Iron absorption estimation

However, it has been estimated that about 80% of the daily dietary intake of iron is in the form of non-heme iron and only about 20% from heme iron. Hence, any product added to the diet which causes a significant decrease in non-heme iron absorption is of concern. 

Iron absorption. Tea, administered by gastric intubation to rats, did not affect iron absorption when tea was consumed for 3 days but when delivered in tea the absorption was decreased. Rats maintained on a commercial diet were fasted overnight with free access to water and then gavaged with 1 mL of Fe labeled FeC13 (0.1 mM or 1 mM) and lactulose (0.5 M) in water or black tea. Iron absorption was estimated from Fe retention. Intestinal permeability was evaluated by lactulose excretion in the urine. Iron absorption was lower with given with tea at both iron concentrations but tea did not affect lactulose excretion "". ... 

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... 

To determine iron absorption with tracers, a known amount of an iron tracer is given orally either by itself or with a meal. The appearance of the tracer, either in the feces or in whole blood, is monitored. In the fecal monitoring method, the feces are collected quantitatively. The collection period may last from as few as 3 (5) to as long as H days (6). Iron absorption is then estimated from the difference between the total amounts of tracer ingested and excreted. Probably, the most common and serious error in this method is introduced by incomplete fecal collection. 

Variability in Absorption Estimates In this study, the occurrence of a negative absorption value for one subject and the absence of a significant vitamin C effect raise some questions about the accuracy of the method However, the expected changes in absorption due to dietary treatments may be masked by the analytical variations associated with absorption measurements and biological variabilities of iron absorption Analytical variations can be introduced at several stages of the analytical procedures incomplete fecal collection, inhomogeneous samples, iron contamination, incomplete colorimetric reaction, non-quantitative recovery after chemical ashing, and variations in isotopic measurements due to ion statistics, memory effects, instrument drift, etc Some of these are not as serious as others, for example, contamination with natural iron woiold not affect the estimate of tracer concentrations provided it occurs before the total iron content is measured ... 

Errors associated with iron quantification and abimdance measurements are common to both fecal monitoring and hemoglobin incorporation methods According to Janghorbani and Young (2 )> acceptable absorption estimates can be obtained if the precision of these measurements is kept below 5% The analytical procedures developed in this study are thus considered satisfactory since the relative standard deviation was 2 48% for total iron quantification and less than 2% for ion abimdance determinations ... 

In a series of studies conducted on human volunteers in the Division of Human Nutrition and Biology at the Institute of Nutrition of Central America and Panama, we employed the radiocobalt absorption test in the context of iron absorption tests. We used a modification of a 6-h cobalt excretion test to estimate absorption (44). Approximately 2.5 fiCi of cobalt-60 mixed with 4.74 mg (20 fimol) of cobalt chloride hexahy-drate was given in 100 mL of water after an overnight fast. The subjects remained fasting for 2 h postingestion and then consumed a standard breakfast. A liter or more of water was consumed during the final 4 h of the study. All urine produced during the 6 h was collected the excreted radioactivity was measured in a well-type y-counter. 

Prevention of iron deficiency in populations not sustaining chronic blood loss is possible by judicious selection of diets which enhance the bioavailability of dietary iron. The recent decades have produced significant research on the availability of iron as it is affected by various dietary components, those which enhance as well as those which inhibit iron absorption. This has allowed for the first time the quantification of dietary effects on a trace metal and the development of a model whereby the quantity of bioavailable iron in a diet may be estimated. 

Absorption of heme iron is estimated to be 23% for the reference individual. Heme iron may be estimated at 40% of the iron in meat, fish and poultry. Nonheme iron would be calculated as the remaining 60% of meat, fish and poultry iron plus the iron in vegetables, grain and other foods. The available nonheme iron and heme iron from each meal and snack can be summed to calculate the total day s available iron. 

Beaton, 1974). After adding to this amount the basal iron losses and applying the estimate of the upper limit of iron absorption adopted by the Canadian committee for subjects with iron stores, the risk curve for iron can be portrayed as in Fig. 2B. The underlying concepts and interpretations of the curves in Fig. 2A and Fig. 2B are consistent. The shape of the requirement distributions differs. 

The above approach is based on estimates of blood volume and efficiency of erythrocyte incorporation of the isotopic label, unless it is determined directly in the studied subject. These potential sources of bias cancel out for relative measurements to compare iron absorption from one test meal against another in the same individual. This is possible by using two different isotopes, such as Fe and Fe, to label meals differently, which are then fed on two consecutive days [9,44]. 

Iron consists of four stable isotopes, Fe, Fe, Fe, and Fe, with average natural abundances of 5.84, 91.75, 2.1, and 0.28%, respectively. Because most functional body iron is present in blood, which is easily accessible to sampling, studies on iron absorption and utilization are nowadays mostly based on the incorporation and subsequent isotopic analysis of iron in red blood cells [9]. As explained earlier, the amount of iron isotopic label in circulation that has been absorbed can be assessed either by estimating blood volume and circulating iron [44] or by injection of a second isotopic label after test meal intake that serves as a reference [45-47]. 

