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Biomedical subjects

C M Weaver

Publications and source records attributed to C M Weaver.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effect of psyllium on absorption of co-ingested calcium.

OBJECTIVE: To determine whether psyllium fiber (in the form of Metamucil) interferes with absorption of calcium ingested at the same meal. DESIGN: Three-way, randomized, cross-over study in 15 healthy postmenopausal women, with calcium-fortified orange juice as the calcium source in all three meals. The test load of calcium was 219 mg (approximately 5.5 mmol). One test meal contained Metamucil, providing 3.4 g psyllium fiber; one had an equivalent amount of neutral cellulose; the third had no added fiber. METHODS: The calcium-fortified orange juice was extrinsically labeled with 45Ca; calcium absorption fraction was calculated from the specific radioactivity of serum calcium at 5 hours after tracer ingestion. RESULTS: Fractional absorption of calcium from orange juice without added fiber averaged 0.341 +/- 0.059; in the presence of psyllium fiber, 0.317 +/- 0.067; and in the presence of neutral fiber, 0.354 +/- 0.083. While the absorption with cellulose was slightly higher than in the absence of fiber, and the absorption with psyllium was slightly lower, neither difference was statistically significant. However, the difference between added psyllium and cellulose was statistically significant (P < .05). CONCLUSION: Psyllium in the form of Metamucil makes little practical difference to availability of co-ingested calcium when ingested at typical therapeutic doses.

Aged↗
PubMed1995

Magnesium supplementation and osteoporosis.

Among other things, magnesium regulates active calcium transport. As a result, there has been a growing interest in the role of magnesium (Mg) in bone metabolism. A group of menopausal women were given magnesium hydroxide to assess the effects of magnesium on bone density. At the end of the 2-year study, magnesium therapy appears to have prevented fractures and resulted in a significant increase in bone density.

Bone Density↗
PubMed1995

Effects of long-term moderate exercise on iron status in young women.

The impact of long-term (6-month) moderate exercise on the iron status of previously sedentary women was determined by randomly assigning 62 college-age women into one of the following four groups: 1) 50 mg.d-1 iron supplement, low iron diet (N = 16); 2) Placebo, free choice diet (N = 13); 3) Meat supplement to achieve 15 mg.d-1 iron intake (N = 13); and 4) Control, free choice diet (N = 20). All groups except the Control group exercised 3 d.wk-1 at 60%-75% of their heart rate reserve. VO2max was measured at baseline and week 24. Blood was sampled at baseline and every 4 wk thereafter for 24 wk to measure iron status and to elucidate the causes for alterations in iron status. Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels (< 15 ng.ml-1). Serum iron, total iron binding capacity and transferrin saturation were not compromised with exercise. Mean hemoglobin level in the Placebo/Ex group was significantly (P < 0.05) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24. However, changes in serum albumin, haptoglobin, and erythropoietin data from the study cannot explain these changes.

Adult↗
PubMed1994

Geometric structure of the femoral neck measured using dual-energy x-ray absorptiometry.

An algorithm was developed to estimate the strength of the femoral neck from data generated by the dual-energy x-ray absorptiometry (DXA). This algorithm considers shape of the proximal femur as well as cross-sectional moment of inertia (CSMI) in the estimate. Proximal femora (10) from cadavers of white adults and an aluminum step wedge were scanned with the Lunar DPX to validate the calculation of CSMI. After scanning, each femoral neck was sectioned at its narrowest portion for direct measurement of CSMI. Three healthy young women were scanned five times each to evaluate the reproducibility of geometric measurements using DXA. There was a strong linear association between the CSMI measured directly and using DXA in both cadaver bones (r2 = 0.96) and the aluminum step wedge (r2 = 0.99). The coefficient of variation for CSMI from repeated measurements using DXA was less than 3%. This indicates that it is possible to estimate reproducibly the bending rigidity of bone from DXA measurements. The data from 306 normal subjects were analyzed to investigate geometric changes in the femoral neck with age. Although there was no strong correlation between CSMI and age in normal subjects of either sex, safety factor (SF, an index of strength of the femoral neck during walking) and fall index (FI, an index of the strength of the femoral neck during a fall) decrease with age in both sexes. We observed an alteration of the geometric structure of the femoral neck with age that may increase the stress on the femoral neck and decrease SF and FI.

