In breast milk calcium concentration influenced by calcium intake during pregnancy.
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Calcium↗
Biomedical subjects
A Prentice
Publications and source records attributed to A Prentice.
Calcium intakes and bone densities of lactating women and breast-fed infants in The Gambia.
The calcium required for breast-milk production and infant growth can be a substantial proportion of dietary intakes especially in regions of the world were calcium consumption is low. Insufficient calcium supply might lead to maternal bone loss, reduced breast-milk calcium secretion and impaired infant bone growth. However, changes in calcium absorption and excretion may be sufficient to allow these requirements to be met without affecting maternal or infant health. A limited number of studies have investigated changes in maternal bone mineral, absorption, excretion and metabolism during lactation but few have addressed whether any changes are influenced by calcium intakes. Ongoing detailed research by the MRC Dunn Nutrition Unit in a rural area of The Gambia amongst mothers and infants with habitually low calcium intakes will provide valuable information about calcium needs during lactation and growth.
Bone Density↗
Maternal calcium requirements during pregnancy and lactation.
Recommendations for calcium intakes during pregnancy and lactation differ around the world, reflecting the inadequacy of knowledge about calcium requirements in human reproduction. In theory, insufficient calcium supply during pregnancy and lactation could result in maternal bone loss, reduced breast-milk calcium secretion or impaired infant bone development. However, although calcium intakes vary widely, no specific problems associated with dietary calcium deficiency have been identified. Alterations in absorption, metabolism, and excretion may conserve calcium when requirements increase. Bone changes have been observed in pregnancy and lactation, but the relationship with diet is unknown. Similarly, the effects of maternal calcium intake on breast-milk calcium and infant bone growth are not understood. Calcium salts (1-2 g Ca/d) may reduce hypertensive disorders in pregnancy, but the role of dietary calcium needs exploration. More research is required before we can be confident about advising women to increase their calcium intakes during pregnancy and lactation.
Bone Density↗
Uncritical use of bone mineral density in absorptiometry may lead to size-related artifacts in the identification of bone mineral determinants.
Epidemiological studies of bone mineral determinants rely heavily on measurements made with absorptiometric techniques such as single-photon absorptiometry and dual-energy x-ray absorptiometry. In general, absorptiometric data are expressed as areal densities (bone mineral density, BMD), obtained by dividing bone mineral content (BMC) by bone area or width (BA, BW). This size correction assumes that BMC and BA (BW) are directly proportional to one another, such that a 1% change in BA (BW) is matched by a 1% change in BMC. This is rarely the case, and the exact relationship depends on the population group, skeletal site, body size, instrumentation, and scanning conditions. Size adjustment determined by using predefined indexes, such as BMD and body mass index (BMI, wt/ht2), may fail to correct BMC fully for bone and body size, and may lead to spurious associations with other size-related variables such as calcium intake, energy expenditure, and grip strength. A general approach to size adjustment is described, in which BA (BW), weight, and height are incorporated in all regression models of BMC. Although BMD plays a valuable role in fracture-risk assessment and clinical management, we advocate that its use in epidemiological research be discontinued.
Absorptiometry, Photon↗
Oestrogen and progesterone do not regulate the expression of retinoic acid receptors and retinoid 'X' receptors in human endometrial stromal cells in vitro.
Elucidation of the gene structure for retinoic acid receptor-beta (RAR-beta) has suggested a potential role for oestrogen in regulating the expression of RAR-beta. We have previously shown that all three RAR types are expressed in human endometrial stromal cells in vitro and that RAR-beta expression is induced in response to retinoic acid. The aim of this study was to ask whether oestradiol and progesterone could play a part in regulating the expression of RARs in human endometrial stromal cells and to establish the patterns of expression of a related group of nuclear retinoid receptors, retinoid 'X' receptors (RXRs) and their potential for regulation by steroid hormones. The RAR expression patterns of endometrial stromal cells, grown in steroid-free medium, did not change in response to the presence of steroid hormones. Furthermore, the retinoic acid-mediated induction of RAR-beta was not affected by oestradiol or progesterone, and was dependent on the continued presence of retinoic acid. Of the three RXR types, only RXR-alpha was detectably expressed in stromal cells in vitro and the expression of RXR-alpha did not change in response to steroid hormones or retinoic acid. These data indicate that oestradiol and progesterone are not important in the regulation of RAR and RXR expression in human endometrial stromal cells.
