Histidine content of low-molecular-weight beef proteins influences nonheme iron bioavailability in Caco-2 cells

Effects of green tea polyphenols on inflammation and iron status

Inflammation is an underlying problem for many disease states and has been implicated in iron deficiency (ID). This study aimed to determine whether iron status is improved by epigallocatechin-3-gallate (EGCG) through reducing inflammation. Thirty-two male Sprague-Dawley rats were fed an iron-deficient diet for 2 weeks and then randomly divided into four groups (n 8 each): positive controls, negative controls, lipopolysaccharide (LPS, 0⋅5 mg/kg body weight), and LPS + EGCG (LPS plus 600 mg EGCG/kg diet) for 3 additional weeks. The study involved testing two control groups, both treated with saline. One group (positive control) was fed a regular diet containing standard iron, while the negative control was fed an iron-deficient diet. Additionally, two treatment groups were tested. The first group was given LPS, while the second group was administered LPS and fed an EGCG diet. Iron status, hepcidin, C-reactive protein (CRP), serum amyloid A (SAA), and interleukin-6 (IL-6) were measured. There were no differences in treatment groups compared with control in CRP, hepcidin, and liver iron concentrations. Serum iron concentrations were significantly lower in the LPS (P = 0⋅02) and the LPS + EGCG (P = 0⋅01) than in the positive control group. Compared to the positive control group, spleen iron concentrations were significantly lower in the negative control (P < 0⋅001) but not with both LPS groups. SAA concentrations were significantly lower in the LPS + EGCG group compared to LPS alone group. EGCG reduced SAA concentrations but did not affect hepcidin or improve serum iron concentration or other iron markers.

Tagging Recombinant Proteins to Enhance Solubility and Aid Purification

Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has a long history, and there is a considerable repertoire of these that can be used to address issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. In this chapter, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.

Opportunities for plant-derived enhancers for iron, zinc, and calcium bioavailability: A review

Understanding of the mechanism of interactions between dietary elements, their salts, and complexing/binding ligands is vital to manage both deficiency and toxicity associated with essential element bioavailability. Numerous mineral ligands are found in both animal and plant foods and are known to exert bioactivity via element chelation resulting in modulation of antioxidant capacity or micobiome metabolism among other physiological outcomes. However, little is explored in the context of dietary mineral ligands and element bioavailability enhancement, particularly with respect to ligands from plant-derived food sources. This review highlights a novel perspective to consider various plant macro/micronutrients as prospective bioavailability enhancing ligands of three essential elements (Fe, Zn, and Ca). We also delineate the molecular mechanisms of the ligand-binding interactions underlying mineral bioaccessibility at the luminal level. We conclude that despite current understandings of some of the structure-activity relationships associated with strong mineral-ligand binding, the physiological links between ligands as element carriers and uptake at targeted sites throughout the gastrointestinal (GI) tract still require more research. The binding behavior of potential ligands in the human diet should be further elucidated and validated using pharmacokinetic approaches and GI models.

Interaction between iron and dihydromyricetin extracted from vine tea

In this research, the interaction between dihydromyricetin (DMY) obtained from vine tea and iron ions (Fe (II) and Fe (III)) was investigated at pH 3.0, 5.0, and 7.0 with UV absorption and fluorescence quenching spectroscopy. The effects of DMY on the stability and solubility of iron ion were also studied. The results showed the presence of iron ions changed the UV absorption spectra of DMY at the experimental pH values. And the fluorescence spectra showed that iron ion had enhanced fluorescence effect on DMY. In addition, DMY was capable of protecting Fe (II) from being oxidized and improving the solubility of Fe (III).

