Algorithms to Assess non-Heme Iron Bioavailability

2005 ◽  
Vol 75 (6) ◽  
pp. 405-412 ◽  
Author(s):  
Manju B. Reddy
Keyword(s):  
Iron Absorption ◽  
Iron Status ◽  
Interactive Effect ◽  
Population Level ◽  
Heme Iron ◽  
Iron Bioavailability ◽  
Dietary Factors ◽  
Interactive Effects ◽  
Sufficient Information ◽  
Non Heme Iron

While sufficient information exists on the effect of individual factors on iron absorption, their net effect in a mixed meal is less well characterized, being dependent on the combination and quantity of the factors present in the meal. Over a period of more than 25 years, several models have been developed to estimate non-heme iron bioavailability, either to assess iron absorption from a meal or iron sufficiency in populations. Initially, a model was developed to calculate iron absorption in individuals with varying iron status that included only enhancers. This model was useful in classifying the diets but has limited value for accurale assessment. Later models were modified and improved by including inhibitors in the calculations. However, some included either phytate or tea but not in combination. The models that included all the factors in calculations assumed their effect was independent and additive rather than interactive, which is an important issue in addressing iron bioavailability. Although some of the models correlated estimated bioavailability with iron status of the population, the accuracy of the estimations is of concern due to lack of quantitative measurements of bioavailability modifiers, inability to consider interactive effects, and the use of non-iron status measurements. Recent research has led to the development of refined models to assess iron bioavailability of complex meals by comprehensively taking into consideration the interactive effect among enhancers and inhibitors. However, the models are based on single-meal studies and their application to whole diets at a population level is not clear. Accurate measurements of dietary factors and independent validation are needed before using these models. To date, no single model is applicable to all diets and additional studies are needed to develop new models to predict bioavailability of whole diets accurately, in addition to addressing dietary adequacy in all populations.

Alternative pathways for absorption of iron from foods

2010 ◽  
Vol 82 (2) ◽  
pp. 429-436 ◽  
Author(s):  
Bo Lönnerdal
Keyword(s):  
Iron Absorption ◽  
Iron Status ◽  
Age Groups ◽  
Heme Iron ◽  
Dietary Factors ◽  
Iron Binding ◽  
Alternative Pathways ◽  
Non Heme Iron ◽  
Lactoferrin Receptor ◽  
Iron Binding Proteins

Iron is known to be absorbed from foods in two major forms, heme iron and non-heme iron. Iron status as well as dietary factors known to affect iron absorption has limited effect on heme iron absorption, whereas inhibitors and enhancers of iron absorption have pronounced effects on non-heme iron absorption. The enterocyte transporter for non-heme iron, DMT1, is strongly up-regulated during iron deficiency and down-regulated during iron overload. A transporter for heme iron, HCP1, was recently characterized and is present on the apical membrane of enterocytes. Two other pathways for iron absorption have been discovered and may serve to facilitate uptake of iron from two unique iron-binding proteins, lactoferrin and ferritin. Lactoferrin is an iron-binding protein in human milk and known to survive proteolytic digestion. It mediates iron uptake in breast-fed infants through endocytosis via a specific lactoferrin receptor (LfR). Recently, lactoferrin has become popular as a food additive and may enhance iron status in several age groups. Ferritin is present in meat, but also in plants. The ferritin content of plants can be enhanced by conventional breeding or genetic engineering, and thereby increase iron intake of populations consuming plant-based diets. Ferritin is a bioavailable source of iron, as shown in recent human studies. Ferritin can be taken up by intestinal cells via endocytosis, suggesting a receptor-mediated mechanism.