Base Sequence↗
Branch retinal artery occlusion in pregnancy.
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Adult↗
Expression of integrin adhesion molecules in endometrium and endometriosis.
OBJECTIVE: To compare the expression of cell adhesion molecules by endometrium and endometriosis. DESIGN: A comparative study of integrin expression, determined immunohistochemically, in eutopic and ectopic endometrium biopsied synchronously from patients with endometriosis diagnosed at laparoscopy or laparotomy. SETTING: University Departments of Obstetrics and Gynaecology, and Pathology, Southampton; Department of Obstetrics and Gynaecology, Newcastle upon Tyne. SAMPLES: Eighteen paired samples of endometria and endometriosis. RESULTS: A wide distribution of collagen-laminin receptor proteins was demonstrated. alpha 1 integrin expression was limited to secretory endometrium. beta 3 expression was only demonstrated on proliferative endometrium. CONCLUSIONS: Expressions of the integrin proteins differed between the various elements of the endometrium. Cyclical changes in integrin expression also were demonstrated. No difference in cell adhesion molecule expression was seen when comparing endometrial and endometriosis samples.
Cell Adhesion Molecules↗
Should lactating women exercise?
The safety of recreational exercise for lactating mothers has been examined in a prospective, intervention study. Thirty-three women, who were 6-8 weeks postpartum and breast-feeding exclusively were randomly chosen to join either an exercise or a control group. The exercise group took part in a program of aerobic activities averaging 4.5 sessions per week. After 12 weeks, aerobic capacity was significantly higher in the women who had exercised than in the controls, but no differences in body weight, body fatness, energy expenditure, or resting metabolic rate (RMR) were noted. The exercise program had no effect on breast milk output or composition or infant weight gain. This demonstrates that recreational exercise sufficient to improve cardiovascular fitness without substantially altering energy balance does not adversely affect lactation performance.
Body Composition↗
Extended breast-feeding and growth in rural China.
The relationship between duration of breast-feeding and growth has been investigated in a cross-sectional study of children living in an economically disadvantaged rural area of Hubei province, People's Republic of China. Data were analyzed from 2148 initially breast-fed children aged 12-47 months. Children who were breast-fed for longer than 12 months had significantly higher mean Z scores for weight-for-age, height-for-age, and weight-for height than children breast-fed for shorter periods. The positive association between duration of breast-feeding remained after adjusting the data for 11 potentially confounding factors, including age, sex, father's occupation, mother's education, recent infections, age of introduction of solids, and the variety of the weaning diet at 1 year. These results support the contention that mothers in developing countries should be encouraged to breast-feed their children for the first 2 years of life with the addition of good quality weaning foods from about 4-6 months.
Anthropometry↗
Calcium requirements in pregnancy and lactation in rural Africa.
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Bone Development↗
Body mass index and lactation performance.
Data from the world literature have been analysed in order to test whether low body mass index (BMI: kg/m2) is a useful indicator of functional impairment of lactation performance. Forty-one databases containing 1726 measurements have been identified as having reliable estimates of breast-milk quantity and/or quality. There is no detectable relationship between maternal BMI and the volume of milk produced by mothers when analysed according to the mean BMI of different populations, or of different subgroups stratified by BMI within populations. This conclusion holds even at BMIs < 18.5. The most remarkable feature of the data is the very high milk volumes produced by very thin mothers. It is accepted that the composition of breast milk is relatively unaffected by general undernutrition of the type that would be indicated by a low BMI with the possible exception of milk fat levels and hence the energy content. Analysis of the available data reveals studies in which there are weak, but significant, correlations between maternal BMI and milk fat. However, other studies show no association or even a negative relationship. Inter-country analysis fails to reveal any detectable association between BMI and milk energy. Milk energy levels seem adequate even at BMIs < 18.5. It is concluded that human lactation performance is extremely robust and that BMI does not provide a useful indicator of function at the levels studied so far. Lactation performance must become compromised when undernutrition is sufficiently severe, but it appears that this must occur only in famine or near famine conditions.