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Protective Role of Histidine Supplementation Against Oxidative Stress Damage in the Management of Anemia of Chronic Kidney Disease

Anemia is a major health condition associated with chronic kidney disease (CKD). A key underlying cause of this disorder is iron deficiency. Although intravenous iron treatment can be beneficial in correcting CKD-associated anemia, surplus iron can be detrimental and cause complications. Excessive generation of reactive oxygen species (ROS), particularly by mitochondria, leads to tissue oxidation and damage to DNA, proteins, and lipids. Oxidative stress increase in CKD has been further implicated in the pathogenesis of vascular calcification. Iron supplementation leads to the availability of excess free iron that is toxic and generates ROS that is linked, in turn, to inflammation, endothelial dysfunction, and cardiovascular disease. Histidine is indispensable to uremic patients because of the tendency toward negative plasma histidine levels. Histidine-deficient diets predispose healthy subjects to anemia and accentuate anemia in chronic uremic patients. Histidine is essential in globin synthesis and erythropoiesis and has also been implicated in the enhancement of iron absorption from human diets. Studies have found that L-histidine exhibits antioxidant capabilities, such as scavenging free radicals and chelating divalent metal ions, hence the advocacy for its use in improving oxidative stress in CKD. The current review advances and discusses evidence for iron-induced toxicity in CKD and the mechanisms by which histidine exerts cytoprotective functions.

Potential of Food Hydrolyzed Proteins and Peptides to Chelate Iron or Calcium and Enhance their Absorption

Iron and calcium are two essential micronutrients that have strong effects on nutrition and human health because of their involvement in several biological and redox processes. Iron is responsible for electron and oxygen transport, cell respiration, and gene expression, whereas calcium is responsible for intracellular metabolism, muscle contraction, cardiac function, and cell proliferation. The bioavailability of these nutrients in the body is dependent on enhancers and inhibitors, some of which are found in consumed foods. Hydrolyzed proteins and peptides from food proteins can bind these essential minerals in the body and facilitate their absorption and bioavailability. The binding is also important because excess free iron will increase oxidative stress and the risks of developing chronic diseases. This paper provides an overview of the function of calcium and iron, and strategies to enhance their absorption with an emphasis on hydrolyzed proteins and peptides from foods. It also discusses the relationship between the structure of peptides and their potential to act as transition metal ligands.

Enzymatic treatment of pork protein for the enhancement of iron bioavailability

The typical intervention for iron-deficiency anaemia is through oral supplementation with iron salts, which have unpleasant side effects. Therefore, there is a need for the development of supplements which will be absorbed more effectively and may have fewer side effects. This study investigated the effects of partially hydrolysed pork proteins on the bioavailability of non-haem iron. The peptides were derived using either pepsin or a combination of bacterial and fungal proteases, and their ability to deliver iron was evaluated in a rat intestine epithelial tissue model. The greatest iron absorption was achieved with peptides hydrolysed by pepsin of low molecular weight (<6-8 kDa). The peptides hydrolysed with bacterial and fungal enzymes may have bound to the iron too strongly, affecting bioavailability. Finally, hydrolysing proteins using pepsin in the presence of iron produces a complex that resulted in more ferritin expression than mixing the peptides with iron after hydrolysis.

Non-Heme Iron Loading Capacities of Anchovy (Engraulis japonicus) Meat Fractions under Simulated Gastrointestinal Digestion

A ferric oxyhydroxide nanoparticle (FeONP)-mediated mechanism has been suggested recently for anchovy (Engraulis japonicus) meat (AM) enhancement of non-heme iron absorption. The current paper fractionates AM biomass into protein (70.67%), lipid (20.98%), and carbohydrate (i.e., glycogen and mucopolysaccharide, 1.07%) and evaluates their capacities in templating the formation of FeONPs under simulated gastrointestinal digestion. Results show that their iron-loading capacities (mg/g) follow the ascending order glycogen (2.43 ± 0.65), protein (20.16 ± 0.56), AM (28.19 ± 0.86), lipid (33.60 ± 1.12), and mucopolysaccharide (541.33 ± 32.33). Protein and lipid act in synergy to contribute the overwhelming majority (about 90%) of AM's iron-loading capacity. l-α-Phosphatidylcholine and l-α-lysophosphatidylcholine are the predominant iron-loading fractions in the lipid digest. Dynamic light scattering and transmission electron microscopy exhibit coating of inorganic cores of the formed FeONPs with peptides or phospholipid-based mixed micelles. Overall, protein and phospholipid are key players in the nanoparticle-mediated "meat factor" mechanism.

Tagging Recombinant Proteins to Enhance Solubility and Aid Purification

Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.

