T. H. Bothwell

The effects of organic acids, phytates and polyphenols on the absorption of iron from vegetables

1. Non-haem iron absorption from a variety of vegetable meals was studied in parous Indian Women, using the erythrocyte utilization of radioactive Fe method. 2. The studies were undertaken to establish whether Fe absorption could be correlatedwith the chemical composition of the foodstuff. 3. Addition of the following organic acids commonly found in vegetables, improved the geometric mean Fe absorption from a basic rice meal as follows: from 0·028 to 0·085 with 1 g citric acid, from 0·031 to 0·081 with 15 mg ascorbic acid, from 0·048 to 0·095 with 1 g L-malic acid, from 0·041 to 0·096 with 1 g tartaric acid. The only exception was oxalic acid; the addition of 1 g calciumoxalate to cabbage ( Brassica oleraceae ) was associated with some depression in Fe absorption from 0·320 to 0·195. 4. There was a marked inhibition of the geometric mean absorption when 500 mg tannic acid was added to a broccoli ( Brassica oleraceae ) meal (0·015 v . 0·297). Sodium phytate (2 g) caused a similar, though less profound inhibition (0·035 to 0·152). 5. When 3 mg ferrous sulphate was added to different vegetables the geometric mean absorption varied widely. Vegetables of low Fe bioavailability were wheat germ ( Triticum aestivum ) 0·007, aubergine ( Solanum melongena ) 0·007, butter beans ( Phaseolus lunatus ) 0·012, spinach ( Spinacea oleraceae ) 0·014, brown lentils ( Lens culinaris ) 0·024, beetroot greens ( Beta vulgaris ) 0·024 and green lentils ( Lens culinaris ) 0·032. In contrast, bioavailability was moderate or good with carrot ( Daucus carota ) 0·098, potato ( Solanum tuberosum ) 0·115, beetroot ( Beta vulgaris ) 0·185, pumpkin ( Cucurbita mixta ) 0·206, broccoli 0·260, tomato ( Lycopersicon esculentum ) 0·224, cauliflower ( Brassica oleraceae ) 0·263, cabbage 0·320, turnip ( Brassica rapa ) 0·327 and sauerkraut 0·327. 6. All the vegetables associated with moderate or good Fe bioavailability contained appreciable amounts of one or more of the organic acids, malic, citric and ascorbic acids. 7. Poor Fe bioavailability was noted in vegetables with high phytate contents (e.g. wheat germ 0·007, butter beans 0·012, brown lentils 0·024 and green lentils 0·032). 8. The fact that a number of vegetables associated with low Fe-absorption turned bluish-black when Fe was added to them, suggested that the total polyphenol content in them was high. The vegetables included aubergine spinach, brown lentils, green lentils and beetroot greens. When the total polyphenol content in all the vegetables tested was formally measured, there was a significant inverse correlation (r 0·859, P r 0·901 (P 9. The major relevance of these findings is the fact that the total absorption of non-haem-Fe from a mixed diet may be profoundly influenced by the presence of single vegetables with either marked enhancing or inhibiting effects on Fe bioavailability.

Body iron excretion in man: a collaborative study.