Body Mass Index↗
Adequacy of dietary mineral supply for human bone growth and mineralisation.
The evidence on the relationship between dietary mineral supply and bone development in children has been extensively reviewed. Data from children and primates suggest that overt deficiencies of Ca, P and Zn are likely to produce rickets and growth retardation, while the effects of Mg deficiency on human bone are unknown. The manifestations of marginal deficiencies are little understood. The biological needs for Ca, P, Mg and Zn in childhood have been calculated based on mineral deposition rates, using published values for the mineral content of the human body, and on obligatory endogenous losses. As a rough guide, the estimated biological requirements for the Ca, P, Mg and Zn can be taken as 200, 100, 4 and 1 mg/d respectively. A comparison of measured daily intakes of children in developing countries with biological requirements was made. This revealed that P and Mg intakes were many times higher than estimated needs. Ca intakes at all ages were found to be close to the biological requirement for children in many Third World societies, before any allowance for possible poor absorption. Zn intakes approach estimated needs in breast-fed infants, particularly during weaning, but are 4-5 times higher in older children. Poor absorption from phytate-rich diets could affect Zn supply. Supplementation studies indicate that raising Zn intakes can increase height gains in certain vulnerable groups, such as infant and adolescent boys. In conclusion, the evidence suggests that inadequate dietary intakes of Ca and Zn may contribute to linear growth retardation in children of developing countries but more research is needed.
Adult↗
Are modern British children too inactive?
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Adolescent↗
Epidemiology of endometriosis.
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Endometriosis↗
A trial of zinc supplementation in young rural Gambian children.
The present study tested the hypothesis that inadequate Zn intake might be responsible for failure to thrive and impaired catch-up growth in young rural Gambian children, and that Zn supplements might be beneficial. Gambian children might be deprived of Zn because of its poor availability from their predominantly plant-based diet. Rural Gambian children (110; fifty boys, sixty girls) aged between 0.57 and 2.30 years were divided into two matched groups, one to receive 70 mg Zn twice weekly for 1.25 years, and the other a placebo. Growth and mid-upper-arm circumference were measured at weekly intervals throughout the study and illnesses were monitored. Capillary blood and urine samples were collected at 0, 2 and 8 weeks. Body weights and arm circumferences showed a linear increase, plus a seasonal effect (rainy season faltering). For body weight there was no significant overall effect of the supplement. For arm circumference, a very small (2%) but significant (P < 0.01) difference favoured the supplemented group. Plasma thymulin was much lower at the first clinic than at the second and third clinics, and in vitro Zn stimulation was greater at the first clinic. There was, however, no effect of Zn in vivo. Likewise, Zn did not significantly benefit T-cell numbers or ratios, secretory IgA in urine, circulating hormone levels or biochemical indices of Zn status. One index of intestinal permeability, i.e. lactulose: creatinine, was improved (P < 0.02) by the supplement, but the lactulose: mannitol value was not; this requires further investigation. Dietary Zn deficiency is, thus, unlikely to be of major overall importance for rural Gambian children's ability to thrive, and blanket Zn supplementation is not justified. There may, however, be vulnerable sub-groups who would benefit from Zn supplements.
Anthropometry↗
The calcium and phosphorus intakes of rural Gambian women during pregnancy and lactation.
