Ferrous sulfate is more bioavailable among preschoolers than other forms of iron in a milk-based weaning food distributed by PROGRESA, a national program in Mexico

After 1 y of distributing a milk-based fortified weaning food provided by the Mexican social program PROGRESA, positive effects on physical growth, prevalence of anemia, and several vitamin deficiencies were observed. There was no effect on iron status, which we hypothesized was related to the poor bioavailability of the reduced iron used as a fortificant in PROGRESA. The objective of this study was to compare the iron bioavailability from different iron sources added as fortificants to the weaning food. Children (n = 54) aged 2-4 y were randomly assigned to receive 44 g of the weaning food fortified with ferrous sulfate, ferrous fumarate, or reduced iron + Na(2)EDTA. Iron absorption was measured using an established double-tracer isotopic methodology. Iron absorption from ferrous sulfate (7.9 +/- 9.8%) was greater than from either ferrous fumarate (2.43 +/- 2.3%) or reduced iron + Na(2)EDTA (1.4 +/- 1.3%) (P < 0.01). The absorption of log-(58)Fe sulfate given with the iron source correlated with serum ferritin (s-ferritin) concentration (n = 13, r = 0.63, P = 0.01) and log-(57)Fe absorption (reference dose) (n = 14, r = -0.52, P = 0.02). Absorption from ferrous fumarate and reduced iron + Na2EDTA did not correlate with s-ferritin or absorption of (57)Fe. The recommended daily portion of the fortified complementary food provides an average of 0.256, 0.096, 0.046 mmol (1.44, 0.54, and 0.26 mg) of absorbed iron, if fortified with sulfate, fumarate and reduced iron + Na(2)EDTA, respectively. Ferrous sulfate was more bioavailable than either ferrous fumarate or reduced iron + Na(2)EDTA when added to the milk-based fortified food and more readily met the average daily iron requirements for children 2-3 y of age.

Sodium iron EDTA [NaFe(III)EDTA] as a food fortificant: erythrocyte incorporation of iron and apparent absorption of zinc, copper, calcium, and magnesium from a complementary food based on wheat and soy in healthy infants

BACKGROUND

Phytic acid is a strong inhibitor of iron absorption from fortified foods. In adults, this inhibitory effect can be overcome by adding ascorbic acid with the iron fortificant or by using a "protected" iron compound such as NaFeEDTA. In addition, the use of NaFeEDTA as an iron fortificant has been reported to increase zinc absorption in adult women. No information is available on iron bioavailability from NaFeEDTA or the influence of NaFeEDTA on minerals and trace elements in infants.

OBJECTIVE

We aimed to compare iron bioavailability from a complementary food based on wheat and soy fortified with either NaFeEDTA or ferrous sulfate plus ascorbic acid. The apparent absorption of zinc, copper, calcium, and magnesium was evaluated in parallel.

DESIGN

Stable-isotope techniques were used in a crossover design to evaluate erythrocyte incorporation of iron 14 d after administration of labeled test meals and the apparent absorption of zinc, copper, calcium, and magnesium on the basis of fecal monitoring in 11 infants.

RESULTS

Geometric mean erythrocyte incorporation of iron was 3.7% (NaFeEDTA) and 4.9% (ferrous sulfate plus ascorbic acid) (P = 0.08). No significant differences in the apparent absorption of zinc, copper, calcium, or magnesium were observed between test meals (n = 10).

CONCLUSIONS

Iron bioavailability from a high-phytate, cereal-based complementary food fortified with either NaFeEDTA or ferrous sulfate plus ascorbic acid was not significantly different. NaFeEDTA did not influence the apparent absorption of zinc, copper, calcium, or magnesium. NaFeEDTA does not provide any nutritional benefit compared with the combination of a highly bioavailable iron compound and ascorbic acid.

