Food iron absorption measured by an extrinsic tag.

The paper describes the use of an extrinsic tag of inorganic radioiron to determine the total absorption of nonheme iron from a complete meal. The method was developed by measuring the iron absorbed from vegetable foods containing biosynthetically incorporated (55)Fe (intrinsic tag) and from (59)Fe added as a small dose of inorganic iron to the same meal (extrinsic tag). In studies with maize, black bean, and wheat, a consistent extrinsic: intrinsic radioiron absorption ratio averaging 1.10 was observed. Similar results were obtained with either ferrous or ferric iron as the extrinsic tag, and with doses of the latter ranging from 0.001 to 0.5 mg iron added to a test meal containing 2-4 mg of food iron. Adding the radioiron at different stages in preparation of the test meal also had little effect. Separate administration of the extrinsic tag was less satisfactory when small portions of a single food were employed, but with a complete meal, the separate dose was preferable. The extrinsic tag provided a valid measure of absorption despite marked differences in the iron status of the subject, and with wide changes in absorption imposed by adding desferrioxamine or ascorbic acid to the test meal. These findings indicate that there is a common pool of nonheme iron, the absorption of which is influenced by various blocking or enhancing substances present in the meal.

Fe(III)-EDTA complex as iron fortification.

Fe(III)-EDTA as iron fortification presents several advantages over the other iron salts previously used including ferrous sulfate. This iron compound exchange completely with vegetable food iron in the lumen of the gut but with the characteristics that the absorption from both, extrinsic and intrinsic food iron, is higher than that expected from other iron salfs. The comparison between the iron absorption from Fe(III)-EDTA and ferrous sulfate as iron fortification indicates that the absorption form EDTA is about twice as high than that observed from ferrous sulfate. The data indicates that only 10 to 15 mg of iron as Fe(III)-EDTA as iron fortification would be necessary to prevent iron deficiency anemia in population relying their subsistence of vegetable food only and free of parastic infection producing blood loss.

Sugar as a vehicle for iron fortification: further studies.

The data presented confirm the advantages of sugar as a vehicle for iron fortification over other vehicles used in the past. The absorption comparison between ferric and ferrous salts added to sugar demonstrated that Fe(III)-EDTA Complex and ferrous sulfate exhibited the highest absorption, while ferric ammonium citrate was poorly absorbed. It was also found that Fe(III)-EDTA reacts slowly with the tannin contained in tea; the color of the tea changes slightly in the first 2 hr after the addition of the fortified sugar. Iron absorption of sugar fortified with ferrous sulfate was tested in seven beverages. The mean absorption ratio from fortified sugar given with beverages to reference dose of iron ascorbate ranged between 0.42 and 0.70, that is, more than 4 times the absorption from fortified sugar when it is administered with a meal containing one or more vegetals. An absorption of between 0.25 and 0.80 mg of iron/soft drink sugar fortified with 3 mg of iron as ferrous sulfate can be expected in subjects with various degrees of iron deficiency. Thus, two soft drinks per day between meals would be enough to meet the iron requirement in more than 95% of menstruating women, even though the daily iron absorption from the diet is about 0.8 to 1.0 mg.

Effect of cysteine on iron absorption in man.

Cysteine significantly increases, about 2-fold, the absorption from nonheme iron present in vegetable foods, hemosiderin, and of a ferric salt, when this amino acid is administered during the ingestion of foods. No enhancing effect was obtained when the amino acid was mixed with the food before the final cooking. A slight but significant enhancement of heme iron absorption was observed when a large dose of cysteine was administered during the ingestion of hemoglobin. This amino acid mimics the enhancing effect from proteins present in animal foods such as beef, lamb, pork, fish, chicken, and liver. It could be possible that proteins and cysteine share the same mechanism by which they induce an increase of iron absorption.

Sugar as a vehicle for iron fortification.

Sugar as a vehicle for iron fortification presents several advantages over the other vehicles used in the last three decades. In vitro studies demonstrated that ferrous sulfate added to sugar in proportion of 1 mg to 1 g, respectively, is maintained in the ferrous form for a period of at least 1 year and does not induce adverse changes in the vehicle. Sugar, by itself, carries practically no inhibitors for the absorption of iron. Iron absorption from fortified sugar mixed with vegetals is the same as that of native vegetal iron. The absorption from fortified sugar is increased more than 50% over that observed from native vegetal when it is administered as a drink during the ingestion of a meal. A further increase in absorption was found when fortified sugar was administered with beverages. The mean absorption ratio of fortified sugar given with orange juice, Coca-Cola, and Pepsi-Cola to a reference dose of iron ascorbate was between 0.45 and 0.66, which is more than 3 times the absorption of this iron fortification mixed with vegetals. The mean absorption ratio from coffee was 0.30, and from coffee with milk, 0.15. These data indicate that the fortification of sugar with iron could be a better procedure for the prevention of iron deficiency than the iron fortification of bread and wheat products, from which iron is poorly absorbed. It could be used in developing countries where beverages are highly consumed by the low socioeconomic class. This program could be extended to all sugar consumption or be restricted to soft drinks.