Abstract A collaborative study was undertaken in an attempt to document obligatory iron losses in adult male subjects, using a variety of isotopic and chemical methods. Total body excretion was measured in four groups of subjects by injecting Fe 55 intravenously and following the decline in red cell activity over several years. Calculated daily iron losses were as follows: Seattle white subjects (group I) 0.95 mg. (±0.30); Venezuelan Mestizos (group II) 0.90 mg. (±0.31); Johannesburg Bantu (group III) 2.42 mg. (±1.09); Durban Indians (group IV) 1.02 mg. (±0.22); and Durban Bantu (group V) 2.01 mg. (±0.94). The higher values in the Bantu subjects were ascribed to the greater than normal iron stores in this population group. That losses in the Durban Indian subjects, who were working in an extremely hot and humid environment, were not greater than those in the white subjects suggests that excessive sweating does not represent a major route for iron excretion. The results of isotopic experiments to determine the quantities of iron lost via the gastrointestinal tract suggested a daily loss of approximately 0.1 mg. within desquamated mucosal cells and 0.4 mg. in blood. Chemical analyses of bile indicated a mean daily content of 0.26 mg. However, it was not possible to establish what proportion of this iron is reabsorbed into the body. Direct chemical measurements of iron in urine revealed a mean daily content of approximately 0.1 mg.; this quantity did not seem to be influenced by the size of the body stores. The amount of iron taken up daily from the plasma by eccrine skin at normal transferrin saturations was between 0.2 and 0.3 mg. When the transferrin saturation was high this figure rose to between 0.6 and 0.7 mg. In a final analysis, the calculated iron losses from individual compartments were added together and compared with those obtained in the long-term excretion study. Agreement was close in all but the Bantu groups. Even when maximum figures for individual compartmental losses were used, the figures were still lower than those obtained for total excretion. These discrepancies may reflect methodologic errors but it is equally possible that subjects with overload lose iron in ways other than those examined in the present study, such as bile and/or iron-loaded reticuloendothelial cells shed into the lumen of the gastrointestinal tract.

Clinical studyBody iron excretion in man: A collaborative study

Abstract A collaborative study was undertaken in an attempt to document obligatory iron losses in adult male subjects, using a variety of isotopic and chemical methods. Total body excretion was measured in four groups of subjects by injecting Fe 55 intravenously and following the decline in red cell activity over several years. Calculated daily iron losses were as follows: Seattle white subjects (group I) 0.95 mg. (±0.30); Venezuelan Mestizos (group II) 0.90 mg. (±0.31); Johannesburg Bantu (group III) 2.42 mg. (±1.09); Durban Indians (group IV) 1.02 mg. (±0.22); and Durban Bantu (group V) 2.01 mg. (±0.94). The higher values in the Bantu subjects were ascribed to the greater than normal iron stores in this population group. That losses in the Durban Indian subjects, who were working in an extremely hot and humid environment, were not greater than those in the white subjects suggests that excessive sweating does not represent a major route for iron excretion. The results of isotopic experiments to determine the quantities of iron lost via the gastrointestinal tract suggested a daily loss of approximately 0.1 mg. within desquamated mucosal cells and 0.4 mg. in blood. Chemical analyses of bile indicated a mean daily content of 0.26 mg. However, it was not possible to establish what proportion of this iron is reabsorbed into the body. Direct chemical measurements of iron in urine revealed a mean daily content of approximately 0.1 mg.; this quantity did not seem to be influenced by the size of the body stores. The amount of iron taken up daily from the plasma by eccrine skin at normal transferrin saturations was between 0.2 and 0.3 mg. When the transferrin saturation was high this figure rose to between 0.6 and 0.7 mg. In a final analysis, the calculated iron losses from individual compartments were added together and compared with those obtained in the long-term excretion study. Agreement was close in all but the Bantu groups. Even when maximum figures for individual compartmental losses were used, the figures were still lower than those obtained for total excretion. These discrepancies may reflect methodologic errors but it is equally possible that subjects with overload lose iron in ways other than those examined in the present study, such as bile and/or iron-loaded reticuloendothelial cells shed into the lumen of the gastrointestinal tract.

