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Biomedical subjects

R P Heaney

Publications and source records attributed to R P Heaney.

At least 19 recordsLinked to original sources
PubMed1992

Bone gain in young adult women.

OBJECTIVE: To test whether bone mass increases in healthy nonpregnant white women during early adult life after cessation of linear growth; and to test whether various self-chosen levels of physical activity and nutrient intake or use of oral contraceptives influences this increase in bone mass. DESIGN: Longitudinal prospective study of up to 5 years of 156 healthy college-aged women full-time students attending professional schools in universities in the Omaha, Neb, area. SETTING: University medical center. PARTICIPANTS: A convenience sample of healthy women students from Omaha-area professional schools. Any candidate with an illness, condition, or medication (except oral contraceptives) thought to affect general health or bone mass was excluded. INTERVENTIONS: None. OUTCOME MEASURES: Clinical and family histories of disease, particularly osteoporosis; oral contraceptive use; bone mineral densities of the spine, forearm, and total body by dual- and single-photon absorptiometry; estimates of nutrient intake by repeated 7-day diet diaries; and measures of physical activity using a physical activity monitor. RESULTS: The median gain in bone mass for the third decade of life, expressed as a percentage per decade, was 4.8% for the forearm, 5.9% for lumbar bone mineral content, 6.8% for lumbar bone mineral density, and 12.5% for total body bone mass (P < .0001 in all cases). By both bivariate and multiple regression analysis the rate of gain in bone density of the spine was negatively correlated with age and positively correlated with calcium/protein intake ratio and physical activity (multiple r = .31; P = .004). Bivariate analysis showed that use of oral contraceptives was associated with greater gain in total body bone mass (r = .31, P = .01). The estimated age when mineral acquisition ceased ranged from 28.3 years to 29.5 years at the several study sites. CONCLUSIONS: Gain in bone mass occurs in healthy young women during the third decade of life. Physical activity and dietary calcium intake both exert a positive effect on this bone gain. Use of oral contraceptives exerts a further independent positive effect. Changes in life-style among college-aged women, involving relatively modest increases in physical activity and calcium intake, may significantly reduce the risk of osteoporosis late in life.

Absorptiometry, Photon↗
PubMed1992

The effects of fluoridated water on bone strength.

Fluoride from fluoridated water accumulates not only in the enamel of teeth but also in the skeleton. The effects of fluoridated water on the skeleton are not well understood, yet there is some evidence that fluoridated water consumption increases the incidence of fractures. In the present study, femoral bending strength was measured in rats on fluoride intakes that ranged from low levels to levels well above natural high fluoride drinking water. Bone strength followed a biphasic relationship with bone fluoride content. Fluoride had a positive effect on bone strength for lower fluoride intakes and a negative influence on bone strength for higher fluoride intakes. The vertebral fluoride content at which femoral strength was maximum was between 1,100 and 1,500 ppm. The increase in femoral strength at this fluoride level was not accompanied by an increase in femoral bone density. The optimal fluoride content is within the range of bone fluoride contents found in persons living in regions with fluoridated water (1 ppm) for greater than 10 years.

Animals↗
PubMed1992

Fracture risk as determined by prospective and retrospective study designs.

Both retrospectively and prospectively designed studies consistently show low bone mass and/or bone mineral content (BMC) to be risk factor for low-trauma fractures in postmenopausal women. Along with the reports of such studies there has been concern expressed that BMC measurements overlap between fracture groups, i.e., some women with high BMC develop fractures and some women with low BMC do not. In these commonly used epidemiologic study designs, BMC does not discriminate between those who have and have not experienced the untoward event at some level of the exposure factor. The ability to discriminate is more properly determined by the sensitivity and specificity of the measured value. To contrast the concepts of risk and sensitivity, a nested case-control study was conducted within a 24-year cohort study of women at risk for osteoporosis. We found that for each 1.0 decrement of BMC z-scores, the adjusted relative risk for the prospective study design was 1.67, while the odds ratio obtained from the most recent BMC z-score measurements was 1.87. A receiver operating characteristic (ROC) curve, calculated from the nested case-control study data, showed that BMC z-scores, measured after low-trauma fracture, have both low sensitivity and low specificity to detect existing fracture status.

Adult↗
PubMed1992

The natural history of vertebral osteoporosis. Is low bone mass an epiphenomenon?

Osteoporotic bone fragility is due not only to decreased bone mass but to inadequate repair of fatigue damage and to trabecular disconnection. The precise roles and relative contributions of these three factors are not known for osteoporosis in general, and certainly not in any individual case. However, it is known that reduced physical activity causes bone loss. It is a virtual certainty, therefore, that, to the extent that the fracture produces disability, osteoporotics lose bone after they first experience a fracture, whatever its antecedent causes. In that sense, some of the bone loss we find in our patients is indeed an epiphenomenon. However, this is not to suggest that reduced bone mass is unimportant. Quite the contrary: prospective studies have clearly established that reduction in bone mass does increase risk of fracture, and hence, when it is consequent upon a fracture, it aggravates the patient's condition. In this way a vicious circle may develop: the pain and fear that follow fracture lead to decreased activity, which leads to bone loss, which can only increase the fragility, and hence predispose to further fracturing, even in cases in which the initial fragility may not have been due to low bone mass. But low bone mass, with its proper fragility, may not be inevitable. That is why pain control and a comprehensive programme of rehabilitation are critically important in the early management of patients with symptomatic vertebral fractures.

