RESUMO
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.
Assuntos
Pão , Eritrócitos/química , Alimentos Fortificados , Ferro/farmacocinética , Disponibilidade Biológica , Pão/análise , Criança , Pré-Escolar , Deutério , Feminino , Compostos Ferrosos/sangue , Compostos Ferrosos/metabolismo , Compostos Ferrosos/farmacocinética , Farinha , Humanos , Absorção Intestinal , Ferro/sangue , Ferro/metabolismo , Isótopos de Ferro , Masculino , Espectrometria de Massas , Tamanho da Partícula , TriticumRESUMO
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.
Assuntos
Cálcio da Dieta/metabolismo , Fenômenos Fisiológicos da Nutrição Infantil , Grão Comestível/metabolismo , Alimentos Fortificados , Ferro da Dieta/metabolismo , Absorção/fisiologia , Animais , Criança , Registros de Dieta , Feminino , Fluorimunoensaio , Humanos , Marcação por Isótopo , Masculino , Leite/metabolismoRESUMO
Prenatal iron supplements may adversely influence zinc absorption during pregnancy. To examine the impact of prenatal iron supplements on supplemental zinc absorption, fractional zinc absorption was measured in 47 pregnant Peruvian women during the third trimester of pregnancy (33 +/- 1 wk gestation). Of these 47 women, 30 received daily prenatal supplements from wk 10-24 of pregnancy until delivery. Supplements contained 60 mg of Fe and 250 microg of folate without [iron group (Fe), n = 16] or with [iron and zinc supplemented group (Fe + Zn), n = 14] 15 mg of Zn. The remaining 17 women [unsupplemented control group (C)] received no prenatal supplementation. Zinc concentrations were measured in plasma, urine and cord blood and percentage zinc absorption was determined following dosing with oral ((67)Zn) and intravenous ((70)Zn) stable zinc isotopes. Percentage zinc absorption was significantly lower than controls in fasting women receiving iron- containing prenatal supplements (20.5 +/- 6.4 vs. 20.2 +/- 4.6 vs. 47.0 +/- 12.6%, Fe, Fe + Zn and C groups, respectively, P: < 0.0001, n = 40). Plasma zinc concentrations were also significantly lower in the Fe group compared to the C group (8.2 +/- 2.2 vs. 9.2 +/- 2.2 vs. 10.9 +/- 1. 8 micromol/L, Fe, Fe + Zn and C groups, respectively, P: = 0.002), and cord zinc concentrations were significantly related to maternal plasma Zn levels (y = 6.383 + 0.555x, r = 0.486, P: = 0.002). The inclusion of zinc in prenatal supplements may reduce the potential for iron supplements to adversely influence zinc status in populations at risk for deficiency of both these nutrients.
Assuntos
Absorção Intestinal/efeitos dos fármacos , Ferro/farmacologia , Gravidez/metabolismo , Zinco/farmacocinética , Adulto , Análise de Variância , Suplementos Nutricionais , Feminino , Sangue Fetal/metabolismo , Humanos , Ferro/uso terapêutico , Peru , Terceiro Trimestre da Gravidez , Zinco/administração & dosagem , Zinco/sangue , Zinco/urinaRESUMO
BACKGROUND: It is estimated that 60% of pregnant women worldwide are anemic. OBJECTIVE: We aimed to examine the influence of iron status on iron absorption during pregnancy by measuring supplemental iron absorption, red blood cell iron incorporation, and iron status in pregnant women. DESIGN: Subjects were 45 pregnant Peruvian women (33+/-1 wk gestation), of whom 28 received daily prenatal supplements containing 60 mg Fe and 250 microg folate without (Fe group, n = 14) or with (Fe+Zn group, n = 14) 15 mg Zn, which were were consumed from week 10 to 24 of gestation until delivery. The remaining 17 women (control) received no prenatal supplementation. Iron status indicators and isotopes were measured in maternal blood collected 2 wk postdosing with oral (57Fe) and intravenous (58Fe) stable iron isotopes. RESULTS: Maternal serum ferritin and folate concentrations were significantly influenced by supplementation (P < 0.05). Serum iron was also significantly higher in the Fe than in the Fe+Zn (P < 0.03) or control (P < 0.001) groups. However, the supplemented groups had significantly lower serum zinc concentrations than the control group (8.4+/-2.3 and 10.9+/-1.8 micromol/L, respectively, P < 0.01). Although percentage iron absorption was inversely related to maternal serum ferritin concentrations (P = 0.036), this effect was limited and percentage iron absorption did not differ significantly between groups. CONCLUSIONS: Because absorption of nonheme iron was not substantially greater in pregnant women with depleted iron reserves, prenatal iron supplementation is important for meeting iron requirements during pregnancy.