Particle size reduction and encapsulation affect the bioavailability of ferric pyrophosphate in rats

Particle size is an important determinant of Fe absorption from poorly soluble Fe compounds in foods. Decreasing the particle size of elemental iron powders increases their absorption. The effect of a reduction in particle size on the bioavailability of ferric pyrophosphate (FePP) is unclear. Encapsulation of iron compounds for food fortification may protect against adverse sensory changes, but at the same time may reduce bioavailability. The hemoglobin (Hb) repletion method in weanling Sprague-Dawley rats (n = 100) was used to compare the relative bioavailability (RBV) of 4 forms of FePP: 1) regular FePP [mean particle size (MPS) approximately 21 microm]; 2) MPS approximately 2.5 microm; 3) MPS approximately 2.5 microm encapsulated in hydrogenated palm oil; and 4) MPS approximately 0.5 microm with emulsifiers. The RBV compared with ferrous sulfate was calculated by the slope-ratio technique. The RBV was 43% for encapsulated MPS approximately 2.5 microm, significantly lower than the other FePP compounds (P < 0.05), 59% for the regular FePP, and 69% for MPS approximately 2.5 microm, not different from each other but significantly lower than ferrous sulfate (P < 0.05), and 95% for emulsified MPS approximately 0.5 microm, comparable to ferrous sulfate. Encapsulation of FePP with hydrogenated palm oil at a capsule:substrate ratio of 60:40 decreased RBV. Particle size reduction increases the RBV of FePP and may make this compound more useful for food fortification.

Determination of iron absorption from intrinsically labeled microencapsulated ferrous fumarate (sprinkles) in infants with different iron and hematologic status by using a dual-stable-isotope method

BACKGROUND

The use of microencapsulated ferrous fumarate sprinkles is a new approach for home fortification. Iron and hematologic status may affect the absorption of iron from sprinkles.

OBJECTIVE

The objective was to measure the absorption (corrected erythrocyte incorporation of (57)Fe) of 2 different doses of iron from sprinkles added to a maize-based complementary food provided to infants with different iron and hematologic status.

DESIGN

Infants aged 6-18 mo were randomly assigned to receive either 30 (n = 45) or 45 (n = 45) mg elemental Fe as (57)Fe-labeled sprinkles added to a maize-based porridge on 3 consecutive days. A (58)Fe tracer (0.2 mg as ferrous citrate) was also infused intravenously (n = 46). Blood was drawn at baseline and 14 d later to determine erythrocyte incorporation of (57)Fe and (58)Fe by using inductively coupled plasma mass spectrometry. On the basis of hemoglobin and soluble transferrin receptor concentrations, subjects were classified as having iron deficiency anemia (IDA), iron deficiency (ID), or sufficient iron status.

RESULTS

There was no significant effect of dose on iron absorption (P > 0.05). Geometric mean iron absorption was 8.25% (range: 2.9-17.8%) in infants with IDA (n = 32), 4.48% (range: 1.1-10.6%) in infants with ID (n = 20), and 4.65% (range: 1.5-12.3%) in iron-sufficient infants (n = 20). Geometric mean iron absorption was significantly higher in infants with IDA than in infants with ID or iron-sufficient infants (P = 0.0004); however, there were no significant differences between infants with ID and iron-sufficient infants.

CONCLUSION

During infancy, iron absorption from sprinkles in a maize-based porridge meets and surpasses requirements for absorbed iron and is up-regulated in infants with IDA.

Fe(II) speciation and its uptake by free and immobilized cells of Pseudomonas fluorescens from industrial waste water

Studies are carried out to remove Fe(II) from wastewater using free and immobilized cells of Pseudomonas fluorescens. Experiments are carried out with free cells between 6 and 8 pH and the uptake of Fe(II) is observed to be maximum at pH 7. Further experiments are done at pH 7. Studies with free and immobilized cells revealed that immobilized cells are more efficient for the removal of Fe(II) than free cells. Fe(II) uptake with Pseudomonas fluorescens is also investigated after the addition of NaCl and MgCl2 to the cells. It is found that the uptake has increased when Sodium chloride (NaCl) and Magnesium Chloride (MgCl2) mixed cells are used. Effect of deficiency of nutrients is also studied. It is found that glucose deficient conditions inhibit Fe(II) uptake more than yeast extract deficient ones. pH also plays an important role in the transport of Fe(II) across the membrane of the cells.

