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Leif Hallberg - One of the best experts on this subject based on the ideXlab platform.
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Wheat fiber, phytates and Iron Absorption.
Scandinavian Journal of Gastroenterology, 2009Co-Authors: Leif HallbergAbstract:The marked inhibitory effect of bran on Iron Absorption can almost completely be explained by its content of phytates. There are other inhibiting factor(s) as well in bran but they play only a minor role especially in meat containing meals. Several studies were made to clarify the role of phytates. Enzymatic dephytinization of bran almost fully removed its inhibiting effect. The same was observed when washing bran with hydrochloric acid. A “physiological” mixture of monoferrric, potassium and magnesium phytates showed the same inhibition of the Absorption of Iron as bran with the same phytate content.There was a strong semilogarithmic relationship (r = 0.99) between the inhibition of Iron Absorption and the amount of phytates. As little as 5-10 mg phytate phosphorus added to a wheat roll containing 3 mg Iron inhibited Iron Absorption by 50 per cent. Ascorbic acid as well as meat strongly counteracted this inhibition.It was concluded that if bran is used to increase the dietary fiber intake that would inte...
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No enhancing effect of vitamin A on Iron Absorption in humans
The American Journal of Clinical Nutrition, 2003Co-Authors: Thomas Walczyk, Lena Davidsson, Leif Hallberg, Lena Rossander-hulthen, Richard F HurrellAbstract:Background: Vitamin A and � -carotene were recently reported to enhance Iron Absorption by counteracting the inhibitory effect of phytic acid in cereal-based meals and of polyphenol-containing beverages on nonheme-Iron Absorption in humans. Objective: Our objective was to further evaluate the influence of vitamin A on Iron Absorption. Design: Iron Absorption from corn bread with or without added vitamin A (retinyl palmitate) was determined in 5 studies in young adult human subjects by using either a stable-isotope method (2 studies) or a radioisotope technique (3 studies). Iron Absorption was measured by erythrocyte incorporation of the isotopic labels and by whole-body retention of 59 Fe. Corn bread was served with water (studies 1 and 3) or coffee (studies 2, 4, and 5). The studies differed in the amounts and chemical forms of added tracer and fortification Iron. The possibility of methodologic artifacts in earlier investigations was evaluated. Results: No effect of vitamin A on Iron Absorption from the test meals was identified in the individual studies by using paired Student’s t test. A slightly negative effect of vitamin A on Iron Absorption was found with the use of analysis of variance. Conclusions: The previously reported findings of a positive effect of vitamin A on nonheme-Iron Absorption in humans was not confirmed. Incomplete isotopic equilibration of the tracer with native Iron in the meal or with fortification Iron cannot explain the previous findings. However, the present study does not exclude the possibility that suboptimal vitamin A status influences the effect of dietary vitamin A on Iron Absorption. Am J Clin Nutr 2003;77:144‐9.
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Perspectives on Iron Absorption.
Blood Cells Molecules and Diseases, 2002Co-Authors: Leif Hallberg, Lena HulthénAbstract:Abstract ABSTRACT Newly established relationships between dietary Iron Absorption and serum ferritin and between serum ferritin and Iron stores permit calculation of amounts of stored Iron under different conditions at steady states when Absorption equals losses. The rate of growth of stores can also be calculated. All calculations are based on observations and require no model assumptions. Present analyses demonstrated an effective control of Iron Absorption preventing development of Iron overload in otherwise healthy subjects even if the diet is fortified with Iron and even if meat intake is high. There are strong relationships between Iron requirements, bioavailability of dietary Iron, and amounts of stored Iron. Our observations that a reduction in Iron stores and a calculated decrease of hemoglobin Iron had the same increasing effect on Iron Absorption suggest that the control of Iron Absorption is mediated from a common cell, which may register both size of Iron stores and hemoglobin Iron deficit. We suggest that the hepatocyte is that cell. Nutritional Iron deficiency is especially critical in menstruating women, in the latter third of pregnancy, during adolescence for both girls and boys, and in the weaning period from 4 to 6 months to 2 years of age. The body possesses remarkable, potential control systems of probable very ancient origin capable of preventing both Iron deficiency and Iron overload. Present problems with Iron deficiency being the most frequent deficiency disorder are related to nonbiological changes in our societies over the most recent 10,000 years. This perspective on Iron homeostasis or Iron balance is mainly based on studies in humans of clinical and epidemiological observations, trying to understand why Iron deficiency is the most frequent deficiency disorder in the world in spite of the ingenious mechanisms in the body that should prevent it. Withdrawal of Iron fortification of flour in Sweden in 1994 led to a significant increase in Iron deficiency (defined as serum ferritin