Affinity chromatography: A versatile technique for antibody purification

Antibodies continue to be extremely utilized entities in myriad applications including basic research, imaging, targeted delivery, chromatography, diagnostics, and therapeutics. At production stage, antibodies are generally present in complex matrices and most of their intended applications necessitate purification. Antibody purification has always been a major bottleneck in downstream processing of antibodies, due to the need of high quality products and associated high costs. Over the years, extensive research has focused on finding better purification methodologies to overcome this holdup. Among a plethora of different techniques, affinity chromatography is one of the most selective, rapid and easy method for antibody purification. This review aims to provide a detailed overview on affinity chromatography and the components involved in purification. An array of support matrices along with various classes of affinity ligands detailing their underlying working principles, together with the advantages and limitations of each system in purifying different types of antibodies, accompanying recent developments and important practical methodological considerations to optimize purification procedure are discussed.

Amino acid composition and antioxidant activities of hydrolysates and peptide fractions from porcine collagen

The amino acid composition and antioxidant activities of different hydrolysates from porcine collagen were analyzed. The gelatin was hydrolyzed for antioxidative peptides with various proteases, namely papain, protease from bovine pancreas, protease from Streptomyces, and cocktail mixture of protease from bovine pancreas and protease from Streptomyces. The hydrolysates were assessed using methods of DPPH radical-scavenging ability, metal-chelating ability and lipid peroxidation inhibition activity. It was found that the collagen hydrolysates by different protease treatments had different amino acid compositions and antioxidant properties. However, the contents of Hyp and Pro were improved and the content of Gly was decreased in each collagen hydrolysate compared with collagen. The hydrolysate prepared with the cocktail mixture of proteases, which exhibited the highest antioxidant activity, was separated into 6 fractions by gel filtration chromatography. Fraction 2 was further separated by ion exchange chromatography. Fraction 2b with abundant basic amino acids and Fraction 2d which was slightly acidic fractions had higher radical-scavenging and metal-chelating activities, and both Fraction 2b and 2d contained more hydrophobic amino acids. The results confirmed that the antioxidative peptides were rich in Hyp, Pro and Gly, which accounted for half of amino acid composition. This article added further support to the preparation of natural antioxidative peptides from porcine skin collagen.

Iron-chelating activity of chickpea protein hydrolysate peptides

Chickpea-chelating peptides were purified and analysed for their iron-chelating activity. These peptides were purified after affinity and gel filtration chromatography from a chickpea protein hydrolysate produced with pepsin and pancreatin. Iron-chelating activity was higher in purified peptide fractions than in the original hydrolysate. Histidine contents were positively correlated with the iron-chelating activity. Hence fractions with histidine contents above 20% showed the highest chelating activity. These results show that iron-chelating peptides are generated after chickpea protein hydrolysis with pepsin plus pancreatin. These peptides, through metal chelation, may increase iron solubility and bioavailability and improve iron absorption.

Separation and identification of zinc-chelating peptides from sesame protein hydrolysate using IMAC-Zn²⁺ and LC-MS/MS

The metal chelating peptides from sesame protein hydrolysates (SPH), treated by papain, alcalase and trypsin, respectively, were investigated. The hydrolysates treated by trypsin had the highest metal chelating ability. The metal chelating peptides were isolated from the trypsin hydrolysates using immobilized metal affinity chromatography (IMAC-Zn(2+)). Further, six zinc-chelating peptides were identified with reversed phase (RP)-HPLC and mass spectrometry (LC-MS/MS). Three of these metal-chelating peptides, Ser-Met, Leu-Ala-Asn and Asn-Cys-Ser, were synthesized and the metal-chelating ability of peptides was measured. The Asn-Cys-Ser peptide showed the highest zinc and iron chelating ability, which was even higher than reduced glutathione (GSH). The results confirm that the zinc or iron chelating activity of these peptides, and provide further support to its feasibility as natural metal chelating agents from sesame protein.

Iron transport machinery of human cells: players and their interactions

Organisms, like cells, maintain tight control of iron. In humans as well as other mammals, control is achieved through the regulation of iron uptake into the body rather than through the excretion of iron. The mechanisms by which humans and mice regulate both iron uptake and the distribution of iron within the body and cells are reviewed. Special emphasis is given to the iron transporters involved in this process.