Iron in ferritin or in salts (ferrous sulfate) is equally bioavailable in nonanemic women

BACKGROUND

Recent studies in humans suggest that ferritin iron in soybeans has high bioavailability. However, direct evidence for this is lacking because the soybeans were intrinsically labeled; thus, iron bound to other ligands, such as phytate, was also labeled.

OBJECTIVE

The objectives of the study were to evaluate the absorption of iron from extrinsically labeled, purified ferritin (horse spleen) reconstituted with either high-phosphate iron mineral (plant-type) or low-phosphate iron mineral (animal-type) and to compare it with iron absorption from ferrous sulfate.

DESIGN

Nonanemic, healthy young women were fed a standard breakfast meal supplemented with (59)Fe-labeled ferritin or ferrous sulfate, in randomized order. Fifteen subjects received ferritin with the low-phosphate iron mineral, and 15 subjects received ferritin with the high-phosphate iron mineral. Iron absorption was measured in a whole-body counter after 14 and 28 d and by red blood cell incorporation after 28 d.

RESULTS

There was no significant difference in iron absorption between ferritin and ferrous sulfate: low-phosphate iron mineral ferritin (x +/- SD: 21.4 +/- 14.7%) compared with ferrous sulfate (21.9 +/- 14.6%), or high-phosphate iron mineral ferritin (22.2 +/- 19.2%) compared with ferrous sulfate (16.7 +/- 7.1%). Results obtained by using whole-body retention of iron and red blood cell incorporation differed with the type of iron, which suggests that pathways for iron uptake and utilization differed for the 2 forms.

CONCLUSIONS

Iron is equally well absorbed from ferritin and ferrous sulfate independent of the phosphate content of the ferritin iron mineral. Thus, dietary ferritin iron is likely to be a good source of iron.

A New Approach to Control of Anemia in “At Risk” Infants and Children Around the World 2004 Ryley-Jeffs Memorial Lecture

An estimated 60-80% of the world's population is affected by iron deficiency. It is the most common preventable nutritional deficiency in the world, despite global goals for its reduction. Young children are the highest risk group, particularly during their rapid period of growth. Anemia in infants and young children is known to have a negative impact on motor and socioemotional development and cognitive function. A new intervention, microencapsulated ferrous fumarate Sprinkles, has been developed to treat iron deficiency. The development process took the intervention from the idea stage to the research stage to the implementation stage. Multiple micronutrient Sprinkles are a breakthrough in meeting the global challenge to reduce childhood anemia due to iron and other micronutrient deficiencies. The goal of the Sprinkles project is to reduce the global burden of childhood anemia by promoting healthy weaning practices, by advocating home-fortification strategies to increase the micronutrient content of weaning foods, and by making Sprinkles widely available, particularly in developing countries.

Helicobacter pylori infection, iron absorption, and gastric acid secretion in Bangladeshi children

BACKGROUND

Nonheme-iron absorption requires an acidic milieu. Reduced gastric acid output as a consequence of Helicobacter pylori infection could be an important limiting factor for iron absorption.

OBJECTIVE

We measured gastric acid output and iron absorption from a non-water-soluble iron compound (ferrous fumarate) and a water-soluble iron compound (ferrous sulfate) in children with and without H. pylori infection.

DESIGN

Gastric acid output was quantified before (basal acid output, or BAO) and after pentagastrin stimulation (stimulated acid output, or SAO) in 2-5-y-old children with iron deficiency anemia who were (n = 13) or were not (n = 12) infected with H. pylori. Iron absorption was measured by using a double-stable-isotope technique. H. pylori-infected children were studied before and after eradication therapy.

RESULTS

BAO and SAO were significantly lower in the H. pylori-infected children (0.2 +/- 0.2 and 1.6 +/- 0.9 mmol/h, respectively) than in the uninfected children (0.9 +/- 0.7 and 3.1 +/- 0.9 mmol/h, respectively; P = 0.01 and P < 0.005). BAO and SAO improved to 0.8 +/- 1.3 and 3.3 +/- 2.4 mmol/h, respectively, after therapy. Iron absorption from ferrous sulfate was significantly greater than that from ferrous fumarate both before (geometric : 19.7% compared with 5.3%; P < 0.0001) and after (22.5% compared with 6.4%; P < 0.0001) treatment in H. pylori-infected children. Corresponding values for uninfected children were 15.6% and 5.4%, respectively (P < 0.001; n = 12).