Absorptiometry, Photon↗
PubMed1994

Dietary calcium: adequacy of a vegetarian diet.

Obtaining sufficient amounts of absorbable dietary calcium to optimize bone density and to protect against bone resorption is a protective measure to lower the risk of osteoporosis. This goal is difficult in Western-style diets without the inclusion of dairy foods, fortified foods, or supplements. Lactovegetarians are able to meet recommended calcium intakes and do not have compromised bone mineral densities. Few other foods provide concentrated sources of absorbable calcium. Estimates of the absorbable calcium content of several plant foods are provided.

Aged↗
PubMed1994

Age related calcium requirements due to changes in absorption and utilization.

An attempt was made to estimate average calcium requirements for various age groups by gender. The factorial method that sums calcium accretion and endogenous losses modified by fractional absorption was used during growth and calcium intakes to achieve calcium balance was used for adults. These estimates exceed the current RDA for females aged 6-16 y and older than 30 y and for males aged 6-30 y. They also exceed current calcium intakes in the U.S. during adolescence for both sexes and for females above the age of 11 y. A number of factors influence calcium requirements with age. Requirements for calcium accretion is dominant until peak daily calcium retention during the adolescent growth spurt is achieved. The rate of calcium accretion with age varies widely, depending on the method of estimation. Urinary calcium losses increase until young adulthood. Contributions of endogenous fecal calcium and sweat calcium to obligatory calcium losses are largely unknown during growth. After growth ceases, calcium requirements increase with menopause, unless estrogen-treated, and with age as calcium absorption efficiency decreases. Data required to estimate calcium requirements during growth are insufficient to precisely define dietary requirements with age. Determining calcium intakes which optimize calcium retention, and therefore, bone mass as has been estimated by Matkovic and Heaney (1992) may be a sound approach. The requirements estimated by this approach will be difficult to achieve given current dietary intakes in the U.S.

Absorption↗
PubMed1994

Calcium supplementation increases bone density in adolescent girls.

In a longitudinal calcium intervention study, bone density was assessed in pubertal girls for 18 months. Significant additional increases in total body bone mineral density (1.3%) and spine bone mineral density (2.9%) and content (4.7%) were noted in the calcium-supplemented group. Increasing bone mass during adolescence with adequate calcium intake, if maintained into adulthood, could decrease the risk of osteoporosis later in life.

Adolescent↗
PubMed1993

Dysprosium as a nonabsorbable marker for studies of mineral absorption with stable isotope tracers in human subjects.

Two studies were conducted to determine if dysprosium (Dy) could be used as a quantitative fecal marker for studies of zinc-70 (70Zn), copper-65 (65Cu) and magnesium-26 (26Mg) absorption in humans. In the first experiment, Dy excretion was shown to be complete (104 +/- 9%; mean +/- SD, n = 6) and the kinetics of fecal Dy excretion closely paralleled that of 70Zn but not 65Cu. Because of the similarity in 70Zn and Dy excretion kinetics, a method for estimating 70Zn absorption was developed which used 70Zn and Dy data from only the first two stools passed after isotope administration. Average estimates of 70Zn absorption based on the two-stool (partial pool) vs total pool (5-day composite) method were not different (28.0 +/- 5.2 vs 24.4 +/- 4.1%, respectively; means +/- SEM; p > 0.10). In the second study, the same questions was addressed relative to 26Mg absorption. 26Mg and Dy also exhibited nearly identical excretion patterns. Average estimates of 26Mg absorption based on the partial pool vs total pool method were comparable yielding mean values of 22.7 +/- 3.4 vs 23.2 +/- 2.5% and 26.1 +/- 1.8 vs 24.3 +/- 1.8%, respectively, from magnesium-26 oxide (26MgO) and 26Mg glycinate. Advantages and limitations of the partial pool method for estimating mineral absorption are discussed.

Absorption↗
PubMed1993

Solubility of calcium salts and carrageenan used in infant formulas did not influence calcium absorption in rats.

