Ascorbic acid offsets the inhibitory effect of bioactive dietary polyphenolic compounds on transepithelial iron transport in Caco-2 intestinal cells

We previously reported that (-)-epigallocatechin-3-gallate (EGCG) and grape seed extract (GSE) at high concentration nearly blocked intestinal iron transport across the enterocyte. In this study, we aimed to determine whether small amounts of EGCG, GSE, and green tea extract (GT) are capable of inhibiting iron absorption, to examine if ascorbic acid counteracts the inhibitory action of polyphenols on iron absorption, and to explore the mechanisms of polyphenol-mediated apical iron uptake and basolateral iron release. An(55)Fe absorption study was conducted by adding various concentrations of EGCG, GSE, and GT using Caco-2 intestinal cells. Polyphenols were found to inhibit the transepithelial (55)Fe transport in a dose-dependent manner. The addition of ascorbic acid offset the inhibitory effects of polyphenols on iron transport. Ascorbic acid modulated the transepithelial iron transport without changing the apical iron uptake and the expression of ferroportin-1 protein in the presence of EGCG. The polyphenol-mediated apical iron uptake was inhibited by membrane impermeable Fe(2+) chelators (P < 0.001), but at a low temperature (4°C), the apical iron uptake was still higher than the control values at 37°C (P < 0.001). These results suggest that polyphenols enhance the apical iron uptake partially by reducing the conversion of ferric to ferrous ions and possibly by increasing the uptake of polyphenol-iron complexes via the energy-independent pathway. The present results indicate that the inhibitory effects of dietary polyphenols on iron absorption can be offset by ascorbic acid. Further studies are needed to confirm the current findings in vivo.     

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.     

Bioactive dietary polyphenolic compounds reduce nonheme iron transport across human intestinal cell monolayers

There is persuasive epidemiological evidence that regular intake of dietary bioactive polyphenolic compounds promotes human health. Because dietary polyphenolic compounds have a wide range of effects in vivo and vitro, including chelation of metals such as iron, it is prudent to test whether the regular consumption of bioactive polyphenolic components impair the utilization of dietary iron. We examined the influence of the dietary polyphenols (-) -epigallocatechin-3-gallate (EGCG) and grape seed extract (GSE) on transepithelial iron transport in Caco-2 intestinal cells. The range of EGCG and GSE concentrations used in this study was within physiological levels and did not affect the integrity of differentiated Caco-2 cell monolayers. Both EGCG and GSE decreased (P < 0.001) transepithelial iron transport. However, apical iron uptake was increased (P < 0.001) by the addition of EGCG and GSE. The increased uptake of iron might be due in part to the reducing activity of EGCG and GSE. Both EGCG and GSE reduced approximately 15% of the applied Fe(3+) to Fe(2+) in the uptake buffer. Despite the increased cellular levels of (55)Fe, the transfer of iron across the basolateral membrane of the enterocyte was extremely low, indicating that basolateral exit via ferroportin-1 was impaired, possibly through formation of a nontransportable polyphenol-iron complex. Our data show that polyphenols inhibit nonheme iron absorption by reducing basolateral iron exit rather than by decreasing apical iron import in intestinal cells.     

Duodenal cytochrome B expression stimulates iron uptake by human intestinal epithelial cells

Duodenal cytochrome B (Dcytb) is localized principally in the apical membrane of the enterocyte. It is thought to act as a ferric reductase that furnishes Fe(II), the specific and selective iron species transported by divalent metal transporter 1 (DMT1) in the duodenal enterocytes. Expression of both genes is strongly iron regulated and is thought to be required for transcellular iron trafficking in concert in response to physiological requirements. We tested this hypothesis by expressing Dcytb in Caco-2 cells, a human cell line model often used to mimic intestinal enterocytes. Iron uptake (59Fe) was significantly higher in Dcytb-transfected Caco-2 cells than in cells transfected with empty vector as a control. Fe(III) reductase activity of Dcytb was measured with ferrozine, a strong chelator of Fe(II) species. Cells expressing Dcytb exhibited enhanced ferric reductase activity as well as increased 59Fe uptake compared with cells transfected with empty vector as a control. Ferrozine blocked iron uptake and preincubation of cells with dehydroascorbate (to increase cellular ascorbate levels) stimulated iron uptake. Cotransfection of Dcytb and DMT1 resulted in an additive increase in iron uptake by the cells. The results confirm Dcytb can act as a ferric reductase that stimulates iron uptake in Caco-2 cells.     