CONCLUSIONS

Iron absorption from ferrous fumarate was significantly lower than that from ferrous sulfate in both H. pylori-infected and uninfected Bangladeshi children. Treatment of H. pylori infection improved gastric acid output but did not significantly influence iron absorption. The efficacy of ferrous fumarate in iron fortification programs to prevent iron deficiency in young children should be evaluated.

Kinetics of two different iron formulations and their effect on diurnal variation of serum iron levels

Iron polymaltose complex (IPC) is a recently marketed preparation with questionable bioavailability. We compared the absorption kinetics of IPC with ferrous sulfate. We also studied the effect of oral iron on diurnal variation. The study was conducted in eight healthy, non-smoking, non-alcoholic volunteers after obtaining their written informed consent and after Institutional Ethical Committee approval. The study was conducted in three phases: during the first phase no drugs were given, whereas in the second and third phases, ferrous sulfate (66 mg elemental iron) and IPC (100 mg elemental iron) were given in a randomized, two-way, cross-over design, with a wash-out period of 1 week. The blood samples were collected, iron levels estimated and the pharmacokinetic parameters calculated. Circadian rhythm in iron levels was demonstrated by cosinor analysis with a mesor of 93.6 microg/dl, acrophase 10.40 h and amplitude of 26.4 microg/dl. Evening levels were higher as compared with morning levels. Drug treatment increased the mesor (115.7 microg/dl; p < 0.05), delayed the acrophase (11.30 h; p < 0.05) and increased the amplitude (38.5 microg/dl; p < 0.05). The bioavailability of ferrous sulfate was significantly greater as compared with IPC with greater Cmax and AUC (p < 0.05). A clear cut circadian rhythm in iron concentrations was demonstrated. Ferrous sulfate was shown to have significantly higher bioavailability as compared with IPC. Further studies having hemoglobin levels as an endpoint may be planned.

Bioavailability of iron and zinc from a multiple micronutrient-fortified beverage

OBJECTIVE

To test the hypothesis that micronutrient beverages can provide the daily iron and zinc needs of small children.

STUDY DESIGN

Forty children aged 6 to 9 years were recruited (Lima, Peru). For 4 weeks, they received a daily serving of a beverage containing multiple micronutrients. Over 2 consecutive days, subjects received stable isotope-labeled servings of the beverage with and without a meal as well as an intravenous dose of zinc. Iron and zinc bioavailability were assessed using mass spectrometry.

RESULTS

Iron absorption was significantly lower with a meal than without (9.8 +/- 6.7% versus 11.6 +/- 6.9%, P=.04), but zinc absorption was not (24.5 +/- 10.7% versus 22.8 +/- 7.6%, P=.2). In either case, however, a single daily serving provided most of the iron and zinc requirements for the children.

CONCLUSIONS

Single daily servings of multinutrient-fortified beverages can meet much of the mineral needs for small children. Food has a small inhibitory effect on iron, but not zinc, absorption; therefore, these beverages can be efficacious even when given with a meal.

Effect of Ascorbic Acid and Particle Size on Iron Absorption from Ferric Pyrophosphate in Adult Women

The effects of added ascorbic acid and particle size on iron absorption from ferric pyrophosphate were evaluated in adult women (9–10 women/study) based on erythrocyte incorporation of iron stable isotopes (57Fe or 58Fe) 14 days after administration. Three separate studies were made with test meals of iron-fortified infant cereal (5 mg iron/meal) and the results are presented as geometric means and relative bioavailability values (RBV, FeSO4 = 100%). The results of study 1 showed that iron absorption was significantly lower from ferric pyrophosphate (mean particle size 8.5 mum) than from FeSO4 in meals without ascorbic acid (0.9 vs. 2.6%, p < 0.0001, RBV 36%) and in the same meals with ascorbic acid added at a 4:1 molar ratio relative to fortification iron (2.3 vs. 9.7%, p < 0.0001, RBV 23%). Ascorbic acid increased iron absorption from ferric pyrophosphate slightly less (2.6-fold) than from FeSO4 (3.7-fold) (p < 0.05). In studies 2 and 3, RBV of ferric pyrophosphate with an average particle size of 6.7 mum and 12.5 mum was not significantly different at 52 and 42% (p > 0.05), respectively. In conclusion, the addition of ascorbic acid increased fractional iron absorption from ferric pyrophosphate significantly, but to a lesser extent than from FeSO4. Decreasing the mean particle size to 6.7 mum did not significantly increase iron absorption from ferric pyrophosphate.

