Elective delivery at 34 weeks vs routine obstetric care in fetal gastroschisis: randomized controlled trial.

OBJECTIVE: To evaluate whether elective preterm delivery (ED) at 34 weeks is of postnatal benefit to infants with isolated gastroschisis compared with routine obstetric care (RC). METHODS: Between May 2013 and September 2015, all women with a sonographic diagnosis of fetal gastroschisis referred to a single tertiary center, before 34 weeks' gestation, were invited to participate in this study. Eligible patients were randomized to ED (induction of labor at 34 weeks) or RC (spontaneous labor or delivery by 37-38 weeks, based on standard obstetric indications). The primary outcome measure was length of time on total parenteral nutrition (TPN). Secondary outcomes were time to closure of gastroschisis and length of stay in hospital. Outcome variables were compared using appropriate statistical methods. Analysis was based on intention-to-treat. RESULTS: Twenty-five women were assessed for eligibility, of whom 21 (84%; 95% CI, 63.9-95.5%) agreed to participate in the study; of these, 10 were randomized to ED and 11 to RC. The trial was stopped at the first planned interim analysis due to patient safety concerns and for futility; thus, only 21 of the expected 86 patients (24.4%; 95% CI, 15.8-34.9%) were enrolled. Median gestational age at delivery was 34.3 (range, 34-36) weeks in the ED group and 36.7 (range, 27-38) weeks in the RC group. One patient in the ED group delivered at 36 weeks following unsuccessful induction at 34 weeks. Neonates of women who underwent ED, compared to those in the RC group, showed no difference in the median number of days on TPN (54 (range, 17-248) vs 21 (range, 9-465) days; P = 0.08), number of days to closure of gastroschisis (7 (range, 0-15) vs 5 (range, 0-8) days; P = 0.28) and length of stay in hospital (70.5 (range, 22-137) vs 31 (range, 19-186) days; P = 0.15). However, neonates in the ED group were significantly more likely to experience late-onset sepsis compared with those in the RC group (40% (95% CI, 12.2-73.8%) vs 0%; P = 0.03). CONCLUSION: This study demonstrates no benefit of ED of fetuses with gastroschisis when postnatal gastroschisis management is similar to that used in routine care. Rather, the data suggest that ED is detrimental to infants with gastroschisis. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Parto inducido a las 34 semanas versus atención obstétrica rutinaria en la gastrosquisis fetal: ensayo controlado aleatorizado OBJETIVO: Evaluar si el parto pretérmino inducido (PI) a las 34 semanas es beneficioso para los recién nacidos con gastrosquisis aislada en comparación con la atención obstétrica rutinaria (AR). MÉTODOS: Entre mayo de 2013 y septiembre de 2015, se invitó a participar en este estudio a todas las mujeres con diagnóstico ecográfico de gastrosquisis fetal remitidas a un mismo centro terciario, antes de las 34 semanas de gestación. Las pacientes elegibles fueron asignadas al azar al PI (inducción del parto a las 34 semanas) o a la AR (parto espontáneo a las 37-38 semanas, en función de los indicios obstétricos estándar). La medida de resultado primaria fue la duración de la nutrición parenteral total (NPT). Las medidas de resultado secundarias fueron el tiempo hasta el cierre de la gastrosquisis y la duración de la estancia hospitalaria. Las variables de resultado se compararon mediante métodos estadísticos apropiados. El análisis se basó en la intención de tratar. RESULTADOS: Se evaluó la elegibilidad de 25 mujeres, de las cuales 21 (84%; IC 95%, 63,9-95,5%) aceptaron participar en el estudio; de ellas, 10 fueron asignadas al azar al PI y 11 a la AR. El ensayo se detuvo después del primer análisis provisional planificado debido a preocupaciones sobre la seguridad de las pacientes y por su intrascendencia; por lo tanto, sólo se reclutaron 21 de las 86 pacientes esperadas (24,4%; IC 95%, 15,8-34,9%). La mediana de la edad gestacional en el momento del parto fue de 34,3 (rango: 34-36) semanas en el grupo de PI y 36,7 (rango: 27-38) semanas en el grupo de AR. Una paciente del grupo de PI tuvo un parto a las 36 semanas, después de una inducción infructuosa a las 34 semanas. Los neonatos de las mujeres que se sometieron a PI, comparados con los del grupo de AR, no mostraron diferencias en la mediana del número de días de NPT (54 (rango: 17-248) vs 21 (rango: 9-465) días; P=0,08), número de días hasta el cierre de la gastrosquisis (7 (rango: 0-15) vs 5 (rango: 0-8) días; P=0,28) y duración de la estancia hospitalaria (70,5 (rango: 22-137) vs 31 (rango: 19-186) días; P=0,15). Sin embargo, la probabilidad de experimentar sepsis de inicio tardío fue mayor en los neonatos del grupo de PI en comparación el grupo de AR (40% (IC 95%, 12,2-73,8%) vs 0%; P=0,03). CONCLUSIÓN: Este estudio demuestra que el PI no presenta ningún beneficio para los fetos con gastrosquisis cuando el tratamiento de la gastrosquisis postnatal es similar al utilizado en la atención rutinaria. Más bien, los datos sugieren que el PI es perjudicial para los lactantes con gastrosquisis.

