Fractional Iron Absorption Research Articles

Phytic Acid Concentration Influences Iron Bioavailability from Biofortified Beans in Rwandese Women with Low Iron Status

Background:The common bean is a staple crop in many African and Latin American countries and is the focus of biofortification initiatives. Bean iron concentration has been doubled by selective plant breeding, but the additional iron is reported to be of low bioavailability, most likely due to high phytic acid (PA) concentrations. Objective:The present study evaluated the impact of PA on iron bioavailability from iron-biofortified beans. Methods:Iron absorption, based on erythrocyte incorporation of stable iron isotopes, was measured in 22 Rwandese women who consumed multiple, composite bean meals with potatoes or rice in a crossover design. Iron absorption from meals containing biofortified beans (8.8 mg Fe, 1320 mg PA/100 g) and control beans (5.4 mg Fe, 980 mg PA/100 g) was measured with beans containing either their native PA concentration or with beans that were ∼50% dephytinized or >95% dephytinized. Results:The iron concentration of the cooked composite meals with biofortified beans was 54% higher than in the same meals with control beans. With native PA concentrations, fractional iron absorption from the control bean meals was 9.2%, 30% higher than that from the biofortified bean meals (P < 0.001). The quantity of iron absorbed from the biofortified bean meals (406 μg) was 19% higher (P < 0.05) than that from the control bean meals. With ∼50% and >95% dephytinization, the quantity of iron absorbed from the biofortified bean meals increased to 599 and 746 μg, respectively, which was 37% (P < 0.005) and 51% (P < 0.0001) higher than from the control bean meals. Conclusions:PA strongly decreases iron bioavailability from iron-biofortified beans, and a high PA concentration is an important impediment to the optimal effectiveness of bean iron biofortification. Plant breeders should focus on lowering the PA concentration of high-iron beans. This trial was registered at clinicaltrials.gov as NCT01521273.

The effect of timing of iron supplementation on iron absorption and haemoglobin in post-malaria anaemia: a longitudinal stable isotope study in Malawian toddlers.

BackgroundIn sub-Saharan Africa, children with Plasmodium falciparum malaria and anaemia are often given iron supplementation at the time of malaria treatment. Inflammation during and after malaria may decrease iron absorption, thus, absorption might be improved if the start of supplementation is delayed. The study objective was to measure iron absorption from iron supplements started immediately or delayed by two weeks after completion of therapy against uncomplicated P. falciparum malaria.MethodsMalawian toddlers (n = 48; age 12–24 months) were alternatively assigned to two groups according to their appearance at the health centre: group A was provided iron supplements (30 mg Fe daily) as a FeSO4-containing syrup for eight weeks starting immediately after malarial treatment; group B was given the iron after a two-week delay. Iron absorption from the syrup was measured on the first day of iron supplementation, and after two and eight weeks in both groups. Haemoglobin (Hb), iron status and inflammation were assessed every two weeks. Fractional iron absorption at each time point and cumulative absorption was quantified by measuring erythrocyte incorporation of 57Fe and compared using mixed models.ResultsComparing group A and B, geometric mean iron absorption did not differ on the first day of supplementation (9.0% vs. 11.4%, P = 0.213) and cumulative iron absorption from the three time points did not differ (6.0% vs. 7.2%, P = 0.124). Hb concentration increased in both groups two weeks after malaria treatment (P < 0.001) and did not differ after eight weeks of supplementation (P = 0.542).ConclusionsIn anaemic toddlers after uncomplicated malaria, a two-week delay in starting iron supplementation did not significantly increase iron absorption or Hb concentration. Iron absorption is sufficiently high in the immediate post-malaria period to warrant supplementation. These findings suggest there is no need to change the current practice of immediate iron supplementation in this setting.Trial registrationThis trial was registered at Pan African Clinical Trials Registry (pactr.org) as PACTR2010050002141682.

