid calcification of soft tissues. Accordingly, absorption and excretion of calcium is closely regulated, and adult humans can adapt to a wide range of calcium intakes from 300 to 2,000 mg/day. The evidence that low calcium intakes contribute to osteoporosis development is weak, as is evidence that increasing these intakes significantly changes fracture risk. Consistent with this view, the United States Preventive Services Task Force does not support the use of calcium supplements in healthy community-dwelling adults. While some groups continue to recommend that supplements of calcium and vitamin D are given with drug treatments for osteoporosis, this view is not supported by clinical trials which demonstrate anti-fracture efficacy of estrogens and bisphosphonates in the absence of such supplementation. Thus, calcium supplements have only a minor place in contemporary medical practice.

Calcium supplements: benefits and risks

Calcium is an essential element in the diet, but there is continuing controversy regarding its optimal intake, and its role in the pathogenesis of osteoporosis. Most studies show little evidence of a relationship between calcium intake and bone density, or the rate of bone loss. Re-analysis of data from the placebo group from the Auckland Calcium Study demonstrates no relationship between dietary calcium intake and rate of bone loss over 5 years in healthy older women with intakes varying from <400 to >1500 mg day(-1) . Thus, supplements are not needed within this range of intakes to compensate for a demonstrable dietary deficiency, but might be acting as weak anti-resorptive agents via effects on parathyroid hormone and calcitonin. Consistent with this, supplements do acutely reduce bone resorption and produce small short-term effects on bone density, without evidence of a cumulative density benefit. As a result, anti-fracture efficacy remains unproven, with no evidence to support hip fracture prevention (other than in a cohort with severe vitamin D deficiency) and total fracture numbers are reduced by 0-10%, depending on which meta-analysis is considered. Five recent large studies have failed to demonstrate fracture prevention in their primary analyses. This must be balanced against an increase in gastrointestinal side effects (including a doubling of hospital admissions for these problems), a 17% increase in renal calculi and a 20-40% increase in risk of myocardial infarction. Each of these adverse events alone neutralizes any possible benefit in fracture prevention. Thus, calcium supplements appear to have a negative risk-benefit effect, and so should not be used routinely in the prevention or treatment of osteoporosis.

Calcium revisited, part III: effect of dietary calcium on BMD and fracture risk

Food can be an excellent source of calcium. Dietary calcium is in general as well absorbed as calcium supplements, and exerts the same effects on bone. The main sources are dairy products, but also some vegetables and fruits contain considerable amounts of calcium. Mineral water can serve as a supplement. Cross-sectional, longitudinal and some interventional trials have shown positive effects on bone metabolism, bone density and bone loss. But the effect on fracture incidence is less certain, and that of milk, the most studied dairy product, still unproven.

Efficacy, effectiveness and side effects of medications used to prevent fractures

There is an increasing number of effective therapies for fracture prevention in adults at risk of osteoporosis. However, shortcomings in the evidence underpinning our management of osteoporosis still exist. Evidence of antifracture efficacy in the groups of patients who most commonly use calcium and vitamin D supplements is lacking, the safety of calcium supplements is in doubt, and the safety and efficacy of high doses of vitamin D give cause for concern. Alendronate, risedronate, zoledronate and denosumab have been shown to prevent spine, nonspine and hip fractures; in addition, teriparatide and strontium ranelate prevent both spine and nonspine fractures, and raloxifene and ibandronate prevent spine fractures. However, most trials provide little information regarding long-term efficacy or safety. A particular concern at present is the possibility that oral bisphosphonates might cause atypical femoral fractures. Observational data suggest that the incidence of this type of fracture increases steeply with duration of bisphosphonate use, resulting in concern that the benefit-risk balance may become negative in the long term, particularly in patients in whom the osteoporotic fracture risk is not high. Therefore, reappraisal of ongoing use of bisphosphonates after about 5 years is endorsed by expert consensus, and 'drug holidays' should be considered at this time. Further studies are needed to guide clinical practice in this area.

Calcium and vitamin D supplementation: state of the art for daily practice

BACKGROUND

Calcium and vitamin D play an essential role in bone metabolism but deficiency and/or inadequate intake are common.

OBJECTIVES

To describe a practical approach based on the literature regarding clinically important aspects of calcium and vitamin D supplementation.

METHODS

A systematic evaluation of relevant literature in Medline was conducted. We included physiological studies, publications on relevant guidelines, meta-analysis, randomized clinical trials, and cohort studies.

RESULTS

An adequate calcium intake and vitamin D supplementation is recommended in most guidelines xon fracture prevention. Daily supplementation with 800 IU is advocated in most guidelines, appears to be safe, and with this approach it is generally not necessary to determine vitamin D levels. There are no data on additional effects of loading doses of vitamin D on fracture or fall prevention. Calcium supplementation should be tailored to the patient's need: usually 500 mg per day is required. The intestinal absorption of calcium citrate is approximately 24% better than that of calcium carbonate independent of intake with meals. Data on difference between calcium absorption with calcium carbonate compared to calcium citrate with simultaneous use of proton pump inhibitors are lacking. Concern has arisen about a possible link between calcium supplementation and an increased risk of myocardial infarction. Probably only well-designed prospective randomized controlled trials will be able to allow definite conclusions on this subject.