Calcium and iron absorption--mechanisms and public health relevance

Studies on human subjects have shown that calcium (Ca) can inhibit iron (Fe) absorption, regardless of whether it is given as Ca salts or in dairy products. This has caused concern as increased Ca intake commonly is recommended for children and women, the same populations that are at risk of Fe deficiency. However, a thorough review of studies on humans in which Ca intake was substantially increased for long periods shows no changes in hematological measures or indicators of iron status. Thus, the inhibitory effect may be of short duration and there also may be compensatory mechanisms. The interaction between Ca and Fe may be a lumenal event, affecting Fe uptake through DMT1 (divalent metal transporter 1) at the apical membrane. However, it is also possible that inhibition occurs during Fe transfer into circulation, suggesting roles for the serosal exporter ferroportin (FPN) and hephaestin. We explored these possibilities in human intestinal Caco-2 cells cultured in monolayers. Iron transport ((59)Fe) and expression of DMT1, FPN, and hephaestin were assessed after 1.5 and 4 hours with 0 or 100 μM CaCl(2.) Although Ca did not affect Fe uptake or DMT1 expression at 1.5 hours, FPN abundance at the basolateral membrane decreased, resulting in increased cellular Fe retention and decreased Fe efflux. After 4 hours, DMT1 and FPN expression increased and there was increased FPN at the membrane, suggesting a rebound effect. Thus, the effect of Ca on Fe absorption may be of short duration and adaptation may occur with time. This may explain why studies on long-term Ca supplementation of different groups fail to show any adverse effects on Fe status.     

Flavonoid structure affects the inhibition of lipid peroxidation in Caco-2 intestinal cells at physiological concentrations

The antioxidant activity of flavonoids in cell-free systems has been studied extensively. We compared flavonoids with different structural features on their abilities to protect live Caco-2 intestinal cells from lipid peroxidation due to hydrogen peroxide and Fe(2+) treatment. Flavonoids with o-dihydroxyl or vicinal-trihydroxyl groups, including quercetin, myricetin (flavonol), luteolin (flavone) and (-)-epigallocatechin gallate (EGCG; flavanol), when co-incubated with a mixture of 30 micro mol/L H(2)O(2) and 30 micro mol/L FeSO(4), prevented the formation of malondialdehyde (MDA) at 1 or 10 micro mol/L in at least one of two separate experiments. In experiments in which flavonoids were preincubated with cells but removed before the 30 micro mol/L H(2)O(2) and Fe(2+) treatment, quercetin at 0.1 micro mol/L, EGCG at 1 micro mol/L and luteolin at 10 micro mol/L exerted protective effects in at least one of two experiments. Kaempferol (flavonol) and the isoflavones, genistein and daidzein, did not prevent lipid peroxidation at 0.1-10 micro mol/L in either co- or preincubation experiments. None of the flavonoids tested at 0.1-10 micro mol/L increased H(2)O(2) and Fe(2+)-induced lipid peroxidation after co- or preincubation. In summary, these observations support the importance of plant-based food items such as vegetables, fruits and teas in the diet.     

