Food Iron Absorption Research Articles

Food iron absorption in patients with dermatitis herpetiformis

No abstract available.

Role of Gastric Acid in Food Iron Absorption

Radioiron absorption tests in human volunteers demonstrated a modest but significant 28% reduction in the absorption of dietary nonheme iron from a meal that was preceded by the administration of 300 mg cimetidine. More pronounced decreases of 42% and 65% were observed with 600 and 900 mg cimetidine, respectively. Antacid caused a 52% decrease in iron absorption whereas pentagastrin had no significant effect. Since 300 mg cimetidine reduces gastric acid secretion by 60%-80% but iron absorption by only 28%, it appears that under normal conditions more gastric acid is secreted than is required for optimal iron absorption; absorption falls only when acid secretion is markedly reduced. Cimetidine in the doses currently recommended would not be expected to have a major effect on iron nutrition, although the combination of high doses of cimetidine with antacids would impair nonheme iron absorption significantly.

Bioavailable nutrient density: a new concept applied in the interpretation of food iron absorption data

The nutritive value of a diet for a certain nutrient must be based on its ability to meet certain requirements for certain target groups. The current low energy intake makes it sometimes difficult to cover the requirements of certain nutrients from the diet. Thus, an important measure of the nutritive value of a food or a meal will be obtained if the amount of a nutrient absorbed is related to the energy content of the meal studied (bioavailable nutrient density). The amount of iron absorbed from a meal depends not only on its contents of heme and nonheme iron and on various dietary factors affecting the bioavailability but also on the iron status of the subjects studied. The bioavailability of iron in a meal must therefore be given for a certain iron status. Thus the following definition of bioavailable nutrient density for iron is suggested: The amount of iron (milligrams) absorbed from a meal per unit energy (1000 kcal) by subjects who are borderline iron deficient, i.e., nonanemic subjects with depleted iron stores.

Iron Absorption in Relation to Iron Status

The absorption from a 3 mg dose of ferrous iron was measured in 250 male subjects. The absorption was related to the log concentration of serum ferritin in 186 subjects of whom 99 were regular blood donors (r = -0.76), and to bone marrow haemosiderin grading in 52 subjects with varying iron status. The purpose was to try and establish a percentage absorption from such a dose that is representative of subjects who are borderline iron deficient. This information is necessary for food iron absorption studies in order (1) to calculate the absorption of iron from the diet at a given iron status and (2) compare the absorption of iron from different meals studied in different groups of subjects by different investigators. The results suggest that an absorption of about 40% of a 3 mg reference dose of ferrous iron is given in a fasting state, roughly corresponds to the absorption in borderline-iron-deficient subjects. The results indicate that this 40% absorption value corresponds to a serum ferritin level of 30 microgram/l and that food iron absorption in a group of subjects should be expressed preferably as the absorption corresponding to a reference-dose absorption of 40%, or possibly a serum ferritin level of 30 microgram/l.

Inhibition of iron absorption by certain foods.

The article of Oski and Landaw (see p 459) and the recently published report by Saarinen and Siimes 1 indicate that the timing and choice of solid foods for infants may have a much greater influence on iron nutrition than was previously realized. In early infancy, most of the demands of iron for growth are supplied by relatively abundant neonatal iron stores, and absorption of food iron plays a subsidiary role. 2 As neonatal stores become depleted after about four months in the term infant, iron must be supplied almost exclusively from dietary sources. The transition between these two phases of iron metabolism coincides with the time when the introduction of solid foods is currently recommended. 3.4 Absorption of food iron is under two major influences: the first is the homeostatic function of the intestinal mucosa, by which the absorption of iron increases as iron stores decrease; second and less

Food iron absorption in human subjects V. Effects of the major dietary constituents of a semisynthetic meal

Studies were performed in adult volunteer subjects to determine the effect on nonheme iron absorption of protein, carbohydrate, and fat. These constituents were administered as egg albumin, dextrimaltose, and corn oil, respectively, in a semisynthetic meal containing 700 kcal and 4.1 mg iron. Because any one of these ingredients are unpalatable when administered alone, their effect was determined by serially deleting or doubling their content in the basal semisynthetic meal. With both approaches, carbohydrate and fat had little influence whereas egg albumin had a significant inhibitory effect on the absorption of nonheme iron.