Intestinal Iron Absorption: Regulation by Dietary & Systemic Factors

2010 ◽  
Vol 80 (45) ◽  
pp. 231-242 ◽  
Author(s):  
Paul A. Sharp
Keyword(s):  
Iron Homeostasis ◽  
Iron Absorption ◽  
Iron Status ◽  
Heme Iron ◽  
Dietary Factors ◽  
The Body ◽  
Excess Iron ◽  
Non Heme Iron ◽  
Systemic Factors ◽  
And Function

Iron is an essential trace metal in human metabolism. However, imbalances in iron homeostasis are prevalent worldwide and have detrimental effects on human health. Humans do not have the ability to remove excess iron and therefore iron homeostasis is maintained by regulating the amount of iron entering the body from the diet. Iron is present in the human diet in number of different forms, including heme (from meat) and a variety of non-heme iron compounds. While heme is absorbed intact, the bioavailability of non-heme iron varies greatly depending on dietary composition. A number of dietary components are capable of interacting with iron to regulate its solubility and oxidation state. Interestingly, there is an emerging body of evidence suggesting that some nutrients also have direct effects on the expression and function of enterocyte iron transporters. In addition to dietary factors, body iron status is a major determinant of iron absorption. The roles of these important dietary and systemic factors in regulating iron absorption will be discussed in this review.

The Precision of in vitro Methods and Algorithms for Predicting the Bioavailability of Dietary Iron

2005 ◽  
Vol 75 (6) ◽  
pp. 436-445 ◽  
Author(s):  
Sean Lynch
Keyword(s):  
Iron Absorption ◽  
Heme Iron ◽  
Iron Bioavailability ◽  
Cell Uptake ◽  
In Vitro Tests ◽  
Cellular Iron ◽  
Non Heme Iron ◽  
Human Volunteers ◽  
Dialyzable Iron

Three factors determine how much iron will be absorbed from a meal. They are the physiological mechanisms that regulate uptake by and transfer through the enterocytes in the upper small intestine, the quantity of iron in the meal, and its availability to the cellular iron transporters. Established methods exist for predicting the effect of physiological regulation and for measuring or estimating meal iron content. Three approaches to estimating bioavailability have been advocated. Two are in vitro screening procedures: measurement of dialyzable iron and Caco-2 cell uptake, both carried out after in vitro simulated gastric and pancreatic digestion. The third is the use of algorithms based on the predicted effects of specific meal components on absorption derived from isotopic studies in human volunteers. The in vitro procedures have been very useful for identifying and characterizing factors that affect non-heme iron absorption, but direct comparisons between absorption predicted from the in vitro tests and measurements in human volunteers have only been made in a limited number of published studies. The available data indicate that dialysis and Caco-2 cell uptake are useful for ranking meals and single food items in terms of predicted iron bioavailability, but may not reflect the magnitudes of the effects of factors that influence absorption accurately. Algorithms based on estimates of the amounts of heme iron and of enhancers and inhibitors of non-heme iron absorption in foods make it possible to classify meals or diets as being of high, medium, or low bioavailability. The precision with which meal iron bioavailability can be predicted in a population, for which a specific algorithm has been developed, is improved by measuring the content of the most important enhancers and inhibitors. However, the accuracy of such predictions appears to be much lower when the algorithm is applied to meals eaten by different populations.

Algorithms for Iron and Zinc Bioavailability: Are they Accurate?

2010 ◽  
Vol 80 (45) ◽  
pp. 257-262 ◽  
Author(s):  
Janet R. Hunt
Keyword(s):  
Iron Absorption ◽  
Iron Status ◽  
Large Data ◽  
Iron Bioavailability ◽  
Dietary Factors ◽  
Current Evidence ◽  
Zinc Absorption ◽  
Data Set ◽  
Zinc Bioavailability ◽  
Iron And Zinc