THE QUANTITATIVE ESTIMATION OF TOTAL IRON STORES IN HUMAN BONE MARROW

In normal adult males, about 25%o of the body iron content is in storage depots (1). This iron exists in two forms: as a diffuse soluble fraction called ferritin, in which the molecules are dispersed , and as insoluble aggregates of hemosiderin, which can be visualized by conventional micros-copy (2). Although the liver is regarded as the chief storage organ, chemical analyses suggest that it normally contains up to 300 mg (3-5), which is only between one-quarter and one-third of what can be mobilized from total stores when healthy young males are repeatedly phlebotomized (6). Although little is known of the quantities present in other organs, hemosiderin can be seen in the reticuloendothelial cells of the bone marrow (7) and spleen (8), and there is some chemical evidence to indicate that significant amounts of storage iron may be present in skeletal muscles (9, 10). The present study was undertaken to find out how much iron is normally stored in the reticulo-endothelial cells of the bone marrow and to define the extent to which these stores can expand when iron overload is present. In addition, a comparison was made between the concentrations of iron present in the bone marrows and livers of subjects with varying quantities of storage iron. MATERIALS AND METHODS Clinical material. The total iron stores present in bone marrow were estimated in 61 adult subjects undergoing thoracotomy. Forty-one were white and the remainder were Bantu. The individual diagnoses are shown in Table I. The chemical concentrations of storage iron were estimated in the livers and bone marrows of adult Bantu and white subjects dying in the hospital. The Bantu specimens (58 males and 44 females) were obtained from Baragwanath Hospital, Johannesburg, and the white specimens (25 males and 28 females) from the General Hospital, Johannesburg. The use of radioiron as a marrow label. When a tracer quantity of radioiron is injected intravenously, most of it is taken up by the red-cell precursors of the bone marrow (11). This iron is subsequently released over the next few days as part of the hemo-globin of new red cells, and the percentage present in circulation at 10 to 14 days has been used as a measure of the fraction initially taken up by the bone marrow (12). If a specimen of bone marrow is therefore removed between 18 and 24 hours after the injection of the radioiron (i.e., at a time …

Factors affecting the absorption of iron from cereals

Non-haem-iron absorption from a variety of cereal and fibre meals was measured in parous Indian women, using the erythrocyte utilization of radioactive Fe method. The present study was undertaken to establish whether alteration of the phytate and polyphenol contents of sorghum (Sorghum vulgare) affected Fe absorption from sorghum meals, and to assess the influence of fibre on Fe absorption. Removing the outer layers of sorghum grain by pearling reduced the polyphenol and phytate contents by 96 and 92% respectively. This treatment significantly increased the geometric mean Fe absorption from 0.017 to 0.035 (t 3.9, P less than 0.005). The geometric mean Fe absorption from a sorghum cultivar that lacked polyphenols (albino sorghum) was 0.043, which was significantly greater than the 0.019 absorbed from bird-proof sorghum, a cultivar with a high polyphenol content (t 2.83, P less than 0.05). Fe was less well absorbed from the phytate-rich pearlings of the albino sorghum than from the pearled albino sorghum (0.015 v. 0.035 (t 8.4, P less than 0.0005]. Addition of sodium phytate to a highly Fe-bioavailable broccoli (Brassica oleracea) meal reduced Fe absorption from 0.185 to 0.037. The geometric mean Fe absorption from malted sorghum porridge was 0.024 when 9.5 mg ascorbic acid were added and 0.094 when the ascorbic acid was increased to 50 mg (t 3.33, P less than 0.005). This enhancing effect of 50 mg ascorbic acid was significantly depressed to 0.04 by tea (t 38.1, P less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

The non-immune inflammatory response: Serial changes in plasma iron, iron-binding capacity, lactoferrin, ferritin and C-reactive protein

The interrelationships between various components of the non-immune inflammatory response (white cell count, plasma lactoferrin, C-reactive protein, ferritin, iron and iron-binding capacity), were studied serially in a variety of inflammatory conditions including acute lobar pneumonia, active pulmonary tuberculosis, rheumatoid arthritis on gold therapy and sepsis in the face of marrow hypoplasia induced by chemotherapy. Lactoferrin concentrations paralleled the white count in all groups. They were highest in pneumonia and tuberculosis, mildly elevated in rheumatoid arthritis and markedly decreased in neutropenic sepsis. Very high initial lactoferrin concentrations were associated with a poor prognosis in acute pneumonia. C-reactive protein and ferritin concentrations remained elevated through the period of study in acute pneumonia and neutropenic sepsis, while they gradually normalised over weeks in subjects with tuberculosis or rheumatoid arthritis on therapy. In pneumonia and tuberculosis moderate hypoferraemia and a reduced iron-binding capacity were evident. In contrast, a raised percentage saturation was present in neutropenic sepsis, probably related to erythroid marrow suppression. Comparisons between ferritin, lactoferrin and C-reactive protein in the various groups supported the concept that ferritin behaves in part as an acute phase reactant and that hypoferraemia in inflammation is due to deviation of iron into ferritin stores. The suggestion that lactoferrin is responsible for the hypoferraemia and hyperferritinaemia was not supported by the present data. Iron deficiency appeared to limit the hyperferritinaemic response in rheumatoid arthritis, while erythropoietic inhibition by chemotherapy dampened the hypoferraemic response in neutropenic sepsis.