PIP: The influence of iron status on iron absorption during pregnancy was examined among pregnant Peruvian women. This was done by measuring supplemental iron absorption, red blood cell iron incorporation and iron status. The subjects were 45 pregnant Peruvian women (33 +or- 1 week gestation) who were divided into 2 groups. The first group of 28 pregnant women received daily prenatal supplements containing 60 mg of iron and 250 mcg of folate with or without 15 mg of zinc, from week 10 to 24 of gestation until delivery. The second group of 17 women served as the control group. The control group was not given prenatal supplementation. The iron status indicators and isotopes were measured in maternal blood collected 2 weeks postdosing with oral iron-57 and intravenous iron-58 stable isotopes. The results showed that supplementation significantly influenced the maternal serum ferritin and folate concentrations (P 0.05). The serum iron of the iron group was significantly higher than that of the iron + zinc group (P 0.03) or control group (P 0.001). However, the serum zinc concentrations were lower in the supplemented group than in the control group. Even though the percentage of iron absorption was inversely related to maternal serum ferritin concentration, the effect was limited and the percentage of iron absorption did not differ significantly between the two groups. Considering that the absorption of nonheme iron was not substantially greater in pregnant women with depleted iron reserves, it was concluded that prenatal iron supplementation is essential for meeting iron requirements, especially during pregnancy.
Assuntos
Ferro/farmacocinética , Cuidado Pré-Natal , Zinco/administração & dosagem , Administração Oral , Adolescente , Adulto , Feminino , Ferritinas/metabolismo , Humanos , Injeções Intravenosas , Absorção Intestinal/efeitos dos fármacos , Ferro/administração & dosagem , Ferro/sangue , Estado Nutricional , Peru , Pobreza , Gravidez , Zinco/farmacologiaRESUMO
To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1. 96 +/- 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 +/- 7.7 vs. 109.4 +/- 8.4 nmol/L, P = 0.001) than in CAU girls, but 1, 25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls.
Assuntos
Calcifediol/sangue , Cálcio/metabolismo , Hispânico ou Latino , Absorção , Composição Corporal , Densidade Óssea , Calcitriol/sangue , Cálcio/urina , Criança , Feminino , Hormônio Foliculoestimulante/sangue , Humanos , Cinética , Hormônio Luteinizante/sangue , México/etnologia , Hormônio Paratireóideo/sangue , Estações do Ano , TexasRESUMO
HYPOTHESIS: Provision of more bioavailable mineral sources as human milk supplements enables very low birth weight (VLBW) infants to meet the intrauterine accretion rate for calcium and phosphorus. DESIGN: Comparison of currently formulated human milk fortifier with previous formulation. SETTING: Neonatal level II and III nurseries. PATIENTS: Twenty-six healthy, VLBW infants, whose mothers chose to breast-feed. INTERVENTIONS: We tested the effects of two formulations designed for VLBW infants as human milk supplements and differing primarily in their quantity and source of Ca, P, and magnesium. The study interval began with a milk intake of 100 ml.kg-1.day-1 and ended when a body weight reached 2.0 kg. MAIN OUTCOME MEASURES: Net absorption and retention of Ca, P, and Mg during a nutritional balance study conducted once during the study interval, growth during the entire study interval, and bone mineral content of the radius were measured at the beginning and end of the study interval. RESULTS: The newer Ca gluconate-glycerophosphate preparation (given to group CaGP) resulted in greater net absorption and retention of Ca and P (p < 0.01) than in infants given Ca phosphate (group CaTB). Mg retention was greater than (in group CaGP) or equivalent to (in group CaTB) the intrauterine accretion rate. Radius bone mineral content was significantly greater in group CaGP than in group CaTB (p < 0.001). Volumes of the fortified human milk preparation needed to meet the needs for gain in body weight were higher in group CaGP than in group CaTB (p < 0.001). CONCLUSIONS: Intrauterine accretion rates for Ca and P can be achieved when VLBW infants are fed human milk supplemented with Ca gluconate-glycerophosphate. Supplementation of human milk with Mg may not be indicated. In this study, greater intakes of Ca and P, and not improvements in bioavailability, result in improved net retention and bone mineral content of VLBW infants.
