Efeito da suplementação com ferro na biodisponibilidade de zinco em uma dieta regional do nordeste do Brasil Effects of supplementation with iron on the bioavailability of zinc in the regional diet of northeastern Brazil

Foram investigados os efeitos da suplementação com ferro na biodisponibilidade de zinco de uma dieta "regional" do Nordeste (DRNE), em ratos albinos Wistar, consumindo rações à base da referida dieta (DRNE) e rações controle. As rações DRNE, continham 16 mg de Zn/kg e níveis de 35 mg, 70 mg e 140mg Fe/kg. As rações controle foram elaboradas segundo o "Committee on Laboratory Animal Diets", contendo níveis de proteína, ferro e zinco ajustados aos das rações experimentais DRNE. Os parâmetros utilizados para medir a biodisponibilidade do zinco foram: Índice de Absorção Aparente do Zn e nível total de Zn nos fêmures. Os resultados obtidos demonstraram que a suplementação com ferro diminuiu a biodisponibilidade do Zn, e os efeitos dessa interferência foram influenciados pela qualidade da dieta e pelas proporções Fe:Zn. Tal fato deve ser considerado nas práticas que envolvem fortificação de alimentos e/ou suplementos medicamentosos, comuns nas populações com carências nutricionais.<br>The effects of supplementation with iron on the zinc bioavailability of the regional diet of northeastern Brazil (RDN), were investigated. One assay with Wistar rats, feed on RDN and control diets was carried out. The RDN diets contained 16 mg Zn/kg and levels of 35 mg, 70 mg and 140 mg Fe/kg, respectively. The control diets were prepared according to the standards of the Committee on Laboratory Animal Diets, with levels of protein, iron and zinc identical to those of RDN diets. Index of apparent absorption and zinc retained in the femur of the animals were the parameters utilized to measure zinc bioavailability. The results demonstrated that the supplementation with iron decreased the zinc bioavailability, and the effects were seen to affect diet quality and the Fe:Zn ratio. This fact must be taken into consideration in practices such as the fortying of foodstuffs and the administration of vitamin-mineral supplements to populations with nutritional deficiencies

Structural and motivational mechanisms of academic achievement: a mediation model of social‐background effects on academic achievement

This paper takes up ongoing discussions on the inequality of educational opportunities and formulates a conceptual model to link separate lines of research. Our particular focus is on combining motivational and structural approaches into a mediation model that explains differences in academic achievement. In the literature, four main mechanisms of social reproduction are discussed. Two main pathways refer to (1) parents’ expectations regarding their children’s academic success and (2) replicating cultural capital through intra‐familial cultural practices. (3) Parents’ perception of children’s abilities depends on social position and is influential for expectations of success. (4) For all three pathways, we expect effects on students’ motivational characteristics, which in turn influence academic achievement. We test our conceptual model by structural equation modelling using longitudinal data from primary school students in Germany. Empirical evidence is in line with the assumptions in the model. Cultural reproduction and expectations of success can be seen as the key components of the model. However, both chains of reproduction are related to each other by parents’ perception of child’s ability, and their effects are mediated by child’s motivational characteristics

The Reliability of Family Background Effects on Status Attainment: Multiple Informant Models

status attainment, reliability, family background, structural equation models, measurement error,