CONCLUSION

Daily supplementation with 800 IU vitamin D is a practical and safe strategy without the need for prior determination of vitamin D levels. Calcium supplementation should be tailored to the patient's need based on total daily dietary calcium intake. In most patients 500 mg per day is required to achieve a total intake of 1,200 mg, or in some 1,000 mg per day. More calcium is absorbed from calcium citrate compared to calcium carbonate.

Mandibular inferior cortex erosion as a sign of elevated total serum calcium in elderly people: a 9-year follow-up study

OBJECTIVES

The mandibular inferior cortex (MIC) classification that was determined by observing the mandible distally from the mental foramen in panoramic radiography can be considered to reflect bone loss in the jaws. The purpose of this 9-year study was to investigate whether there is a relationship between MIC condition and total serum calcium (TSC) in elderly Japanese people.

METHODS

A total of 280 subjects aged 70 years at baseline (137 males and 143 females) took part in this longitudinal study design. TSC and dental panoramic radiographs were carried out at the baseline in 1998 and the final year in 2007.

RESULTS

The results of the MIC measurement were divided into two groups according to changes in MIC after the 9-year study period, namely no change group and change group. A significant relationship was found in females but not in males between the MIC condition and the TSC. The regression showed that female subjects are 3.26 times more likely to have increased erosion of the inferior border of the mandible than male subjects after the 9-year study period.

CONCLUSIONS

These results suggest that an increase in erosion of the inferior border of the mandible was significantly associated with an elevated TSC after 9 years and only in females.

Change in bone mineral density and its determinants in pre- and perimenopausal Chinese women: the Hong Kong Perimenopausal Women Osteoporosis Study

This 30-month study investigating bone change and its determinants in 438 perimenopausal Chinese women revealed that the fastest bone loss occurred in women undergoing menopausal transition but maintenance of body weight and physical fitness were beneficial for bone health. Soy protein intake also seemed to exert a protective effect.

INTRODUCTION

This 30-month follow-up study aims to investigate change in bone mineral density and its determinants in Hong Kong Chinese perimenopausal women.

METHODS

Four hundred and thirty-eight women aged 45 to 55 years were recruited through random telephone dialing and primary care clinic. Bone mass, body composition, lifestyle measurements were obtained at baseline and at 9-, 18- and 30-month follow-ups. Univariate and stepwise multiple regression analyses were performed with the regression coefficients of BMD/C (derived from baseline and follow-up measurements) as the outcome variables. Menopausal status was classified as pre- or postmenopausal or transitional.

RESULTS

Menopausal status was the strongest determinant of bone changes. An annual bone loss of about 0.5% was observed among premenopausal, 2% to 2.5% among transitional, and about 1.5% in postmenopausal women. Multiple regression analyses, revealed that a positive regression slope of body weight was protective for follow-up bone loss at all sites. Number of pregnancy, soy protein intake and walking were protective for total body BMC. Higher baseline LM was also protective for neck of femur BMD.

CONCLUSION

Maintenance of body weight and physical fitness were observed to have a protective effect on for bone loss in Chinese perimenopausal women.

High bone mineral density among perimenopausal women

Studies regarding high bone mineral density (HBMD) are few. In the population-based Kuopio Osteoporosis Risk Factor and Prevention Study, BMDs of women were measured from 1990-1991 and 1995-1997. The mean age of the 1,873 women studied was 53.5 years at baseline (range 48.0-59.6). In all, 248 women were excluded because of BMD measurement errors or artifacts: 41 from the HBMD group (20.6%) and 207 (12.4%) from the control group. The final study group consisted of 1,551 women, 168 in the HBMD group (baseline lumbar BMD >1.23 g/cm2; femoral BMD >1.01 g/cm2, and 5-year follow-up lumbar BMD >1.21 g/cm2; femoral BMD >0.98 g/cm2, respectively) and 1,383 in the control group. The predictors for HBMD in the multivariate regression analysis were as follows: hormone therapy (HT) during the follow-up from 0.5 to 2 years and for over 2 years (OR 2.06, CI: 1.11-3.81 and OR 2.16, CI 1.43-3.26) and being overweight (BMI from 25 kg/m2 to 30 kg/m2, and BMI >30 kg/m2) at baseline (OR 2.84, CI: 1.82-4.42; OR 5.94, CI: 3.47-10.16, respectively). High physical activity while 11-18 years of age was associated with HBMD (OR 1.69, CI: 1.17-2.45). Parity predicted HBMD so that after one to two births the OR was 2.66 (CI: 1.03-6.88) and 3.03 (CI: 1.16-7.90) after three or more births. Menopause was negatively associated with HBMD (OR 0.57, CI 0.38-0.85). There were more premenopausal women in the HBMD group (53.9 vs. 34.6%, P <0.001). The HBMD group showed fewer fractures. In conclusion, being overweight, parity, HT use, premenopause and high physical activity in adolescence seemed to be predictors for persistently high BMD in early postmenopausal women. We suggest that the fracture risk is low in these women, and thus they are neither primary candidates for BMD screening nor for osteoporosis medication.

The relative effect of endogenous estradiol and androgens on menopausal bone loss: a longitudinal study

OBJECTIVE

The aim of this study was to assess the relative strength of the association of endogenous estradiol and androgens with bone loss at the lumbar spine and femoral neck during the menopausal transition.