Bone Density↗
PubMed1992

Extrinsic vs intrinsic labeling of the calcium in whole-wheat flour.

Fractional absorption of calcium from bread made either from intrinsically or extrinsically labeled whole-wheat flour was compared in 11 healthy adult women. The intrinsic label was provided by 45Ca injected individually into stems of wheat plants during growth. The extrinsic tag was introduced by adding 45Ca to unlabeled flour via the water used in dough making. The two labeled breads were tested in a randomized crossover design using a standardized breakfast administered after an overnight fast. Approximately 80 g labeled bread was consumed by each subject, providing a total calcium load of 13.3 mg. Fractional absorption from the intrinsically labeled bread averaged 0.812 +/- 0.130 (mean +/- SE) and from the extrinsically labeled bread 0.792 +/- 0.113. The mean difference, within subject, was only 0.025 +/- 0.016 and was not significantly different from zero. Extrinsic labeling of the calcium of whole-wheat flour results in a degree of labeling homogeneity equivalent to that of intrinsic labeling, at least for a leavened bread product.

Absorption↗
PubMed1992

Calcium balance during human growth: evidence for threshold behavior.

Calcium balances performed on 519 individuals from birth to 30 years of age, derived from 34 published reports, were pooled by age group and the relationship between intake and balance for each group was compared at both extremes of the intake range. At all ages, from infancy through the young adult years, balance values tended to flatten and become constant at higher intakes, while at lower intakes balance was invariably highly correlated with intake. Threshold intakes and balances were estimated by fitting the data to a two-component, split, linear-regression model. The threshold values at which balance no longer rose with intake exceeded the US recommended dietary allowances for calcium for all the age groups concerned.

Adolescent↗
PubMed1992

Calcium in the prevention and treatment of osteoporosis.

Osteoporotic fractures have many sources. Low bone mass is one such, and inadequate calcium intake, in turn, is one of the causes of low bone mass. Calcium intake may be inadequate because it is low in its own right or, even if 'normal', it may not be sufficient to compensate for exaggerated obligatory losses. Inadequate calcium intake may cause bone mass to be low either because calcium intake during growth limits achievement of genetically programmed skeletal mass, or because low intake later in life aggravates involutional loss, or both. Ensuring a generous calcium intake throughout life will prevent both of these consequences. However, it is important to stress that even a calcium surfeit will not prevent or reverse bone loss due to inactivity, gonadal hormone deficiency, alcohol abuse or, indeed, any other factor. Calcium is a nutrient, not a drug. The only disorder it can be expected to alleviate is calcium deficiency. However, the evidence suggests that calcium deficiency is prevalent among Western populations, particularly in North America, and that it thereby contributes substantially to their osteoporotic fracture burden. This component of that burden is therefore entirely preventable.

Aging↗
PubMed1992

Hip fracture: a nutritional perspective.

Hip fracture is the most important skeletal problem confronting the developed nations. In Finland, for example, it accounts for nearly 10% of all acute surgical beds and it annually costs every Western nation in the range of 8 to 20 million U.S. dollars per million population. These already high figures are certain to rise as the number of the old elderly increase. Nutrition plays a role in this problem not simply through the effect of calcium intake on bone mass, but in the falls that precede most fractures, in the amount of soft tissue hip padding to cushion the impact of a fall, and in the recovery both from the injury and from the even greater assault of its repair.

Aging↗
PubMed1991

Effect of calcium on skeletal development, bone loss, and risk of fractures.

In assessing the role of calcium, it must be stressed that calcium is not the cause of bone health but simply a necessary condition for it. It is mechanical usage that is of primary importance for bone. In just the same way iron is essential for hemoglobin synthesis and protein is essential for muscle mass, but neither is sufficient by itself. What, then, ought we to expect from a high calcium intake? Can we prevent estrogen-withdrawal bone loss? No. Calcium is not a substitute for estrogen, anymore than it is a substitute for exercise. Will calcium slow the remodeling loss that occurs with aging? Yes, to some extent; as calcium slows remodeling, it will inevitably slow remodeling-related loss. But most importantly, a high calcium intake will prevent calcium-deficiency bone loss. The only question, therefore, is the extent to which calcium deficiency loss may contribute significantly to bone fragility in various populations. The bone loss and fracture data reviewed briefly here indicate that an important portion of the osteoporotic fracture burden is calcium-related. What that portion is will be a function of the fraction of the population with inadequate intakes in any given country. Better than half of all adult American women have calcium intakes less than 500 mg/day, whereas only a small fraction of Dutch or Danish women, for example, would be under that level. Hence, a population-wide program to increase calcium intake in the United States would be likely to yield a greater benefit than in either the Netherlands or Denmark. That does not mean, of course, that there could not be substantial benefit to individuals with low intakes in all countries. Calcium intakes of greater than or equal to 1,500 mg are both safe and natural. While not all bone loss and low trauma fractures are due to low calcium intake, some almost certainly are. Adaptation to low intakes does occur, but it is seldom sufficient to compensate for the low intake. We cannot easily distinguish those who need more calcium from those who need less, and for that reason it makes good sense to ensure an adequate calcium intake for the entire adult population. What should that intake be? During adolescence, 1,500 mg will come close to ensuring the achievement of genetically programmed levels of peak bone mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone and Bones↗
PubMed1991