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prediction of dietary Iron Absorption an algorithm for calculating Absorption and bioavailability of dietary Iron
The American Journal of Clinical Nutrition, 2000Co-Authors: Leif Hallberg, Lena HulthénAbstract:BACKGROUND: Dietary Iron Absorption from a meal is determined by Iron status, heme- and nonheme-Iron contents, and amounts of various dietary factors that influence Iron Absorption. Limited information is available about the net effect of these factors. OBJECTIVE: The objective was to develop an algorithm for predicting the effects of factors known to influence heme- and nonheme-Iron Absorption from meals and diets. DESIGN: The basis for the algorithm was the Absorption of Iron from a wheat roll (22.1 +/- 0.18%) containing no known inhibitors or enhancers of Iron Absorption and adjusted to a reference dose Absorption of 40%. This basal Absorption was multiplied by the expected effect of different amounts of dietary factors known to influence Iron Absorption: phytate, polyphenols, ascorbic acid, meat, fish and seafood, calcium, egg, soy protein, and alcohol. For each factor, an equation describing the dose-effect relation was developed. Special considerations were made for interactions between individual factors. RESULTS: Good agreement was seen when measurements of Iron Absorption from 24 complete meals were compared with results from use of the algorithm (r(2) = 0.987) and when mean Iron Absorption in 31 subjects served a varied whole diet labeled with heme- and nonheme-Iron tracers over a period of 5 d was compared with the mean total Iron Absorption calculated by using the algorithm (P = 0.958). CONCLUSIONS: This algorithm has several applications. It can be used to predict Iron Absorption from various diets, to estimate the effects expected by dietary modification, and to translate physiologic into dietary Iron requirements from different types of diets.
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inositol phosphates with different numbers of phosphate groups influence Iron Absorption in humans
The American Journal of Clinical Nutrition, 1999Co-Authors: Annsofie Sandberg, Leif Hallberg, Mats Brune, Nilsgunnar Carlsson, Erika Skoglund, Lena RossanderhulthenAbstract:Background: Inositol hexaphosphate (IP 6 ) is a well-known inhibitor of Iron Absorption, whereas the effects of the less-phosphorylated derivatives of IP 6 are less known. Objectives: The objective was to investigate the effects of inositol tri-, tetra-, and pentaphosphates (IP 3 , IP 4 , and IP 5 , respectively) on Iron Absorption in humans. Design: Iron Absorption was measured in 5 experiments from single meals by extrinsic labeling with 55 Fe and 59 Fe and determination of whole-body retention and the erythrocyte uptake of isotopes. In experiments 1-3 the meals contained white-wheat rolls to which 10 mg P as IP 5 , IP 4 , or IP 3 , respectively, was added. Inositol 1,2,6-triphosphate [Ins(1,2,6)P 3 ] and a mixture of isomers of IP 4 and IP 5 were studied. White-wheat rolls contained 10 mg P as IP 3 + IP 4 and 2 mg P as IP 5 + IP 6 in experiment 4 and 20 mg P as IP 3 + IP 4 and 3 mg P as IP 5 + IP 6 in experiment 5; inositol phosphates were obtained via fermentation of sodium phytate. Each experiment had 8-11 subjects. Results: In experiment 1, Iron Absorption was reduced by 39%, whereas there was no significant effect on Iron Absorption in experiments 2 and 3. In experiments 4 and 5, Iron Absorption was reduced by 54% and 64%, respectively, suggesting that IP 3 and IP 4 contributed to the inhibitory effect. Conclusions: IP 5 has an inhibitory effect on Iron Absorption, whereas IP 3 and IP 4 in isolated form have no such effect. IP 3 and IP 4 in processed food contribute to the negative effect on Iron Absorption, presumably by binding Iron between different inositol phosphates. To improve Iron Absorption from cereals and legumes, degradation of inositol phosphates needs to be to less-phosphorylated inositol phosphates than IP 3 .
James D. Cook - One of the best experts on this subject based on the ideXlab platform.
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Meat Protein Fractions Enhance Nonheme Iron Absorption in Humans
Journal of Nutrition, 2006Co-Authors: Richard F Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, James D. CookAbstract: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 hemefree 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. J. Nutr. 136: 2808–2812, 2006.