Bioavailability of elemental iron powder in white wheat bread

OBJECTIVE

Iron fortification of wheat flour is widely used. In most cases, elemental iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H(2)-reduced elemental iron powder in white wheat bread made from 72% extraction flour.

DESIGN

A stable isotope of H(2)-reduced iron powder (mean particle size 15 microm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5- to 7-y-old children were fed bread with 4 mg of H(2)-reduced (58)Fe /100 g of flour. The next day (57)Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry.

RESULTS

When normalized to 40% absorption of the reference dose, the geometric mean (+/-range of 1 s.d.) bioavailability of reduced (58)Fe in wheat bread rolls was 6.5% (3.7-11.8).

CONCLUSIONS

When compared to previous radioiron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size (58)Fe (15 microm) is likely to be higher than that of commercial iron powder (45 microm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial elemental iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate.

SPONSORSHIP

This work was funded in part by Grant No 910313 by Micronutrient Initiative, IDRC, Ottawa, Canada.

The mechanisms for regulating absorption of Fe bis-glycine chelate and Fe-ascorbate in caco-2 cells are similar

Inorganic iron (Fe) absorption from the diet is controlled mainly in the intestinal tract where apical Fe uptake is inversely related to the Fe content in the enterocyte. Iron bis-glycine chelate is an iron compound that may be absorbed by a mechanism different from the regulated nonheme Fe pathway. Because Fe bis-glycine chelate is used increasingly as an Fe fortificant in foods, the critical question is whether this compound is a safe Fe supplement. We compared apical Fe uptake and transepithelial transport offered either as (59)Fe bis-glycine chelate or a (59)Fe-ascorbate (Fe-AA) complex in Caco-2 cells, as a model of human intestinal epithelia, grown in different Fe concentrations in the media (0.5, 5 and 20 micro mol/L Fe). Apical Fe uptake from (59)Fe-AA and (59)Fe bis-glycine chelate did not differ nor did transepithelial transport rates. The rate of (59)Fe uptake decreased with increasing intracellular Fe concentration (P < 0.001), an indication of a common absorption regulatory mechanism. We also evaluated the effect of an excess of Fe (100 micro mol/L) provided as Fe bis-glycine chelate or Fe-AA on the incorporation of 1 micro mol/L (55)Fe-AA into Fe-replete Caco-2 cells. The inhibition of Fe bis-glycine chelate on the absorption of the extrinsic tag of (55)Fe-AA (87.5%) did not differ from that of Fe added as Fe-AA (86.8%). These results suggest that Fe derived from Fe bis-glycine chelate and Fe-AA have similar regulatory absorption mechanisms.

Iron Absorption and Bioavailability in Rats of Micronized Dispersible Ferric Pyrophosphate

Unlike commercial ferric pyrophosphate, micronized dispersible ferric pyrophosphate (MDFP: SunActive FeTM) does not precipitate and is completely dispersible in liquid form. MDFP shows a sharp particle size distribution at a nanometer level, which is several times smaller than that of commercial ferric pyrophosphate. The bioavailability of MDFP was compared to ferric pyrophosphate, sodium ferrous citrate, and ferrous sulfate by three bioavailability tests in rats; namely the serum iron concentration curve, the hemoglobin regeneration efficiency, and Association of Official Analytical Chemists' hemoglobin repletion test. The high area under curve value, a lag in peak time, and continued high serum iron concentration by MDFP over the other iron compounds indicates a sustained release of iron in the serum iron concentration curve method. MDFP showed the highest hemoglobin regeneration efficiency among all the iron compounds tested. The relative biological value of MDFP per unit of ferrous sulfate in each bioavailability test showed a high value as compared to other iron compounds. The above results suggest that MDFP is an ideal compound with high bioavailability for iron fortification in various liquid applications.