A Higher Proportion of Iron-Rich Leafy Vegetables in a Typical Burkinabe Maize Meal Does Not Increase the Amount of Iron Absorbed in Young Women

Food-to-food fortification can be a promising approach to improve the low dietary iron intake and bioavailability from monotonous diets based on a small number of staple plant foods. In Burkina Faso, the common diet consists of a thick, cereal-based paste consumed with sauces composed of mainly green leaves, such as amaranth and jute leaves. Increasing the quantity of leaves in the sauces substantially increases their iron concentration. To evaluate whether increasing the quantity of leaves in sauces would provide additional bioavailable iron, an iron absorption study in 18 young women was conducted in Zurich, Switzerland. Burkinabe composite test meals consisting of the maize paste tô accompanied by an iron-improved amaranth sauce, an iron-improved jute sauce, or a traditional amaranth sauce were provided as multiple meals twice a day for 2 consecutive days. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes. Mean fractional iron absorption from maize paste consumed with an iron-improved amaranth sauce (4.9%) did not differ from the same meal consumed with an iron-improved jute sauce (4.9%; P = 0.9), resulting in a similar quantity of total iron absorbed (679 vs. 578 μg; P = 0.3). Mean fractional iron absorption from maize paste accompanied by a traditional amaranth sauce (7.4%) was significantly higher than that from the other 2 meal types (P < 0.05), but the quantity of total iron absorbed was similar (591 μg; P = 0.4 and 0.7, respectively). A food-to-food fortification approach based on an increase in leafy vegetables does not provide additional bioavailable iron, presumably due to the high phenolic compound concentration of the leaves tested. Alternative measures, such as adding iron absorption enhancers to the sauces, need to be investigated to improve iron nutrition from Burkinabe maize meals.

Dephytinisation with Intrinsic Wheat Phytase and Iron Fortification Significantly Increase Iron Absorption from Fonio (Digitaria exilis) Meals in West African Women

Low iron and high phytic acid content make fonio based meals a poor source of bioavailable iron. Phytic acid degradation in fonio porridge using whole grain cereals as phytase source and effect on iron bioavailability when added to iron fortified fonio meals were investigated. Grains, nuts and seeds collected in Mali markets were screened for phytic acid and phytase activity. We performed an iron absorption study in Beninese women (n = 16), using non-dephytinised fonio porridge (FFP) and dephytinised fonio porridge (FWFP; 75% fonio-25% wheat), each fortified with 57Fe or 58Fe labeled FeSO4. Iron absorption was quantified by measuring the erythrocyte incorporation of stable iron isotopes. Phytic acid varied from 0.39 (bambara nut) to 4.26 g/100 g DM (pumpkin seed), with oilseeds values higher than grains and nuts. Phytase activity ranged from 0.17±1.61 (fonio) to 2.9±1.3 phytase unit (PU) per g (whole wheat). Phytic acid was almost completely degraded in FWFP after 60 min of incubation (pH≈5.0, 50°C). Phytate∶iron molar ratios decreased from 23.7∶1 in FFP to 2.7∶1 in FWFP. Iron fortification further reduced phytate∶iron molar ratio to 1.9∶1 in FFP and 0.3∶1 in FWFP, respectively. Geometric mean (95% CI) iron absorption significantly increased from 2.6% (0.8–7.8) in FFP to 8.3% (3.8–17.9) in FWFP (P<0.0001). Dephytinisation of fonio porridge with intrinsic wheat phytase increased fractional iron absorption 3.2 times, suggesting it could be a possible strategy to decrease PA in cereal-based porridges.

