Calcium supplementation does not augment bone gain in young women consuming diets moderately low in calcium.

In earlier observational work, the dietary calcium:protein ratio was directly related to bone accrual in healthy postadolescent women. In this study, we sought to test the hypothesis that augmented calcium intake would increase postadolescent skeletal consolidation, using a double-blind, randomized, placebo-controlled design. We recruited 152 healthy young women (age 23.

The elusive concept of bone quality.

This paper outlines information from recent publications that aid our understanding of bone quality in relation to osteoporosis. In practical terms, bone quality designates the properties of bone that contribute to strength but are not assessed by bone densitometry. While osteoporosis is still defined in terms of bone density, the limitations of this approach, long questioned, have become indisputable.

Calcium absorptive efficiency is positively related to body size.

Background: Calcium absorption efficiency is a more important determinant of calcium balance than calcium intake itself. The sources of variability in absorptive performance are only partly elucidated.

Purpose: The aim of the study was to explore the relationship between body size and calcium absorption efficiency.

Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol.

Background: The cholecalciferol inputs required to achieve or maintain any given serum 25-hydroxycholecalciferol concentration are not known, particularly within ranges comparable to the probable physiologic supply of the vitamin.

Objectives: The objectives were to establish the quantitative relation between steady state cholecalciferol input and the resulting serum 25-hydroxycholecalciferol concentration and to estimate the proportion of the daily requirement during winter that is met by cholecalciferol reserves in body tissue stores.

Design: Cholecalciferol was administered daily in controlled oral doses labeled at 0, 25, 125, and 250 micro g cholecalciferol for approximately 20 wk during the winter to 67 men living in Omaha (41.

Bone microstructure in osteoporosis: transilial biopsy and histomorphometry.

The bone fragility of osteoporosis is not fully explained by a deficit in bone mass. Histomorphometric examination of transilial bone biopsies has identified microstructural defects that-in light of what is known about the mechanical properties of structural materials-further compromise bone strength. Histomorphometric measures describe the biopsy specimen, the configuration of its trabeculae in space, and the extent to which its trabecular lattice is intact.

Effects of above average summer sun exposure on serum 25-hydroxyvitamin D and calcium absorption.

The purpose of this study was to examine the effects of summer sun exposure on serum 25-hydroxyvitamin D [25(OH)D], calcium absorption fraction, and urinary calcium excretion. Subjects were 30 healthy men who had just completed a summer season of extended outdoor activity (e.g.

Calcium and weight: clinical studies.

Data from six observational studies and three controlled trials in which calcium intake was the independent variable (and either bone mass or blood pressure the original outcome variable) have been reanalyzed to evaluate the effect of calcium intake on body weight and body fat. Analysis reveals a consistent effect of higher calcium intakes, expressed as lower body fat and/or body weight, and reduced weight gain at midlife. Similarly, studies relating nutrient intake to body composition report negative associations between calcium intake and body weight at midlife and between calcium and body fat accumulation during childhood.

Hormones, weight change and menopause.

Objective: To determine total body weight change occurring in women at mid-life, specifically with respect to occurrence of menopause and use of estrogen.

Design: Retrospective analysis of body weight measurements accumulated in two cohorts of healthy women participating in studies of skeletal metabolism.

Subjects: Cohort 1: 191 healthy nuns enrolled in a prospective study of osteoporosis risk, aged 35-45 in 1967; cohort 2: 75 women aged 46 or older and still menstruating, enrolled in 1988 in a study of bone cell dynamics across menopause.

Calcium intake and body weight.

Five clinical studies of calcium intake, designed with a primary skeletal end point, were reevaluated to explore associations between calcium intake and body weight. All subjects were women, clustered in three main age groups: 3rd, 5th, and 8th decades. Total sample size was 780.

Association of bone dimensions with a parathyroid hormone gene polymorphism in women.

We have recently shown that bone radiogrammetric dimensions are associated with vitamin D receptor gene polymorphism. Since parathyroid hormone (PTH) plays a central role in maintaining calcium homeostasis and in bone remodeling, we investigated whether bone radiogrammetric dimensions are associated with a PTH gene polymorphism in 91 healthy Caucasian women, who were premenopausal at entry into the study. These women had assessments of bone by radiogrammetry every five years for a median period of 20 years (range 4-27).

Absorption of calcium as the carbonate and citrate salts, with some observations on method.

Calcium supplement use has increased and there is confusion about the relative absorbability of various sources. Absorbability of calcium from the carbonate and citrate salts was compared at 300 mg and 1000 mg calcium loads, ingested as part of a light breakfast meal. Absorption was measured at the high load both by tracer appearance in serum and by the absorptive increment in urinary calcium, and at the low load by the tracer method only.