The measurement of food iron absorption in man

1. The present study was considered as a first step to develop a method to measure food iron absorption from realistic common meals prepared and consumed by the subjects themselves in their own homes. The absorption of Fe from the meals was measured by means of the extrinsic-tag method modified to allow for a free choice of food items. 2. The mean Fe intake was 2.79 mg and the mean Fe absorption approximately 0.30 mg. The Fe status of the subjects corresponded to 31.5% absorption from a reference dose solution containing 3 mg elemental Fe as ferrous ascorbate. The variation in food Fe absorption obtained in this field study was found to be of the same magnitude as that obtained in studies performed under more controlled conditions as in the laboratory. 3. The conclusion was drawn that the proposed method could be used in realistic field studies aimed at, for example, explaining or preventing a high prevalence of deficiency. A suffciently long run-in period and a careful instruction of the subjects was considered essential for the design of future field studies.

The Effect of Parietal Cell Vagotomy and Selective Vagotomy with Pyloroplasty on Iron Absorption

Iron absorption from a composite meal was studied in 37 male patients before and 1 year after parietal cell vagotomy (PCV) and selective vagotomy with pyloroplasty (SV + P) in a prospective randomized series. The ability to absorb dietary non-haem iron was studied by relating in each subjects the food iron absorption to the absorption from a small dose of ferrous iron, which has been shown to be unaffected by gastric surgery. After both PCV and SV + P there was a malabsorption of food iron which was statistically significant in patients with increased iron requirements caused by phlebotomy. Malabsorption of food iron was less marked after PCV and SV + P than in patients after gastric resection, and it is concluded that there may be no need for a general prophylactic iron supplementation in patients operated on with PCV and SV + P.

Effect of animal proteins on the absorption of food iron in man.

The way in which meat and fish act to promote the absorption of nonheme iron in food is not known. The present paper is a report of the results of a series of studies aimed at obtaining some insight into the mechanism of action of meat and other animal proteins on the absorption of food iron. Beef, fish, chicken and calf thymus all increased the iron absorption to about the same extent. Neither egg albumin, cysteine or a water extract of beef did, however, affect the absorption of food iron. Beef increased the absorption of a solution of inorganic iron given without food only when the iron salt was trivalent or when sodium phytate was added to the solution. It was concluded that meat acts by counteracting luminal factors that inhibit iron absorption. The most probable mechanism for this action is formation of a luminal carrier which transports the iron to the mucosal cell membrane.

Experimental Study on Food Iron Absorption by the Whole Body Counter

Experimental Study on Food Iron Absorption by the Whole Body Counter

Food iron absorption in iron deficiency

The absorption of food iron in relation to the diet was studied in 10 phlebotomized normal young male subjects during 3 to 5 months. The iron absorption was calculated from the net increase of the hemoglobin mass. There was pronounced individual variation in the mean dietary absorption ranging between 1.9 and 5.0 mg. There was no correlation between the amount of iron absorbed and the amount of iron ingested. There was no apparent influence of a high or a low intake of animal products, cereals, vegetables, tea, or alcohol on the individual absorption values. A negative correlation between the iron absorption and the total amount of fecal dry substance was observed. This might be ascribed to an influence of dietary fibers on the absorption of food iron

Influence of Food Iron Absorption on the Plasma Iron Level in Idiopathic Hemochromatosis

The relationship between food iron absorption, iron stores, and plasma iron level was studied. On a low iron diet subjects with idiopathic hemochromatosis (IH) during reaccumulation of iron after phlebotomies showed a fall in plasma iron. Fortification of the diet with 22--135 mg of iron/day for 3 days caused little or no change in the plasma iron in subjects with normal iron stores, whereas in subjects with iron deficiency a significant rise in plasma iron occurred with the addition of 45 mg of iron/day. In subjects with IH with normal iron stores, plasma iron increased with the addition of 22.5 mg/day. These studies indicate that iron absorption is an important determinant of the elevated plasma iron in IH and that the plasma iron tolerance test combined with the serum ferritin may be used to detect excessive absorption of iron.