The Ca and P intakes of 148 pregnant and lactating women in a rural village in The Gambia, West Africa, have been estimated by direct weighing of food on a total of 4188 d. The Ca and P contents of local foods were determined by analysis of raw ingredients, snack foods and prepared dishes. Information about the contribution of mineral-rich seasonings was obtained. Efforts were made to discover unusual sources of Ca that might not be perceived as food by subject or observer. The main contributors to daily Ca intake were shown to be leaves, fish, cereals, groundnuts and local salt. Cow's milk accounted for only 5% of Ca intake. Unusual sources of Ca were discovered, namely baobab (Adansonia digitata) fruit and selected earths, but these were consumed infrequently and their contributions to Ca intakes were small. Cereals and groundnuts were the main sources of P. Ca and P intakes (mg/d) were shown to average 404 (SD 110) and 887 (SD 219) respectively. Seasonal changes in the availability of leaves, cereals and groundnuts resulted in variations in Ca and P intakes. The rainy season was associated with increased Ca intakes (by 16%) but decreased P consumption (by 15%). No difference was observed in Ca intake between pregnant and lactating women but P intake in lactation was 11% higher than that in pregnancy during the post-harvest season. The implications of these low Ca intakes require investigation.
Adolescent↗
Relationships between parathyroid hormone, 25-hydroxyvitamin D, and bone mineral density in elderly men.
This study aimed to determine the relationships between parathyroid hormone, vitamin D status and bone mineral density (BMD) in healthy older men. Subjects [n = 133, mean age (SD) 69.5 (3.1), range 65-76 years] were recruited from two general practices in Cambridge. Blood samples were drawn for measurement of intact parathyroid hormone (1-84, hPTH) and total 25-hydroxyvitamin D. Bone mineral density at the hip and spine was measured by dual-energy X-ray absorptiometry (DEXA). After adjusting for age and body mass index (BMI), PTH was negatively correlated with trochanteric (r = -0.24, p = 0.007), intertrochanteric (r = -0.29, p = 0.001), and Ward's Triangle BMD (r = -0.15, p = 0.087). By analysis of variance, controlling for age and BMI, PTH showed a relatively consistent downward trend with increasing tertiles of bone mineral density, especially at the hip. These results suggest a role of parathyroid hormone in determining hip bone mineral density in a community-based sample of healthy elderly men.
Aged↗
Immunohistochemical localization of acidic and basic fibroblast growth factors in normal human endometrium and endometriosis and the detection of their mRNA by polymerase chain reaction.
Growth factors play a role in the cyclical growth and vascularization of normal endometrium. Abnormal endometrial proliferation and neovascularization may result in endometriosis. This study determines the presence and localization of acidic and basic fibroblast growth factors (aFGF and bFGF respectively) in endometrium of normal women, and in normal and ectopic endometrium of women with endometriosis. Endometrium was obtained at curettage or hysterectomy for benign disease, or laparoscopy for endometriosis. aFGF- and bFGF-immunoreactivity was detected at different phases of the menstrual cycle by immunohistochemistry using primary polyclonal rabbit antibodies. Expression of mRNA for aFGF and bFGF was determined in normal endometrium by nested reverse transcriptase polymerase chain reaction (RT-PCR). aFGF- and bFGF-immunoreactivity were both detected in endometrium from normal women, and in normal and ectopic endometrium of women with endometriosis. The pattern of staining with the two different FGFs was the same: immunoreactivity was predominantly confined to glandular epithelial cells and did not change throughout the menstrual cycle. Little or only light staining was seen in stromal cells and myometrium, and the pattern of staining did not differ between endometriotic and normal tissue. The presence of mRNA for aFGF and bFGF was demonstrated in normal endometrium. The detection of aFGF and bFGF mRNA in normal endometrium and aFGF- and bFGF-immunoreactivity in normal and endometriotic tissues suggests that these peptides may play a role in the proliferation and angiogenesis of normal and ectopic human endometrium.
Base Sequence↗