Assuntos
Osso e Ossos/metabolismo , Cálcio/farmacocinética , Alimentos Fortificados , Recém-Nascido de Baixo Peso/metabolismo , Leite Humano/metabolismo , Fósforo/farmacocinética , Absorção , Disponibilidade Biológica , Densidade Óssea , Humanos , Recém-Nascido de Baixo Peso/crescimento & desenvolvimento , Recém-Nascido , Magnésio/farmacocinéticaRESUMO
We evaluated seven female adolescents with anorexia nervosa to determine whether calcium metabolism was affected by their disorder. We measured calcium absorption, urinary calcium excretion, and calcium kinetics, using a dual-tracer, stable-isotope technique during the first weeks of an inpatient nutritional rehabilitation program. Results were compared with those from a control group of seven healthy adolescent girls of similar ages. The percentage of absorption of calcium was lower in subjects with anorexia nervosa than in control subjects (16.2% +/- 6.3% vs 24.6% +/- 7.2%; p < 0.05). Urinary calcium excretion was greater in subjects with anorexia nervosa than in control subjects (6.4 +/- 2.5 vs 1.6 +/- 0.7 mg.kg-1 x day-1; p < 0.01) and was associated with bone resorption rather than calcium hyper-absorption. Calcium kinetic studies demonstrated a decreased rate of bone formation and an increased rate of bone resorption. These results suggest marked abnormalities in mineral metabolism in patients with anorexia nervosa. From these results, we hypothesize that improvement in bone mineralization during recovery from anorexia nervosa will require resolution of hormonal abnormalities, including hypercortisolism, in addition to increased calcium intake.
Assuntos
Anorexia Nervosa/metabolismo , Cálcio da Dieta/farmacocinética , Cálcio/metabolismo , Absorção , Adolescente , Adulto , Anorexia Nervosa/complicações , Anorexia Nervosa/dietoterapia , Densidade Óssea , Reabsorção Óssea/complicações , Reabsorção Óssea/metabolismo , Feminino , Humanos , Hidrocortisona/metabolismoRESUMO
Mineral homeostasis often is disrupted in the very low birth weight (VLBW) infant fed either human milk or commercial formula that contains insufficient quantities of available calcium (Ca) and phosphorus (P). Alterations in mineral homeostasis include abnormal patterns of serum (Ca and P concentrations and alkaline phosphatase activity) and urine (Ca and P) biochemical markers, low net Ca and P retentions in comparison with intrauterine estimates of mineral accretion, and decreased bone mineral content. A two-phase study was conducted in our laboratory to test for these alterations in mineral homeostasis. In phase 1, VLBW infants fed a preparation of fortified human milk (either human milk-derived fortifier I or II or cow milk-derived fortifier) or cow milk-based formula specially designed for VLBW infants were evaluated during their hospitalization. In phase 2, after hospitalization, these infants were evaluated during the first 6 months of life when fed either their mother's milk or routine formula exclusively. The bioavailability of Ca and P from the tested preparations varied widely. Although the fortification of human milk resulted in both an improved biochemical pattern and net retention of Ca and P, optimal intrauterine mineral accretion was not achieved in any group tested. Longitudinal assessments of bone mineralization, by single photon absorptiometry, demonstrated that human milk-fed former VLBW infants had reduced bone mineral content. These investigations suggest that former VLBW infants fed human milk exclusively may be at risk for Ca and P deficiencies.