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Degradation of phytic acid in cereal porridges improves Iron Absorption by human subjects
The American Journal of Clinical Nutrition, 2003Co-Authors: Richard Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, James D. CookAbstract:Phytic acid in cereal-based and legume-based complementary foods inhibits Iron Absorption. Low Iron Absorption from cereal porridges contributes to the high prevalence of Iron deficiency in infants from developing countries. The objective was to measure the influence of phytic acid degradation on Iron Absorption from cereal porridges. An exogenous phytase was used to fully degrade phytic acid during the manufacture of 9 roller-dried complementary foods based on rice wheat maize oat sorghum and a wheat-soy blend. Iron Absorption from the phytate-free and native phytate porridges prepared with water or milk (wheat only) was measured in adult humans with an extrinsic-label radioIron technique. Ascorbic acid was added to some porridges. When the foods were reconstituted with water dephytinization increased Iron Absorption from rice porridge from 1.73% to 5.34% (P < 0.001) from oat from 0.33% to 2.79% (P < 0.0001) from maize from 1.80% to 8.92% (P < 0.0001) from wheat from 0.99% to 11.54% (P < 0.0001) from the wheat-soy blend without ascorbic acid from 1.15% to 3.75% (P < 0.005) and from the wheat-soy blend with ascorbic acid from 2.40% to 8.46% (P < 0.005). Reconstituting wheat porridge with milk instead of water markedly decreased or completely removed the enhancing effect of dephytinization on Iron Absorption in the presence and absence of ascorbic acid. Dephytinization did not increase Iron Absorption from high-tannin sorghum porridge reconstituted with water but increased Iron Absorption from low-tannin sorghum porridge by ˜ 2-fold (P < 0.01). Phytate degradation improves Iron Absorption from cereal porridges prepared with water but not with milk except from high-tannin sorghum. (authors)
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Effect of enhanced erythropoiesis on Iron Absorption.
Journal of Laboratory and Clinical Medicine, 1992Co-Authors: Barry S. Skikne, James D. CookAbstract:: To examine the influence of erythropoiesis on Iron Absorption, radioIron Absorption tests were performed in normal subjects before and after a course of recombinant erythropoietin. The Absorption of heme and nonheme Iron from a standard meal was measured in nine subjects, and the Absorption of a therapeutic dose of ferrous sulfate given with or without food was determined in an additional 11 subjects. The subcutaneous administration of 100 U recombinant human erythropoietin/kg body weight given on 10 successive days over a 2-week period induced a brisk increase in erythropoiesis and a sharp decrease in Iron stores. With the standard meal, there was a modest increase in heme Iron Absorption from 47.0% to 58.6% (p < 0.05) and a dramatic five-fold rise in nonheme Iron Absorption from 5.9% to 31.8% (p < 0.001). The Absorption of 50 mg Iron as ferrous sulfate increased from 2.0% to 17.9% when given with food (p < 0.001) and from 7.0% to 24.6% when given with water (p < 0.001). To assess the effect of erythropoiesis independently of the induced changes in Iron status, the Absorption data were adjusted to a common serum ferritin level. The relative increase in Iron Absorption was still significant for both dietary nonheme Iron (ratio 2.51, p < 0.02) and ferrous sulfate given with food (ratio 2.99, p < 0.01). It is concluded that the striking enhancement of Iron Absorption following regular erythropoietin administration in normal subjects is related to the combined effect of diminished Iron stores and augmented erythropoiesis.
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soy protein phytate and Iron Absorption in humans
The American Journal of Clinical Nutrition, 1992Co-Authors: Richard Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, Sean R. Lynch, S A Dassenko, James D. CookAbstract:: The effect of reducing the phytate in soy-protein isolates on nonheme-Iron Absorption was examined in 32 human subjects. Iron Absorption was measured by using an extrinsic radioIron label in liquid-formula meals containing hydrolyzed corn starch, corn oil, and either egg white or one of a series of soy-protein isolates with different phytate contents. Iron Absorption increased four- to fivefold when phytic acid was reduced from its native amount of 4.9-8.4 to less than 0.01 mg/g of isolate. Even relatively small quantities of residual phytate were strongly inhibitory and phytic acid had to be reduced to less than 0.3 mg/g of isolate (corresponding to less than 10 mg phytic acid/meal) before a meaningful increase in Iron Absorption was observed. However, even after removal of virtually all the phytic acid, Iron Absorption from the soy-protein meal was still only half that of the egg white control. It is concluded that phytic acid is a major inhibitory factor of Iron Absorption in soy-protein isolates but that other factors contribute to the poor bioavailability of Iron from these products.