Calcium does not inhibit iron absorption or alter iron status in infant piglets adapted to a high calcium diet

The purpose of this study was to investigate whether a dietary calcium:iron ratio similar to that often consumed by premature human infants inhibits iron absorption in infant piglets adapted to a high calcium diet. Male Yorkshire piglets were randomized at 3 to 4 d of age to a high calcium diet (4.67 g/L = HC) or a normal calcium diet (2.0 g/L = NC) and fed for 2 to 2.5 wk. An iron dextran injection was administered in amounts to achieve a marginal state of iron repletion to simulate iron status of premature infants. In vivo iron absorption from the diet was determined using the radiotracers 55Fe and 59Fe and whole body counting. Calcium:iron interactions at absorption sites in piglets fed HC and NC were investigated by measurements of time-dependent 59Fe uptake in response to different calcium:iron ratios in vitro in brush border membrane vesicles (BBMV). In vivo iron absorption from the diet did not differ between NC and HC diet groups [57 +/- 8% versus 55 +/- 17% (mean +/- SD), respectively]. Iron status and iron contencentrations in spleen, liver, intestine, kidney and heart did not differ between diet groups. Iron uptake in BBMV was significantly reduced by calcium in both HC and NC (P < 0.001); but there were no significant differences in iron uptake in response to different calcium:iron ratios between HC and NC. With feeding a HC diet for 2 wk there may be an adaptive response to counteract the inhibitory effects of calcium on iron absorption, thus resulting in similar in vivo iron absorption and iron status irrespective of the 1.3-fold difference in dietary calcium:iron ratio between piglet groups. However, future studies are needed to determine the specific sites of calcium:iron interactions and adaptation mechanisms. Since the calcium:iron ratios used in this study reflect the usual calcium:iron ratios in diets for premature infants, it is unlikely that interactive effects of calcium with iron will compromise iron status in this infant population when diets are supplemented with calcium.     

Nonheme-iron absorption from a phytate-rich meal is increased by the addition of small amounts of pork meat

BACKGROUND: Muscle tissue from various sources is known to promote nonheme-iron absorption. However, systematic studies of the dose dependency of this effect of meat on iron absorption from an inhibitory meal with low amounts of meat are lacking. OBJECTIVE: We investigated the dose-response effect of small amounts of meat on nonheme-iron absorption from a meal presumed to have low iron bioavailability. DESIGN: Forty-five healthy women with a mean (+/-SD) age of 24 +/- 3 y were randomly assigned to 1 of 3 groups, each of which was served (A) a basic meal (rice, tomato sauce, pea purée, and a wheat roll) and (B) the basic meal with either 25, 50, or 75 g pork (longissimus muscle). Meal A contained 2.3 mg nonheme iron, 7.4 mg vitamin C, and 220 mg (358 micro mol) phytate. Each meal was served twice, and the order of the meals was ABBA or BAAB. The meals were extrinsically labeled with (55)Fe or (59)Fe. Iron absorption was determined from measurements of (59)Fe whole-body retention and the activity of (55)Fe and (59)Fe in blood samples. RESULTS: Twenty-five grams meat did not increase nonheme-iron absorption significantly (P = 0.13), whereas absorption increased 44% (P < 0.001) and 57% (P < 0.001), respectively, when 50 and 75 g meat were added to the basic meal. In absolute values, this corresponds to an absorption that was 2.6% and 3.4% higher, respectively, than that with the basic meal after adjustment of the data to a level of 40% absorption from a reference dose. CONCLUSION: Small amounts of meat (>or=50 g) significantly increase nonheme-iron absorption from a phytate-rich meal low in vitamin C.     

