Mark Benson Andon

Timing of peak bone mass in Caucasian females and its implication for the prevention of osteoporosis. Inference from a cross-sectional model.

To determine the timing of peak bone mass and density, we conducted a cross-sectional study of bone mass measurements in 265 premenopausal Caucasian females, aged 8-50 yr. Bone mass and bone mineral density were measured using dual X-ray absorptiometry and single-photon absorptiometry at the spine (anteroposterior, lateral), proximal femur, radius shaft, distal forearm, and the whole body. Bone mass parameters were analyzed using a quadratic regression model and segmented regression models with quadratic-quadratic or quadratic-linear form. The results show that most of the bone mass at multiple skeletal locations will be accumulated by late adolescence. This is particularly notable for bone mineral density of the proximal femur and the vertebral body. Bone mass of the other regions of interest is either no different in women between the age of 18 yr and the menopause or it is maximal in 50-yr-old women, indicating slow but permanent bone accumulation continuing at some sites up to the time of menopause. This gain in bone mass in premenopausal adult women is probably the result of continuous periosteal expansion with age. Since rapid skeletal mineral acquisition at all sites occurs relatively early in life, the exogenous factors which might optimize peak bone mass need to be more precisely identified and characterized.

The effect of calcium supplementation and tanner stage on bone density, content and area in teenage women

One hundred and twelve Caucasian girls, 11.9±0.5 years of age at entry, were randomized into a 24-month, double-masked, placebo-controlled trial to determine the effect of calcium supplementation on bone mineral content, bone area and bone density. Supplementation was 500 mg calcium as calcium citrate malate (CCM) per day. Controls received placebo pills, and compliance of both groups averaged 72%. Bone mineral content, bone mineral area and bone mineral density of the lumbar spine and total body were measured by dual energy X-ray absorptiometry (DXA). Calcium intake from dietary sources averaged 983 mg/day for the entire study group. The supplemented group received, on average, an additional 360 mg calcium/day from CCM. At baseline and after 24 months, the two groups did not differ with respect to anthropometric measurements, urinary reproductive hormone levels or any measurement of pubertal progression. The supplemented group had greater increases of total body bone measures: content 39.9% versus 35.7% (p=0.01), area 24.2% versus 22.5% (p=0.15) and density 12.2% versus 10.1% (p=0.005). Region-of-interest analyses showed that the supplemented group had greater gains compared with the control group for bone mineral density, content and area. In particular, in the lumbar spine and pelvis, the gains made by the supplemented group were 12%–24% greater than the increases made by the control group. Bone acquisition rates in the two study groups were further compared by subdividing the groups into those with below- or above-median values for Tanner score and dietary calcium intake. In subjects with below-median Tanner scores, bone acquisition was not affected by calcium supplementation or dietary calicum level. However, the calcium supplemented subjects with above-median Tanner had higher bone acqusition rates than the placebo group with above-median Tanner scores. Relative to the placebo group, the supplemented group had increased yearly gains of bone content, area and density which represented about 1.5% of adult female values. Such increases, if held to adult skeletal maturity, could provide protection against future risk of osteoporotic fractures.

Intraduodenal delivery of intrinsically and extrinsically labelled CaCO3 in the rat: effect of solubilization on calcium bioavailability*

Abstract— The dissolution of CaCO3 before intraduodenal administration was found to be an important factor determining calcium (Ca) bioavailability. Extrinsically and intrinsically labelled 47CaCO3 preparations were sequentially dissolved by serial additions of HCl. Aliquots of these preparations were collected before (no HCl added) and during the solubilization process and administered intraduodenally to rats. Whole body 47Ca retention 72 h post‐dose was used as a measure of Ca bioavailability. Although dissolution of CaCO3 significantly increased Ca bioavailability (p < 0·001), Ca from both intrinsically and extrinsically labelled CaCO3 was absorbed and retained to some extent without prior acid dissolution. Due to a disproportionately high concentration of 47Ca on the particle surface, extrinsically labelled 47CaCO3 overestimated bioavailability when unsolubilized or partially solubilized CaCO3 preparations were used (P < 0·05). These data indicate that dissolution is a determining factor for Ca bioavailability from CaCO3. Incomplete dissolution will significantly limit but not completely prevent Ca bioavailability. The disintegration and dissolution characteristics of commercial CaCO3 preparations, which vary widely, may produce important differences in Ca absorption.

Effects of Long-Term Calcium Supplementation on Iron Status in Adolescent Females

Abstract LEARNING OUTCOME: The 4-year calcium supplementation did not affect serum ferritin and iron deficiency anemia indices in adolescent females. The recent recommendations of National Institutes of Health for increasing calcium (Ca) intake in adolescent females to 1200-1500mg/day raised a concern about its effects on other minerals, namely iron. The previous studies examining the effects of Ca supplementation on iron status in humans resulted in mixed conclusions. The objective of our study was to investigate the effects of Ca supplementation on iron status during a 4-year period. A sample of 354 healthy, Caucasian females were enrolled in the study at the average age of 10.8 y; one half was randomly assigned to receive 1000mg/d Ca as Ca citrate malate and another half placebo. Blood was drawn once a year and serum ferritin was analyzed by the automated procedure (Hitachi Analyzer), while red blood cell indices and hemoglobin were determined at the end of the 4-year follow-up. The subjects completed 3-day dietary records annualy, which were analyzed on Nutritionist III. The average annual compliance with pill intake was 70%. Table presents yearly data (mean±SD): There was no statistical difference between placebo and Ca supplemented group in corresponding hemoglobin (13.4±0.8 vs. 13.2±0.9, p=0.1), hematocrit (38.5±2.4 vs. 37.9±2.5, p=0.2), red blood cell count (4.4±0.3 vs. 4.4±0.3, p=0.3), mean corpuscular volume (86.6±3.5 vs. 86.5±4.0, p=0.8), and mean corpuscular hemoglobin concentration (34.8±0.6 vs. 34.7±0.7, p=0.1). Our results indicate that long-term (4 years) calcium supplementation in adolescent females has no effect on iron stores, as measured by serum ferritin, or indices of iron deficiency anemia.