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Serum transferrin receptor as an index of Iron Absorption.
British Journal of Haematology, 1990Co-Authors: James D. Cook, S A Dassenko, Barry S. SkikneAbstract:Summary. Recent studies indicate that serum transferrin receptor levels are a quantitative index of tissue receptor mass. To determine whether the latter plays a role in the regulation of Iron Absorption, we examined the relationship between serum receptor, serum ferritin and Iron Absorption in healthy subjects. Using radioisotopic techniques we measured Absorption of inorganic Iron in 174 subjects and dietary nonhaem Iron in 60 subjects. With both forms of Iron, the correlation with Absorption was far lower for serum receptor than for serum ferritin and was no longer significant when subjects with depleted Iron stores were excluded. These results indicate that in normal subjects the Iron store is the main physiological determinant of Iron Absorption and that in the absence of Iron deficiency, tissue receptor mass, reflected by serum transferrin receptor levels, has no discernible influence.
Richard F Hurrell - One of the best experts on this subject based on the ideXlab platform.
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Meat Protein Fractions Enhance Nonheme Iron Absorption in Humans
Journal of Nutrition, 2006Co-Authors: Richard F Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, James D. CookAbstract: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 hemefree 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. J. Nutr. 136: 2808–2812, 2006.
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phytic acid degradation as a means of improving Iron Absorption
International Journal for Vitamin and Nutrition Research, 2004Co-Authors: Richard F HurrellAbstract:Phytic acid is a potent inhibitor of native and fortification Iron Absorption and low Absorption of Iron from cereal- and/or legume-based complementary foods is a major factor in the etiology of Iron deficiency in infants. Dephytinization of complementary foods or soy-based infant formulas is technically possible but, as phytic acid is strongly inhibitory at low concentrations, complete enzymatic degradation is recommended. If this is not possible, the phytic acid to Iron molar ratio should be decreased to below 1:1 and preferably below 0.4:1. Complete dephytinization of cereal- and legume-based complementary foods has been shown to increase the percentage of Iron Absorption by as much as 12-fold (0.99% to 11.54%) in a single-meal study when the foods were reconstituted with water. The addition of milk, however, inhibits Iron Absorption and overcomes the enhancing effect of phytic acid degradation. Dephytinization can therefore be strongly recommended only for cereal/legume mixtures reconstituted with water, especially low-cost complementary foods destined for infants in developing countries. In countries where infant cereals are consumed with milk, ascorbic acid addition can more easily be used to overcome the negative effect of phytic acid on Iron Absorption. Similarly with soy-based infant formulas, especially if manufactured from low-phytate isolates, ascorbic acid can be used to ensure adequate Iron Absorption.
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helicobacter pylori infection Iron Absorption and gastric acid secretion in bangladeshi children
The American Journal of Clinical Nutrition, 2004Co-Authors: Shafiqul Alam Sarker, Lena Davidsson, Richard F Hurrell, Thomas Walczyk, Hasan Mahmud, George J. FuchsAbstract:Background: Nonheme-Iron Absorption requires an acidic milieu. Reduced gastric acid output as a consequence of Helicobacter pylori infection could be an important limiting factor for Iron Absorption. Objective: We measured gastric acid output and Iron Absorption from a non-water-soluble Iron compound (ferrous fumarate) and a water-soluble Iron compound (ferrous sulfate) in children with and without H. pylori infection. Design: Gastric acid output was quantified before (basal acid output, or BAO) and after pentagastrin stimulation (stimulated acid output, or SAO) in 2–5-y-old children with Iron deficiency anemia who were (n 13) or were not (n 12) infected with H. pylori. Iron Absorption was measured by using a double-stable-isotope technique. H. pylori–infected children were studied before and after eradication therapy. Results: BAO and SAO were significantly lower in the H. pylori– infected children (0.2 0.2 and 1.6 0.9 mmol/h, respectively) than in the uninfected children (0.9 0.7 and 3.1 0.9 mmol/h, respectively; P 0.01 and P 0.005). BAO and SAO improved to 0.8 1.3 and 3.3 2.4 mmol/h, respectively, after therapy. Iron Absorption from ferrous sulfate was significantly greater than that from ferrous fumarate both before (geometric x: 19.7% compared with 5.3%; P 0.0001) and after (22.5% compared with 6.4%; P 0.0001) treatment in H. pylori–infected children. Corresponding values for uninfected children were 15.6% and 5.4%, respectively (P 0.001; n 12). Conclusions: Iron Absorption from ferrous fumarate was significantly lower than that from ferrous sulfate in both H. pylori–infected and uninfected Bangladeshi children. Treatment of H. pylori infection improved gastric acid output but did not significantly influence Iron Absorption. The efficacy of ferrous fumarate in Iron fortification programs to prevent Iron deficiency in young children should be evaluated. Am J Clin Nutr 2004;80:149 –53.