Fifty years of human space travel: implications for bone and calcium research.

Calcium and bone metabolism remain key concerns for space travelers, and ground-based models of space flight have provided a vast literature to complement the smaller set of reports from flight studies. Increased bone resorption and largely unchanged bone formation result in the loss of calcium and bone mineral during space flight, which alters the endocrine regulation of calcium metabolism. Physical, pharmacologic, and nutritional means have been used to counteract these changes. In 2012, heavy resistance exercise plus good nutritional and vitamin D status were demonstrated to reduce loss of bone mineral density on long-duration International Space Station missions. Uncertainty continues to exist, however, as to whether the bone is as strong after flight as it was before flight and whether nutritional and exercise prescriptions can be optimized during space flight. Findings from these studies not only will help future space explorers but also will broaden our understanding of the regulation of bone and calcium homeostasis on Earth.

Calcium kinetics during bed rest with artificial gravity and exercise countermeasures.

UNLABELLED: We assessed the potential for countermeasures to lessen the loss of bone calcium during bed rest. Subjects ingested less calcium during bed rest, and with artificial gravity, they also absorbed less calcium. With exercise, they excreted less calcium. To retain bone during bed rest, calcium intake needs to be maintained. INTRODUCTION: This study aims to assess the potential for artificial gravity (AG) and exercise (EX) to mitigate loss of bone calcium during space flight. METHODS: We performed two studies: (1) a 21-day bed rest (BR) study with subjects receiving 1 h/day AG (n = 8) or no AG (n = 7) and (2) a 28-day BR study with 1 h/day resistance EX (n = 10) or no EX (n = 3). In both studies, stable isotopes of Ca were administered orally and intravenously, at baseline and after 10 days of BR, and blood, urine, and feces were sampled for up to 14 days post dosing. Tracers were measured using thermal ionization mass spectrometry. Data were analyzed by compartmental modeling. RESULTS: Less Ca was absorbed during BR, resulting in lower Ca balance in BR+AG (-6.04 ± 3.38 mmol/day, P = 0.023). However, Ca balance did not change with BR+EX, even though absorbed Ca decreased and urinary Ca excretion increased, because endogenous excretion decreased, and there was a trend for increased bone deposition (P = 0.06). Urinary N-telopeptide excretion increased in controls during BR, but not in the EX group. Markers of bone formation were not different between treatment groups for either study. Ca intake decreased during BR (by 5.4 mmol/day in the AG study and 2.8 mmol/day in the EX study), resulting in lower absorbed Ca. CONCLUSIONS: During BR (or space flight), Ca intake needs to be maintained or even increased with countermeasures such as exercise, to enable maintenance of bone Ca.

Efficacy of a multi micronutrient-fortified drink in improving iron and micronutrient status among schoolchildren with low iron stores in India: a randomised, double-masked placebo-controlled trial.

