Bioavailability, iron

Casein-derived phosphorylated peptides are believed to enhance the bioavailability of calcium from milk and dairy products (Pihlanto and Korhonen, 2003), and a phosphopeptide derived from (3-casein has been shown to increase iron bioavailability (Bouhallab et ah, 2002 Peres, 1999). Other casein-derived peptides have been found to contain antihypertensive activity in rats (Leclerc et ah, 2002 Miguel et ah, 2009). A number of casein fragments demonstrate antibacterial activity (Kilara and Panyam, 2003). 

The regulatory network of IRPs appears also to connect the synthesis of protoporphyrin IX in erythroid cells, and of certain mitochondrial iron-sulfur proteins to iron bioavailability (reviewed in Hentze and Kuhn, 1996). mRNAs encoding erythroid... 

On the other hand, the uptake of colloidal iron has been studied in greater detail. For example, some bacteria have been demonstrated to reduce ferric oxide particles to increase iron bioavailability [341,342], As was observed in Section 5.2.4, Fe reaction kinetics with metal carriers are thought to be rate-limiting. In the presence of colloidal iron, the thermodynamic stability or... 

The effecf of fhe source of Ca on fhe magnifude of Ca-Fe interactions in vivo was assessed in rodents (Smith, 1988), using a whole body radioisotopic retention test as an endpoint to determine true iron bioavailability (i.e., Fe that is absorbed and utilized). A single 50 gg liquid dose of Fe-labeled FeCla was administered by oral gavage to rats at a Ca Fe ratio of 60 1 and 120 1 fo replicate a human iron intake of 15 mg/day and a Ca intake of 800 mg/day or 1600 mg/day, respectively. Ca sources included CaCOa, Ca Phosphate (CaP), bone meal, and Ca hydroxyapatite (CaHA), while the control dose contained no Ca and was normalized to represent 100% Fe retention for comparison purposes. Isotope counts were performed immediafely after dosing (to measure 100% retention) and subsequent counts over 6 days were divided by the 100% count to estimate Fe retention. For CaCOa, Fe retention was 68% at a Ca Fe ratio of 60 1, and only declined a furfher 2% when the ratio was increased to 120 1. Fe retention values for ofher forms of Ca at a 60 1 Ca Fe ratio were as follows 77% for bone meal, 89% for CaP, and 99% for CaHA. Fe retention decreased in response to the higher Ca Fe ratio of 120 1 (i.e., Fe retention in the presence of bone meal, CaHA, and CaP was 49%, 72%, and 78%, respecfively). This is indicative of a dose-response effect of Ca on Fe retention. This sfudy also underscored fhe importance of the source of Ca in relation fo Fe refenfion. 

Prather, T. A., and Miller, D. D. (1992). Calcium carbonate depresses iron bioavailability in rats more than calcium sulphate or sodium carbonate. /. Nutr. 122, 327-332. 

Roughead, Z.K., Zito, C. A., and Flunt, J. R. (2002). Initial uptake and absorption of nonheme iron and absorption of heme iron in humans are unaffected by the addition of calcium as cheese to a meal with high iron bioavailability. Am. ]. Clin. Nutr. 76, 419 25. 

Iron bioavailability. Oil, administered to suckling rats dosed with Fe-laheled diet, produced a higher percentage of Fe in the blood than those fed other fat sources. Administration to weanling rats produced a significantly higher percentage of Fe retention than rats fed a formula-hlend fat diet . 

GN168 Pabon, M. L., and B. Lonnerdal. Effects of type of fat in the diet on iron bioavailability assessed in suckling and weanling rats. J Trace Elem Med Biol 2001 15(1) 18-23. 

Much of the current research has centered upon the role of phytic acid on zinc and iron bioavailability (110-124). Work performed at the authors institution with several different types of soy foods suggests that phytic acid is a major factor affecting availability of zinc from foods derived from the legume (110-114). In addition, it appears that endogenous zinc in high-phytate foods may be a limiting factor in optimal utilization of these foods for man. We have found that fortification of soy foods (under proper conditions) with zinc, iron, magnesium, or calcium results in excellent... 

Investigations have focused on the content or polyphenolics. tannins, and related compounds in various foods and the influence on nutrient availability and protein digestibility. It has been established that naturally occurring concentrations ofpolyphcnoloxtda.se and polyphenols in products such as mushrooms can result in reduced iron bioavailability. Likewise, several studies have locused on decreased protein digestibility caused hy the tannins of common beans and rapeseed (canola). 

