Background Inadequate dietary intake of calcium and vitamin D may contribute to the high prevalence of osteoporosis among older persons. Methods We studied the effects of three years of dietary supplementation with calcium and vitamin D on bone mineral density, biochemical measures of bone metabolism, and the incidence of nonvertebral fractures in 176 men and 213 women 65 years of age or older who were living at home. They received either 500 mg of calcium plus 700 IU of vitamin D3 (cholecalciferol) per day or placebo. Bone mineral density was measured by dual-energy x-ray absorptiometry, blood and urine were analyzed every six months, and cases of nonvertebral fracture were ascertained by means of interviews and verified with use of hospital records. Results The mean (±SD) changes in bone mineral density in the calcium–vitamin D and placebo groups were as follows: femoral neck, +0.50±4.80 and -0.70±5.03 percent, respectively (P = 0.02); spine, +2.12±4.06 and +1.22±4.25 percent (P = 0.04); and total body,...

Effect of Calcium and Vitamin D Supplementation on Bone Density in Men and Women 65 Years of Age or Older

We propose here a new unitary model for the pathophysiology of involutional osteoporosis that identifies estrogen (E) deficiency as the cause of both the early, accelerated and the late, slow phases of bone loss in postmenopausal women and as a contributing cause of the continuous phase of bone loss in aging men. The accelerated phase in women is most apparent during the first decade after menopause, involves disproportionate loss of cancellous bone, and is mediated mainly by loss of the direct restraining effects of E on bone cell function. The ensuing slow phase continues throughout life in women, involves proportionate losses of cancellous and cortical bone, and is associated with progressive secondary hyperparathyroidism. This phase is mediated mainly by loss of E action on extraskeletal calcium homeostasis which results in net calcium wasting and increases in the level of dietary calcium intake required to maintain bone balance. Because elderly men have low circulating levels of both bioavailable E and bioavailable testosterone (T) and because recent data suggest that E is at least as important as T in determining bone mass in aging men, E deficiency may also contribute substantially to the continuous bone loss of aging men. In both genders, E deficiency increases bone resorption and may also impair a compensatory increase in bone formation. For the most part, this unitary model is well supported by observational and experimental data and provides plausible explanations to traditional objections to a unitary hypothesis.

A Unitary Model for Involutional Osteoporosis: Estrogen Deficiency Causes Both Type I and Type II Osteoporosis in Postmenopausal Women and Contributes to Bone Loss in Aging Men

Intestinal calcium absorption assessed by a double-isotope method, decreased significantly with aging in 94 normal subjects (r = -0.22, P < 0.025). In 52 untreated patients with postmenopausal osteoporosis, calcium absorption was significantly lower than normal when either age or habitual calcium intake was used as a covariable (P < 0.001). Serum 25-hydroxyvitamin D (25-OH-D) and 1,25-dihydroxyvitamin D (1,25(OH)(2)D) were measured in 44 normal subjects and 27 osteoporotic patients. For all normals, calcium absorption and serum 1,25(OH)(2)D were positively correlated (r = 0.50, P < 0.001). In nonelderly normal subjects (ages 30-65 yr), dietary calcium intake correlated inversely with both calcium absorption (r = -0.39, P < 0.01) and with serum 1,25(OH)(2)D (r = -0.50, P < 0.01). Both osteoporotic patients and elderly normal subjects (ages 65-90 yr) differed from nonelderly normals in that these correlations were not present. In addition although serum 25-OH-D was normal, serum 1,25(OH)(2)D was significantly decreased in both osteoporotic patients and elderly normals (P < 0.001). In osteoporotic patients, calcium absorption increased significantly (P < 0.001) after 7 d administration of a small dose (0.4 mug/d) of synthetic 1,25(OH)(2)D(3). In osteoporotics mean serum immunoreactive parathyroid hormone was either normal (COOH-terminal assay) or low (NH(2)-terminal assay) relative to age-matched controls, and mean serum phosphate was increased. The data suggest that inadequate metabolism of 25-OH-D to 1,25(OH)(2)D contributes significantly to decreased calcium absorption and adaptation in both osteoporotics and elderly normal subjects. In patients with osteoporosis this abnormality could result from a decrease in factors that normally stimulate 1,25(OH)(2)D production, such as the decreased parathyroid hormone secretion and increased serum phosphate demonstrated in this group. In elderly subjects a primary abnormality in metabolism of 25-OH-D to 1,25(OH)(2)D, analagous to that seen in aging rats, cannot be excluded.

/pdf/intestinal-calcium-absorption-and-serum-vitamin-d-31gk91r32m.pdf

Intestinal Calcium Absorption and Serum Vitamin D Metabolites in Normal Subjects and Osteoporotic Patients: EFFECT OF AGE AND DIETARY CALCIUM

OSTEOPOROSIS is one of the most important disorders associated with aging.1 , 2 More than 1.5 million Americans have fractures related to osteoporosis each year, with attendant pain, deformity, and loss of independence. The annual cost to the U.S. health care system is at least $10 billion.1 , 2 Because of the aging of the population and increases over time in the incidence of fractures, these already huge costs will more than double over the next 30 years3 unless a comprehensive program of prevention and treatment is initiated soon. The most important preventable cause of fractures is low bone mass. During the course of . . .

The Prevention and Treatment of Osteoporosis

Prevention and treatment of postmenopausal osteoporosis

Effect of age on calcium absorption

A dose of 500 mg polyethylene glycol 4000 (Peg) as a non-absorbable ma rke r is given three t imes daily and the subject eats a constant diet daily for the durat ion of the study. After a seven day period of equil ibration on m arke r and diet daily collection of faeces and urine commence and are cont inued for seven days. The diet, faeces and urine are analysed for calcium b y convent ional methods. The Peg content of the faeces is determined b y a turbidimetr ic technique and the creatinine content of the urines b y AutoAnalyser. The faecal calcium of each day ' s faeces is corrected for the Peg content and daily urine calcium is corrected against the mean daily urine creatinine ou tpu t of the seven day period. This permits a daily calcium balance to be calculated for every day on which a faecal sample is obta ined and the mean balance • s tandard error can be determined for the week,

J. R. Bullamore

Papers

Effect of age on calcium absorption

Measurement of calcium balance and bone turnover by new techniques.