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Erythorbic acid is a potent enhancer of nonheme-Iron Absorption
The American Journal of Clinical Nutrition, 2004Co-Authors: Meredith C. Fidler, Lena Davidsson, Christophe Zeder, Richard F HurrellAbstract:Background: Erythorbic acid, a stereoisomer of ascorbic acid with similar physicochemical properties, is widely used as an antioxidant in processed foods. Objectives: The aims of the present study were to evaluate the effect of erythorbic acid on Iron Absorption from ferrous sulfate at molar ratios of 2:1 and 4:1 (relative to Iron) and to compare the effect of erythorbic acid directly with that of ascorbic acid at a molar ratio of 4:1. Design: Iron Absorption from Iron-fortified cereal was measured in 10 women on the basis of erythrocyte incorporation of stable Iron isotopes ( 57 Fe or 58 Fe) 14 d after administration. Each woman consumed 4 ferrous-sulfate-fortified test meals (containing 5 mg Fe/meal) with or without added erythorbic or ascorbic acid. The data were evaluated by use of paired t tests, and the results are presented as geometric means. Results: Iron Absorption from the test meal without any added enhancer was 4.1%. The addition of erythorbic acid (at molar ratios of 2:1 and 4:1 relative to Iron) increased Iron Absorption 2.6-fold (10.8%; P 0.0001) and 4.6-fold (18.8%; P 0.0001), respectively. The addition of ascorbic acid (molar ratio of 4:1) increased Iron Absorption 2.9-fold (11.7%; P 0.0004). At a molar ratio of 4:1, erythorbic acid was 1.6-fold (P 0.0002) as potent an enhancer of Iron Absorption as was ascorbic acid. Conclusion: Although erythorbic acid is a potent enhancer of Iron Absorption, its lack of antiscorbutic activity limits its usefulness in Iron-fortification programs. However, it may play a major role in enhancing Iron bioavailability from mixed diets that include foods preserved with erythorbic acid. Am J Clin Nutr 2004;79: 99–102.
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No enhancing effect of vitamin A on Iron Absorption in humans
The American Journal of Clinical Nutrition, 2003Co-Authors: Thomas Walczyk, Lena Davidsson, Leif Hallberg, Lena Rossander-hulthen, Richard F HurrellAbstract:Background: Vitamin A and � -carotene were recently reported to enhance Iron Absorption by counteracting the inhibitory effect of phytic acid in cereal-based meals and of polyphenol-containing beverages on nonheme-Iron Absorption in humans. Objective: Our objective was to further evaluate the influence of vitamin A on Iron Absorption. Design: Iron Absorption from corn bread with or without added vitamin A (retinyl palmitate) was determined in 5 studies in young adult human subjects by using either a stable-isotope method (2 studies) or a radioisotope technique (3 studies). Iron Absorption was measured by erythrocyte incorporation of the isotopic labels and by whole-body retention of 59 Fe. Corn bread was served with water (studies 1 and 3) or coffee (studies 2, 4, and 5). The studies differed in the amounts and chemical forms of added tracer and fortification Iron. The possibility of methodologic artifacts in earlier investigations was evaluated. Results: No effect of vitamin A on Iron Absorption from the test meals was identified in the individual studies by using paired Student’s t test. A slightly negative effect of vitamin A on Iron Absorption was found with the use of analysis of variance. Conclusions: The previously reported findings of a positive effect of vitamin A on nonheme-Iron Absorption in humans was not confirmed. Incomplete isotopic equilibration of the tracer with native Iron in the meal or with fortification Iron cannot explain the previous findings. However, the present study does not exclude the possibility that suboptimal vitamin A status influences the effect of dietary vitamin A on Iron Absorption. Am J Clin Nutr 2003;77:144‐9.