47Ca alert.

Explore the source record for details and available documents.

Calcium Radioisotopes↗
PubMed1991

Fecal calcium density: a measure of calcium compliance.

We evaluated fecal calcium density (mass of calcium per g dry weight of feces) as a measure of compliance with a prescribed calcium intake regimen using 4 day fecal pools collected on a metabolic research unit from subjects ingesting measured, constant intakes. Fecal calcium density was highly correlated with intake (r = 0.897, P less than 0.001). Intake estimates based on fecal calcium density exhibited a standard error of the mean equal to 3.76 mmol calcium. Since a typical calcium supplement table contains 12.5 mmol calcium, the measurement of fecal calcium density is sensitive enough to detect regular omission of one or more pills daily. Applicability of this approach to convenience samples of feces was evaluated in 15 individuals by testing homogeneity of fecal calcium density values on up to six different 3-9 g portions (wet weight) of each volunteer's fecal sample. The within-sample coefficient of variation was 9.5% for all subsamples and 7.3% for samples from individuals with intakes above 25 mmol calcium per day. Thus feces are reasonably homogeneous in regard to calcium density. Accordingly, reasonably small fecal collections should suffice for its measurement.

Calcium↗
PubMed1991

Tallness versus shrinkage: do women shrink with age or grow taller with recent birth date?

This paper presents evidence that much of the high rate of age-related height loss in women reported in cross-sectional studies is actually a cohort effect rather than an aging effect. Data from a large cross-sectional study of healthy, white American women indicate that there has been a gain in peak adult height of 1.0 cm per decade for several decades from 1900 through 1965. Data from the HES, HANES I, and HANES II studies concur on this point. By contrast, data from a longitudinal study of 191 healthy white U.S. women show only a trivial rate of decline from peak adult height in the fifth and sixth decades of life. In an unselected population, some apparent height loss with age is probably due to disease processes, such as vertebral collapse. Caution is needed in using aging to interpret differences in height and in height-dependent variables, such as bone density, in cross-sectional studies.

Adolescent↗
PubMed1991

Calcium supplements: practical considerations.

The preferable source of calcium is a balanced diet, but medicinal supplements are sometimes necessary if patients are to reach desired intakes. A divided dose regimen (4x/d; i.e., with meals and at bedtime) results in substantially greater absorption of a supplement than does 1x/d dosing. However, differences in chemical solubility between supplement preparations are of little importance, with calcium carbonate preparations, for example, being absorbed as well or better than some much more highly soluble salts. Gastric acid is not necessary for absorption of even poorly soluble preparations, so long as they are taken with meals. Because typical patients exhibit a wide range of absorption efficiencies, it is desirable to assess absorption fraction before beginning a supplement regimen. (Some patients will need three times as large a dose as others to absorb the same amount of calcium.) Calcium intakes up to at least 62.5 mmol (2500 mg) are safe for virtually all patients.

Biological Availability↗
PubMed1991

Lifelong calcium intake and prevention of bone fragility in the aged.

Primary prevention of osteoporosis involves achieving the full genetic potential for bone mass. Secondary prevention is concerned with protecting what bone mass a woman may have at her current age. Calcium plays an important role in both. Calcium requirement varies with stage of growth, with physiological drains (e.g., pregnancy and lactation), and with factors that influence absorption and excretory loss (e.g., gonadal hormone status and sodium and protein intakes). The evidence is strong that prevailing calcium intakes contribute to the low bone mass component of osteoporotic fragility and that increases in intake would reduce the osteoporotic fracture burden. At the same time it needs to be emphasized that bone health is a multifactorial affair and that meeting calcium requirements alone will neither guarantee optimal bone growth nor protect against bone loss if other critical factors are missing. For example, calcium affords only minimal protection against either immobilization or estrogen withdrawal bone loss. Thus, while assuring an adequate calcium intake remains a sound strategy, it cannot be considered a total preventive for osteoporosis.

Adolescent↗
PubMed1991

47Ca alert.

Explore the source record for details and available documents.

Calcium Radioisotopes↗