DESIGN

A longitudinal study of a population-based cohort of 159 Australian-born women who at baseline had a mean age of 50.0 years (SD=2.4) and had menstruated in the prior 3 months. BMD was measured by dual-energy X-ray absorptiometry at the lumbar spine and femoral neck on up to three occasions.

RESULTS

Of the 159 participants, 50 had two BMD measurements and 109 had a third measure. The mean time between the first and final measures for the whole group was 39 months and at the time of the final measures 49% of the participants had become postmenopausal. The mean percentage change/year in lumbar spine BMD was -0.9% (95% CI, -1.1 to -0.6) and at the femoral neck, -0.5% (95% CI, -0.7 to -0.2). A highly significant association with estradiol at the final time point was found, whereas the contribution of estradiol at baseline was negligible. The variance explained by estradiol levels was 19% and 11% for change in BMD at the LS and FN, respectively. Excluding baseline estradiol values and using the average of change in BMD at the LS and FN, the final regression equation estimated that an estradiol level of 330 pmol/l (95% CI, 274 to 386) and 245 pmol/l (95% CI, 194 to 296) is required for preservation of LS and FN BMD, respectively. A stepwise linear regression model was used to assess the effect of age, BMI, estradiol, testosterone, DHEAS, SHBG, and free testosterone index on changes in BMD and found that only the final estradiol level had a significant association with change in BMD.

CONCLUSION

Endogenous estradiol was the only hormone among those investigated to have a significant effect on bone mineral density during the menopausal transition.

Beneficial effect of soy isoflavones on bone mineral content was modified by years since menopause, body weight, and calcium intake: a double-blind, randomized, controlled trial

OBJECTIVE

Many studies have shown that soy isoflavones have an effect in preventing estrogen-related bone loss, but no data reported whether such an effect could be influenced by other important factors affecting bone loss. This study examines whether the associations between isoflavone supplementation and rates of change in bone mineral content (BMC) could be modified by years since menopause (YSM), body weight (BW), and dietary calcium intake in postmenopausal Chinese women aged 48 to 62 years.

DESIGN

A group of 203 eligible women were randomly assigned to three treatment groups: placebo (daily dose of 0 mg isoflavones + 500 mg calcium, n = 67), mid-dose (40 mg isoflavones + 500 mg calcium, n = 68); and high-dose (80 mg isoflavones + 500 mg calcium, n = 68). Bone mineral density (BMD) and BMC at the whole body, spine, and hip were measured by dual-energy x-ray absorptiometry at baseline and posttreatment after 1 year. YSM, BW, and dietary calcium intake stratified analyses were performed to evaluate whether the associations between isoflavones supplementation and BMC change rates were varied with these factors.

RESULTS

Both univariate and multivariate analyses observed significant favorable effect of isoflavone supplementation on rates of change in BMC at the total hip and trochanter among later postmenopausal women (> 4 y), in women with lower BW (< or =median, 55.5 kg), or among women with lower level of calcium intake (< or =median, 1095 mg/d).

CONCLUSIONS

The independent effect of soy on the maintenance of hip BMC is more marked in women in later menopause or those with lower BW or calcium intake.

Separate assessment of forearm cortical and trabecular bone density from standard densitometry data

BACKGROUND

Cortical and trabecular bone are different bone components. Their mineral density cannot be measured directly by areal bone densitometry.

AIM

To introduce a method for assessment of pure radial cortical and trabecular bone density based on standard densitometry data.

METHOD

The study included 418 healthy females (aged 20-83 years, body mass index between 19 and 30) free of previous fractures and conditions or drugs affecting bone metabolism; as well as a group of 64 age-matched females with early menopause. Forearm bone density was measured by single X-ray absorptiometry and calculated separately for cortical and trabecular bone. Age-adjusted bone density curves were built.

RESULTS

Peak bone density was found to occur between 30 and 34 years of age and was 0.561 g/cm2 for cortical and 0.281 g/cm2 for trabecular bone. In comparison, lowest values were registered between 70 and 74 years of age; cortical bone density reduced by 26% and trabecular density by 44%. Both bone density profiles through life reflected the earlier peri- and postmenopausal (mainly trabecular) and later senile (cortical bone also involved) changes in bone mass. A step-wise pattern of trabecular bone reduction was registered with acceleration around 45, 55 and 65 years. The effects of early menopause on trabecular and cortical bone were tested in the prematurely menopausal women.

CONCLUSIONS

The ability of our model to discriminate between natural and premature menopause was moderate. Although hypothetical (based on calculations from integral densitometry data rather than on direct measurements), our method could differentiate between cortical and trabecular osteopenia and may prove helpful in assessing the type of osteoporosis, in making therapy choices and monitoring response to therapy based on forearm bone density.

Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women

Our previous study on bone health among premenopausal women showed that bone mass consolidation is attained by the early 30s, and small loss of spinal bone mineral density (SBMD) occurs soon after peak bone mass attainment. Recent interest has been shown in the potential beneficial effects of phytoestrogens on bone health. However, data are lacking, particularly in Asian women. This study aims to investigate the effect of soy isoflavones intake on the maintenance of peak bone mass in a cohort of 132 women aged 30-40 years who were followed up for 3 years. Baseline measurements of SBMD (L2-L4) were obtained using dual-energy X-ray densitometry, and dietary intake of soy foods and other key nutrients, including dietary calcium, were obtained through a quantitative food frequency method. Information on body measurements; physical activity (PA), weight-bearing activity in particular; age of menarche; and number of pregnancies were obtained at baseline. Repeated measurements of SBMD were obtained yearly for a further 3 years with an average follow-up time of 38 months. Analyses were performed on 116 subjects with at least three SBMD measurements (at baseline, 3-year follow-up, and at least one measurement during follow-up). The individual SBMD regression slope was computed for each of the subjects. Soy isoflavones consumption was categorized as quartiles of intake. We observed a significant difference in the SBMD individual regression slopes between women belonging to the fourth and first soy isoflavones intake quartiles. The positive effect of soy isoflavones on SBMD remained after adjusting for age and body size (height, weight, and bone area). Multiple linear regression analysis including the other known covariates (lean body mass, PA, energy adjusted calcium, and follow-up time) showed that soy isoflavones, together with these variables, accounted for 24% of the variances of the SBMD individual regression slope. This longitudinal study shows that soy intake had a significant effect on the maintenance of SBMD in women aged 30-40 years. The effects of phytoestrogens on bone health should be explored further in a population with habitual dietary soy but low calcium intake.

Calcium, dairy products and osteoporosis

Osteoporosis is a multifactorial disorder in which nutrition plays a role but does not account for the totality of the problem. 139 papers published since 1975 and describing studies of the relationship of calcium intake and bone health are briefly analyzed. Of 52 investigator-controlled calcium intervention studies, all but two showed better bone balance at high intakes, or greater bone gain during growth, or reduced bone loss in the elderly, or reduced fracture risk. This evidence firmly establishes that high calcium intakes promote bone health. Additionally, three-fourths of 86 observational studies were also positive, indicating that the causal link established in investigator-controlled trials can be found in free-living subjects as well. The principal reason for failure to find an association in observational studies is the weakness of the methods available for estimating long-term calcium intake. While most of the investigator-controlled studies used calcium supplements, six used dairy sources of calcium; all were positive. Most of the observational studies were based on dairy calcium also, since at the time the studies were done, higher calcium intakes meant higher dairy intakes. All studies evaluating the issue reported substantial augmentation of the osteoprotective effect of estrogen by high calcium intakes. Discussion is provided in regard to the multifactorial complexity of osteoporotic response to interventions and to the perturbing effect in controlled trials of the bone remodeling transient, as well as about how inferences can validly be drawn from the various study types represented in this compilation.

Longitudinal changes in adult fat-free mass: influence of body weight

BACKGROUND

Almost all of the data on changes in body composition during aging are cross-sectional in nature. These show that fat-free mass (FFM) declines with age.

OBJECTIVE

The goal was to analyze results of assays done in the author's laboratory of the FFM of normal adults studied at intervals for >/=2 decades to ascertain longitudinal changes.

DESIGN

(40)K counting was used to estimate FFM in adult university personnel (15 men, 5 women) over periods ranging from 21 to 38 y. No advice was given about diet or exercise.

RESULTS

There was considerable variation in the change of FFM over time. Some subjects lost FFM as the years went by, whereas others actually gained FFM. Analysis of the data showed that change in body weight was a prime factor in determining the magnitude and direction of the FFM change (R(2) = 0.54). Adults who maintained their weight lost an average of 1.5 kg FFM per decade and so gained an equal amount of fat; those who lost weight lost even more FFM, whereas those who gained weight either gained FFM or lost it more slowly than the others. Data from the literature confirmed this trend.

CONCLUSIONS

FFM loss is not inevitable during adulthood-at least up to age 81 y, the oldest age yet studied. The magnitude and direction of the FFM change, be it positive or negative, is strongly influenced by change in body weight.

Association between calcium ingested from drinking water and femoral bone density in elderly women: evidence from the EPIDOS cohort

Although the main source of dietary calcium is dairy products, the calcium contained in mineral water, which is as available as that of milk, could provide a valuable source of calcium. We analyzed the data from the EPIDOS multicenter study to evaluate the relationship between both dietary calcium and that supplied by drinking water and bone density measured at the femoral neck by dual-energy X-ray absorptiometry. The study included 4434 women over 75 years of age who had not received any treatment likely to interfere with calcium metabolism. A significant correlation was found between total calcium intake and bone density at the femoral neck (r = 0.10, p < 0. 001). After adjustment for the main variables influencing bone density, an increase of 100 mg/day in calcium from drinking water was associated to a 0.5% increase in femoral bone density, while a similar increase in dietary calcium from other sources only led to a 0.2% increase; however, this difference was not significant. The consumption of calcium-rich mineral water may be of interest, especially in older women who consume little calcium from dairy products.