May depend on iron "bioavailability" though iron may be present in the diet, it may not be absorbed because of the presence of various binding agents such as phytate. 

Iron bioavailability may be increased in the presence of meat (Politz and Clydesdale 1988). This is the so-called meat factor. The exact mechanism of this effect is not known, but it has been suggested that amino acids or polypeptides that result from digestion are able to chelate nonheme iron. These complexes would facilitate the absorption of iron. In nitrite-cured meats some factors promote iron bioavailability (the meat factor), particularly heme iron and ascorbic acid or erythor-bic acid. Negative factors may in-clude nitrite and nitrosated heme (Lee and Greger 1983). 

While a wide range of light-mediated transformations of iron are possible, it is important to place these transformations in perspective and assess the extent of their occurrence in natural aquatic systems. Within this context, evidence from field studies for light-mediated transformations of iron is reviewed in Sect. 4 and a brief discussion provided of the implications of these transformations to both iron bioavailability and contaminant mobilisation. 

The acid enviromnent of the stomach provides a mechanism for solubifizing finely divided metalhc iron as well as metal hydroxides prior to their entry into the small intestine. There, neutrahzation in the presence of suitable ligands makes the iron bioavailable. The oldest form of iron fortification employed iron filings added to sweet wine. Today, colloidal metallic iron, ferrum reductum, is still a widely used fortificant in food. 

Absorption of iron from the diet is an inefficient process which may be enhanced or inhibited by the iron status of the individual consuming the diet, the form of iron in individual foods, and interactions between foods consumed in a single meal (1-4) Because of this, estimates of iron bioavailability obtained from iron absorption measurements are necessary in... 

Some trace-metal transport systems are even more complex than the one described in Figure 5 and involve the release of metallophores into the medium. The archetypes of these—and the only ones characterized so far—are the side-rophores produced by various species of marine bacteria to acquire iron. In the model organisms in which they have been characterized, the mechanisms of uptake are quite varied and complex, often involving intermediate siderophores in the peri-plasmic space and several transport proteins (Neilands, 1981). The effect of such siderophores on iron bioavailability is clearly not the same as that of EDTA. While complexation by a siderophore makes iron directly available to the bacteria which take up the complex (and whose rate of iron uptake is proportional to FeY), it drastically reduces the bioavailability of iron to most other organisms (whose rate of iron uptake is proportional to Fe ). For organisms which are able to promote the release of iron from the siderophore, e.g., by reduction of Fe(III), the effect of complexation is a less drastic decrease in iron... 

Efficiency of Hemoglobin Regeneration as a Method of Assessing Iron Bioavailability in Food Products... 

The bioavailability of iron from any source (e.g., iron supplement, food or meal composite) is considered to be that portion of the total iron which is metabolizable. Philosophically, this concept is important because the amount of iron utilized by avian and mammalian species is directly associated with iron need. When assaying iron bioavailability, it is therefore necessary to use an organism whose need will exceed the amount provided. In animal assays of iron bioavailability, iron need is assured by a growth phase and/or creation of iron deficiency through feeding an iron deficient diet and phlebotomy. Because healthy subjects are usually used in human assays of iron bioavailability (Cook et al., 1981 Cook and Monson, 1976 Radhakrishman and Sivaprasad, 1980), it is inappropriate to compare the data obtained from animal and human assays. In fact it is questionable if assays of iron bioavailability yield good information on the quantities of metabolizable iron available when healthy human subjects are used. 

In ten cases, Che corrected values were less than the uncorrected ones. Because of this inconsistency and because correction does not reduce variability within nor among experiments, attempting to correct for the iron contribution of Che basal ingredients Co Che hematinic response does not seem to improve this assay of iron bioavailability. 

An extensive series of studies performed at the FDA Division of Nutrition established a wide range of bioavailabilities for the iron sources used in food enrichment (8-12). However, the rank in Table 11 was based on direct feeding of the iron source to test animals. The impact of food processing or of the food matrix on iron bioavailability is not apparent in these rankings. Large differences in bioavailability between iron sources will become smaller or change completely as a result of some types of processing, while other processes have little effect. 

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