Ascorbic acid reduces the frequency of iron induced micronuclei in bone marrow cells of mice

Iron is a potent oxidant that can lead to the formation of genotoxic lipid peroxides. Ascorbic acid, which enhances dietary iron absorption, has been suggested to enhance the oxidant effects of iron and to directly lead to the formation of lipid peroxides. The combined effects of dietary iron and ascorbic acid on genotoxicity were investigated by measuring the frequency of micronuclei in the bone marrow cells of C3H/He mice. In addition, liver iron concentration was measured in all treated groups. Three weeks old mice were fed diets for 3 weeks containing iron at 100 or 300 mg/kg diet in the form of FeSO(4) that were supplemented either with or without ascorbic acid (15 g/kg diet). The results of the bone marrow micronucleus test revealed that the high iron diet resulted in an increased frequency of micronucleated polychromatic erythrocytes (MnPCEs) as compared to low iron. Ascorbic acid supplementation in the low iron diet did not show any effect on incidence of MnPCEs and protected against the increased frequency of MnPCEs induced by the high iron diet. However, liver iron concentration was significantly increased only in the high iron treated and ascorbic acid supplemented group as compared to all other groups. These results demonstrate that ascorbic acid protects against the clastogenic effects of iron.

Iron bioavailability in corn-masa tortillas is improved by the addition of disodium EDTA

Corn-masa flour flat bread tortillas are the main staple of Mexican and Central American populations. Due to high concentrations of inhibitors of iron absorption, the bioavailability from this matrix is unknown. We wanted to determine the most suitable fortificant that would efficaciously improve iron bioavailability. In tortillas prepared with commercial precooked, lime-treated, corn-masa flour, we examined the in vitro solubility of the following forms of iron: native iron with and without Na2EDTA, elemental reduced iron plus Na2EDTA, ferrous fumarate with and without Na2EDTA, bisglycine iron, ferrous sulfate and NaFeEDTA. We also examined the in vivo bioavailability in humans with double radioiron erythrocyte incorporation of ferrous fumarate with and without Na2EDTA, bisglycine iron, NaFeEDTA and native iron plus Na2EDTA, beans and rice. In vitro, solubility ranged from 1% in iron forms without Na2EDTA to 19.4% for NaFeEDTA. Forms of iron with Na2EDTA had intermediate values. In vivo radioiron studies showed that iron forms without Na2EDTA also had low bioavailability (< or =1%). NaFeEDTA had the highest bioavailability (5.3%). The bioavailability of all iron forms improved significantly when tested with Na2EDTA (<0.05). Adding Na2EDTA to ferrous fumarate increased bioavailability from 0.87% to 2.9% (P < 0.001). We conclude that NaFeEDTA is the form of iron best absorbed, but alternatively, ferrous fumarate plus Na2EDTA comprises a feasible option as a fortificant.

Bioavailability of Elemental Iron Powders to Rats Is Less than Bakery-Grade Ferrous Sulfate and Predicted by Iron Solubility and Particle Surface Area

Foods are fortified with elemental forms of iron to reduce iron deficiency. However, the nutritional efficacy of current, commercially produced elemental iron powders has not been verified. We determined the bioavailability of six commercial elemental iron powders and examined how physicochemistry influences bioavailability. Relative biological value (RBV) of the iron powders was determined using a hemoglobin repletion/slope ratio method, treating iron-deficient rats with repletion diets fortified with graded quantities of iron powders, bakery-grade ferrous sulfate or no added iron. Iron powders were assessed physicochemically by measuring iron solubility in hydrochloric acid at pH 1.0 and 1.7, surface area by nitrogen gas adsorption and surface microstructure by electron microscopy. Bioavailability from the iron powders, based on absolute iron intake, was significantly less than from FeSO4 (100%; P < 0.05) with the following rank order: Carbonyl (64%; Ferronyl, U.S.) > Electrolytic (54%; A-131, U.S.) > Electrolytic (46%; Electrolytic Iron, India) > H-Reduced (42%; AC-325, U.S.) > Reduced (24%; ATOMET 95SP, Canada) > CO-Reduced (21%; RSI-325, Sweden). Solubility testing of the iron powders resulted in different relative rankings and better RBV predictability with increasing time at pH 1.7 (R2 = 0.65 at 150 min). The prediction was improved with less time and lower pH (R2 = 0.82, pH 1.0 at 30 min). Surface area, ranging from 90 to 370 m2/kg, was also highly predictive of RBV (R2 = 0.80). Bioavailability of iron powders is less than bakery-grade ferrous sulfate and varies up to three times among different commercial forms. Solubility at pH 1.0 and surface area were predictive of iron bioavailability in rats.