Assuntos
Osso e Ossos/metabolismo , Alimentos Fortificados , Alimentos Infantis , Recém-Nascido de Baixo Peso , Leite Humano , Minerais/metabolismo , Animais , Osso e Ossos/diagnóstico por imagem , Cálcio da Dieta/administração & dosagem , Bovinos , Homeostase , Humanos , Recém-Nascido , Leite , Necessidades Nutricionais , Fósforo/administração & dosagem , CintilografiaRESUMO
Growth, 96-hour balance of nutrients (nitrogen, fat, calcium (Ca), phosphorus (P), and magnesium), metabolizable energy, and serum biochemical markers of mineral status (Ca and P concentrations and alkaline phosphatase activity) were measured in 22 very low birth weight infants to investigate the bioavailability of minerals from specialized formula and from human milk fortifiers. The intakes of Ca and P were similar between group FORM ("Preemie" SMA) and group CMF (1:1 wt/wt, human milk and Similac Natural Care or Similac Special Care). The intakes of nitrogen, energy, fat, and magnesium differed between groups. Group CMF had significantly greater fecal losses and significantly lower absorption and retention of Ca and P in comparison with those of group FORM. Retention of Ca and P in both groups, however, was greater than 25% below intrauterine estimates of accretion. Retention rates of Ca, P, and magnesium were not correlated with their respective intakes. Weight gain during the balance study and during the entire study interval was significantly less in group CMF. The ratio of Ca retention to either weight gained or nitrogen retained was lower in group CMF, which suggested that the low retention of Ca was related less to the slower rate of growth in these infants than to their greater fecal losses of Ca. Although the cause of the greater fecal losses of Ca and P in this group is unclear, the data suggest an insolubility of the mineral sources. Our results indicate that sole reliance on the absolute mineral concentrations of the milk selected for very low birth weight infants may be unrealistic; the bioavailability of Ca and P from particular mineral sources should be evaluated.
Assuntos
Cálcio/farmacocinética , Alimentos Infantis , Recém-Nascido de Baixo Peso/metabolismo , Leite Humano , Fósforo/farmacocinética , Absorção , Disponibilidade Biológica , Peso Corporal , Metabolismo Energético , Fezes/metabolismo , Humanos , Recém-NascidoRESUMO
The bone mineral status of former very low birth weight infants previously fed fortified human milk was evaluated during the posthospitalization period. Anthropometric measurements, bone mineral content, bone width, serum calcium, phosphorus, and albumin concentrations, and alkaline phosphatase activity were evaluated at 10, 16, and 25 postnatal weeks. Infants were fed either commercial formula or unfortified human milk after their hospital discharge. At 16 and 25 weeks postnatally, human milk-fed infants (group HM) had lower bone mineral content (P less than 0.01), bone mineral content/bone width ratio (p less than 0.01), serum phosphorus concentration (p less than 0.03), and higher alkaline phosphatase activity (p less than 0.01) than commercial formula-fed infants (group CM). Growth was similar in both groups. Bone mineral content was correlated positively to serum phosphorus (r = 0.52, p less than 0.05) and inversely to alkaline phosphatase activity (r = -0.63, p less than 0.01) at 25 weeks postnatally. The use of serum biochemical markers, however, could account for only 44% of the variability in bone mineral content. The exclusive feeding of human milk to very low birth weight infants after hospital discharge may place them at risk for mineral deficiencies.