Associations of physical activity and calcium intake with bone mass and size in healthy women at different ages

Weight-bearing exercise and calcium intake are known to contribute to bone density. However, the relative significance of physical activity and calcium intake in the development of bone characteristics in functionally different weight-bearing and nonweight-bearing bone sites at different ages is poorly known. A total of 422 women in three age groups (25-30, 40-45, and 60-65 years) were screened from 1017 women and divided into four groups by their level of physical activity (high [PA+] and low [PA-]) and calcium intake (high [Ca+] and low [Ca-]). Total body bone mineral content (TBBMC), areal bone mineral density (BMD) of the femoral neck and distal radius, and selected dimensions and estimated strength variables (bone width, cortical wall thickness, cross-sectional moment of inertia, and section modulus of the femoral and radial shafts) were measured with dual-energy X-ray absorptiometry. Both high physical activity and high calcium intake were associated with a higher TBBMC when compared with low activity and calcium intake (1.8% and 4.6%, respectively). The BMD of the weight-bearing femoral neck was 5% higher in the PA+ groups than in the PA- groups, whereas calcium intake showed no such significant association. Neither physical activity nor calcium intake was associated with the BMD of the nonweight-bearing radius. However, both high physical activity and high calcium intake were related to larger and mechanically more competent bones in the femoral and radial shafts, the association for physical activity being stronger with increasing age. No significant interaction between physical activity and calcium intake was found with respect to any of the bone variables. These data from a cross-sectional study suggest that a moderate level of physical activity or a sufficient level of calcium intake, if maintained from childhood, can result in considerable long-term improvement in the mechanical competence of the skeleton. The clinical relevance of these findings is further emphasized by the fact that the observed patterns of physical activity and calcium intake pertain to customary lifestyle and are thus feasible targets for the primary prevention of osteoporosis.

Influence of inhaled corticosteroids and dietary intake on bone density and metabolism in patients with moderate to severe asthma

OBJECTIVES

Compare the effect of high doses of inhaled corticosteroids on bone loss in subjects with moderate to severe asthma or mild asthma, and examine the influence of dietary intake on bone metabolism.

DESIGN

A survey on the effects of corticotherapy and nutrition on bone density was conducted in 74 subjects currently being treated for asthma in the asthma clinic of Hôpital Laval (Sainte-Foy, Quebec, Canada). Fifty-eight subjects completed the study (attrition rate = 15%).

MAIN OUTCOME MEASURES

In all subjects expiratory volumes were determined and urinary analysis was conducted for hydroxyproline, calcium, phosphorus, and cortisol levels. Osteocalcin, calcium, phosphorus, cortisol, alkaline phosphatase, and gamma-glutamyltransferase levels were measured in blood samples. Bone density of the lumbar spine was determined by means of dual-energy x-ray absorptiometry. Nutrition evaluation was based on a 3-day food diary analyzed using progiciel Nutri 91. The nutritional parameters examined were calcium; phosphorus; magnesium; zinc; vitamins A, C, and D; protein; total fiber; oxalates; energy; caffeine; and alcohol in relation to bone density.

SUBJECTS

Thirty-one patients with moderate to severe asthma who had been taking more than 1,000 micrograms beclomethasone per day or the equivalent for more than 2 years and 27 patients with mild asthma who were taking less than 500 micrograms beclomethasone per day or the equivalent.

STATISTICAL ANALYSES PERFORMED

Four-factor analysis of variance with hierarchized interactions of four levels, Duncan's test, Pearson correlation coefficients.

RESULTS

Blood levels of osteocalcin and protein intake were lower in patients with moderate to severe asthma than in those with mild asthma (P < .05). Significant correlations (P < .02) were observed between bone density and calcium intake (r = .40), phosphorus intake (r = .35), protein intake (r = .30), and serum alkaline phosphatase level (r = -.30). Bone density was not significantly different between the two groups of patients with asthma.

APPLICATIONS

A follow-up of patients with asthma who are taking inhaled corticosteroids is needed to assess bone density, osteocalcin levels, and dietary intakes of calcium. Verify if osteocalcin level decreases over time in patients with moderate to severe asthma, monitor possible modifications in bone density, and verify if the correlation between dietary calcium and bone density is maintained.

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

Ageing and calcium metabolism

Ageing alters the metabolism of calcium and vitamin D in a number of ways. Intake of calcium and vitamin D, exposure to sunlight, cutaneous production of vitamin D3, renal production of 1,25-dihydroxyvitamin D (1,25(OH)2D3), intestinal absorption of calcium and the ability to adapt to a low calcium diet may all be reduced in elderly subjects. As a consequence, secondary hyperparathyroidism often occurs with ageing and can contribute to accelerated bone loss. In fact, alterations in calcium and vitamin D metabolism may be widespread in the ageing population and play a central role in the pathogenesis of senile (age-related) osteoporosis. From a preventive point of view, recent intervention studies have indicated the need to optimize calcium intake and to maintain serum 25(OH)D3 levels within the normal range in elderly people.

Physical activity, nutrition, and chronic disease

Epidemiologic, animal, clinical, and metabolic studies demonstrate the independent roles of physical activity and nutrition in the prevention and treatment of several chronic diseases. Fewer data are available to describe the synergistic effects of exercise and diet, and questions remain as to whether and how these two lifestyle factors work together to promote health and prevent disease. This paper briefly reviews many of the known effects of physical activity and nutrition on the prevention and treatment of coronary heart disease, non-insulin-dependent diabetes mellitus, obesity, and osteoporosis as well as how exercise and diet may work together. A discussion of how to increase physical activity levels and how to improve dietary intake also is included. Finally, current exercise and dietary recommendations are summarized, as are directions for future research.