BACKGROUND/OBJECTIVES: A multiple micronutrient-fortified drink could be an effective strategy to combating micronutrient deficiencies in school going children. To assess the efficacy of a multiple micronutrient-fortified drink in reducing iron deficiency (ID), ID anemia (IDA), anemia and improving micronutrient status among schoolchildren with low iron stores. The study employed a school-based, randomized, double-blind, placebo-controlled design. SUBJECTS/METHODS: Schoolchildren with low serum ferritin (SF <20 µg/l) (n=246), aged 6-12 years were randomly assigned to receive either a multi-micronutrient fortified or an unfortified identical control drink. The drinks were provided 6 days/week for 8 weeks. Anthropometric and biochemical assessments were taken at baseline and endline. RESULTS: Study groups at baseline were comparable, and compliance to the intervention was similar. The overall prevalence of ID, IDA and anemia was 64%, 19% and 24%, respectively. The prevalence of ID, IDA, vitamin C and vitamin B12 deficiencies significantly reduced by 42%, 18%, 21% and 5%, respectively, in the intervention arm (P<0.01) as compared with the control arm at the end of the study. Similarly, the concentration of hemoglobin, SF, vitamin A, vitamin B12, vitamin C and body iron stores were significantly higher in the intervention arm in comparison to the control arm (P<0.001). Red cell folate levels also improved significantly in the intervention arm (P=0.04), however, serum zinc status did not change in either of the study arms. Children who had received the fortified drink had significantly lower odds of being ID (0.15; 95% confidence interval (CI): 0.09-0.27), IDA (0.14; 95% CI: 0.04-0.52), vitamin B12 deficient (0.36; 95% CI: 0.18-0.73) and vitamin C deficient (0.24; 95% CI: 0.13-0.46), after adjusting for baseline age, gender and weight. CONCLUSIONS: The multi micronutrient-fortified drink was efficacious in reducing the prevalence of ID, IDA, vitamin C and vitamin B12 deficiency and improved micronutrient status in schoolchildren.

Chronic dietary fiber supplementation with wheat dextrin does not inhibit calcium and magnesium absorption in premenopausal and postmenopausal women.

This placebo-controlled, randomized, crossover clinical study examined the effect of chronic wheat dextrin intake on calcium and magnesium absorption. Forty premenopausal and post menopausal women (mean ± SD age 49.9 ± 9.8 years) consumed wheat dextrin or placebo (15 g/day) for 2 weeks prior to (45)calcium ((45)Ca) and (26)magnesium ((26)Mg) absorption testing. After a standardized breakfast, serial blood and urine samples were obtained. The mean ± SD area under the curve from 0 to 9 h for (45)Ca specific activity was 0.81 ± 0.21 for wheat dextrin and 0.82 ± 0.22 for placebo, showing that wheat dextrin had no effect on calcium absorption. The mean ± SD percentage excess of (26)Mg/(24)Mg was 7.8% ± 2.1% for wheat dextrin and 7.9% ± 2.6% for placebo, showing that wheat dextrin had no effect on magnesium absorption. In conclusion, chronic wheat dextrin consumption did not inhibit calcium or magnesium absorption from the gastrointestinal tract in women.

A simple single serum method to measure fractional calcium absorption using dual stable isotopes.

The dual stable isotope method with a timed 24-h urine collection is the gold standard approach to measure fractional calcium absorption. However, the need to collect urine for 24 h makes this technique time-consuming and laborious. Our study sought to determine whether a dual isotope method using a single serum sample obtained 4 h after administration of the initial isotope provides a useful approach to measure fractional calcium absorption. Following a metabolic diet with a fixed calcium intake of 30 mmol/day for 10 days, nineteen healthy subjects age 54-74 were given a test meal with an oral isotope ((44)Ca) followed 2 h later by an intravenous isotope ((42)Ca). Once the oral isotope was administered, urine was collected for 24 h, and a serum sample was obtained after 4 h. The ratio of the oral to intravenous isotopes was measured in the urine and serum by mass spectroscopy. Fractional calcium absorption was 16.2 ± 7.7% by the 4-h single serum method versus 18.5 ± 7.5% by the 24-h urine method. There was a small mean difference between the urine and serum methods of 2.33% with a confidence interval -3.97 to 8.60%. The two methods showed a strong linear association (r = 0.912, p<0.001). Use of dual stable isotopes with a 4-h single serum method gives fractional calcium absorption values that are 12.5% lower than with the 24-h urine method; however, it rank orders subjects accurately thus making it a useful alternative method in clinical research applications.