Heating chicken breast muscle reduces the amount of dialyzable iron after extraction and digestion

We studied the effect of heating chicken breast muscle on the amount of dialyzable iron derived from added ferric iron. The chicken was homogenized and heated to temperatures in the range of 130-195°F. The heated muscle was mixed with ferric iron and either extracted with acid or digested with pepsin and pancreatin. Similar amounts of dialyzable iron were observed after extraction and proteolytic digestion; however, digestion led to more dialyzable ferrous iron. Heating caused markedly reduced levels of dialyzable iron and dialyzable ferrous iron both by extraction and digestion. In the range of 130-165°F the losses were due mainly to reduced levels of ferrous iron. At 195°F both ferric and ferrous dialyzable iron levels were markedly reduced (>80%) compared to raw muscle. At 165°F losses in dialyzable iron after extraction were much greater than after digestion. Heating caused progressive losses in sulfhydryl and histidine residues and mostly lowered protein digestibility. Our results demonstrate that heating muscle above 130°F causes losses in dialyzable iron, coincident with (and possibly due to) losses in amino acid residues that reduce and chelate iron. The results suggest that cooking chicken muscle will reduce its ability to promote non-haem iron uptake and that the magnitude of the reduction will tend to increase with increasing temperature.

Affinity chromatography as a tool for antibody purification

The global antibody market has grown exponentially due to increasing applications in research, diagnostics and therapy. Antibodies are present in complex matrices (e.g. serum, milk, egg yolk, fermentation broth or plant-derived extracts). This has led to the need for development of novel platforms for purification of large quantities of antibody with defined clinical and performance requirements. However, the choice of method is strictly limited by the manufacturing cost and the quality of the end product required. Affinity chromatography is one of the most extensively used methods for antibody purification, due to its high selectivity and rapidity. Its effectiveness is largely based on the binding characteristics of the required antibody and the ligand used for antibody capture. The approaches used for antibody purification are critically examined with the aim of providing the reader with the principles and practical insights required to understand the intricacies of the procedures. Affinity support matrices and ligands for affinity chromatography are discussed, including their relevant underlying principles of use, their potential value and their performance in purifying different types of antibodies, along with a list of commercially available alternatives. Furthermore, the principal factors influencing purification procedures at various stages are highlighted. Practical considerations for development and/or optimizations of efficient antibody-purification protocols are suggested.

Affinity purification and characterisation of chelating peptides from chickpea protein hydrolysates

A chickpea protein hydrolysate produced with pepsin and pancreatin was used for the affinity purification of chickpea chelating peptides. Three chelating peptide fractions were obtained after affinity chromatography with immobilised copper. These peptide fractions showed a higher chelating activity and histidine contents than the original protein hydrolysate. Chelating activity was positively correlated with the histidine content of the purified fractions. Different subfractions were also obtained after gel filtration chromatography from the affinity purified peptide fractions. Some of these subfractions showed a higher chelating activity and histidine contents than the original fractions. These results suggest that a combination of high His contents, around 20-30%, and small peptide size provide the best chelating activities. Thus sequential purification with affinity and gel filtration chromatography is a useful procedure for the purification of chickpea peptides with high chelating activity. These results show that a range of chelating peptides are generated during digestion of the chickpea proteins that, after metal chelation, may prevent the generation of reactive oxygen species (ROS) and favour metal absorption.

Molecular mechanism of intestinal iron absorption

Iron is an essential trace metal in the human diet because of its role in a number of metabolic processes including oxygen transport. In the diet, iron is present in two fundamental forms, heme and non-heme iron. This article presents a brief overview of the molecular mechanisms of intestinal iron absorption and its regulation. While many proteins that orchestrate iron transport pathway have been identified, a number of key factors that control the regulation of iron absorption still remain to be elucidated. This review also summarizes new and emerging information about iron metabolic regulators that coordinate regulation of intestinal iron absorption.

Tagging recombinant proteins to enhance solubility and aid purification

Protein fusion technology has enormously facilitated the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags are outlined.

