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Biomedical subjects

C M Weaver

Publications and source records attributed to C M Weaver.

At least 19 recordsLinked to original sources
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↗
PubMed1990

Influence of calcium load on absorption fraction.

True calcium absorption was studied as a function of the size of the ingested load in healthy adult women, under meal conditions and at loads ranging from 15 to 500 mg calcium. Fractional absorption was highly inversely correlated with the logarithm of load (P less than 0.001). At the lowest loads, absorption averaged 64.0% and at the highest, 28.6%. The parameters of the best-fit relationship permit reasonably precise calculation of the impact of various calcium dosing and dietary strategies.

Adult↗
PubMed1990

Calcium absorptive consistency.

Calcium absorption efficiency was measured two or three times each in 74 premenopausal and 142 postmenopausal women under conditions predicted to alter absorptive performance. A woman's absorptive consistency was evaluated across differing loads, differing intervals, and substances of differing intrinsic absorbability. In all these circumstances there was a statistically significant correlation between a woman's absorption under differing test situations accounting for up to 60% of the variance typically found in cross-sectional studies. For example, when the same substance but at differing load levels was tested three times over an 8 week period, various coefficients of correlation ranged from +0.773 to +0.849 (P less than 0.001). Even over intervals as long as 5 years correlation of absorption fraction within individuals remained significant (r = +0.487, P less than 0.001).

Adult↗
PubMed1990

Absorbability of calcium sources: the limited role of solubility.

Fractional absorption of seven chemically defined calcium sources was measured in normal adult women under standardized load conditions. Solubility of the sources in water at neutral pH ranged from a low of 0.04 mM to a high of 1500 mM. The relationship of solubility to absorbability was weak. In the range from 0.1 to 10 mM, within which most calcium supplement sources fall, there was no detectable effect of solubility on absorption. Data from four food sources are presented for comparison. Absorbability of food calcium was not clearly related to absorbability of the dominant chemical form in the food concerned. These findings suggests that (1) even under controlled, chemically defined conditions, solubility of a source has very little influence on its absorbability; and (2) absorbability of calcium from food sources is determined mainly by other food components.

Adult↗
PubMed1990

Calcium absorption from kale.

Absorption of calcium from intrinsically labeled kale was measured in 11 normal women and compared in these same subjects with absorption of calcium from labeled milk. The average test load was 300 mg. Fractional calcium absorption from kale averaged 0.409 +/- 0.101 (means +/- SD) and from milk, 0.321 +/- 0.089 (P less than 0.025). In contrast with the poor absorption previously reported for spinach calcium, kale, a low-oxalate vegetable, exhibits excellent absorbability for its calcium.

Adult↗
PubMed1990

Assessing calcium status and metabolism.

Currently, there is no commonly practiced tool for assessing calcium status of individuals or populations. Few biochemical markers reflect calcium status. Fasting urinary calcium:creatinine ratios may hold promise as an easy, inexpensive method to indicate recent calcium status. Calcium status may best be assessed by integrated measures of calcium assimilation, such as total-body calcium. Although bone-mass measurements do not correlate well with recent dietary intakes of calcium, long-term adequacy of calcium intake influences bone mass. Whether low calcium intakes lead to calcium deficiencies depends on one's ability to adapt and conserve calcium. The relationship between calcium status and a particular disease state, such as osteoporosis, hypertension, or colon cancer, cannot be established until a reliable indicator of calcium status is found.

Absorption↗
PubMed1990

Association of magnesium deficiency with the blood pressure-lowering effects of calcium.

The role of dietary calcium and magnesium in the development of hypertension was studied in nine groups, each consisting of nine spontaneously hypertensive rats aged 8-31 weeks. The animals were fed AIN 76A semi-purified diets varying in calcium (0.075, 0.5 and 2.5%) and magnesium (0.01, 0.05 and 0.75%) concentrations according to a 3 x 3 factorial design. Dietary calcium and systolic blood pressure were inversely related, significantly (P less than 0.05) after 12 weeks. Total and ultrafilterable serum calcium concentrations were also significantly negatively correlated with blood pressure (r = -0.46; P = 0.001 and r = -0.57; P = 0.001, respectively). Repeated measures analysis of variance indicated that dietary magnesium had no effect on systolic blood pressure, and no calcium x magnesium interaction on blood pressure was observed. Signs of magnesium deficiency, calcium deposits in the kidneys, and histological lesions were observed in groups on a high-calcium diet receiving normal and low levels of magnesium. Thus a lowering of blood pressure by calcium supplementation, without concomitant magnesium supplementation, was accompanied by biochemical and histological abnormalities in this animal model.

Animals↗
PubMed1990

Agreement between analytical values and label declarations of sodium content of processed packaged foods.

As part of the Food Labeling and Product Surveillance Program of the Food and Drug Administration, samples from 1982, 1984, and 1986 surveys of processed packaged foods (canned, frozen, and dry packaged) were analyzed to determine how closely the foods' actual sodium content matched their label claims for sodium. Samples were classified into three groups: "sodium-free" products (less than 5 mg sodium per serving), and "very-low-sodium" products (5 to 35 mg per serving), and a larger group of products that were labeled as containing more than 35 mg sodium per serving. In the third group, the distribution of actual sodium content fell around 100% of label claims for sodium. For the three survey years, analyzed sodium averaged 101% of label claim (standard deviation [SD] = 25%) for 1982 samples (20 products), 99% of label claim (SD = 28%) for 1984 samples (108 products), and 94% of label claim (SD = 21%) for 1986 samples (265 products). Products labeled "very low sodium" were treated separately because sodium analyses varied widely from the label declarations. However, most "very-low-sodium" products were well under 35 mg sodium per serving. Results indicated that consumers receive reasonably accurate information about the sodium content of processed packaged foods from label claims.

Food Analysis↗
PubMed1989

Oxalate: effect on calcium absorbability.

Absorption of calcium from intrinsically labeled Ca oxalate was measured in 18 normal women and compared with absorption of Ca from milk in these same subjects, both when the test substances were ingested in separate meals and when ingested together. Fractional Ca absorption from oxalate averaged 0.100 +/- 0.043 when ingested alone and 0.140 +/- 0.063 when ingested together with milk. Absorption was, as expected, substantially lower than absorption from milk (0.358 +/- 0.113). Nevertheless Ca oxalate absorbability in these women was higher than we had previously found for spinach Ca. When milk and Ca oxalate were ingested together, there was no interference of oxalate in milk Ca absorption and no evidence of tracer exchange between the two labeled Ca species.

Adult↗
PubMed1989

Dietary magnesium does not affect blood pressure in spontaneously hypertensive rats.

To determine the therapeutic effectiveness of dietary magnesium in the treatment of established hypertension, 21 male spontaneously hypertensive rats were fed altered levels of magnesium oxide from 17 to 29 weeks of age. The rats were divided into three groups of approximately equal mean baseline systolic blood pressures and fed AIN 76A purified diets containing magnesium at 0.01% (low), 0.05% (normal), and 0.40% (high) levels. Mean systolic blood pressures in the conscious SHR during the 12 week period and terminal direct blood pressures under anesthesia were not significantly different among treatment groups. Total and ultrafilterable serum magnesium concentrations reflected dietary magnesium intake. Total and ultrafilterable serum calcium levels were significantly higher (p less than 0.05) in the low magnesium-fed SHR. Histopathologic alterations indicative of aging did not differ among treatment groups. Therefore, in spite of altered serum mineral status, blood pressure and histopathology were not affected by dietary magnesium.

Animals↗