Incorporation of iron from an oral dose into the ferritin of the duodenal mucosa and the liver of normal and iron-deficient rats

To further characterize the role of ferritin in regulating iron absorption, uptake of an oral dose of 59Fe (0.2 mg Fe/kg body wt.) into duodenal and hepatic ferritin of control and iron-deficient (ID) rats was studied. Retention and uptake of 59Fe from Fe(II)-sulfate, Fe(III)-chloride, or Fe(III)-polymaltose were measured up to 28 h after dosing. Ferritin was determined by radioimmunoassay (RIA) and 59Fe ferritin-iron by gel electrophoresis. Retention and liver content of 59Fe was higher in ID rats than in controls. The mucosa of ID rats, however, retained only one third of the amount of 59Fe retained by the mucosa of controls. The mucosal and hepatic ferritin levels were lower in ID rats than in controls. The percentage of orally administered 59Fe found in the liver ferritin was therefore higher in control than in ID rats. However, when expressed as per unit of ferritin, iron uptake was eight times higher in ID rats. In contrast, mucosa ferritin of ID rats contained one-third of 59Fe per unit of ferritin than that of controls. Assuming no change in the mechanism of iron uptake into ferritin of control and ID rats, the differential uptake of oral iron into mucosa and liver ferritin indicates either a different compartmentation of the tissue ferritin or differences in the iron transport processes, but mucosal ferritin does not withdraw iron from intestinal absorption.     

Iron supplements inhibit zinc but not copper absorption in vivo in ileostomy subjects

BACKGROUND: Iron supplements may inhibit intestinal zinc and copper uptake because these elements may compete for binding to a transporter molecule (divalent metal transporter 1) that is located on the apical side of the small intestinal epithelium. OBJECTIVE: We quantified the interaction between different amounts of administered iron and the absorption of zinc and copper in humans. DESIGN: Eleven subjects with an ileostomy [mean (+/- SD) age: 55 +/- 9 y] ingested a stable-isotope-labeled zinc and copper solution containing 12 mg Zn ((66)Zn and (67)Zn) and 3 mg Cu ((65)Cu) in the presence of 0, 100, or 400 mg Fe as ferrous gluconate on 3 respective test days. Subsequently, 1 mg (70)Zn was injected intravenously. Subjects collected ileostomy effluent and urine for 24 h and 7 d, respectively. Zinc status and true zinc absorption were calculated from the urinary excretion of the zinc isotopes. Apparent copper absorption was calculated from ileostomy effluent excretion of the orally administered copper isotopes. RESULTS: Zinc status did not differ significantly between the 3 iron doses. Mean (+/- SEM) zinc absorption was significantly higher in the absence of iron than with the concomitant ingestion of 100 or 400 mg Fe (44 +/- 22% compared with 26 +/- 14% and 23 +/- 6%, respectively; P < 0.05), whereas zinc absorption did not differ significantly between the 100- and 400-mg Fe doses. Apparent copper absorption was 48 +/- 14%, 54 +/- 26%, and 53 +/- 7% in the presence of 0, 100, and 400 mg Fe, respectively, and did not differ significantly between the 3 iron doses. CONCLUSION: Oral iron therapy may impair zinc absorption and thus zinc status in a dose-independent fashion but does not affect copper absorption.     

Lactobacillus casei alters hPEPT1-mediated glycylsarcosine uptake in Caco-2 cells

Augmentation of the normal flora of the gastrointestinal tract with probiotic bacteria is currently under investigation as a therapeutic tool for several diseases. However, it is unknown whether probiotic bacteria such as Lactobacillus casei alter the expression and function of intestinal transport proteins such as hPEPT1. The effects of 24 and 48 h incubation of Caco-2 cells with 10(8)/L L. casei on the hPEPT1-mediated uptake rate of 20 micro mol/L [(3)H]glycylsarcosine were examined. Dipeptide uptake did not differ from the control at 24 h (15.9 +/- 2.4 vs. 11.5 +/- 1.4 cm.s(-1).mg protein(-1)); however, a significant increase in uptake occurred after 48 h of L. casei treatment (23.7 +/- 1.5 vs. 12.0 +/- 1.9 cm.s(-1).mg protein(-1); P = 0.005). hPEPT1 involvement was confirmed in experiments using excess substrate. Increased uptake of [(3)H]glycylsarcosine appeared to be the result of the direct interaction of the bacteria with Caco-2 cells because conditioned medium had no effect on dipeptide uptake. hPEPT1 mRNA levels did not differ at any time point. These results show that prolonged incubation of Caco-2 cells leads to increased hPEPT1 activity and that this occurs by a mechanism distinct from increased gene expression.     