Identification and characteristics of iron-chelating peptides from soybean protein hydrolysates using IMAC-Fe3+

The iron-chelating peptides from soybean protein hydrolysates (SPH) were investigated using immobilized metal affinity chromatography (IMAC). The results demonstrated that SPH could absorb on the IMAC-Fe(3+) column, while the capability of the binding iron was different in SPH (10-30 kDa), SPH (3-10 kDa), and SPH (1-3 kDa). The highest binding amount on the column occurred with SPH (10-30 kDa). With the IMAC method, the iron-chelating peptides were shown to be formed at pH lower than 5.5, and they were not affected by NaCL with the concentration between 0.1 mol/L and 1 mol/L, while the iron-chelating peptides could be partially disrupted by 0.02 mol/L Na(2)HPO(4) at pH 8.0. Furthermore, the iron-chelating peptides were identified with reversed phase (RP)-HPLC, SDS-PAGE, and MALDI-TOF MS/MS. The binding characteristics of the SPH on IMAC-Fe(3+) and the sequences of the iron-chelating peptides revealed that binding sites between SPH and iron might be the carboxyl groups of Glu and Asp residues.

Homogenization, lyophilization or acid-extraction of meat products improves iron uptake from cereal–meat product combinations in an in vitro digestion/Caco-2 cell model

The effect of processing (homogenization, lyophilization, acid-extraction) meat products on iron uptake from meat combined with uncooked iron-fortified cereal was evaluated using an in vitro digestion/Caco-2 cell model. Beef was cooked, blended to create smaller meat particles, and combined with electrolytic iron-fortified infant rice cereal. Chicken liver was cooked and blended, lyophilized, or acid-extracted, and combined with FeSO4-fortified wheat flour. In the beef–cereal combination, Caco-2 cell iron uptake, assessed by measuring the ferritin formed by cells, was greater when the beef was blended for the greatest amount of time (360 s) compared with 30 s (P < 0·05). Smaller liver particles (blended for 360 s or lyophilized) significantly enhanced iron uptake compared to liver blended for 60 s (P < 0·001) in the liver–flour combination. Compared to liver blended for 60 s, acid-extraction of liver significantly enhanced iron uptake (P = 0·03) in the liver–flour combination. Homogenization of beef and homogenization, lyophilization, or acid-extraction of chicken liver increases the enhancing effect of meat products on iron absorption in iron-fortified cereals.

Molecular mechanisms involved in intestinal iron absorption

Iron is an essential trace metal in the human diet due to its obligate role in a number of metabolic processes. In the diet, iron is present in a number of different forms, generally described as haem (from haemoglobin and myoglobin in animal tissue) and non-haem iron (including ferric oxides and salts, ferritin and lactoferrin). This review describes the molecular mechanisms that co-ordinate the absorption of iron from the diet and its release into the circulation. While many components of the iron transport pathway have been elucidated, a number of key issues still remain to be resolved. Future work in this area will provide a clearer picture regarding the transcellular flux of iron and its regulation by dietary and humoral factors.

Fermentation and lactic acid addition enhance iron bioavailability of maize

Maize is one of the most important cereal crops for human consumption, yet it is of concern due to its low iron bioavailability. The objective of this study was to determine the effects of processing on iron bioavailability in common maize products and elucidate better processing techniques for enhancing iron bioavailability. Maize products were processed to represent different processing techniques: heating (porridge), fermentation (ogi), nixtamalization (tortillas), and decortication (arepas). Iron and phytate contents were evaluated. Iron bioavailability was assessed using the Caco-2 cell model. Phytate content of maize products was significantly reduced by decortication (25.6%, p = 0.003) and nixtamalization (15%, p = 0.03), and iron content was reduced by decortication (29.1%, p = 0.002). The relative bioavailability (RBA, compared to 100% bioavailability of porridge with FeSO4) of ogi was significantly higher than that of other products when fortified with FeSO4 (p < 0.001) or reduced iron (p < 0.001). Addition of lactic acid (6 mg/g of maize) significantly increased iron solubility and increased bioavailability by about 2-fold (p < 0.01), especially in tortillas. The consumer panel results showed that lactic acid addition does not significantly affect the organoleptic characteristics of tortillas and arepas (p = 0.166 and 0.831, respectively). The results suggest that fermentation, or the addition of small amounts of lactic acid to unfermented maize products, may significantly improve iron bioavailability. Lactic acid addition may be more feasible than the addition of highly bioavailable but expensive fortificants. This approach may be a novel means to increase the iron bioavailability of maize products to reduce the incidence of iron deficiency anemia.