Estimation of available dietary iron

Dietary iron requirements are dependent on the amount and availability of food iron ingested. On the basis of recent studies of food iron absorption employing extrinsic tag techniques, the availability of heme iron has been defined and estimates of the availability of nonheme iron based on the amounts of enhancing substances appear possible. A model has been developed whereby the availability of iron in a given meal may be estimated. Calculations are made on a meal basis of 1) the amount of heme iron and its availability, and 2) the amount of nonheme iron and its availability as influenced by the meal's content of enhancing factors. Examples of these calculations are provided

Iron balance in hemodialysis patients.

Iron deficiency is a frequent complication in chronically hemodialyzed patients because of the significant blood losses associated with this technique. Quantitating iron stores (by marrow examination or serum iron and total iron-binding capacity) on a repetitive basis had been difficult or unreliable, often resulting in failure to recognize iron deficiency superimposed on the existing anemia of chronic renal failure, or overtreating, which can lead to iron excess. Use of the serum ferritin allows easier quantitation of iron stores and, when measured serially in dialysis patients, can predict the emergence of iron deficiency. There was no correlation between serum ferritin levels and serum iron, total iron-binding capacity, or percent transferrin saturation. Iron absorption studies show that food iron absorption is physiologic, increasing when the serum ferritin is below 30 ng/ml, decreasing when more than 300 ng/ml. Treatment of iron deficiency with oral iron compounds increases serum ferritin levels and usually can maintain iron balance.

Absorption of inorganic iron- (59Fe2?) in relation to iron stores in pancreatic exocrine insufficiency due to cystic fibrosis

The absorption of 59Fe from a diagnostic 0.56 mg 59Fe2+ dose was measured by 4pi-geometry whole body counting and related to the amount of stainable diffuse cytoplasmatic non heme storage iron in the bone marrow macrophages of children with cystic fibrosis. When the storage iron was within the normal range (+/2+) children with cystic fibrosis absorbed 10-38% (Xa+/-S.D.=21+/-9.3) of the oral 59Fe2+ dose which is identical with the 59Fe-absorption in normal children with normal iron stores (9-45:23+/-8.7%). Depleted iron stores caused an increase of 59Fe-absorption to 43-95% (Xa+/-S.D.=62+/-19) in children with cystic fibrosis and to 45-100% (Xa+/-S.D.=73+/-18) in control children. The interruption or continuation of pancreatin maintenance therapy and the simultaneous administration of 1-1.5 g pancreatin did not influence 59Fe2+ absorption in cystic fibrosis. There is no evidence for a pancreatic factor required for or inhibiting inorganic and food iron absorption in human beings. Iron absorption is controlled also in cystic fibrosis chiefly by the amounts of available storage iron. It is therefore not justified to apprehend the development of hemosiderosis in children with cystic fibrosis who are not or not sufficiently treated with pancreatin.

Food iron absorption in human subjects IV. The effects of calcium and phosphate salts on the absorption of nonheme iron

The influence of physiological levels of calcium and phosphorus on the absorption of nonheme iron from a semisynthetic meal was evaluated. Each of the 34 participating subjects received two to four test meals. In three studies where both calcium and phosphate were added, absorption of nonheme iron was reduced to 27 to 47% of that absorbed when no salts were added. However, with the single addition of either calcium or phosphate to the test meals no significantly inhibiting effect was observed. As the absorption of nonheme iron was significantly reduced only with the combined addition of calcium and phosphate, it is suggested that a calcium-phosphate-iron complex forms which inhibits iron absorption.

Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption

The ability of various animal proteins to enhance the absorption of dietary nonheme iron was evaluated by performing multiple radioiron absorption measurements in 70 volunteer subjects. Protein equivalent substitutions of nine animal foods were made in two basic test meals. The first was a standard meal of high iron availability (mean absorption, 8.3%) containing beef muscle as the animal protein. The second was a semisynthetic meal of low iron availability (mean absorption, 1.4%) containing ovalbumin as the protein source. Two categories of animal protein were defined. Substitution of beef, lamb, pork, liver, fish, and chicken for the egg ovalbumin in the sannisynthetic meal resulted in a significant, 2-fold to 4-fold increase in iron absorption whereas no increase was observed with milk, cheese, or egg. Reciprocal findings were obtained when these foods were substituted for the beef contained in the standard meal. All sources of animal proteins are not equivalent in their effect on nonheme iron absorption.

Patterns of food iron absorption in iron-deficient white and indian subjects and in venesected haemochromatotic patients.

The absorption of radioactive iron from a solution of ferrous ascorbate, and from a standard meal containing intrinsically labelled haemoglobin and wheat, was measured in 12 Indian housewives, 18 white hospital patients and 12 subjects with idiopathic haemochromatosis. Eight of the latter had been fully treated by multiple venesections, so that their serum ferritin concentrations were below 25 mug/1. Since the serum ferritin concentrations of the housewives and the hospital patients were comparable, their body iron stores were considered to be depleted to a similar degree. There were no significant differences between the absorptions of ferrous ascorbate or of the haem iron in the standard meal by each group, but the housewives and the hospital patients absorbed significantly less of the non-haem food iron. The mean non-haem food iron absorptions were 36.4%, 5.8% and 18.9% for the treated haemochromatotic subjects, the Indian housewives and the white hospital patients respectively. The discrepancies between the absorptions of the different forms of food iron were highlighted by calculating the ratios between them. The mean non-haem: haem food iron absorption ratio for the group of treated haemochromatotic subjects was 0.98, and for the Indian housewives only 0.18. The white hospital patients did not form a homogenous population: the ratios of the five males and three of the females were greater than 1.0, whereas those of the remaining 10 females were less than 0.5. The results of this study suggest that mal-absorption of non-haem iron from a meal containing bread, presumably due to a defect at the luminal level, may be an important factor in the pathogenesis of iron deficiency in some subjects. The abnormality appears to be particularly prevalent among Indian women living in Durban.

Food iron absorption in man II. The effect of EDTA on absorption of dietary non-heme iron

One hundred and eighty iron absorption tests were performed in 45 normal men to determine the effect of EDTA on the absorption of dietary non-heme iron. The addition of 50 mg EDTA to test meals containing 4.1 mg iron reduced absorption by approximately one-half from meals of both high (standard meal) and low (semisynthetic meal) iron availability. Studies employing dual radioiron labels demonstrated complete isotopic exchange of ferric EDTA with dietary non-heme iron. Further studies were carried out to determine the decrease in food iron absorption at varying levels of EDTA. At a 1:1 molar ratio of EDTA to iron, absorption of non-heme iron was reduced to 72% and at a 2:1 molar ratio, to 50% of absorption without EDTA. These levels of EDTA are within the range believed to be present in the United States diet.

Food iron absorption. I. Use of semisynthetic diet to study absorption of nonheme iron

Recent studies have established the validity of employing an extrinsic radioiron tag to measure the absorption of nonheme iron from a complex meal. In the present study, extrinsic tagging was used to measure absorption of nonheme iron from a standard meal chosen as representative of a typical American meal, and from a semisynthetic meal having the same total chemical composition. The latter was designed so that the major dietary components could be systematically altered to determine their separate effects on food iron absorption. Absorption from the standard meal in 32 healthy women averaged 10.0% as compared with a mean absorption of 1.8% from semisynthetic meal. Most but not all of this fivefold difference in absorption could be explained by the enhancing effect of meat in the standard meal. The low availability of iron from the semisynthetic meal will be of particular value in studying factors which enhance food iron absorption, whereas the standard meal is suitable for studying factors which reduce availability of food iron.