Iron absorption from NaFeEDTA-fortified oat beverages with or without added vitamin C

Background: Food fortification is the best long-term approach for reducing the incidence of iron deficiency. Objective: To determine iron absorption from NaFeEDTA-fortified oat beverages without and with vitamin C. Materials and methods: Iron absorption in 19 apparently healthy 6-year-old children was studied. Two oat beverages fortified with iron (labeled with stable isotopes of NaFeEDTA), zinc, and vitamin A, without and with vitamin C was consumed in two consecutive days in random order. Blood samples were taken 14 days later for stable isotope measurements. Results: The mean fractional iron absorption from the fortified oat beverage without vitamin C (5.65 ± 0.54%) was significantly lower than that from the beverage with vitamin C (7.14 ± 0.90%; p < 0.05). Conclusion: Fortified oat beverages may offer a convenient and effective mechanism to improve the iron status of children. The addition of vitamin C improved iron absorption by an additional 1.5%.

Total Iron Absorption by Young Women from Iron-Biofortified Pearl Millet Composite Meals Is Double That from Regular Millet Meals but Less Than That from Post-Harvest Iron-Fortified Millet Meals

Iron biofortification of pearl millet (Pennisetum glaucum) is a promising approach to combat iron deficiency (ID) in the millet-consuming communities of developing countries. To evaluate the potential of iron-biofortified millet to provide additional bioavailable iron compared with regular millet and post-harvest iron-fortified millet, an iron absorption study was conducted in 20 Beninese women with marginal iron status. Composite test meals consisting of millet paste based on regular-iron, iron-biofortified, or post-harvest iron-fortified pearl millet flour accompanied by a leafy vegetable sauce or an okra sauce were fed as multiple meals for 5 d. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes. Fractional iron absorption from test meals based on regular-iron millet (7.5%) did not differ from iron-biofortified millet meals (7.5%; P = 1.0), resulting in a higher quantity of total iron absorbed from the meals based on iron-biofortified millet (1125 vs. 527 μg; P < 0.0001). Fractional iron absorption from post-harvest iron-fortified millet meals (10.4%) was higher than from regular-iron and iron-biofortified millet meals (P < 0.05 and P < 0.01, respectively), resulting in a higher quantity of total iron absorbed from the post-harvest iron-fortified millet meals (1500 μg; P < 0.0001 and P < 0.05, respectively). Results indicate that consumption of iron-biofortified millet would double the amount of iron absorbed and, although fractional absorption of iron from biofortification is less than that from fortification, iron-biofortified millet should be highly effective in combatting ID in millet-consuming populations.

Genetic Reduction of Phytate in Common Bean (Phaseolus vulgaris L.) Seeds Increases Iron Absorption in Young Women1–4

Iron bioavailability from common beans is negatively influenced by phytic acid (PA) and polyphenols (PPs). Newly developed low-PA (lpa) beans with 90% less PA and variable PPs might improve iron bioavailability. The aim of this study was to evaluate the influence of lpa beans on iron bioavailability in women (n = 20). We compared iron absorption from 4 different beans using a paired, double meal, crossover design. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes (Fe57, Fe58) from 2 lpa bean lines, one high in PPs (means ± SDs; PA = 124 ± 10 mg/100 g; PPs = 462 ± 25 mg/100 g) and one low in PPs (PA = 70 ± 10 mg/100 g; PPs = 54 ± 2 mg/100 g). The other 2 beans used were their parents with a normal PA concentration, one high in PPs (PA = 1030 ± 30 mg/100 g; PPs = 676 ± 19 mg/100 g) and one low in PPs (PA = 1360 ± 10 mg/100 g; PPs = 58 ± 1 mg/100 g). Fractional iron absorption from the lpa bean high in PPs was 6.1% (95% CI: 2.6, 14.7), which was 60 and 130% higher compared with the parent high in PPs (P < 0.001) and low in PPs (P < 0.001), respectively. The total amount of iron absorbed per test meal from the lpa bean high in PPs (372 μg; 95% CI: 160, 890) was 60 and 163% higher compared with the parent high in PPs (P < 0.001) and low in PPs (P < 0.001), respectively. Fractional iron absorption from the lpa line low in PPs (4%; 95% CI: 1.8, 8.7) was 50% higher and the total amount of iron absorbed per test meal (261 μg; 95% CI: 120, 570) was 85% higher than iron from the parent low in PPs (P < 0.001). There was no difference between the lpa beans high or low in PPs or between the parents high or low in PPs. A 90% reduction in PA leads to an increase in bioavailable iron from beans, independent of the PP concentration. The lpa mutation could be a key tool for improving iron bioavailability from beans.

