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Iron is a trace element involved in many cardinal metabolic processes of almost all living organisms. It is well known that iron participates in oxygen transport as well as it is a cofactor in many fundamental enzymatic and nonenzymatic processes. Accordingly, disturbances of iron homeostasis can cause serious clinical consequences. In humans, dietary iron can enter the body in two main forms: heme and nonheme. The former is a component of many hemoproteins (including myoglobin, hemoglobin, cytochromes b and c) and is easily absorbed in the duodenal enterocytes. Red meat is an excellent source of heme iron, while the less bioavailable nonheme form is found in large amounts in milk products and vegetables. For this reason, consumers of meat have a better iron status than vegetarians and vegans. The aim of this paper was to discuss the role of heme iron in the human diet. Heme iron found in muscle protein should be supplied to humans to prevent iron deficiency, which can lead to anemia. It is easily absorbed by the human body and its main source is red meat. In addition, heme iron, which is mainly found in myoglobin in meat, contributes to the desirable bright red color and to the most undesirable brown color of meat. Both heme and nonheme iron are catalysts of lipid oxidation in meat. This process lowers the nutritive value through oxidation of polyunsaturated fatty acids, which produces an undesirable flavor and aroma. The present review is focused on the role of heme iron, which is mainly found in meat and is the principal source of iron in the human diet.
Background. Fortified food products contain usually higher amounts of certain nutrients. However, the information about the nutritional quality of such products is limited. The objective of this study was to determine the content and the release of iron from fortified and non-fortified food products available on the Polish market. Material and methods. A group of 29 fortified with Fe and non-fortified food products, such as cereal products (16) and confectionaries (13), were purchased from local market between October and November 2009. The content of Fe in these products, as well as the amount of Fe released in enzymatic digestion in vitro was determined by the flame atomic absorption spectrometry method. Results. It was found that most of the fortified with Fe food products had significantly higher amount and the potential bioavailability of this element in comparison with the non-fortified analogues, however the content of Fe determined analytically not always matched the values declared on the label. Conclusions. Products fortified with Fe appear to be better sources of potentially bioavailable Fe in comparison with the non-fortified analogues.
Ferric iron reductases activities have been occurred in 91% of investigated enterococci strains. Maximum activity occurred with coenzyme NADH as the reductant and the presence of cofactor FMN was necessary. Mg(II) ions has not stimulated reductases activity. Treatment of cells with proteolytic enzymes had not effect on iron reduction. The whole cells and cell fraction - cytoplasmic membrane and cytoplasm showed Fe(III) - reducing activity. The highest specific activity was associated with cytoplasm. The activity in cytoplasmic membrane was not related to iron concentration in the growth medium. In cytoplasm the activity was stimulated after growth in low-iron medium. Ferric iron reductases of enterococci characterized the broad substrate specificity. The iron in form of ferric ammonium citrate, lactoferrin and ferrioxamine B were the best iron sources for enterococcal ferric iron reductases.
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