Quantification of unlabelled non-haem iron absorption in human subjects: a pilot study

A method for measuring unlabelled Fe absorption has been investigated in a pilot study using a simple mathematical model. The metabolism of newly absorbed Fe can be approximated as a single-compartment model with the sampled compartment being the plasma pool. Five female volunteers (aged 30-55 years) were recruited to participate in the pilot study. After a 10 mg oral dose of unlabelled ferrous sulfate, the change in plasma Fe concentration over the following 6 h was used to estimate the quantity of absorbed Fe from the mathematical model. To assess the accuracy of the new technique, a 1 mg oral dose of (57)Fe-labelled iron sulfate was given simultaneously with a 225 microg intravenous dose of (58)Fe as iron citrate. The plasma appearance of the labelled Fe was used to estimate the absorption of the oral label from the traditional area under the curve method. There was no significant difference (P=0.61) between the geometric mean absorption of the unlabelled (19 (-1 sd 12, +1 sd 28) %) and the labelled Fe (17 (-1 sd 10, +1 sd 29) %). These initial results are encouraging, but further work needs to be undertaken with smaller doses, as typically found in meals. The effect of diurnal variation in serum Fe concentration on the estimation of unlabelled Fe absorption needs further assessment.

Activated charcoal and the absorption of ferrous sulfate in rats

The treatment of iron poisoning has typically not included the administration of activated charcoal due to the lack of evidence supporting its efficacy. Several in vitro studies have demonstrated good adsorption of iron in a variety of pH ranges that were comparable to those found with other drugs for which activated charcoal is clinically used. This study was designed to determine whether activated charcoal altered the gastrointestinal absorption of toxic doses of iron as ferrous sulfate in an in vivo model. Seventy-five male Sprague-Dawley rats were randomly assigned into 5 groups: control given only distilled water; 100 mg elemental Iron and water; 1:1 charcoal to iron; 2:1 charcoal to iron; and 4:1 charcoal to iron. All treatments were administered consecutively by gavage within 5 min. Physiological measurements and blood samples were taken at 0, 1, 4 and 8 h after treatment. There were no consistent differences in physiological measurements among the 5 groups. Mean serum iron concentrations did not differ among Groups 2, 3, 4 and 5 at the 4 sampling times except at I h between Groups 4 and 5. The area under the curve for serum iron concentrations did not differ among the treatment groups. Activated charcoal did not alter the extent of iron absorption in the experimental model.

Evaluation of iron bioavailability from bonito dark muscle using anemic rats

The bioavailability of iron from ferrous sulfate (FeII-S), heme iron prepared from hemoglobin (HIP), and bonito dark muscle (BDM) was assessed in anemic rats using a hemoglobin regeneration efficiency (HRE) method. Freeze-dried BDM (FD), boiled and freeze-dried BDM (B/FD), and boiled and smoke-dried BDM (B/SD) were used as BDM source. Rats were made anemic by feeding on an iron-deficient diet for 28 days. To replete their iron levels, anemic rats were then fed on a diet containing iron at a level of 17 ppm for 14 days. Rats receiving FeII-S gained significantly more weight and had greater food intake and higher HRE compared to the other four groups. The bioavailability of iron from HIP was poor compared with that from FeII-S and BDM. When the HRE of rats fed FeII-S was 100, that of rats fed BDF was approximately 80. These results suggest that BMD is an effective dietary source of iron.