Inulin modifies the bifidobacteria population, fecal lactate concentration, and fecal pH but does not influence iron absorption in women with low iron status

Bioavailability of nonheme iron is influenced by the concentration of inhibitors and enhancers in the diet. The fructans inulin and oligofructose have been shown to improve iron absorption in animals through colonic uptake, but this has not been confirmed in humans. The aim of the intervention study was to evaluate the influence of inulin on iron absorption, bifidobacteria, total bacteria, short-chain fatty acids (SCFAs), and fecal pH in women with low iron status (plasma ferritin <25 μg/L). The subjects (n = 32) consumed inulin or placebo 3 times/d (∼20 g/d) for 4 wk, separated by a 2-wk washout period. Iron absorption was measured after 3 wk of inulin and placebo consumption from a standard test meal by using stable-iron-isotope techniques. Fecal bacteria were measured by quantitative polymerase chain reaction, and fecal acids by HPLC. Mean fractional iron absorption in the inulin (15.2%; 95% CI: 8.0%, 28.9%) and placebo (13.3%; 95% CI: 8.1%, 24.3%) periods did not differ significantly (P = 0.10). Inulin decreased fecal pH (P < 0.001) and increased fecal bifidobacteria (P < 0.001) and fecal lactate (P < 0.001) but had no effect on fecal SCFAs and total bacteria. Changes in lactate and acetate concentrations were positively correlated with changes in propionate (P < 0.001) and butyrate (P < 0.02) concentrations, respectively. Iron absorption correlated with fecal pH in the placebo period (P < 0.01) but not in the inulin period (P = 0.37). Although inulin showed prebiotic activity, we were unable to show an increase in iron absorption in women with low iron status. This trial was registered at clinicaltrials.gov as NCT0148309.

Iron absorption from fortified oat drinks

Prevalence of anemia is 19.5% in the Filipino population. The objective was to determine iron bioavailability from oat drinks fortified with iron, zinc, and vitamin A with/without vitamin C. The study followed a double blind randomized cross‐over design. Nineteen healthy 6‐year old children participated. Children consumed 2 drinks fortified with iron, zinc, and vitamin A labeled with stable isotopes of iron as NaFeEDTA; drink A without and drink B with vitamin C. On 2 consecutive days, participants were given drink A (57Fe) or drink B (58Fe) in random order. Blood samples were taken for stable isotope measurements 14 days later. Results indicated no significant differences in nutrient composition (except vitamin C), dietary fiber or total phytic acid content between the two drinks. The percent fractional iron absorption (7.14±0.90) from the oat drink with vitamin C was significantly higher than that from the oat drink without vitamin C (5.65±0.54; P&lt;0.05). In conclusion, results showed that vitamin C added to NaFeEDTA fortified oats enhanced iron absorption. Fortifying oats may offer a convenient, and effective mechanism to improve the iron status of children.

Fortification Iron as Ferrous Sulfate Plus Ascorbic Acid Is More Rapidly Absorbed Than as Sodium Iron EDTA but Neither Increases Serum Nontransferrin-Bound Iron in Women1–3