Several bioavailability algorithms have been proposed for iron and zinc, confirming the need for these tools while emphasizing the challenge of deriving algorithms with accepted accuracy. This manuscript briefly reviews current evidence on the accuracy of proposed algorithms. Iron absorption is strongly influenced by both body iron status and dietary availability, and most evidence suggests that these do not interact. There is considerable evidence of a logarithmic relationship between percent iron absorption and serum ferritin that allows a simple and accurate computation of how human iron status affects absorption (in the absence of inflammation). Computing the effect of dietary variation on nonheme iron absorption has been challenging because of multiple influential dietary factors and incomplete knowledge of their chemical characteristics, food composition, interactions, and dose-response relationships. At present there is no fully validated algorithm for dietary iron bioavailability. Predicting zinc absorption is less complex. Fractional zinc absorption is substantially influenced by the amount of zinc consumed, and this factor, together with ingested phytic acid, account for a considerable degree of the variance. A multivariate saturation model based on these two variables has been derived using data from multiple studies and independently validated with a single large data set.

scholarly journals GENERIC ALGORITHM SOLUTION IN ESTIMATION OF THE IRON ABSORPTION POTENTIAL FROM COMPLEX SCHOOL MEALS

2021 ◽  
Vol XXVIII (4) ◽  
pp. 167-179
Author(s):  
Rodica Sturza ◽  
◽  
Nina Mija ◽  
Olga Deseatnicov ◽  
Eugenia Covaliov ◽  
...  
Keyword(s):  
Absorption Rate ◽  
Iron Absorption ◽  
Heme Iron ◽  
Iron Bioavailability ◽  
Dietary Factors ◽  
School Meals ◽  
Vitro Assay ◽  
Nutritional Factors ◽  
Dialyzable Iron

New analytical tools to study iron bioavailability are proposed in this article. An algorithm was devised to predict dietary iron abortion from school meals based on the contents of dietary factors that have the ability to promote or inhibit heme or non-heme iron absorption. The highest absorption rate of iron from representative meals was observed in the presence of ascorbic acid (27,73%) or meat ingredients (27,70%), and the lowest absorption rate – in the presence of Ca (12,40%), tannins (5,83%) and polyphenols (5,36%). Relationships between quantities of total iron intake from foods (dialyzable iron, in vitro assay) and the value of nutritional factors in those are described as exponential equations allowing calculations at any stationary state. In elaborated formula the rate of iron absorbance can be predicted considering one, two or three nutritional factors at the same time. The results emphasize the fact that it is important to understand the meal composition for the correct estimation of iron bioavailability.

Importance of iron absorption in human health: An overview

2020 ◽  
Vol 16 ◽  
Author(s):  
Satya Prasad Dixit ◽  
Logesh Rajan ◽  
Dhanabal Palaniswamy ◽  
Suresh Kumar Mohankumar
Keyword(s):  
Iron Deficiency ◽  
Human Health ◽  
Genetic Factors ◽  
Iron Absorption ◽  
Iron Status ◽  
Essential Elements ◽  
Iron Bioavailability ◽  
Dietary Factors ◽  
Dietary Recommendations ◽  
Ferritin Concentration

: Iron is one of the essential elements required for human health, as it plays a vital role in a number of metabolic, growth and developmental processes, including erythropoiesis, DNA synthesis, electron transport and others. Iron deficiency is a concern in both developing and developed (industrialized) countries, and in particular young women are highly vulnerable. This review investigates dietary and genetic determinants of iron metabolism in the human body and a possible solution to combat the iron deficiency by exploring via various targets. Hence, this review mainly focuses on the assessment of dietary and genetic factors affecting the iron bioavailability and homeostasis and collates the available information from 2000 to till date from Pubmed. The dietary factors including ascorbic acid an important factor in animal protein foods (meat, fish and poultry) enhance iron absorption whereas the phytic acid, soy protein, calcium and polyphenols have been reported to inhibit iron absorption. However, the effects of these dietary factors on iron absorption do not necessarily translate into an association with iron status and iron stores (serum ferritin concentration). Moreover, the genetic factors influence the absorption of iron involving HFE, TFR2, FPN1 and HAMP in humans. Further research is needed to determine optimal dietary recommendations for both the prevention and treatment of iron deficiency.