Calcium absorption from tricalcium phosphate (TCP) was compared to that from calcium chloride, CaCl2, in the presence and absence of carrageenan in the rat model. There was no difference in percent calcium absorption as indicated by femur uptake of TCP or CaCl2 intrinsically labeled with 45Ca given by gavage (78.4 +/- 9.6 vs. 80.0 +/- 5.9, respectively). Thus, the difference in solubility of the two salts did not influence calcium absorption. When TCP was delivered by gavage in a solution containing 1% carrageenan, calcium absorption was not decreased compared to that of a control without carrageenan. In this model, calcium from TCP in the presence of up to 1% carrageenan is well absorbed.

Animals↗
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

Iron status in exercising women: the effect of oral iron therapy vs increased consumption of muscle foods.

Forty-seven previously sedentary women participating in a 12-wk moderate aerobic-exercise program were randomly assigned to one of four dietary groups: 50-mg/d iron supplement and a low food-iron diet (50 FE + EX), 10-mg/d iron supplement and a low food-iron diet (10 FE + EX), placebo and unrestricted diet (P + EX), and meat supplement and high food-iron diet (M + EX). A sedentary control group (n = 13) received no dietary interventions. Hematocrit, total iron-binding capacity, and hemoglobin, serum iron, serum ferritin, and serum albumin concentrations were measured every 4 wk. Hemoglobin values decreased at the end of 4 wk in all exercising groups compared with the control group. Iron status in the 50 FE + EX and M + EX groups improved after week 4 as indicated by an increase in serum ferritin, serum iron, and hemoglobin concentrations, and a decline in total iron-binding capacity. Thus, short-term, moderate aerobic exercise resulted in compromised iron status that was offset to varying degrees by ingesting iron or meat supplements. However, meat supplements were more effective in protecting hemoglobin and ferritin status than were iron supplements.

Adolescent↗
PubMed1992

Exercise and iron status.

Total iron losses in feces, urine and sweat in endurance-trained athletes are approximately 1.75 mg/d (compared with the reference value of 1 mg/d) in males and approximately 2.3 mg/d (compared with the reference value of 1.4 mg/d) in females because of the additional iron losses with menses. Therefore, it is not surprising that many investigators report that iron deficiency is a common problem in athletes who do not increase their iron intake above that of the general population. Recently, several observations of iron deficiency associated with mild exercise have been reported. Investigation of the extent of iron loss and utilization in individuals exercising for fitness is needed. Because compromised iron status can affect athletic performance as well as general health, including immune functions, cognitive development and ability to thermoregulate, it is advisable to emphasize meeting the recommended dietary allowances for iron during exercise training.

Animals↗
PubMed1992

Calcium bioavailability and its relation to osteoporosis.

The balance of data suggests that calcium intake has a positive influence on bone mass in premenopausal women and has a preventive effect on the rate of bone loss in postmenopausal women. Even small advantages in bone mass provide great reductions in fracture rates. However, the majority of studies have tested the relationship of calcium intake and bone mass using calcium supplements. Few intervention studies have manipulated calcium intake through foods. Calcium is only useful to the skeleton once it is absorbed. Therefore, the bioavailability of dietary calcium becomes important in the prevention and treatment of osteoporosis. Isotopic tracer techniques have only recently been employed in the labeling of foods with calcium isotopes for evaluation of calcium absorption. Milk calcium is usually the referent food which is typically absorbed at 20-40% depending on the calcium status of the subject. The absorptive efficiency of most vegetable sources is as good or better than for dairy foods, unless they have high concentrations of oxalic acid (spinach, for example) or phytic acid (wheat bran cereal, for example). Few vegetable sources are concentrated sources of calcium. Therefore, it would be difficult to obtain adequate intakes of calcium to protect against osteoporosis without liberal use of dairy products in the diet. Alternately, calcium supplements provide concentrated amounts of absorbable calcium, but they do not provide other nutrients necessary for skeletal growth and maintenance.

Biological Availability↗
PubMed1991

Isotopic exchange of ingested calcium between labeled sources. Evidence that ingested calcium does not form a common absorptive pool.