AbstractThe absorption profile of iron fortificants may be a determinant of their ability to generate nontransferrin-bound iron (NTBI) and, thus, their potential safety. Ferrous iron may be absorbed more rapidly than chelated ferric iron, but differences at the fortification level cannot be distinguished with nonisotopically labeled serum iron curves. Using stable isotope appearance curves (SIAC) in serum, we measured iron absorption profiles from FeSO4 with ascorbic acid (AA) and from NaFeEDTA, as well as the serum hepcidin and NTBI response following the meals. Healthy women (n = 16) were given 6 mg oral iron as labeled FeSO4 and NaFeEDTA with a maize porridge using a crossover design. SIAC, NTBI, and serum hepcidin were measured over 8 h after the meal. Iron from FeSO4 plus AA was more rapidly absorbed, resulting in a 35% greater relative AUC during the first 2 h than for NaFeEDTA (P < 0.001). Median (95% CI) fractional iron absorption from the FeSO4- and NaFeEDTA-fortified meals was 15.2% (11.0–19.5) and 6.0% (5.0–9.2), respectively (P < 0.001). In response to the FeSO4-fortified meal, there was an ~60% increase in median serum hepcidin (P < 0.05) but no significant change in NTBI. There was no significant change in serum hepcidin or NTBI after the NaFeEDTA-fortified meal. SIAC are a useful new tool to compare iron absorption profiles from different iron compounds in fortified foods. Even with the use of a very well absorbed ferrous iron compound, iron fortification in this population does not increase NTBI, suggesting a low risk for adverse health consequences.

19 A-Lactalbumin and Casein-Glycomacropeptide Have No Effect on Iron Absorption From Low-Iron Formula in Healthy Term Infants

Background and aims: Iron absorption from infant formula is low. α-Lactalbumin and casein-glycomacropeptide are thought to enhance mineral absorption. We evaluated the effects of α-lactalbumin and casein-glycomacropeptide on iron absorption from low-iron infant formula in healthy term non-iron-deficient infants. Methods: In a double-blind randomized controlled trial, 32 infants were assigned to receive one of three low-iron (4mg iron/L) formulas from 6 weeks to 12 6 months of age. The formulas contained the same protein amount (13.1g/L) but different concentrations of α-lactalbumin and casein-glycomacropeptide: (1) standard formula (11% α-lactalbumin/14% casein-glycomacropeptide; n=10), (2) α-lactalbuminenriched formula (25% α-lactalbumin/15% casein-glycomacropeptide; n=11), and (3) α-lactalbumin-enriched/casein-glycomacropeptide-reduced formula (25% α-lactalbumin/10% casein-glycomacropeptide; n=11). Ten exclusively breastfed infants were recruited as a reference. At 5.5 months of age, infants were given 58 Fe with one of their feeds. Blood samples were collected 14 days later for fractional iron absorption and serum ferritin determination. Results: Mean (±SD) iron absorption was 10.3±7.0% from standard formula, 8.6±3.8% from α-lactalbumin-enriched formula, and 9.2±6.5% from α-lactalbumin-enriched/casein-glycomacropeptide-reduced formula, with no difference among the three formula groups (P=0.92). Iron absorption from all three formulas was 9.4±5.8% compared to 12.9±6.5% from breastmilk (P=0.73). In the formulafed infants, but not the breastfed infants (P=0.51), iron absorption was negatively correlated with serum ferritin (P=0.01), and was higher (P=0.01) in infants with serum ferritin < 12μg/L (16.4±12.4%) compared to those with serum ferritin ≥12μg/L (8.6±4.4%). Conclusions: α-Lactalbumin and casein-glycomacropeptide do not affect iron absorption from low-iron formula in healthy term infants. Low serum ferritin concentrations enhance iron absorption from infant formula.