Choline uptake in human intestinal Caco-2 cells is carrier-mediated

The objective of the current investigation was to examine the transport characteristics of choline, an endogenous quaternary ammonium compound, into human intestinal Caco-2 cells; the transport of choline has not been characterized in human intestine. The cellular accumulation of choline was independent of an inwardly directed Na(+) gradient and demonstrated temperature dependence and saturability. Using the initial uptake rates, choline accumulation was best characterized by a Michaelis-Menten equation and a diffusion component with a K(m) and V(max) of 110 +/- 3 micro mol/L and 2800 +/- 250 pmol/(mg protein. 10 min), respectively. Choline uptake was significantly inhibited by an excess of choline itself and by hemicholinium-3, a structural analog of choline. However other hydrophilic organic cations, such as tetraethylammonium (TEA) and N-methylnicotinamide (NMN), did not affect choline uptake in Caco-2 cells. Additionally, two typical p-glycoprotein substrates, daunomycin and verapamil, both inhibited choline accumulation. However the opposite was not true: choline did not inhibit DNM accumulation in Caco-2 cells. These results indicate the presence of a carrier-mediated transport system for choline in Caco-2 cells. The substrate specificity of this carrier is unlike that seen in the rat intestinal epithelium, and the human transport protein is distinct from those for TEA and NMN. P-glycoprotein substrates may inhibit choline uptake through specific or nonspecific interactions with the choline transporter.     

Beta-carotene and inhibitors of iron absorption modify iron uptake by Caco-2 cells

A National fortification program instituted in Venezuela in 1993 reduced iron deficiency and anemia by half in only 1 y. The fortification mixture contained ferrous fumarate, vitamin A and other vitamins. We conducted experiments to characterize ferrous fumarate uptake by Caco-2 cells. Increasing amounts of ferrous fumarate, vitamin A, phytate, tannic acid and beta-carotene were added to incubation mixtures using a range of concentrations that included the molar ratios used in the Venezuelan fortification program. Cells were incubated for 1 h at 37 degrees C with 37 kBq (59)Fe and the compound to be evaluated. They were then rinsed, trypsinized and counted to measure uptake. Effects of ascorbic acid, days in culture and use of flasks or inserts were also evaluated. Optimal conditions for uptake experiments were pH 5.5, in the presence of ascorbic acid and at 16 d in culture. Use of flasks or inserts did not affect uptake. Vitamin A did not significantly increase iron uptake under the experimental conditions employed. However, beta-carotene (6 micromol/L) significantly increased iron uptake compared to no beta-carotene addition (114.9 +/- 6.3 and 47.2 +/- 5.9 pmol/mg cell protein, respectively). Moreover, in the presence of phytates or tannic acid, beta-carotene generally overcame the inhibitory effects of both compounds depending on their concentrations. We conclude that beta-carotene improves iron uptake and overcomes the inhibition by potent inhibitors of iron absorption. These experiments also validated the usefulness of Caco-2 cell model system to evaluate iron metabolism.     

Caco-2 intestinal epithelial cells absorb soybean ferritin by mu2 (AP2)-dependent endocytosis