Richard Hurrell - One of the best experts on this subject based on the ideXlab platform.
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Degradation of phytic acid in cereal porridges improves Iron Absorption by human subjects
The American Journal of Clinical Nutrition, 2003Co-Authors: Richard Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, James D. CookAbstract:Phytic acid in cereal-based and legume-based complementary foods inhibits Iron Absorption. Low Iron Absorption from cereal porridges contributes to the high prevalence of Iron deficiency in infants from developing countries. The objective was to measure the influence of phytic acid degradation on Iron Absorption from cereal porridges. An exogenous phytase was used to fully degrade phytic acid during the manufacture of 9 roller-dried complementary foods based on rice wheat maize oat sorghum and a wheat-soy blend. Iron Absorption from the phytate-free and native phytate porridges prepared with water or milk (wheat only) was measured in adult humans with an extrinsic-label radioIron technique. Ascorbic acid was added to some porridges. When the foods were reconstituted with water dephytinization increased Iron Absorption from rice porridge from 1.73% to 5.34% (P < 0.001) from oat from 0.33% to 2.79% (P < 0.0001) from maize from 1.80% to 8.92% (P < 0.0001) from wheat from 0.99% to 11.54% (P < 0.0001) from the wheat-soy blend without ascorbic acid from 1.15% to 3.75% (P < 0.005) and from the wheat-soy blend with ascorbic acid from 2.40% to 8.46% (P < 0.005). Reconstituting wheat porridge with milk instead of water markedly decreased or completely removed the enhancing effect of dephytinization on Iron Absorption in the presence and absence of ascorbic acid. Dephytinization did not increase Iron Absorption from high-tannin sorghum porridge reconstituted with water but increased Iron Absorption from low-tannin sorghum porridge by ˜ 2-fold (P < 0.01). Phytate degradation improves Iron Absorption from cereal porridges prepared with water but not with milk except from high-tannin sorghum. (authors)
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soy protein phytate and Iron Absorption in humans
The American Journal of Clinical Nutrition, 1992Co-Authors: Richard Hurrell, Manju B. Reddy, Marcel Alexandre Juillerat, Sean R. Lynch, S A Dassenko, James D. CookAbstract:: The effect of reducing the phytate in soy-protein isolates on nonheme-Iron Absorption was examined in 32 human subjects. Iron Absorption was measured by using an extrinsic radioIron label in liquid-formula meals containing hydrolyzed corn starch, corn oil, and either egg white or one of a series of soy-protein isolates with different phytate contents. Iron Absorption increased four- to fivefold when phytic acid was reduced from its native amount of 4.9-8.4 to less than 0.01 mg/g of isolate. Even relatively small quantities of residual phytate were strongly inhibitory and phytic acid had to be reduced to less than 0.3 mg/g of isolate (corresponding to less than 10 mg phytic acid/meal) before a meaningful increase in Iron Absorption was observed. However, even after removal of virtually all the phytic acid, Iron Absorption from the soy-protein meal was still only half that of the egg white control. It is concluded that phytic acid is a major inhibitory factor of Iron Absorption in soy-protein isolates but that other factors contribute to the poor bioavailability of Iron from these products.
Gregory J. Anderson - One of the best experts on this subject based on the ideXlab platform.
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mechanistic and regulatory aspects of intestinal Iron Absorption
American Journal of Physiology-gastrointestinal and Liver Physiology, 2014Co-Authors: Sukru Gulec, Gregory J. Anderson, James F CollinsAbstract:Iron is an essential trace mineral that plays a number of important physiological roles in humans, including oxygen transport, energy metabolism, and neurotransmitter synthesis. Iron Absorption by the proximal small bowel is a critical checkpoint in the maintenance of whole-body Iron levels since, unlike most other essential nutrients, no regulated excretory systems exist for Iron in humans. Maintaining proper Iron levels is critical to avoid the adverse physiological consequences of either low or high tissue Iron concentrations, as commonly occurs in Iron-deficiency anemia and hereditary hemochromatosis, respectively. Exquisite regulatory mechanisms have thus evolved to modulate how much Iron is acquired from the diet. Systemic sensing of Iron levels is accomplished by a network of molecules that regulate transcription of the HAMP gene in hepatocytes, thus modulating levels of the serum-borne, Iron-regulatory hormone hepcidin. Hepcidin decreases intestinal Iron Absorption by binding to the Iron exporter ferroportin 1 on the basolateral surface of duodenal enterocytes, causing its internalization and degradation. Mucosal regulation of Iron transport also occurs during low-Iron states, via transcriptional (by hypoxia-inducible factor 2α) and posttranscriptional (by the Iron-sensing Iron-regulatory protein/Iron-responsive element system) mechanisms. Recent studies demonstrated that these regulatory loops function in tandem to control expression or activity of key modulators of Iron homeostasis. In health, body Iron levels are maintained at appropriate levels; however, in several inherited disorders and in other pathophysiological states, Iron sensing is perturbed and intestinal Iron Absorption is dysregulated. The Iron-related phenotypes of these diseases exemplify the necessity of precisely regulating Iron Absorption to meet body demands.