Iron nutrition in the UK: getting the balance right

Fe homeostasis is considered in the context of the UK diet, using information on Fe intake and status from the National Diet and Nutrition Surveys. The importance of assessing Fe availability rather than total Fe intake is discussed. Dietary and host-related factors that determine Fe bioavailability (Fe utilised for Hb production) are reviewed using information from single-meal studies. When adaptive responses are taken into consideration, foods associated with higher Fe status include meat (haem-Fe and the ‘meat factor’) and fruits and fruit juice (vitamin C). Foods that may have a negative impact include dairy products (Ca), high-fibre foods (phytate) and tea and coffee (polyphenols), but the effects are more apparent in groups with marginal Fe deficiency, such as women of childbearing age. Analysis of dietary intake data on a meal-by-meal basis is needed to predict the influence of changing dietary patterns on Fe nutrition in the UK. Current information suggests that in the UK Fe deficiency is a greater problem than Fe overload.

Meat protein fractions enhance nonheme iron absorption in humans

The nature of the enhancing effect of muscle tissue on nonheme iron absorption in humans is unclear but thought to be related to muscle proteins. We conducted radioiron absorption studies to compare iron absorption from proteins isolated from beef and chicken muscle with that from freeze-dried beef and chicken muscle and from egg albumin. All meals contained an equivalent amount of protein as part of a semisynthetic liquid formula. Freeze-dried beef and chicken muscle increased iron absorption 180% (P < 0.001) and 100% (P < 0.001), respectively, relative to egg albumin. When added to the meal at an equivalent protein level (15 g), the isolated beef protein and the isolated heme-free beef protein with 94 and 98% protein content, respectively, increased iron absorption to the same extent as the native beef muscle. Similarly, when added to the meal at an equivalent protein level (30 g), isolated chicken muscle protein (94% protein) increased iron absorption similarly to native chicken muscle. Iron absorption from the meal containing the isolated heme-free chicken protein, however, was 120% (P < 0.01) greater than from the meal containing freeze-dried chicken muscle, indicating that a nonprotein component of muscle tissue with iron-binding potential may have been removed or concentrated by the protein extraction and separation procedures. Our results support the hypothesis that the enhancing effect of muscle tissue on iron absorption is mainly protein related but indicate that other factors may also play a role.

Comparative effects of the addition of mutton or beef to a bean seed ragout on iron status in growing rats

AIMS

The objective was to compare the effects of the addition of mutton or beef to a bean seed ragout (BSR) on iron status in growing rats. In addition, we have studied the possible interference of fat from mutton on iron status because this type of animal contains a high amount of subcutaneous fat.

METHODS

The iron status was investigated through the exploration of the total iron in the blood and the reserve of iron stored in the liver, spleen, intestine, heart and tibia.

RESULTS

Our findings showed that the iron concentration in the total blood significantly increased in the BSR + beef (reference group), an increase of 23% (p < 0.008) as compared to the control group (BSR). However, it significantly decreased in BSR + mutton and BSR + mutton fat groups by 23% and 30%, respectively. The reserve of iron stored in the liver and intestine significantly increased only in the BSR + beef group by 69.5% and 120% (p < 0.01), respectively. Therefore, this reserve was lower in the BSR + mutton or mutton fat groups than BSR + beef group. The iron content in the tibia significantly increased only in the BSR + beef group, an increase of 88% (p < 0.05). However, it was unchanged or decreased in the BSR + mutton and mutton fat groups as compared to the control group. Only, the reserve of iron stored in the spleen significantly increased in all groups. In the heart, our results demonstrated no significant increase of the iron level among all the groups.

CONCLUSION

This preliminary study suggested that mutton, in contrast to beef, has a small or negative effect on the iron status. This negative effect might be related to the high fat, especially polyunsaturated fatty acids content in mutton.