We studied the extent of salt dissociation during absorption of calcium from sources of differing absorbability by measuring fractional absorption from loads in the range of 200-300 mg in healthy adult women. Sources were labeled both intrinsically and extrinsically with 45Ca and 47Ca, respectively, and were fed alone and in combination with one another. We first confirmed our previous observation of superior absorbability of calcium oxalate over spinach calcium in a randomized cross-over design in 20 women. Spinach calcium exhibited only half the absorbability of the same load of calcium presented as the oxalate. Then, in 14 women fed spinach with both an intrinsic and an extrinsic label, apparent absorption of the extrinsic label averaged 0.130 +/- 0.041 and of the intrinsic label, 0.029 +/- 0.023. Thus, the extrinsic tag was partially, but not completely, bound by the spinach. In the same 14 women, milk absorption averaged 0.331 +/- 0.092 when ingested alone. However, when co-ingested with spinach, apparent milk calcium absorption fell to 0.267 +/- 0.079 and apparent spinach calcium absorption rose to 0.111 +/- 0.039. Thus, there was significant but incomplete label exchange between the two sources, indicating that at least some of the calcium from both sources enters a common preabsorptive, ionic pool. By contrast, we had previously shown no tracer exchange when labeled oxalate was co-fed with labeled milk. We conclude that (1) the presence of calcium as the oxalate in spinach is not a sufficient explanation for the poor absorbability of spinach calcium; and (2) oxalate calcium and spinach calcium are absorbed by different mechanisms, one involving a common preabsorptive pool and the other not.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Soybean phytate content: effect on calcium absorption.

Absorption of calcium from soybeans with low and high phytate contents, intrinsically labeled with 45Ca, was measured in 16 normal women and compared in 15 of these same subjects with absorption of calcium from labeled milk. The average test load of calcium for all three sources was 2.45 mmol. Fractional calcium absorption (+/- SD) from the high-phytate soybeans averaged 0.310 +/- 0.070; from the low phytate soybeans, 0.414 +/- 0.074; and from milk, 0.377 +/- 0.056. The mean difference (+/- SEM) in fractional calcium absorption for the two phytate levels was 0.104 +/- 0.014 (P less than 0.001).

Absorption↗
PubMed1991

Human calcium absorption from whole-wheat products.

Fractional calcium absorption from wheat products and the influence of co-ingested wheat products on calcium absorption from milk were measured in a series of randomized crossover studies in healthy adult women. The wheat had been intrinsically labeled with 45Ca during growth. In the first study, fractional calcium absorption from leavened whole-wheat bread averaged 0.817 +/- 0.124. By comparison, absorption from milk, ingested at a comparable load in the same women, averaged only 0.589 +/- 0.111. When labeled bread was co-ingested with milk, at the same aggregate load as for bread alone, bread calcium absorption fell to 0.748 +/- 0.103 (P less than 0.05). In a second study, calcium absorption from an extruded cereal prepared from intrinsically labeled wheat bran was compared with milk. Calcium absorption from the cereal (0.223 +/- 0.046) was significantly less than from milk (0.375 +/- 0.072) (P less than 0.001). When the two were co-fed at the same total load, milk calcium absorption fell to 0.258 +/- 0.055 (P less than 0.001). In a third study, the effect of phytate hydrolysis through yeast fermentation and of Maillard browning on calcium absorption was investigated using leavened bread and underbaked and overbaked cookies, each made with intrinsically labeled wheat flour. Calcium absorption from cookies was not affected by the extent of browning and averaged 0.652 +/- 0.087. However, calcium absorption from bread in these same women averaged 0.703 +/- 0.108. This was significantly more than from the cookies (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The Berkeley Group: ten years' experience of a group for non-violent sex offenders.

During the first ten years of a group started in February 1977 by the Avon Probation Service for the treatment of non-violent sex offenders, many of the offenders have shown a high degree of commitment to the group, and attendance levels have run consistently at over 70%. Of 63 men who came to the group during the ten-year study period, 33 completed their stay at the group, 11 left the group prematurely, and 11 never engaged satisfactorily. The remaining eight were still attending the group at the end of the study period. Of the 55 men whose contact with the group had ended, 36 (65%) had not been convicted of further sex offences by the end of the study period.

Adult↗