The efficacy of micronutrient supplementation in reducing the prevalence of anaemia and deficiencies of zinc and iron among adolescents in Sri Lanka.

OBJECTIVE: To determine the effectiveness of combined iron and zinc over the iron or zinc-only supplementation in correcting deficiency and possible interactive effects in a group of adolescent school children. SUBJECTS AND METHODS: Schoolchildren (n=821) of 12-16 years of age were randomized into four groups and supplemented with iron (50 mg/day), zinc (14 mg/day), iron+zinc or placebo capsules 5 days per week for 24 weeks. Anthropometry, and haemoglobin (Hb), serum zinc (SZn) and serum ferritin (SF) concentrations were determined before and after the intervention. RESULTS: There were no significant effects between-groups in their weight, height and Hb concentrations with the intervention when compared with the placebo group. Iron-only and combination-supplemented groups had reached mean SF concentrations of 55.1 microg/l with no difference between them (P=0.99). The zinc-only group had a mean change of 4.3 micromol//l whereas the combine-supplemented group had a mean change of 4.0 micromol/l (P=0.82). The prevalence of anaemia was found to be 70.3% in the iron group at baseline; this was reduced to 14.5% after the supplementation. In the combine-supplemented group anaemia, prevalence was reduced from 64.8 to 19.3%. CONCLUSIONS: Zinc alone or in combination with iron has not shown a significant improvement in growth in adolescence. Severe and moderate forms of anaemia were successfully treated in children who received iron supplementation. Initial high prevalence of low SZn and iron stores was significantly improved with micronutrient supplementation.

Current issues in nutritional management of very low birth weight infants.

Infants less than 1,500 g birth weight (very low birth weight, VLBW) are at risk for significant nutritional deficiencies. Enhancing nutritional care of these infants during their first months of life may have important short and long-term benefits. In this article we will consider several areas of recent research in the nutritional management of VLBW infants. In particular we will focus on issues related to the introduction and use of enteral nutrition. These issues include avoiding mineral deficiencies, early (minimal) enteral nutrition, human milk fortification, and postdischarge nutrition. Transitioning VLBW infants successfully to enteral nutrition is a key to their achieving adequate growth and development without the long-term risks related to parenteral nutrition. Human milk is a key component of any strategy for enteral nutrition of all infants. Its introduction in the first days of life leads to improved growth and better health outcomes for infants. However, although some nutrients are initially increased in the milk of mothers delivering prematurely, there are inadequate amounts of calcium, phosphorus, zinc and other nutrients to meet the needs of the VLBW infant during growth. Therefore, safe and effective means of fortifying human milk are essential to the care of VLBW infants. The optimal approaches for this fortification and the potential risks related to human milk fortification remain controversial. Limited data are available for the optimal content, initiation and methods for mixing fortifier with human milk.

Calcium and bone mineral metabolism in children with chronic illnesses.

Increased longevity and improved medical management of children with chronic illnesses has led to a focus on the short- and long-term consequences of these conditions on bone health. Bone loss is influenced by diet, malabsorption, and disease-related imbalances in bone turnover. It may be exacerbated by common medications, especially corticosteroids. Assessment of bone mass and quality, calcium absorption, kinetically derived rates of bone turnover, and biochemical markers of bone turnover have increased our knowledge of the pathophysiology of bone loss in these children as well as provided insights into possible therapeutic interventions. Increased intake of calcium and vitamin D, while useful, is unlikely to prevent or resolve bone loss in many chronically ill children. Emphasis on combination of nutritional interventions with exercise and newer bone-sparing therapies may be necessary.

Bioavailability of elemental iron powder in white wheat bread.