Nonheme-iron absorption in first-degree relatives is highly correlated: a stable-isotope study in mother-child pairs

Iron absorption in humans is highly variable even after iron status and dietary components that influence iron absorption are controlled for. Inherited factors may help explain this variance. Our objective was to compare nonheme-iron absorption from a noninhibitory, stable-isotope-labeled test meal in preschool-aged children and their mothers. We provided 72 test meals based on degermed maize flour and milk powder and fortified with [(57)Fe]ferrous fumarate or [(58)Fe]ferrous sulfate to healthy Mexican preschool children [n = 18; mean (+/-SD) age: 3.6 +/- 1.0 y] and their mothers [n = 18; mean (+/-SD) age: 28.0 +/- 5.2 y]. Iron absorption was calculated on the basis of incorporation of isotopes into erythrocytes after 14 d and was adjusted for differences in iron status. There was a wide variation in iron absorption from the test meals: in the mothers and children, the median fractional absorption of ferrous sulfate was 22.55% (range: 1.65-54.83%) and 5.51% (range: 2.23-17.20%), respectively (P < 0.0001). After adjustment for serum ferritin, the significant difference in absorption between mothers and their children disappeared. Despite this broad range of iron absorption, corrected fractional iron absorption from the ferrous fumarate-fortified (r(2) = 0.582) and the ferrous sulfate-fortified test meals (r(2) = 0.557) was strongly correlated in mothers and their children (P < 0.0001). There was a striking positive correlation between the mean corrected fractional iron absorption from both test meals in mothers and their children (r(2) = 0.782, P < 0.0001). In regression analyses that included age, sex, and hemoglobin, the only significant predictor of corrected fractional iron absorption in children was corrected fractional iron absorption in their mothers (standardized beta = 0.884, P < 0.001). Nonheme-iron absorption exhibits a strong familial tendency. After differences in meal matrix and serum ferritin are accounted for, these data suggest that inheritance and/or shared environmental factors explain most of the variance in dietary iron absorption.

Iron metabolism in heterozygotes for hemoglobin E (HbE), α-thalassemia 1, or β-thalassemia and in compound heterozygotes for HbE/β-thalassemia

Background: Despite large populations carrying traits for thalassemia in countries implementing universal iron fortification, there are few data on the absorption and utilization of iron in these persons.Objective: We aimed to determine whether iron absorption or utilization (or both) in women heterozygous for β-thalassemia, α-thalassemia 1, or hemoglobin E (HbE) differed from that in control subjects and compound HbE/β-thalassemia heterozygotes.Design: In Thai women (n = 103), red blood cell indexes, iron status, non-transferrin-bound iron, and growth differentiation factor 15 were measured, and body iron was calculated. Fractional iron absorption was measured from meals fortified with isotopically labeled (57Fe) Fe sulfate, and iron utilization was measured by the infusion of (58Fe) Fe citrate.Results: Iron utilization was ≈15% lower in α-thalassemia 1 or β-thalassemia heterozygotes than in controls. When corrected for differences in serum ferritin, absorption was significantly higher in the α- and β-thalassemia groups, but not the HbE heterozygotes, than in controls. HbE/β-thalassemia compound heterozygotes had lower iron utilization and higher iron absorption and body iron than did controls. Nontransferrin-bound iron and growth differentiation factor 15 were higher in the compound heterozygotes, but not in the other groups, than in the controls.Conclusions: In α-thalassemia 1 and β-thalassemia heterozygotes with ineffective erythropoesis, dietary iron absorption is not adequately down-regulated, despite a modest increase in body iron stores. In populations with a high prevalence of these traits, a program of iron fortification could include monitoring for possible iron excess and for iron deficiency.

Ferric reductase activity of low molecular weight human milk fraction is associated with enhanced iron solubility and uptake in Caco-2 cells

It is known that the fractional absorption of extrinsic iron from human milk is higher in infants and adults. A low molecular weight milk fraction has been proposed to increase the bioavailability of iron from human milk. Nevertheless, the mechanisms remained elusive. Here in we demonstrate ferric reductase activity (Km 7.73 × 10 −6 M) in low molecular weight human milk fraction (10kF, filtrate derived from ultra filtration of milk whey through 10 kDa cutoff membrane), which increased ferric iron solubility and iron uptake in Caco-2 cells. The 10kF fraction was as effective as ascorbic acid (1:20 iron to ascorbic acid) in increasing the ferric iron solubility and uptake in Caco-2 cells. Further, gel filtration chromatography on peptide column led to co-elution of ferric reductase and iron solubilization activities at an apparent molecular mass of <1500 Da. Interestingly, only these fractions containing ferric reductase activity also stimulated the uptake of iron in Caco-2 cells. Thus, it is concluded that human milk possesses ferric reductase activity and is associated with ferric iron solubilization and enhanced absorption.