Vitamin D and its major metabolites: serum levels after graded oral dosing in healthy men.

We determined the quantitative relationships between graded oral dosing with vitamin D3, 25(OH)D3, and 1,25(OH)2D3 for short treatment periods and changes in circulating levels of these substances. The subjects were 116 healthy men (mean age, 28 +/- 4 years, with usual milk consumption of < or = 0.47 l/day and mean serum 25(OH)D of 67 +/- 25 nmol/l).

Calcium absorptive effects of vitamin D and its major metabolites.

The absorptive response to graded doses of vitamin D3, 25(OH)D, and 1,25(OH)2D was measured in healthy adult men after treatment periods of eight, four, and two weeks, respectively. While no relationship was found between baseline absorption and serum vitamin D metabolite levels, all three vitamin D compounds significantly elevated 45Ca absorption from a 300 mg calcium load given as part of a standard test meal. 1,25(OH)2D was active even at the lowest dose (0.

Bone dimensional change with age: interactions of genetic, hormonal, and body size variables.

Changes in bony dimensions with age were assessed longitudinally from standardized X-ray films in 170 middle-aged Caucasian women, starting at age 40 years and with a median duration of observation of 21.125 years. Consistent with earlier work, cortical area of the metacarpals and radial shaft declined with age at rates ranging from 0.

Vitamin D receptor gene polymorphism, bone mass, body size, and vitamin D receptor density.

We determined vitamin D receptor (VDR) gene alleles (based on the BsmI restriction site polymorphism), duodenal mucosal receptor density, bone mass at spine and total body, and body size in 32 healthy premenopausal females. While we found no relationship between allele and receptor density in duodenal mucosa, bone mineral content (BMC) at both spine and total body was significantly associated with VDR gene alleles. BMC was highest for the bb allele, lowest for BB, and intermediate for Bb.

Caffeine and the calcium economy revisited.

We report an analysis of data from 560 calcium balance studies carried out on 190 women aged 34.8-69.3 years at the time of study.

An investigation of sources of variation in calcium absorption efficiency.

To examine putative sources of interindividual variation in calcium absorption efficiency, we studied 41 healthy premenopausal women (mean age, 36.4 yr). About half were randomized to pretreatment with supplemental 25-hydroxyvitamin D (25OHD; 20 micrograms/day [corrected] for approximately 34 days) before testing.

The role of calcium intake in preventing bone fragility, hypertension, and certain cancers.

This paper examines the evidence that connects calcium intake and vitamin D status to bone fragility, hypertension, colon cancer, and breast cancer. Human calcium physiology, with an intestinal absorptive barrier and inefficient conservation, reflects the abundance of calcium in the primordial human food supply. The calcium intake of stone-age adults is estimated at 50 to 75 mmol/d, three to five times the median calcium intake of present-day U.

ADSA Foundation Lecture. Low calcium intake: the culprit in many chronic diseases.

Calcium is the fifth most abundant element in the earth's crust and is necessary for both plant and animal life today. Moreover, the natural diets of all mammals are rich in calcium. The diet of Stone Age human adults is estimated to have contained from 50 to 75 mmol of calcium (2000 to 3000 mg)/d, three to five times the median calcium intake of present-day US adults.

Effects of calcium restriction on metabolic characteristics of premenopausal women.

We studied 28 healthy premenopausal women before and after manipulating Ca intake, and then in response to a hypercalcemic challenge. Women with low Ca intakes at entry (< 17.5 mmol/day) were restricted to about 5 mmol/day (low-Ca), and those with higher self-selected intakes were supplemented to about 70 mmol/d (high-Ca).

Effects of moderate caffeine intake on the calcium economy of premenopausal women.

We examined directly the effects of a moderate dosage of caffeine (400 mg/d) on the calcium economy in 16 healthy premenopausal women in a double-blind, placebo-controlled crossover design. The subjects took divided doses of caffeine (100 mg/tablet) or identical-appearing placebos with decaffeinated coffee on personalized schedules for treatment periods lasting 19 d each and with 37-d interstudy intervals. We randomized the treatment sequence among subjects and studied them as inpatients under metabolic-balance conditions.

Time course of calcium absorption in humans: evidence for a colonic component.

We examined the time course of calcium absorption (CaAbs) in 155 studies, using a double isotope technique. The subjects were 118 healthy peri-menopausal women (mean age 53.3 years), studied as inpatients under metabolic balance conditions.