scholarly journals An intensified training schedule in recreational male runners is associated with increases in erythropoiesis and inflammation and a net reduction in plasma hepcidin

2018 ◽  
Vol 108 (6) ◽  
pp. 1324-1333 ◽  
Author(s):  
Diego Moretti ◽  
Samuel Mettler ◽  
Christophe Zeder ◽  
Carsten Lundby ◽  
Anneke Geurts-Moetspot ◽  
...  
Keyword(s):  
Exercise Training ◽  
Iron Absorption ◽  
Iron Status ◽  
Geometric Mean ◽  
Iron Bioavailability ◽  
Oral Iron ◽  
Low Grade ◽  
Hemoglobin Mass ◽  
Low Grade Inflammation ◽  
Iron Utilization

ABSTRACT Background Iron status is a determinant of physical performance, but training may induce both low-grade inflammation and erythropoiesis, exerting opposing influences on hepcidin and iron metabolism. To our knowledge, the combined effects on iron absorption and utilization during training have not been examined directly in humans. Objective We hypothesized that 3 wk of exercise training in recreational male runners would decrease oral iron bioavailability by increasing inflammation and hepcidin concentrations. Design In a prospective intervention, nonanemic, iron-sufficient men (n = 10) completed a 34-d study consisting of a 16-d control phase and a 22-d exercise-training phase of 8 km running every second day. We measured oral iron absorption and erythroid iron utilization using oral 57Fe and intravenous 58Fe tracers administered before and during training. We measured hemoglobin mass (mHb) and total red blood cell volume (RCV) by carbon monoxide rebreathing. Iron status, interleukin-6 (IL-6), plasma hepcidin (PHep), erythropoietin (EPO), and erythroferrone were measured before, during, and after training. Results Exercise training induced inflammation, as indicated by an increased mean ± SD IL-6 (0.87 ± 1.1 to 5.17 ± 2.2 pg/mL; P < 0.01), while also enhancing erythropoiesis, as indicated by an increase in mean EPO (0.66 ± 0.42 to 2.06 ± 1.6 IU/L), mHb (10.5 ± 1.6 to 10.8 ± 1.8 g/kg body weight), and mean RCV (30.7 ± 4.3 to 32.7 ± 4.6 mL/kg) (all P < 0.05). Training tended to increase geometric mean iron absorption by 24% (P = 0.083), consistent with a decreased mean ± SD PHep (7.25 ± 2.14 to 5.17 ± 2.24 nM; P < 0.05). The increase in mHb and erythroid iron utilization were associated with the decrease in PHep (P < 0.05). Compartmental modeling indicated that iron for the increase in mHb was obtained predominantly (>80%) from stores mobilization rather than from increased dietary absorption. Conclusions In iron-sufficient men, mild intensification of exercise intensity increases both inflammation and erythropoiesis. The net effect is to decrease hepcidin concentrations and to tend to increase oral iron absorption. This trial was registered at clinicaltrials.gov as NCT01730521.

Acute Copper Supplementation Does Not Inhibit Non-Heme Iron Bioavailability in Humans

2009 ◽  
Vol 136 (2) ◽  
pp. 180-186 ◽  
Author(s):  
Manuel Olivares ◽  
Fernando Pizarro ◽  
Daniel López de Romaña ◽  
Manuel Ruz
Keyword(s):  
Heme Iron ◽  
Iron Bioavailability ◽  
Non Heme Iron ◽  
Copper Supplementation

Food iron absorption in idiopathic hemochromatosis

Blood ◽  
1989 ◽  
Vol 74 (6) ◽  
pp. 2187-2193 ◽  
Author(s):  
SR Lynch ◽  
BS Skikne ◽  
JD Cook
Keyword(s):  
Serum Ferritin ◽  
Iron Absorption ◽  
Iron Status ◽  
Normal Subjects ◽  
Heme Iron ◽  
Nonheme Iron ◽  
Ferritin Concentration ◽  
Normal Volunteers ◽  
Idiopathic Hemochromatosis ◽  
The Relationship