Iron absorption in young Indian women: the interaction of iron status with the influence of tea and ascorbic acid

BackgroundAscorbic acid (AA) enhances and tea inhibits iron absorption. It is unclear whether iron status influences the magnitude of this effect. ObjectiveWe evaluated the influence of the iron status of young women on iron absorption from a rice meal with or without added tea or AA. DesignTwo stable-isotope iron absorption studies were made in 2 groups of 10 subjects with iron deficiency anemia (IDA) and 10 subjects who were iron replete (control subjects). In study 1, the reference rice meal was fed alone or with 1 or 2 cups of black tea. In study 2, the reference meal was fed alone or with AA (molar ratio to iron, 2:1 or 4:1). Iron absorption was measured by the erythrocyte incorporation of 57Fe and 58Fe labels at 14 d. ResultsMean fractional iron absorption from the reference rice meal was ≈2.5 times as great in the IDA group as in the control group (P < 0.05). The consumption of 1 or 2 cups of tea decreased iron absorption in the control subjects by 49% (P < 0.05) or 66% (P < 0.01), respectively, and in the IDA group by 59% or 67% (P < 0.001 for both), respectively. AA (molar ratio to iron, 2:1 or 4:1) increased iron absorption by 270% or 343%, respectively, in control subjects and by 291% or 350%, respectively, in subjects with IDA (P < 0.001). ConclusionsThe inhibitory effect of tea and the enhancing effect of AA on iron absorption were similar in the 2 groups. Overall differences in iron absorption in the 2 groups, however, continued to be dictated by iron status.

Production of stable-isotope-labeled bovine heme and its use to measure heme-iron absorption in children

Background:The use of stable isotopes has provided valuable insights into iron absorption in humans, but the data have been limited to nonheme iron.Objective:Our objectives were to produce heme iron enriched in 58Fe and to use it to study the absorption of heme iron and the effect of iron and zinc intakes on heme-iron absorption in children.Design:Labeled bovine heme was produced in a bovine model. Forty-eight children were randomly assigned to consume identical meals containing 1 of 3 doses of labeled heme iron (2, 4, or 8 mg as hemoglobin) and 1 of 2 doses of inorganic zinc (1 or 9 mg); successful measurements of iron absorption, zinc absorption, or both were made in 40 of these subjects. We hypothesized that fractional heme-iron absorption would decrease as heme-iron intake increased and that higher zinc intakes would decrease heme-iron absorption.Results:58Fe heme was produced with an enrichment (mass/mass) of 9.5%. Fractional iron absorption in children was significantly affected by the intake of heme iron (P= 0.0013) and of zinc (P= 0.0375), but, contrary to expectations, heme-iron absorption was higher at higher zinc intakes. Absolute heme-iron absorption was higher in the group with higher zinc intakes, but only for those with the lowest heme-iron intake (2 mg; P= 0.0147). Although fractional zinc absorption decreased as zinc intake increased (P= 0.031), absolute zinc absorption continued to increase across the intake range studied (P= 0.018).Conclusions:Heme iron intrinsically labeled with 58Fe can be produced at sufficient enrichments for use in human studies. In children, heme iron and zinc absorption decrease as the dose of each mineral increases. Heme iron did not inhibit zinc absorption. At lower heme intakes, zinc intakes may increase heme-iron absorption.