Comparison of the treatment effects of ossein-hydroxyapatite compound and calcium carbonate in osteoporotic females

The aim of the study was to evaluate whether ossein-hydroxyapatite (OHC) is more effective than calcium carbonate (CC) in preventing further bone loss in postmenopausal osteoporosis. Forty osteoporotic patients were monitored for 20 months. The patients were randomly assigned to one of two groups and treated in a double-masked manner with 1400 mg calcium per day, in the form of either OHC or CC. OHC consists of hydroxyapatite, collagens and non-collagenous proteins/peptides containing insulin-like growth factor I (IGF-I; 1341 ng), insulin-like growth factor II (IGF-II; 670 ng), transforming growth factor beta (TGF-beta; 166 ng) and osteocalcin (47 micrograms). The bone densities were evaluated at intervals of 4 months with high-precision peripheral quantitative computed tomography. After 20 months of treatment the loss of trabecular bone was 0.8 +/- 0.5% in the OHC group and 1.8 +/- 0.7% in the CC group. The difference between the OHC and CC groups was statistically significant. This study shows that OHC is more effective than CC in slowing peripheral trabecular bone loss in patients with manifest osteoporosis.

Bone mineral density and risk factors for osteoporosis--a population-based study of 1600 perimenopausal women

Population-based epidemiological studies on osteoporosis are few. Our study evaluated the effects of menopause and certain putative behavioural risk factors on bone mineral density (BMD). Spinal and femoral neck BMD were measured with dual X-ray absorptiometry (DXA) from 1600 perimenopausal women aged 48-59 years (mean 53.2 years) with no diseases or medications known to affect bone metabolism. These women were a selected sample of the Kuopio Osteoporosis Risk Factor and Prevention Study population (n = 14,220). There was a wide variation of BMD among perimenopausal women. Menopause had a major effect on BMD. Postmenopausal women had significantly lower BMD in both spine (-6.2%) and femoral neck (-3.9%) as compared with premenopausal women. Multiple regression analysis showed that weight, menopausal status, age, and grip strength were significant independent predictors of both spinal and femoral BMD. Additionally, physical activity was found to be a significant predictor of femoral BMD, and alcohol consumption was a significant predictor of spinal BMD. However, current anthropometric and lifestyle factors explained only 18.7-25.4% of the variability of BMD. Therefore, the estimation of the risk factor status at menopause is not an adequate substitute for bone densitometry. However, our results may in part help clinicians to identify the risk groups at which to direct bone density measurements.

Determinants of bone mass in Chinese women aged 21-40 years. II. Pattern of dietary calcium intake and association with bone mineral density

A study on the determinants of bone mass in young women is being carried out among 287 young Chinese women aged 21-40 years. The baseline cross-sectional data show that the mean dietary calcium intake, estimated from the quantitative food frequency method, was 448 mg/day (standard deviation = 219). About 50% of the calcium source was from vegetables and 22% from dairy products. Among women aged 21-30 years, those with a dietary calcium intake of at least 600 mg/day had a 4%-7% higher mean bone mineral density at the spine and femur when compared with those with a mean intake below 300 mg/day. In women aged 31-40 years, subjects belonging to the highest quartile of calcium density (> or = 35 mg/420 kJ) had a 3%-8% higher mean bone mineral density at the spine and femur when compared with those in the lowest quartile (< 20.8 mg/420 kJ). Favorable calcium intake is beneficial in this population of young women with habitual low dietary calcium intake.

Dietary calcium intake relates to bone mineral density in premenopausal women

Bone density and Ca intake were assessed in fifty-six healthy premenopausal women, aged 21-47 years. Bone density was measured at the spine (lumbar vertebrae 1-4, anterio-posterior view), the non-dominant femur (neck, Ward's triangle and trochanter) and radius (33% distal and ultradistal) using dual energy X-ray absorptiometry (Lunar DPX-L). The mean values (SD) for bone density (g/cm2) were 1.18 (0.10) at the lumbar spine, 0.81(0.10) at the trochanter and for Ca intake 783 (329) mg. Bone density values were close to published normal values for young women and the Ca intakes were close to the recommended levels for the UK. However, there was a wide range especially in dietary Ca intake, and 27% of the group were at or below 500 mg/d. Correlations between Ca intake and bone density were highly significant at all three femoral sites (neck r 0.41; Ward's triangle r 0.40, P < 0.01; trochanter r 0.47, P < 0.001), significant at the spine (r 0.27, P < 0.05) but not found at the radius. These correlations were independent of body mass. The low levels of Ca intake found in a substantial proportion of this selected group of young women and their association with low femoral bone density are cause for concern.