Laby21 demonstrated in 1930, with a photographic plate as detector, that copper or iron in zinc could be detected in concentrations approaching 1 part per million by weight. To be sure, he used electron excitation so that absorption effects were minimized (7.10). By contrast, attempts made in the authors laboratory to estimate alkaline-earth metals in brines were unsuccessful, primarily because of the high absorption effects that accompanied x-ray excitation. The use of dilution with a relatively transparent solvent can sometimes reduce or eliminate absorption effects (7.8), but this procedure will fail if the element to be determined is present at too low a concentration in the presence of another substance (the salt in brine in the example cited) primarily responsible for the absorption effect. A case in which dilution is helpful in connection with the absorption effect of the. element sought is that of tetraethyllead fluid in gasoline (7.13). 

The experimental results imply that the main reaction (eq. 1) is an equilibrium reaction and first order in nitrogen monoxide and iron chelate. The equilibrium constants at various temperatures were determined by modeling the experimental NO absorption profile using the penetration theory for mass transfer. Parameter estimation using well established numerical methods (Newton-Raphson) allowed detrxmination of the equilibrium constant (Fig. 1) as well as the ratio of the diffusion coefficients of Fe"(EDTA) andNO[3]. 

Porphyrin is a multi-detectable molecule, that is, a number of its properties are detectable by many physical methods. Not only the most popular nuclear magnetic resonance and light absorption and emission spectroscopic methods, but also the electron spin resonance method for paramagnetic metallopor-phyrins and Mossbauer spectroscopy for iron and tin porphyrins are frequently used to estimate the electronic structure of porphyrins. By using these multi-detectable properties of the porphyrins of CPOs, a novel physical phenomenon is expected to be found. In particular, the topology of the cyclic shape is an ideal one-dimensional state of the materials used in quantum physics [ 16]. The concept of aromaticity found in fuUerenes, spherical aromaticity, will be revised using TT-conjugated CPOs [17]. 

An extractive spectrophotometric procedure based on the complexation of reduced Iron(II) with 5-Chloro-7-iodo-8-hydroxyquinoline (CIHQ) for the estimation of micro amounts of vitamin C. The resulting brown colored complex was extracted into chloroform to give a reddish brown extract which shows an absorption band at 485 nm. This chelate was formed immediately and the apparent molar absorptivity and Sandell s sensitivity for vitamin C was found to be 8.5 x 105 dm3 mol"1 cm 1 and 2.072xl0 4g cm 2. Linear relationship between absorbance and concentration of ascorbic acid is observed up to 0.8 pg ml"1. Interference studies of different substances including sugars, vitamins and amino acids, metal ions and organic acids were carried out. The utility of the method was tested by analysing some of the marketed products of vitamin C... 

WARNING Anaphylactic Rxns w/ use use only if oral Fe not possible administer where resuscitation techniques available Uses Fe deficiency when cannot supl PO Action Fe supl Dose Adul. Iron defic anemia Estimate Fe deficiency, give 25-100 mg IM/IV /d until total dose total dose (mL) = [-.0442 x (desired Hgb - observed Hgb) x LBW] + (0.26 x LBW) Iron replacement, blood loss Total dose (mg) = blood loss (mL) x Hct (as decimal fraction) max 100 mg/d Peds >4 mo. As for adults max 0.5 mL (wt <5 kg), 1 mL (5-10 kg), 2 mL (>10 kg) p dose IM or direct IV Caution [C, M] Contra Anemia w/o Fe deficiency. Disp Inj SE Anaphylaxis, flushing, dizziness, inj site inf Rxns, metallic taste Interactions X Effects W/ chloramphenicol, X absorption of oral Fe EMS Anaphylactic Rxns common taking oral Fe t risk of tox and SEs OD May cause N/V, HA, muscle/joint pain and fev symptomatic and supportive Iron Sucrose (Venofer) [Iron Supplement] Uses Fe deficiency anemia w/ chronic HD in those receiving erythropoietin Actions Fe r lacement. Dose 5 mL (100 mg) IV on dialysis, 1 mL (20 mg)/min max Caution [C, M] Contra Anemia w/o Fe deficiency Disp Inj SE Anaphylaxis, -1- BP, cramps, N/V/D, HA Interactions i Absorption OF oral Fe supls EMS See Iron Dextran OD See Iron Dextran... 

The iron is transferred by the mucosal epithelium to the body and is bound to plasma transferrin in the ferric state. In the plasma, iron takes part in a dynamic transferrin-iron equilibrium and is distributed into vascular and interstitial extravascular compartment. 50 to 60% of transferrin is extravascular. The plasma iron pool in adults is about 3 mg and has an estimated turnover of 20 to 30 mg per 24 hours. Daily and obligatory losses of iron in healthy men are about 1 mg in healthy menstruating women these average 2 mg and in either case are compensated by a net absorption of 1 to 2 mg from the intestine, which enters the mobile pool of transferrin iron. 

Spectral Properties. The absorption spectra of these three pyrocatechase are very similar to each other. A concentrated solution of the enzyme shows a distinct red color with a broad absorption between 390 and 650 nm. The peak is at about 440 nm and the molecular absorbance at 440 nm is estimated to be 4,670s5. The trivalent iron bound to the enzyme is responsible for the visible absorption since the apo-enzyme shows neither significant absorption in the visible region nor enzyme activity which is restored upon reconstitution56. The visible absorption also de-... 

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