Pork meat increases iron absorption from a 5-day fully controlled diet when compared to a vegetarian diet with similar vitamin C and phytic acid content

Meat increases absorption of non-haem iron in single-meal studies. The aim of the present study was to investigate, over a 5 d period, the potential increasing effect of consumption of pork meat in a whole diet on the fractional absorption of non-haem iron and the total absorption of iron, when compared to a vegetarian diet. A randomised cross-over design with 3 x 5 d whole-diet periods with diets containing Danish-produced meat, Polish-produced meat or a vegetarian diet was conducted. Nineteen healthy female subjects completed the study. All main meals in the meat diets contained 60 g of pork meat and all diets had high phytic acid content (1250 mumol/d). All main meals were extrinsically labelled with the radioactive isotope (59)Fe and absorption of iron was measured in a whole body counter. The non-haem iron absorption from the Danish meat diet was significantly higher compared to the vegetarian diet (P=0.031). The mean fractional absorption of non-haem iron was 7.9 (se1.1), 6.8 (se 1.0) and 5.3 (se 0.6) % for the Danish and Polish meat diets and vegetarian diet, respectively. Total absorption of iron was higher for both meat diets compared to the vegetarian diet (Danish meat diet: P=0.006, Polish meat diet: P=0.003). The absorption ratios of the present study were well in accordance with absorption ratios estimated using algorithms on iron bioavailability. Neither the meat diets nor the vegetarian diets fulfilled the estimated daily requirements of absorbed iron in spite of a meat intake of 180 g/d in the meat diets.

Iron absorption by human subjects from different iron fortification compounds added to Thai fish sauce

(a) To measure iron absorption by human subjects from citric acid stabilized fish sauce fortified with ferrous sulfate, ferric ammonium citrate or ferrous lactate and (b) to identify the effect of added citric acid (3 g/l) on iron absorption from ferrous sulfate fortified fish sauce. Iron absorption from the intrinsically labeled compounds was determined via erythrocyte incorporation of isotopic labels ((57)Fe and (58)Fe) using a randomized crossover design. In three separate absorption studies, 10 adult women each consumed a basic test meal of rice and vegetable soup seasoned with isotopically labeled, iron fortified fish sauce. Iron absorption was significantly lower from ferrous lactate and from ferric ammonium citrate fortified fish sauce than from ferrous sulfate fortified fish sauce. Fractional iron absorption (geometric mean; -1s.d., +1s.d.) was 8.7(3.6; 21.4)% for ferrous lactate compared to 13.0(5.4; 31.4)% from ferrous sulfate, P = 0.003 (study 1) and 6.0(2.5; 14.3)% from ferric ammonium citrate relative to 11.7(4.4; 30.7)% from ferrous sulfate, P < 0.001, in study 2. Citric acid added at a molar ratio of approximately 2.5 to iron had no effect on iron absorption from ferrous sulfate (study 3). Iron absorption in the presence of citric acid was 14.1(6.4; 30.8)% compared to 12.0(5.8; 24.7)% in its absence (P = 0.26). Iron absorption was 50-100% higher from ferrous sulphate fortified fish sauce than from fish sauce fortified with ferric ammonium citrate or ferrous lactate. In the presence of citric acid as a chelator, ferrous sulfate would appear to be a useful fortificant for fish sauce. International Atomic Energy Agency (IAEA), Vienna, Austria.

Caco-2 cell iron uptake from human milk and infant formula

Knowledge of the nutritional quality of iron in human milk and infant formula is of great interest to nutritionists and food scientists. In this paper we review the reasons for a larger fractional (but not absolute) iron absorption from human milk than from infant formulas. We also present the results of an in vitro digestion/Caco-2 cell model system comparing the cell iron uptake of different infant formulas to that from human milk.

Caco-2 cell iron uptake from human milk and infant formula

Knowledge of the nutritional quality of iron in human milk and infant formula is of great interest to nutritionists and food scientists. In this paper we review the reasons for a larger fractional (but not absolute) iron absorption from human milk than from infant formulas. We also present the results of an in vitro digestion/Caco-2 cell model system comparing the cell iron uptake of different infant formulas to that from human milk.