Enhancing the absorption of fortification iron. A SUSTAIN Task Force report.

Iron deficiency remains a major global health problem affecting an estimated 2 billion people. The World Health Organization ranked it as the seventh most important preventable risk for disease, disability, and death in 2002. Since an important factor in its causation is the poor bioavailability of iron in the cereal-based diets of many developing countries, SUSTAIN set up a Task Force, consisting of nutritional, medical, industry, and government experts to consider strategies for enhancing the absorption of fortification iron. This paper summarizes the findings of this Task Force. Detailed reviews of each strategy follow this overview. Highly soluble compounds of iron like ferrous sulfate are desirable food fortificants but cannot be used in many food vehicles because of sensory issues. Thus, potentially less well-absorbed forms of iron commonly are used in food fortification. The bioavailability of iron fortificants can, however, be enhanced with innovative ingredient technologies. Ascorbic acid, NaFeEDTA, ferrous bisglycinate, and dephytinization all enhance the absorption of fortification iron, but add to the overall costs of fortification. While all strategies cannot be recommended for all food fortification vehicles, individual strategies can be recommended for specific foods. For example, the addition of ascorbic acid is appropriate for dry blended foods such as infant foods and other dry products made for reconstitution that are packaged, stored, and prepared in a way that maximizes retention of this vitamin. NaFeEDTA can be recommended for fortification of fish sauce and soy sauce, whereas amino acid chelates may be more useful in milk products and beverages. With further development, dephytinization may be possible for low-cost, cereal-based complementary foods in developing countries. Encapsulation of iron salts in lipid coatings, while not an iron absorption-enhancing strategy per se, can prevent soluble forms of iron from interacting undesirably with some food vehicles and hence broaden the application of some fortificants. Research relevant to each of these strategies for enhancing the bioavailability or utility of iron food fortificants is reviewed. Individual strategies are evaluated in terms of enhancing effect and stability, organoleptic qualities, cost, and regulatory issues of interest to the nutrition community, industry, and consumers. Recommendations are made on potential usages and further research needs. Effective fortification depends on the selection of technically feasible and efficacious strategies. Once suitable strategies have been identified, cost becomes very important in selecting the best approach to implement. However it is essential to calculate cost in relation to the amount of bioavailable iron delivered. An approach to the calculation of cost using a conservative estimate of the enhancing effects of the innovative technologies discussed in the supplement is given in the final section.

Nutritional iron requirements and food iron absorption

Abstract Bothwell TH, Baynes RD, MacFarlane BJ, MacPhail AP (MRC Iron and Red Cell Metabolism Research Unit, Department of Medicine, University of the Witwatersrand Medical School, Parktown, Johannesburg, South Africa). Nutritional iron requirements and food iron absorption.

Iron absorption from a cereal-based meal containing cane sugar fortified with ascorbic acid