Acute toxicity of carbonyl iron and sodium iron EDTA compared with ferrous sulfate in young rats

According to the American Association of Poison Control Centers, exposures to excessive doses of iron supplements still occur in children less than 6 years of age. Since 1998, there has been one death among U.S. children in this age group. Exposures, including adverse events, to iron supplements and iron-containing vitamins for the years 1999 and 2000 were 23,215 and 24,249, respectively. To reduce the potential seriousness of such exposures, carbonyl iron (Fe(0)) has been suggested as a possible replacement for ferrous sulfate (FeSO(4)). Carbonyl Fe is a unique form of elemental iron because of its small particle size. It is highly bioavailable when used to correct iron deficiency anemia. There is also current interest in using sodium iron(III) ethylenediaminetetraacetate (NaFeEDTA) for food fortification. In this study both NaFeEDTA and carbonyl Fe were compared with FeSO(4), the most common form of iron for dietary supplements, to obtain information relevant to the acute toxicological profile in young rats. With FeSO(4) and NaFeEDTA, total liver nonheme iron increased with increasing dose, but the response was approximately 50% lower with NaFeEDTA compared with FeSO(4). Serum iron peaked at approximately 0.5 to 1 h for both FeSO(4) and carbonyl Fe, while NaFeEDTA was elevated up to 4 h. FeSO(4) had an LD(50) of 1.1 g Fe/kg and was approximately 45 times more toxic than carbonyl Fe, which had an LD(50) greater then 50 g Fe/kg. NaFeEDTA had an LD(50) of 1.3 g Fe/kg and, when compared with FeSO(4), had approximately the same level of toxicity.

Iron bis-glycine chelate competes for the nonheme-iron absorption pathway

BACKGROUND

The enterocytic absorption pathway of the food fortificant iron bis-glycine chelate has been the subject of controversy because it is not clear whether that substance uses the classic nonheme-iron absorption pathway or a pathway similar to that of heme absorption.

OBJECTIVE

The objective was to study the absorption pathway of iron bis-glycine chelate in human subjects.

DESIGN

Eighty-five healthy adult women were selected to participate in 1 of 6 iron-absorption studies. Study A involved the measurement of the dose-response curve of the absorption of ferrous sulfate (through a nonheme-iron absorption pathway); study B involved the competition of iron bis-glycine chelate with ferrous sulfate for the nonheme-iron absorption pathway; study C involved the measurement of the dose-response curve of heme-iron absorption; study D involved the competition of iron bis-glycine chelate with hemoglobin for the heme-iron absorption pathway; and studies E and F were the same as studies A and B, except that the iron bis-glycine chelate was encapsulated in enteric gelatin capsules so that it would not be processed in the stomach.

RESULTS

Iron from the bis-glycine chelate competed with ferrous sulfate for the nonheme-iron absorption pathway. Iron from the bis-glycine chelate also competed with ferrous sulfate for absorption when liberated directly into the intestinal lumen. Iron from the bis-glycine chelate did not compete with heme iron for the heme-iron absorption pathway.

CONCLUSION

The iron from iron bis-glycine chelate delivered at the level of the stomach or duodenum becomes part of the nonheme-iron pool and is absorbed as such.

Bioavailability of iron from micro-encapsulated iron sprinkle supplement

To improve the iron status of infants an effort was made to increase the iron content of complementary foods by adding 12.5 mg of elemental iron to the meal in the form of micro-encapsulated ferrous fumarate coated with a lipid. The contents of the packet were sprinkled directly on to infant foods. Relative absorption of iron from this supplement was determined in a prospective randomized study with 39 infants (mean age 33.6 +/- 5.2 weeks) with initial hemoglobin values greater than 100 g/L. They were fed two complementary foods (rice-based and wheat-based) in which the supplement labeled with stable isotopes of iron 57Fe and 58Fe was incorporated. The erythrocyte iron incorporation was measured in the blood by inductively coupled plasma mass spectrophotometry. The incorporation of iron was significantly higher 11.9% p < .001 and 13.3% p < .001 and no difference was observed with the type of cereal in complementary foods. The use of ferrous fumarate sprinkles has proved to be efficacious in increasing the available iron intake of the infants.