OBJECTIVE: Iron fortification of wheat flour is widely used. In most cases, elemental iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H(2)-reduced elemental iron powder in white wheat bread made from 72% extraction flour. DESIGN: A stable isotope of H(2)-reduced iron powder (mean particle size 15 microm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5- to 7-y-old children were fed bread with 4 mg of H(2)-reduced (58)Fe /100 g of flour. The next day (57)Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry. RESULTS: When normalized to 40% absorption of the reference dose, the geometric mean (+/-range of 1 s.d.) bioavailability of reduced (58)Fe in wheat bread rolls was 6.5% (3.7-11.8). CONCLUSIONS: When compared to previous radioiron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size (58)Fe (15 microm) is likely to be higher than that of commercial iron powder (45 microm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial elemental iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate. SPONSORSHIP: This work was funded in part by Grant No 910313 by Micronutrient Initiative, IDRC, Ottawa, Canada.

Bone mineral mass in overweight and obese children: diminished or enhanced?

Childhood obesity has become a worldwide health problem. Recent studies have suggested that obese and overweight children have lower bone mass. We used dual-energy X-ray absorptiometry to examine the relation between bone mineral content (BMC) and body fatness (%Fat) in healthy children. Obese children (%Fat>30%) had higher BMC compared with age-, gender-, and ethnic-matched children with normal adiposity (%Fat<25%). When adjusted for height, these differences were less significant. We conclude obese children do not have lower whole-body BMC when compared with leaner children, even when adjusted for height, age, gender, and ethnicity.

Zinc absorption by infants.

UNLABELLED: Zinc is a vital mineral in human nutrition and rare cases of overt zinc deficiency are well described in term and preterm infants. A variety of methods have been developed to assess zinc absorption, retention and balance in humans, either using mass (metabolic) balance or stable isotope-based METHODS: The different methods have different benefits and disadvantageous. Many studies have used such methods to examine zinc absorption in term and preterm infants. In preterm infants the main interest has been establishing whether different diets lead to positive zinc balance and approached in utero accretion rates. The earliest studies were concerning as they suggested that preterm infants may be in negative zinc balances for prolonged periods after birth. Subsequent studies have been more contradictory and it remains unclear from the literature how much zinc preterm infants absorb early in life. Nor is it clear whether poor zinc absorption during this period has any long-term consequences. Studies in term infants have suggested no such prolonged period of negative zinc balance. Generally the absorption values are in line with those used by the Institute of Medicine in the most recent edition of the Dietary Reference Intakes. Other studies have been designed to assess the effect of changes in formula composition on zinc intake (e.g. the presence or absence of lactose, high vs low zinc contents, etc.). Ho-wever, despite almost 20 studies of zinc absorption in infants many physiologically important questions remain unanswered, especially in preterm infants.

Using stable isotopes to assess the bioavailability of minerals in food-fortification programs.

Food fortification with minerals is often undertaken without consideration of the bioavailability or nutrient-nutrient interactions related to its use. Stable isotopes provide a safe and accessible approach to providing direct evidence regarding these issues. Studies can be applied in all areas of the world and in all population groups. Mineral stable isotopes are safe and meet stringent ethical standards for use in children. Clinical studies in children allowing scientists, policy makers and the food industry to obtain data needed to understand how best to fortify foods to enhance the nutritional health of children of all ages. It is not necessary to have analytical mass spectrometry equipment available in each country where studies are performed. Rather, international collaborations can be developed to allow clinical studies to be performed in the field setting with analysis elsewhere if needed. The combination of isotope studies with field intervention trials may be beneficial.

Using stable isotopes to assess the bioavailability of minerals in food fortification programs.

The fortification of various types of food with minerals is often undertaken without consideration of either their bioavailability or the potential nutrient-nutrient interactions resulting from their use. Stable isotopes provide a safe and accessible method of resolving these issues by providing the proper evidence in each case. They must be conducted according to strict safety and ethical guidelines and may be readily conducted in a field setting. Clinical studies in children enable researchers, policymakers, and food manufacturers to obtain the data necessary to determine the best way to fortify specific foods and beverages, in order to optimally enhance the nutritional health of growing children. We have shown the utility of this approach in studies in both developing countries and in the United States.

Non-digestible oligosaccharides and calcium absorption in girls with adequate calcium intakes.