1. The feasibility of improving iron nutrition by fortifying cane sugar with ascorbic acid was studied. 2. The absorption of Fe added to maize-weal porridge was measured in 116 volunteer multiparous Indian women using the radio-Fe erythrocyte utilization method. The meals were fed with and without tea or coffee and with and without varying amounts of ascorbic acid. 3. The mean absorption of Fe from maize-meal porridge was very low (3.8 %), being even further reduced (2.1 %) when tea was drunk with the meal. 4. The addition of 50 or 100 mg ascorbic acid to maize-meal porridge caused approximately a 10-fold increase in Fe absorption. The increase was much less when tea was present, being 2-fold and 5-fold with 50 and 100 mg ascorbic acid respectively. The inhibitory effect of tea on Fe absorption could, however, be overcome by giving larger doses of ascorbic acid (250 and 500 mg). 5. When contaminating Fe (2.5 mg) in the form of labelled rust (Fe,O,) or ferric hydroxide was added to maize-meal porridge it was poorly absorbed (mean values were 0.01 % and 1.5 % respectively). The addition of 100 mg ascorbic acid increased the mean Fe absorption rates to 0.5 % and 6.7 %with Fep03 and Fe(OH), respectively. Fe(OH), was found to be absorbed about half as well as the intrinsic Fe present in maize-meal porridge. 6. It is concluded that ascorbic acid is capable of improving Fe absorption from a cereal source. It can partially overcome the inhibitory effect of tea and might be expected to facilitate the absorption of at least some forms of Fe that may contaminate food. Current methods aimed at promoting adequate iron nutrition in communities that are at risk of Fe deficiency have relied on the fortification of dietary staples with added Fe. How

Factors affecting the absorption of iron from Fe(III)EDTA

1. The modification of iron absorption from Fe(III)EDTA by agents known to promote or inhibit absorption was examined in 101 volunteer multiparous Indian women. Fe absorption from Fe(III)EDTA was compared with absorption of intrinsic food Fe in a further twenty-eight subjects. Finally the urinary excretion of radio-Fe after oral administration of 59Fe(III)EDTA was studied in twenty-four subjects and evidence of intraluminal exchange of Fe was examined. 2. Fe absorption from maize porridge fortified with Fe(III)EDTA was more than twice that from porridge fortified with FeSO4 . 7H2O. 3. Although bran decreased Fe absorption from FeSO4 . 7H2O approximately 11-fold, it had no significant effect on Fe absorption from Fe(III)EDTA. Nevertheless tea, which is a more potent inhibitor of Fe absorption, decreased absorption from Fe(III)EDTA 7-fold. 4. Fe absorption from Fe(III)EDTA given in water was only increased 40% by addition of 3 mol ascorbic acid/mol Fe but by 7-fold when the relative proportions were increased to 6:1. This enhancing effect was blunted when the Fe(III)EDTA was given with maize porridge. In these circumstances, an ascorbate:iron value of 3:1 (which doubles absorption from FeSO4 . 7H2O) produced no significant increase in Fe absorption, while a value of 6:1 produced only a 2 . 5-fold increase. 5. Fe absorption from Fe(III)EDTA was not altered by addition of maize porridge unless ascorbic acid was present. 6. Less than 1% of 59Fe administered as 59Fe(III)EDTA was excreted in the urine and there was no inverse relationship between Fe absorption and the amounts excreted (r 0 . 58, P less than 0 . 05). 7. Isotope exchange between 59Fe(III)EDTA and 59FeSO4 . 7H2O was demonstrated by finding a similar relative value for the two isotopes in urine and erythrocytes when the two labelled compounds were given together orally. This finding was confirmed by in vitro studies, which showed enhanced 59Fe solubilization from 59FeSO4 . 7H2O in maize porridge when unlabelled Fe(III)EDTA was added. 8. Although Fe absorption from Fe(III)EDTA was marginally higher it appeared to form a common pool with intrinsic food iron in most studies. It is postulated that the mechanism whereby Fe(III)EDTA forms a common pool with intrinsic food Fe differs from that occurring with simple Fe salts. When Fe is present in the chelated form it remains in solution and is relatively well absorbed because it is protected from inhibitory ligands. Simple Fe salts, however, are not similarly protected and are absorbed as poorly as the intrinsic food Fe. 9. It is concluded that Fe(III)EDTA may be a useful compound for food fortification of cereals because the Fe is well absorbed and utilized for haemoglobin synthesis. The substances in cereals which inhibit absorption of simple Fe salts do not appear to inhibit absorption of Fe from Fe(III)EDTA.