Iron deficiency, a condition currently affecting approximately 3 billion people, persists in the 21st century despite half a millennium of medical treatment. Soybean ferritin (SBFn), a large, stable protein nanocage around a mineral with hundreds of iron and oxygen atoms, is a source of nutritional iron with an unknown mechanism for intestinal absorption. Iron absorption from SBFn is insensitive to phytate, suggesting an absorption mechanism different from for the ferrous transport. Here, we investigated the mechanism of iron absorption from mineralized SBFn using Caco-2 cells (polarized in bicameral inserts) as an intestinal cell mode and analyzed binding, internalization and degradation with labeled SBFn ((131)I or fluorescent labels), confocal microscopy, and immunoanalyses to show: 1) saturable binding to the apical cell surface; dissociation constant of 7.75 +/- 0.88 nmol/L; 2) internalization of SBFn that was dependent on temperature, concentration, and time; 3) entrance of SBFn iron into the labile iron pool (calcein quenching); 4) degradation of the SBFn protein cage; and 5) assembly peptide 2 (AP2)-/clathrin-dependent endocytosis (sensitivity of SBFn uptake to hyperosmolarity, acidity, and RNA interference to the mu(2) subunit of AP2), and resistance to filipin, a caveolar endocytosis inhibitor. The results support a model of SBFn endocytosis through the apical cell membrane, followed by protein cage degradation, mineral reduction/dissolution, and iron entry to the cytosolic iron pool. The large number of iron atoms in SBFn makes iron transport across the cell membrane a much more efficient event for SBFn than for single iron atoms as heme or ferrous ions.     

Lactic acid fermentation stimulated iron absorption by Caco-2 cells is associated with increased soluble iron content in carrot juice

An in vitro digestion/Caco-2 cell model was applied to explore the impact of lactic acid (LA) fermentation by Lactobacillus pentosus FSC1 and Leuconostoc mesenteroides FSC2 on the Fe bioavailability of carrot juice. The redox state of Fe in fermented carrot juice was also assessed as a crucial factor for absorption. LA fermentation was shown to improve mineral solubility to different extents at simulated physiological conditions: Mn (2-fold); Fe (1.5-1.7-fold); Zn (1.2-fold); Cu (1-fold). Soluble Fe2+ was increased about 16-fold by LA fermentation, and about one third of the Fe2+ remained soluble after in vitro digestion (about 4-5-fold higher than in fresh juice). Data on cell-line studies showed a 4-fold increase in the efficiency of Fe uptake, but not in transepithelial transfer by Caco2 cells, as a result of fermentation. The increases in Fe2+ level and the efficiency of cellular Fe uptake were strain-dependent. To sum up the effect on both Fe solubility and cellular uptake efficiency, the amount of cellularly absorbed Fe from Ln. mesenteroides FSC2-fermented juice was about 20 % higher than that from L. pentosus FSC1-fermented juice (22.7 v. 19.2 microg/l juice per mg protein). To conclude, LA fermentation enhanced Fe absorption by Caco-2 cells from carrot juice because of increases in not only Fe solubility after digestion, but also the efficiency of cellular Fe uptake. The fermentation-improved efficiency of Fe uptake was possibly due to the increased level of soluble Fe2+ rather than a being a strain-specific event.     

Unique uptake and transport of isoflavone aglycones by human intestinal caco-2 cells: comparison of isoflavonoids and flavonoids

Soy isoflavonoids have attracted much attention because of their estrogenic activity. To study the intestinal absorption of the isoflavonoids, we investigated the cellular uptake and metabolism of genistein and daidzein and their glucosides, genistin and daidzin, by Caco-2 cell monolayers as a model of the human intestinal epithelium. When Caco-2 monolayers were incubated with genistein or daidzein at 10 micromol/L from the apical (mucosal) side, aglycone was lost from the apical solution for 2.0 h (P < 0.05) and the glucuronide/sulfates appeared at the level of 1-2 micromol/L. In the basolateral (serosal) solution, both intact aglycones and their glucuronide/sulfates increased (P < 0.05) with time and reached approximately 20 and 15% of the initial dose, respectively. The transport of their glucosides, genistin and daidzin, through Caco-2 monolayers was less than one tenth that of the aglycones. The cellular metabolism of genistein was compared with quercetin, kaempferol, luteolin and apigenin. Only genistein aglycone was transported intact to the basolateral solution. Transport was greater (P < 0.05) than that of flavonoid aglycones and was without an appreciable decrease of transepithelial resistance. Radical scavenging activity was not related to the susceptibility to conjugation of flavonoids/isoflavonoids. Affinity to the liposomal membrane was increased in the order of genistin = daidzin < daidzein < genistein < flavonoid aglycones. These results strongly suggest that isoflavone aglycones are taken up into enterocytes more efficiently than their glucosides because of their moderate lipophilicity. Furthermore, they are generally transported to the basolateral side in intact form in contrast to flavonoids, probably due to their unique isoflavonoid structure.     