Non-digestible oligosaccharides such as inulin and oligofructose have been shown to consistently increase calcium absorption in experimental animals, but data in humans are less clear-cut. The objective of this study was to assess the effect of 8 g/d of oligofructose or a mixture of inulin and oligofructose on calcium absorption in girls at or near menarche. A total of fifty-nine subjects were studied using a balanced, randomized, cross-over design. They received, in random order, 8 g/d placebo (sucrose), oligofructose or the mixture inulin+oligofructose for 3 weeks, separated by a 2-week washout period. Throughout the study, subjects consumed a total of approximately 1500 mg/d dietary calcium, by adding two glasses of calcium-fortified orange juice to their diet. Four grams of placebo, oligofructose or the mixture inulin+oligofructose was added to each glass of orange juice immediately before it was consumed. At the end of each 3-week adaptation period, calcium absorption was measured, using a dual stable isotope technique, from the cumulative fractional excretion of an oral and an intravenous tracer over 48 hours. Calcium absorption was significantly higher in the group receiving the inulin+oligofructose mixture than in the placebo group v. P=0.01), but no significant difference was seen between the oligofructose group and the placebo group v. P=NS). We conclude that modest intakes of an inulin+oligofructose mixture increases calcium absorption in girls at or near menarche.

Calcium fortification of breakfast cereal enhances calcium absorption in children without affecting iron absorption.

OBJECTIVES: Provision of calcium-fortified foods may represent an important component of improving the calcium intake of children. We sought to determine whether the addition of calcium to cereal would have a net positive effect on calcium absorption without decreasing iron absorption. METHODS: Twenty-seven children, 6 to 9 years of age, were provided two servings per day (30 g of cereal per serving) of either a low (39 mg/serving) or fortified (156 mg/serving) calcium-containing cereal product for 14 days. Calcium absorption was measured by using stable isotopes added to milk (extrinsically labeled) and to the calcium-fortified cereal (intrinsically labeled). RESULTS: Fractional calcium absorption from the fortified cereal was virtually identical to that from milk. Fractional absorption of calcium from milk did not differ significantly when given with enriched or low-calcium-containing cereal. Total calcium absorption increased from 215 +/- 45 mg/d to 269 +/- 45 mg/d with the addition of the calcium-fortified cereal (P <.001). Iron absorption was similar when children received the calcium-fortified cereal or unfortified cereal. CONCLUSIONS: The addition of a moderate amount of calcium to a cereal product was beneficial to calcium absorption and did not interfere with iron absorption. Use of calcium-fortified food products may be considered a practical approach to increasing the calcium intake of children.

Calcium turnover and nutrition through the life cycle.

Ca nutritional requirements and bone Ca turnover can be assessed using numerous techniques. Among these techniques are bone mass measurements, tracer kinetic studies, bone histomorphometry and biochemical studies. Stable-isotope-based kinetic studies offer unique advantages in their ability to assess both Ca absorption and turnover. This approach is safe and readily applicable to subjects of all ages. Ca is essential for growth and maintenance of bone mineral throughout life. During pregnancy, increased intestinal absorption of Ca by the mother provides much of the Ca supplied to the fetus. During infancy, Ca supplied in human milk is primarily derived from maternal bone stores, which are quickly replenished during and after weaning. Early childhood is a time of relatively slow bone growth, with a rapid increase occurring during puberty. Recent kinetic studies demonstrate an increase in both Ca absorption and bone Ca deposition associated with early puberty. Bone Ca deposition reaches a maximum in females shortly before menarche. At that time the bone Ca deposition rate is approximately five times that of adulthood. The decline in bone Ca deposition rate is gradual after menarche. Ca absorption from the diet shows a gradual decline in adulthood as well. Ca supplementation, in the presence of adequate vitamin D, is effective in enhancing bone mineral content in childhood and in helping to maintain bone mineral content in adults. Maintaining adequate Ca nutriture throughout life may be necessary to minimize the risk of bone-loss disorders.

Z score prediction model for assessment of bone mineral content in pediatric diseases.