A 5-year longitudinal study of forearm bone mass in 307 postmenopausal women

We measured forearm bone mineral content at the beginning and end of a 5 year period in 307 untreated postmenopausal volunteers. We also measured height, weight, and a number of biochemical variables in plasma and urine after an overnight fast. The initial mean age of the subjects was 59.0 years (range 39-72), and the mean years since menopause was 10.0 (range 1-37). The mean forearm BMC fell from 1034 +/- 9.6 (SEM) to 982 +/- 9.3 mg/cm (P < 0.001). The coefficient of correlation between the first and second measurements was 0.96. The mean rate of change was -1.0% per annum (with a 99% range of -4 to 1% per annum), which agreed well with previous estimates from cross-sectional data. There was a significant negative correlation between rate of change in bone mass and initial value (r = -0.23; P < 0.001), which was eliminated by expressing change as a percentage of initial bone mass. Of the other variables measured, the one that was most significantly related to the percentage change in bone mass was the urinary hydroxyproline/creatinine ratio (r = -0.35; P < 0.001), which we regard as a marker only. By stepwise regression, the only significant determinants of the rate of change in bone mass were body weight (positive, P < 0.001), years since menopause (positive, P < 0.005), urine calcium (negative, P < 0.01), and serum estrone (positive, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The association of lifetime weight and weight control patterns with bone mineral density in an adult community

We examined the association of lifetime weight and weight change to bone mineral density (BMD) at four skeletal sites, the radial shaft, the ultradistal wrist, the total hip and lumbar spine, in a community-based population of 1043 older white men and women. In those currently overweight (body mass indices (BMI) > 26), the age-adjusted mean BMD at all sites was significantly higher than in those with BMI less than 26. Lifetime maximum BMI was also positively and significantly associated with a higher age-adjusted BMD at all sites except the ultradistal wrist in men. Weight gain or fluctuation of 10 lbs or more between the ages of 40 and 60 was associated with significantly higher age-adjusted mean BMD at all sites compared to weight loss or no weight change in both men and women. Weight at age 18 was unassociated with BMD but weight gain after age 18 was associated with significantly higher age-adjusted mean BMD at all sites. Conversely, dieting, weight loss or a lifetime maximum BMI of less than 24 were all associated with markedly lower BMD at all sites in both sexes. Weight patterns were closely correlated with current BMI; most of these trends persisted but were no longer statistically significant after controlling for current weight.

Change in bone mass immediately before menopause

A group of 75 healthy women nearing menopause were entered into a longitudinal study of bone mass and bone cell function. All were at least 46 years, were still menstruating, and had premenopausal levels of follicle stimulating hormone (FSH) and estradiol (E2). Bone density measurements of the spine (dual-photon absorptiometry, DPA) and total-body (DPA) and forearm (single-photon absorptiometry, SPA) were made at 6 month intervals along with measurements of FSH and E2 over an average of 2.04 +/- 0.45 years. The annual rate of change in bone mass was determined for each individual by regressing the bone mass measurement at each site at the time of observation. The slopes were pooled, and the percentage annual change was calculated as the mean slope divided by the initial mean bone mass value. The mean rates of change in bone mass were calculated with and without weighting by length of observation. No meaningful differences in the results were seen in the weighted values compared to the unweighted values, and none of the sites showed a slope significantly different from zero. Demonstrated reproducibility and sample size provided sufficient power to detect annual weighted rates of change of 0.81% for spine BMC, 0.69% for spine BMD, 1.31% for forearm BMC, 1.55% for forearm BMC/BW, and 1.09% for total body bone mineral. We conclude that if changes in bone mineral are occurring in women at this age, they are substantially less than 1%/year for spine and not much more for the forearm or total skeleton.

The bisphosphonate, alendronate, prevents bone loss in ovariectomized baboons

We examined the effect of the amino bisphosphonate alendronate, administered IV every 2 weeks at 0.05 and 0.25 mg/kg for 1 year, on bone loss and parameters related to bone metabolism in ovariectomized baboons. Relative to non-OVX animals, the OVX baboons experienced increased bone turnover, reflected in biochemical and histomorphometric measurements, and bone loss assessed by dual-beam absorptiometry in the lumbar spine, which was similar to changes observed in ovariectomized women. Alendronate treatment maintained all parameters of bone turnover at control (nonovariectomized) levels and prevented the bone loss in a dose-dependent manner. We concluded that ovariectomized baboons offer a suitable model for the bone changes observed in ovariectomized women and that these changes can be prevented by sustained administration of an appropriate dose of this aminobisphosphonate.

Bone mineral density measured by dual-energy X-ray absorptiometry in normal men

A cross-sectional study of 222 healthy Finnish men aged 20-69 years was performed to establish reference values of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA). The effects of age, and of some physical and lifestyle factors on BMD of the lumbar spine and proximal femur (femoral neck, Ward's triangle and trochanter) were investigated. The maximal mean BMD was observed at the age of 20-29 years in all the measurement sites. Except for the trochanteric area, BMD diminished along with age, the over-all decrements being 4%, 11%, and 23% in the lumbar, femoral neck and Ward's triangle areas, respectively. BMD was in a positive relationship to weight and height in all the measurement sites. The adjusted (for age, height and weight) BMDs were higher (P less than 0.05) in the group of daily dietary calcium intake greater than 1200 mg as compared with the group of lowest calcium intake (less than 800 mg day-1) in the three femoral areas. Cigarette smoking or alcohol drinking had no obvious effect on BMD.