Effect of beef and soy proteins on the absorption of non-heme iron and inorganic zinc in children

BACKGROUND

Iron and zinc deficiency remain substantial problems in small children in both developed and developing nations. Optimizing mineral absorption is an important strategy in minimizing this problem.

OBJECTIVES

To assess the effects of beef and soy proteins on the bioavailability of non-heme iron and zinc in children.

METHODS

We measured iron (n = 26) and zinc (n = 36) absorption in 4-8 y old children from meals differing only in protein source (beef or a low-phytate soy protein concentrate). Iron and zinc absorption were measured using multi-tracer stable isotope techniques. Iron absorption was calculated from the red blood cell iron incorporation measured after 14 days and zinc absorption from the ratio of the oral and intravenous excretion of the zinc tracers 48 hours after dosing.

RESULTS

Iron absorption from the beef meal was significantly greater (geometric mean, 7.6%) than from the soy meal (3.5%, p = 0.0015). Zinc absorption from the beef meal was greater (mean +/- SD, 13.7 +/- 6.0%) than from the soy meal (10.1 +/- 4.1%, p = 0.047).

CONCLUSION

These findings indicate that beef protein increases both non-heme iron and zinc absorption compared to soy protein. The effect of protein source on non-heme iron and inorganic zinc absorption should be one of the factors taken into account when designing diets for children. The inhibitory effect of the soy based meal on iron and zinc absorption could be overcome by fortifying the soy protein with these minerals during the production process.

Meat consumption in a varied diet marginally influences nonheme iron absorption in normal individuals

It is widely recognized that the intake of animal foods is the most important dietary determinant of the iron status of a population. The primary reason is the high bioavailability of heme iron, but it is also known from radiolabeled single-meal feeding studies in humans that muscle tissue facilitates absorption of nonheme iron. In the present study, we examined the effect of meat intake on nonheme iron absorption from a whole diet. Iron absorption was measured during 3 separate dietary periods in 14 volunteers (7 men and 7 women) by having them ingest a radioiron-labeled wheat roll with every meal for 5 d. The diet was freely chosen for the first dietary period and altered to eliminate or maximally increase the intake of muscle foods during the second and third periods. Nonheme iron absorption did not differ for the 3 dietary periods although the geometric mean of 4.81% when subjects consumed a freely chosen diet increased by 35% to 6.47% with maximum meat consumption (P = 0.075). When nonheme absorption was adjusted to normalize for differences in iron status using serum ferritin correction and the 3 absorption periods were pooled, multiple regression analysis indicated no significant relation with heme or nonheme iron, vitamin C, calcium, phosphorus, fiber, or tea content of the diet with the exception of animal tissue (P = 0.013). We conclude that the higher iron status associated with the consumption of an omnivorous diet is due more to the intake of heme iron than to the enhancing effect on nonheme iron absorption.

Iron bioavailability of hemoglobin from soy root nodules using a Caco-2 cell culture model

Heme iron has been identified in many plant sources-most commonly in the root nodules of leguminous plants, such as soy. Our objective was to test the effectiveness of soy root nodule (SRN) and purified soy hemoglobin (LHb) in improving iron bioavailability using an in vitro Caco-2 cell model, with ferritin response as the bioavailability index. We assessed bioavailability of iron from LHb (either partially purified (LHbA) or purified (LHbD)) with and without food matrix and compared it with that from bovine hemoglobin (BHb), ferrous sulfate (FeSO4), or SRN. Bioavailability of each treatment was normalized to 100% of the FeSO4 treatment. When iron sources were tested alone (100 ug iron/mL), ferritin synthesis by LHbD and BHb were 19% (P > 0.05) and 113% (P < 0.001) higher than FeSO4, respectively. However, when iron sources were used for fortification of maize tortillas (50 ppm), LHbA and BHb showed similar bioavailability, being 27% (P < 0.05) and 33% (P < 0.05) higher than FeSO4. Heat treatment had no effect on heme iron but had a significant reduction on FeSO4 bioavailability. Adding heme (LHbA) iron with nonheme (FeSO4) had no enhancement on nonheme iron absorption. Our data suggest that heme iron from plant sources may be a novel value-added product that can provide highly bioavailable iron as a food fortificant.