Experience with ferrous bis-glycine chelate as an iron fortificant in milk

The objective of this study was to test whether milk is an appropriate vehicle for fortification with ferrous bis-glycine chelate and whether it has any effect on milk's organoleptic properties. In addition, the study examined the children's acceptability and tolerance of the fortifying agent. One hundred thirty-one children aged 6-14 years (79 males and 52 females) from two dormitories of the Ministry of Social Welfare in Riyadh City, Saudi Arabia participated in this study. The results of this trial showed that milk fortified with this iron chelate has unaltered organoleptic properties and is well accepted by the children. Hemoglobin and serum ferritin levels were measured before and after consuming one liter of milk fortified with 30 mg ferrous bis-glycine chelate per liter (6 mg elemental iron per liter) per day, for a period of three months. The prevalence of anemia (Hb < 12 g/dL) significantly dropped from 25.3 to 5.0%, and 23.0 to 9.6%, among boys and girls respectively. The prevalence of low serum ferritin values among boys dropped from 8.8 to 5.9% and significantly from 21.1 to 12.1% among girls. No control group was included in this study. It is concluded that ferrous bis-glycine chelate in milk does not alter milk's organoleptic properties; furthermore, it improved hemoglobin and ferritin serum levels among anemic children, suggesting milk as an appropriate vehicle for fortification with this chelate.     

Iron absorption from ferrous bisglycinate and ferric trisglycinate in whole maize is regulated by iron status

BACKGROUND: There is a need to determine whether iron absorption from iron amino acid chelates is protected from inhibition by dietary phytate and regulated normally by iron status. OBJECTIVE: The objective of this study was to compare iron absorption from ferrous sulfate, ferrous bisglycinate, and ferric trisglycinate in whole-maize meal; to determine whether iron from ferrous bisglycinate and ferrous sulfate exchanges in the intestinal pool; and to assess iron absorption from ferrous bisglycinate and ferric trisglycinate over a range of iron statuses. DESIGN: In study 1A, 10 iron-sufficient men consumed ferrous sulfate-fortified whole-maize meal porridge equilibrated with (59)Fe-sulfate on day 1 and (55)Fe-bisglycinate on day 2. In study 1B, these volunteers consumed ferrous sulfate-fortified porridge equilibrated with (59)Fe-sulfate and (55)Fe-bisglycinate simultaneously. In studies 2A and 2B, iron absorption from 3 mg Fe as (59)Fe-ascorbate, (55)Fe-bisglycinate, or (59)Fe-trisglycinate in water and in porridge was compared in 23 subjects with a range of iron statuses. Iron absorption was determined from blood radioactivity on day 16. RESULTS: In study 1A, geometric mean iron absorption from ferrous bisglycinate was 6.0% (range: 2.6-13.6%), 4 times higher than that from ferrous sulfate (1. 7%; range: 1.0-3.3%; P < 0.05). In study 1B, absorption from neither source was different from that in study 1A. In studies 2A and 2B, absorption from all sources was strongly inversely related to serum ferritin, with geometric means of 32.5% (iron ascorbate), 9.1% (bisglycinate), and 15.3% (trisglycinate). Iron from ferric trisglycinate was poorly absorbed (2.3%; range: 0.5-9.2%) from maize. CONCLUSION: In whole-maize meal, iron from ferrous bisglycinate is better absorbed than is iron from ferrous sulfate and does not exchange with iron from maize or ferrous sulfate in the intestinal pool. Absorption of iron from bisglycinate and trisglycinate is regulated normally by iron status.