Effect of milk and casein on the absorption of supplemental iron in the mouse and chick

Effect of iron fortification on microstructural, textural, and sensory characteristics of caprine milk Cheddar cheeses under different storage treatments

In this study, we manufactured 3 types of caprine milk Cheddar cheese: a control cheese (unfortified) and 2 iron-fortified cheeses, one of which used regular ferrous sulfate (RFS) and the other used large microencapsulated ferrous sulfate (LMFS). We then compared the iron recovery rates and the microstructural, textural, and sensory properties of the 3 cheeses under different storage conditions (temperature and duration). Compositional analysis included fat, protein, ash, and moisture contents. The RFS (FeSO₄·7H₂O) and LMFS (with 700- to 800-μm large particle ferrous sulfate encapsulated in nonhydrogenated vegetable fat) were added to cheese curds after whey draining and were thoroughly mixed before hooping and pressing the cheese. Three batches of each type of goat cheese were stored at 2 temperatures (4°C and -18°C) for 0, 2, and 4 mo. We analyzed the microstructure of cheese using scanning electron microscopy and image analysis software. A sensory panel (n = 8) evaluated flavors and overall acceptability of cheeses using a 10-point intensity score. Results showed that the control, RFS, and LMFS cheeses contained 0.0162, 0.822, and 0.932 mg of Fe/g of cheese, respectively, with substantially higher iron levels in both fortified cheeses. The iron recovery rates of RFS and LMFS were 71.9 and 73.5%, respectively. Protein, fat, and ash contents (%) of RFS and LMFS cheeses were higher than those of the control. Scanning electron microscopy analyses revealed that LMFS cheese contained smaller and more elongated sharp-edged iron particles, whereas RFS cheese had larger-perimeter rectangular iron crystals. Iron-fortified cheeses generally had higher hardness and gumminess scores than the control cheese. The higher hardness in iron-fortified cheeses compared with the control may be attributed to proteolysis of the protein matrix and its binding with iron crystals during storage. Control cheese had higher sensory scores than the 2 iron-fortified cheeses, and LMFS cheese had the lowest scores for all tested sensory properties.

The effect of dairy products on iron availability

Many researchers report substantial reductions in iron availability when dairy products are consumed with solutions of iron. Yet other studies indicate that dairy products have little effect on iron availability when added to complex meals. The conflicting data may be due to differences in the technique used to measure availability, species of animal used, form of iron in the diet, and meal composition. Human studies show superior bioavailability of iron in human milk when compared with cow's milk. Definitive causes for the differences between human and cow's milk have not been identified. Human milk contains lower amounts of casein, phosphate, and calcium, components thought to inhibit iron absorption. More work is needed to identify the factors that influence iron-dairy interactions. The nutritional benefits provided by dairy products outweigh the slight inhibitory effect they may have on iron availability.

Bioavailability of iron-milk-protein complexes and fortified cheddar cheese

Iron fortification is used to increase dietary iron intake. Dairy products are widely consumed but contain almost no iron. Cheddar cheese was fortified with ferric chloride or iron-casein, ferripolyphosphate-whey protein, and iron-whey protein complexes. Hemoglobin regeneration efficiency was determined to evaluate iron bioavailability. Maximal and basal iron bioavailabilities were measured in anemic weanling rats fed low iron diets (about 22 mg iron/kg) and normal adult rats fed high iron diets (about 145 mg iron/kg) of iron density (32 mg iron/1000 kcal) found in some high iron human diets. Maximal iron bioavailabilities for ferric chloride or iron-casein, ferripolyphosphate-whey protein, and iron-whey protein complexes were 85, 71, 73, and 72%, respectively, and for the respective iron-fortified cheeses they were 75, 66, 74, and 67%. Differences were not significant in maximal iron bioavailabilities among iron sources and between fortified cheeses and fortification iron sources. Basal iron bioavailabilities for 10-d feeding of the respective fortification iron sources were 5, 8, 6 and 7%, respectively, and 4, 4, 3, and 3% for 14 d feeding; the differences among the iron sources were not significant. Maximal and basal iron bioavailabilities of ferrous sulfate were 85 and 5%, respectively. Practical implications of these observations are discussed.

The oral assimilation of radiomanganese by the mouse

The metabolism of orally administered radiomanganese was studied in mice. Assimilation of absorbed manganese (Mn) was determined using whole body counting techniques. When(54)MnCl2 was administered, 2.7% of the dose was retained after 10 d compared with 1.2% from the(54)Mn-nitrilotriacetate (NTA) complex. However, this difference was accounted for by the rapid and persistent adsorption of the Mn onto the teeth of the lower jaw when fed as the ionic salt at pH 2.0 compared with the NTA-chelate fed at pH 9.0. Once corrected for the amount adsorbed onto the teeth, the biodistribution and relative specific activity of the assimilated radiomanganese into a variety of tissues were similar for both forms of the metal.

Distribution and metabolism of iron in muscles of iron-deficient rats

Iron-deficiency anemia leads directly to both reduced hemoglobin levels and work performance in humans and experimental animals. In an attempt to observe a direct link between work performance and insufficient iron at the cellular level, we produced severe iron deficiency in female weanling Sprague-Dawley rats following five weeks on a low-iron diet. Deficient rats were compared with normal animals to observe major changes in hematological parameters, body weight, and growth of certain organs and tissues. The overall growth of iron-deficient animals was approximately 50% of normal. The ratio of organ weight: body weight increased in heart, liver, spleen, kidney, brain, and soleus muscle in response to iron deficiency. Further, mitochondria from heart and red muscle retained their iron more effectively under the stress of iron deficiency than mitochondria from liver and spleen.Metabolism of iron in normal and depleted tissue was measured using tracer amounts of(59)Fe administered orally. As expected, there was greater uptake of tracer iron by iron-deficient animals. The major organ of iron accumulation was the spleen, but significant amounts of isotope were also localized in heart and brain. In all muscle tissue examined the(59)Fe preferentially entered the mitochondria. Enhanced mitochondrial uptake of iron prior to any detectable change in the hemoglobin level in experimental animals may be indicative of nonhemoglobin related biochemical changes and/or decrements in work capacity.