Iron absorption from infant formula and iron-fortified cow’s milk: experimental model in weanling rats

Abstract

Objective: To compare iron absorption from infant formula and iron-fortified cow's milk.Methods: Twenty-four weanling Wistar rats were maintained in metabolic cages during the whole experiment (10 days). On the first day, the animals were divided into three similar groups according to their weight, length, hematocrit and hemoglobin levels: 1) infant formula; 2) powdered whole cow's milk fortified with iron in the same quantity and type as the formula; 3) control -powdered whole cow's milk not fortified with iron. Deionized water and diet were offered ad libitum, and the volume consumed was measured. Weight, hematocrit, and hemoglobin levels were measured on the fifth and 10th days when length, fecal occult blood, and hepatic iron levels were also analyzed.Results: Group 1 consumed less diet (450.5±26.50 mL) than group 2 (658.8±53.73 mL) and control group (532.7±19.06 mL, p < 0.001). Hemoglobin levels were higher (p < 0.001) in group 1 (12.1±1.13 g/dL) than in group 2 (9.6±1.59 g/dL) and in control group (6.2±0.97 g/dL). Hepatic iron level showed the same pattern as hemoglobin (p < 0.001). There was no difference in weight and length between the three groups (p = 0.342). There was no fecal occult blood in the any of the animals. Conclusions:Despite the lower volume consumed, the group that received formula presented higher iron absorption and hemoglobin levels than the group fed with fortified whole cow's milk. Growth was similar in the three groups. J Pediatr (Rio J). 2009;85(5):449-454:Breast milk substitutes, dietary iron, biological availability, iron deficiency. ResumoObjetivo: Comparar a absorção do ferro da fórmula de partida e do leite de vaca integral fortificado. Métodos:Foram utilizados 24 ratos machos Wistar recém-desmamados, mantidos em gaiolas metabólicas durante todo o período do experimento (10 dias). No primeiro dia, os animais foram distribuídos em três grupos semelhantes quanto ao peso, comprimento, hematócrito e hemoglobina: 1) fórmula de partida para lactentes; 2) leite de vaca integral em pó fortificado com a mesma quantidade e tipo de sal de ferro da fórmula; e 3) controle -leite de vaca integral em pó não fortificado com ferro. Água e dieta foram oferecidas ad libitum com mensuração do volume consumido. Peso, hematócrito e hemoglobina foram mensurados no quinto e no 10º dia do experimento, quando foram analisados também comprimento, sangue oculto nas fezes e teor de ferro hepático.Resultados: O grupo 1 ingeriu menor volume de dieta (450,5±26,50 mL) que os grupos 2 (658,8±53,73 mL) e controle (532,7±19,06 mL; p < 0,001). As concentrações de hemoglobina foram maiores (p < 0,001) no grupo 1 (12,1±1,13 g/dL) que nos grupos 2 (9,6±1,59 g/dL) e controle (6,2±0,97 g/dL). O teor de ferro hepático apresentou o mesmo comportamento da hemoglobina (p < 0,001). Não foi observada diferença de peso e comprimento nos três grupos (p = 0,342). Não foi detectado sangue oculto nas fezes de nenhum dos animais. Conclusões:Apesar do menor volume ingerido, o grupo que recebeu fórmula apresentou maior abso...

Intestinal absorption of iron and calcium from soy and cow's milk-based infant formulas in weanling rats pups

“…The intention was to ensure that the animals had more than enough food available to meet their needs. Based on previous experience and nutritional content of the formulas, it was known that these volumes were sufficient, although this was confirmed during the experiment 28 . As the desire was to evaluate the absorption of minerals from the products analyzed, no adjustments for animal growth compared to rats fed an AIN-93G diet were made.…”

“…This experimental model allows us to evaluate the effects of a single fluid food, as occurs in the feeding of infants before the introduction of complementary foods. In this study, one group received a lactose-free cow's milk-based infant formula, as previous studies have found that weaned mice fed formula with higher amounts of lactose experienced loose stools, suggesting lactose intolerance 28 . Thus, a lactose-free reference product was used to compare to the soy-based infant formula.…”

“…This study used an experimental model previously developed in our laboratory that allowed us to evaluate the interactions of nutrients supplied to recently weaned rats fed exclusively with different types of fluid formulas used to feed infants [28][29][30] . Throughout the experiment, the animals in both groups did not receive rations other than their liquid foods.…”

“…The ten-day period was selected based on previous studies conducted on our service, which proved satisfactory to meet our goals [28][29][30] . Table 3.…”

“…To use of research resources rationally and to limit the number of animals used in experiments, it was considered unnecessary to set up a group fed a conventional diet (e.g., American institute of Nutrition-93G [AIN-93G]). That is, the objective was to analyze the tested formulas (which are used for human infants) rather than to meet the needs of experimental animals during the growth stage [28][29][30] .…”