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intestinal Iron Absorption
Journal of Trace Elements in Medicine and Biology, 2012Co-Authors: Brie K Fuqua, Chris D Vulpe, Gregory J. AndersonAbstract:Intestinal Iron Absorption is a critical process for maintaining body Iron levels within the optimal physiological range. Iron in the diet is found in a wide variety of forms, but the Absorption of non-heme Iron is best understood. Most of this Iron is moved across the enterocyte brush border membrane by the Iron transporter divalent metal-ion transporter 1, a process enhanced by the prior reduction of the Iron by duodenal cytochrome B and possibly other reductases. Enterocyte Iron is exported to the blood via ferroportin 1 on the basolateral membrane. This transporter acts in partnership with the ferroxidase hephaestin that oxidizes exported ferrous Iron to facilitate its binding to plasma transferrin. Iron Absorption is controlled by a complex network of systemic and local influences. The liver-derived peptide hepcidin binds to ferroportin, leading to its internalization and a reduction in Absorption. Hepcidin expression in turn responds to body Iron demands and the BMP-SMAD signaling pathway plays a key role in this process. The levels of Iron and oxygen in the enterocyte also exert important influences on Iron Absorption. Disturbances in the regulation of Iron Absorption are responsible for both Iron loading and Iron deficiency disorders in humans.
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Iron Absorption and metabolism
Current Opinion in Gastroenterology, 2009Co-Authors: Gregory J. Anderson, David M Frazer, Gordon D MclarenAbstract:PURPOSE OF REVIEW: Intestinal Iron Absorption is an essential physiological process that is regulated by the liver-derived peptide hepcidin. This review will describe recent advances in hepcidin biology and enterocyte Iron transport. RECENT FINDINGS: Hepcidin acts as a repressor of Iron Absorption and its expression in turn reflects a range of systemic cues, including Iron status, hypoxia, erythropoiesis and inflammation. These act through proteins on the hepatocyte plasma membrane such as HFE, hemojuvelin and transferrin receptor 2 to alter transcription of the hepcidin gene. Bone morphogenetic protein-SMAD signaling provides a key pathway of hepcidin activation, whereas the membrane-bound serine protease matriptase-2 and the erythroid factor growth differentiation factor 15 have emerged as important negative regulators of hepcidin expression. At the enterocyte itself, the recent demonstration of a chaperone for delivering Iron to ferritin and new data on Iron release from the hepcidin target ferroportin are helping to define the pathway of Iron movement across the intestinal epithelium. SUMMARY: Disturbances in the hepcidin regulatory pathway underlie a range of Iron metabolism disorders, from Iron deficiency to Iron loading, and there is considerable promise that the exciting recent advances in understanding hepcidin action will be translated into improved diagnostic and therapeutic modalities in the near future.
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Control of Iron Absorption
Journal of Gastroenterology and Hepatology, 1996Co-Authors: Gregory J. AndersonAbstract:Intestinal Iron Absorption plays an essential role in body Iron homeostasis, although the mechansim by which Iron moves across the cells of the intestinal epithelium and the way in which this process is regulated are poorly understood. Signals to alter Iron Absorption are received from the body by cells of the intestinal crypt and these signals are translated into an absortion response after the cells have migrated up the villus and differentiated into mature absorptive enterocytes. The intracellular Iron concentration of the crypt cell may play an important role in the regulation of this process. Biochemical investigations on the mechanism of Iron Absorption have met with only limited success and a molecular understanding of this mechanism appears most likely to come from the identification of the genes affected in various inherited disturbances of Iron Absorption in several mammalian species.