Abstract The relationship between iron status and food iron absorption was evaluated in 75 normal volunteers, 15 patients with idiopathic hemochromatosis, and 22 heterozygotes by using double extrinsic radioiron tags to label independently the nonheme and heme iron components of a hamburger meal. In normal subjects, absorption from each of these pools was inversely correlated with storage iron, as measured by the serum ferritin concentration. In patients with hemochromatosis, absorption of both forms of iron was far greater than would be predicted from the relationship between absorption and serum ferritin observed in normal volunteers. Nevertheless, there was still a modest but statistically significant reduction in absorption of nonheme iron with increasing serum ferritin. This relationship could not be demonstrated in the case of heme iron absorption. In heterozygotes, nonheme iron absorption from a hamburger meal containing no supplementary iron did not differ significantly from that observed in normal volunteers. However, when this meal was both modified to promote bioavailability and supplemented with iron, absorption of nonheme iron was significantly elevated. These studies confirm the presence of excessive nonheme iron absorption even from unfortified meals in patients with idiopathic hemochromatosis and suggest in addition that they are particularly susceptible to iron loading from diets containing a high proportion of heme iron. Impaired regulation of nonheme iron absorption was also observed in heterozygous individuals, but a statistically significant abnormality was demonstrable only when the test meal contained a large highly bioavailable iron supplement.

scholarly journals Dietary Factors Moderate the Relation between Groundwater Iron and Anemia in Women and Children in Rural Bangladesh

2019 ◽  
Vol 3 (10) ◽  
Author(s):  
Amanda S Wendt ◽  
Jillian L Waid ◽  
Sabine Gabrysch
Keyword(s):  
Iron Deficiency ◽  
Vitamin C ◽  
Fruits And Vegetables ◽  
Iron Absorption ◽  
Cluster Randomized Trial ◽  
Heme Iron ◽  
Dietary Factors ◽  
Baseline Survey ◽  
Women And Children ◽  
Cluster Randomized

ABSTRACT Background Anemia affects ∼1.6 billion people worldwide, often owing to iron deficiency. In Bangladesh, high levels of anemia have been observed alongside little iron deficiency. Elevated concentrations of groundwater iron could constitute a significant source of dietary iron. Objective We aimed to quantify the effect of groundwater iron on anemia in nonpregnant women and young children in Bangladesh, taking into account dietary factors that may affect iron absorption. Methods We analyzed data on 1871 nonpregnant women and 987 children (6–37 mo) from the 2015 baseline survey of the Food and Agricultural Approaches to Reducing Malnutrition cluster-randomized trial in Sylhet, Bangladesh. We used logistic regression with robust standard errors to assess effects of self-reported groundwater iron, dietary intake, and sociodemographic characteristics on anemia, considering interactions between groundwater iron and dietary factors. Results Groundwater iron presence was associated with less anemia in women (OR: 0.74; 95% CI: 0.60, 0.90) and children (OR: 0.58; 95% CI: 0.44, 0.76). This effect was modified by dietary factors. In women, the effect of groundwater iron on anemia was stronger if no vitamin C–rich or heme-iron foods were consumed, and there was a clear dose–response relation. In children, intake of vitamin C–rich foods strengthened the effect of groundwater iron on anemia, and there was no evidence for interaction by intake of iron-rich foods. Conclusions Heme-iron and vitamin C consumption reduced the effect of groundwater iron on anemia among women but not children in Bangladesh, which may be due to higher levels of iron deficiency and lower levels of iron intake among children. Vitamin C consumption appears to enhance iron absorption from groundwater in children and they may thus benefit from consuming more vitamin C–rich fruits and vegetables. Even among women and children consuming heme-iron or vitamin C–rich foods and groundwater iron, anemia prevalence remained elevated, pointing to additional causes of anemia beyond iron deficiency. This trial was registered at clinicaltrials.gov as NCT02505711.

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