The objective of this study was to develop an anthropometry-based prediction model for the assessment of bone mineral content (BMC) in children. Dual-energy X-ray absorptiometry (DXA) was used to measure whole-body BMC in a heterogeneous cohort of 982 healthy children, aged 5-18 years, from three ethnic groups (407 European- American [EA], 285 black, and 290 Mexican-American [MA]). The best model was based on log transformations of BMC and height, adjusted for age, gender, and ethnicity. The mean +/- SD for the measured/predicted in ratio was 1.000 +/- 0.017 for the calibration population. The model was verified in a second independent group of 588 healthy children (measured/predicted In ratio = 1.000 +/- 0.018). For clinical use, the ratio values were converted to a standardized Z score scale. The whole-body BMC status of 106 children with various diseases (42 cystic fibrosis [CF], 29 juvenile dermatomyositis [JDM], 15 liver disease [LD], 6 Rett syndrome [RS], and 14 human immunodeficiency virus [HIV]) was evaluated. Thirty-nine patients had Z scores less than -1.5, which suggest low bone mineral mass. Furthermore, 22 of these patients had severe abnormalities as indicated by Z scores less than -2.5. These preliminary findings indicate that the prediction model should prove useful in determining potential bone mineral deficits in individual pediatric patients.

Effect of acute zinc depletion on zinc homeostasis and plasma zinc kinetics in men.

BACKGROUND: Zinc homeostasis and normal plasma zinc concentrations are maintained over a wide range of intakes. OBJECTIVE: The objective was to identify the homeostatic response to severe zinc depletion by using compartmental analysis. DESIGN: Stable zinc isotope tracers were administered intravenously to 5 men at baseline (12.2 mg dietary Zn/d) and after 5 wk of acute zinc depletion (0.23 mg/d). Compartmental modeling of zinc metabolism was performed by using tracer and mass data in plasma, urine, and feces collected over 6-14 d. RESULTS: The plasma zinc concentration fell 65% on average after 5 wk of zinc depletion. The model predicted that fractional zinc absorption increased from 26% to essentially 100%. The rate constants for zinc excretion in the urine and gastrointestinal tract decreased 96% and 74%, respectively. The rate constants describing the distribution kinetics of plasma zinc did not change significantly. When zinc depletion was simulated by using an average mass model of zinc metabolism at baseline, the only change that accounted for the observed fall in plasma zinc concentration was a 60% reduction in the rate constant for zinc release from the most slowly turning over zinc pool. The large changes in zinc intake, excretion, and absorption-even when considered together-only explained modest reductions in plasma zinc mass. CONCLUSION: The kinetic analysis with a compartmental model suggests that the profound decrease in plasma zinc concentrations after 5 wk of severe zinc depletion was mainly due to a decrease in the rate of zinc release from the most slowly turning over body zinc pool.

Iron and breastfeeding.

Given the importance of iron nutrition during the first year of life, there are surprisingly few true, randomized, controlled studies addressing this issue; however, it seems that iron deficiency is unlikely in full-term, breastfed infants during the first 6 months of life because these infants' body iron stores are sufficient to meet requirements. After this time, many infants exhaust their iron stores and become dependent on a secondary dietary iron supply. Although iron deficiency is a significant nutritional problem worldwide, most of the adverse effects of iron deficiency in this age group are hypothetical and rely on extrapolation from animal studies or studies at different ages. This, however, also is true of most of the adverse effects of iron excess in this age group. Given this uncertainty, it seems prudent to use the lowest dose of iron that prevents iron-deficiency anemia. Currently, the best evidence is that this is achieved by prolonged breastfeeding, avoidance of unfortified formulas and cow's milk, and the introduction of iron-fortified and vitamin C-fortified weaning foods at approximately 6 months of age. Despite much research, there are many areas of uncertainty regarding iron supplementation of infants, including that: 1. The optimal age for introducing iron-fortified supplemental foods is poorly defined and should be further evaluated. 2. The natural history of iron deficiency and iron-deficiency anemia during the first year of life is unclear, as are the possible long-term effects of this, especially on developmental outcome. 3. The biologic variability among infants and among their mothers that allows many infants who do not receive iron-fortified foods to prevent iron deficiency while receiving only human milk throughout the first year of life is intriguing and warrants additional study. 4. The iron requirements of small-for-gestational-age, term infants are unknown. Their iron requirements are likely to be higher than those of average term infants, but whether iron supplements are required is unclear. 5. The optimum amount of dietary iron in the weaning diet needs to be further defined. Similarly, the optimal source and amount of iron in infant formulas given to infants who receive a mixture of human milk and formula is unclear.