Radial bone mineral density in pre- and perimenopausal women: a prospective study of rates and risk factors for loss

Radial bone mineral density (BMD) of 217 white women aged 22-54 years from a single rural community was evaluated in 1984 using single-photon absorptiometry. BMD was measured at a site one-third the distance from the wrist to the elbow, a site that represents predominantly cortical bone tissue. Most of these women (181; 83%) were reexamined 5 years later. The overall average 5 year radial BMD loss was -5.6%. The average rate of loss was -4.5% for women retaining positive estrogen status at follow-up (n = 108) and -7.4% for women who were in negative estrogen status at follow-up (n = 73). Baseline radial BMD measures were highly predictive of the follow-up BMD values (r = 0.80). Women with positive estrogen status and greater baseline BMD also had less BMD change. Greater baseline BMD did not predict the amount of change in women with negative estrogen status. The bone turnover markers osteocalcin and bone-specific alkaline phosphatase were significantly associated with BMD change in women with negative, but not positive estrogen status. There was no conclusive evidence of a "peak age" in the baseline and follow-up BMD measures. Based on rates of BMD change, "peak" bone mineral content appears to occur before age 25 years. Factors significantly associated with lower levels of BMD were menopause without estrogen replacement, nulliparity, smoking, and age at first pregnancy. Factors associated with more bone loss were menopause without estrogen replacement, smoking, shorter duration of oral contraceptive use, and older age. Quetelet index, muscle area, number of lost pregnancies, ever breast-feeding, or calcium intake were not associated with BMD level or its 5 year rate of loss. Physical activity and alcohol intake were not associated with BMD level or change after data were adjusted for age or estrogen status.

The scientific basis of recommended dietary allowances for calcium

Dietary calcium is required for bone development during growth (attainment of peak bone mass), for maintenance of skeletal integrity during adult life, and thus for prevention of osteoporosis. The Recommended Dietary Allowance (RDA) of a nutrient for a particular group is considered to cover the needs of 98% of all individuals of that group, and thus takes into account a margin of safety to allow for interindividual variation in minimum requirements. It appears to be possible, on the basis of the available scientific literature, to calculate the daily amount of calcium that must be absorbed from the diet to compensate for the endogenous calcium losses (through urine, faeces and skin) and the calcium retention in bone. Similarly, it seems to be possible to obtain a reasonable estimate of calcium absorption for the different groups of the population. From these data, and taking into account a margin of safety, figures are obtained for calcium intake that are in reasonably close agreement with the authoritative 1989 RDAs of the USA Food and Nutrition Board, with the exception of the USA allowance for girls aged 19-25 years (probably too high) and older adults (possibly too low). With regard to optimal calcium intake, some important questions still remain unanswered. These bear upon the issue of calcium intake and peak bone mass development, and upon the effects of non-nutritional factors (e.g. genetics and physical activity) and nutritional factors (e.g. sodium, protein, alcohol and caffeine) on calcium requirements. Furthermore, it would appear that bone development and maintenance of bone health may not be the sole criteria for setting RDAs in the near future. These issues are briefly discussed.

Radial bone mineral changes in pre- and postmenopausal healthy Japanese women: cross-sectional and longitudinal studies

Healthy premenopausal and postmenopausal Japanese women were evaluated by longitudinal and cross-sectional studies to assess changes in radial bone mineral density. A total of 300 healthy Japanese women were enrolled in the cross-sectional study, and 126 of them were chosen for the longitudinal study. In the cross-sectional study significantly lower bone mineral density was found in the women over 50 years old. In the longitudinal study, premenopausal women aged 45-54 years showed rate of change of -0.61%/year at the distal radius and 0.49%/year at the radial shaft. The perimenopausal changes were -1.95 and -0.93%/year and the postmenopausal changes were -1.88 and -1.37%/year at the distal radius and at the radial shaft, respectively, in the women aged 45-54 years. These rates of premenopausal and postmenopausal change were similar to those reported for whites in the United States. The strength of the relationship between the rate of change in radial bone mineral density and the anthropometric values, biochemical data, and menopausal status was evaluated by multiple linear regression analysis. Menopausal status had the greatest influence on the rate of change in radial bone mineral density. It is concluded that menopausal status was the most important variable related to bone loss in our longitudinal study and the rate of bone loss was greatest during the early postmenopausal period in healthy Japanese women.

Development and evaluation of an index to predict early postmenopausal bone loss

An index to predict individual postmenopausal bone loss is presented. The index is developed by means of data from a 10-year prospective Norwegian study in which bone mass of the distal forearm was measured annually in 73 women. All the women were 47 years old and premenopausal at inclusion. Independent risk factors for postmenopausal bone loss were identified by applying multivariate regression analysis on anthropometric, biochemical, nutritional, and life-style variables measured at menopause. The analysis identified low body weight, reduced renal phosphate reabsorption, and smoking as significant independent risk factors, and by means of these three factors a predictive index for postmenopausal bone loss was developed. This index was validated by using data from a 10-year longitudinal Dutch study, in which bone mass of the proximal radius was measured annually in 86 women, aged between 49 and 57 years and perimenopausal at inclusion. We defined women with the highest index score as "high-risk persons." According to this definition approximately 25% of the perimenopausal women were classified as high-risk persons, and the estimated sensitivity/specificity/positive predictive power were 36%, 89%, and 74%, respectively, when used to select women with a postmenopausal bone loss above average. We conclude that the index may be helpful in identifying healthy perimenopausal women in whom bone mass measurements should be considered.