Fe(III)-EDTA complex as iron fortification. Further studies.

The data presented confirm the advantages of Fe(III)-EDTA as a salt for iron fortification. This iron compound exchanges completely with intrinsic wheat iron in the lumen of the gut. The iron absorption data from this salt tested with six different food vehicles compared with the absorption of ferrous sulfate administered with the same vehicles indicate that while the mean absorption from ferrous sulfate varies from 2 to 30% according to the food vehicle mixed with the salt, the absorption from Fe(III)-EDTA remains practically the same. Apparently, the iron absorption from Fe(III)-EDTA complex is slightly or not affected by the presence of vegetable foods or milk. All these data suggest that only a small amount of iron from this salt, about 10 mg/day, would be necessary to prevent iron deficiency anemia even in those populations relying for their subsistence on vegetable food only.

The effect of cysteine-containing peptides released during meat digestion on iron absorption in humans.

In order to investigate the constituents responsible for the enhancing effect of meat on intestinal iron absorption in humans, two different types of peptic digestion extracts were prepared from 100 g of beef, in which the thiol groups of the resulting peptides were either oxidized (CYS-), or left untreated (CYS+). The absorption of radioiron mixed with 250 g of maize was more than twofold greater when consumed along with the CYS+ extract than with the CYS- (p less than 0.05). It is suggested that the enhancing effect of meat on nonheme iron absorption is due to cysteine, and that cysteine-containing peptides, rather than the free amino acid, are responsible for this effect.

Early response to the effect of iron fortification in the Venezuelan population.

In Venezuela a severe economic crisis beginning in 1983 provoked a progressive reduction of the quality and quantity of food consumed by the low socioeconomic strata of the population. In these strata, which represent > or = 80% of the Venezuelan population, we had seen a continuous increase in the prevalence of iron deficiency during that recent decade. As a result, in 1993 the Venezuela Government created the Special Commission for Enrichment of Foods. That same year a fortification program began in which precooked yellow and white maize and wheat flours were enriched with 20 and 50 mg Fe (as ferrous fumarate)/kg flour, respectively. The corn flour was also enriched with vitamin A, thiamine, riboflavin, and niacin, whereas the wheat flour was enriched with these same vitamins, except vitamin A. These two cereals represent 45% of the total energy consumed daily by the low socioeconomic strata of the population. A preliminary survey carried out in Caracas in 1994 in a population of 307 children aged 7, 11, and 15 y showed that the prevalence of iron deficiency determined by measuring the serum ferritin concentration and the prevalence of anemia were reduced from 37% and 19%, respectively, in 1992 to 15% and 10%, respectively in 1994.

Iron absorption from typical Latin American diets.

The availability and daily absorption of iron was determined by the extrinsic label method in typical lower middle to lower class diets consumed in regions of Argentina, Brazil, Chile, Mexico, Peru, and Venezuela. Differences in iron absorption from meals up to 7-fold, could be attributed to the varying contents of absorption enhancers, eg, in meat, and of inhibitors in tea, vegetables, and wheat or maize bread. The total iron available in the diets from four countries did not meet the physiological requirements for normal subjects but deficient subjects fulfilled their requirements absorbing from 1.0 to 2.1 mg/day. In five diets heme iron (6 to 24% of the total) provided 34 to 73% of the iron absorbed. These data suggest that such absorption and utilization studies may be used to correlate the prevalence of iron deficiency in a population with certain diets and to guide fortification programs.

Estimation of available dietary iron.

Dietary iron requirements are dependent on the amount and availability of food iron ingested. On the basis of recent studies of food iron absorption employing extrinsic tag techniques, the availability of heme iron has been defined and estimates of the availability of nonheme iron based on the amounts of enhancing substances appear possible. A model has been developed whereby the availability of iron in a given meal may be estimated. Calculations are made on a meal basis of 1) the amount of heme iron and its availability, and 2) the amount of nonheme iron and its availability as influenced by the meal's content of enhancing factors. Examples of these calculations are provided.

The relationship between iron deficiency and anemia in Venezuelan children.

The iron status of 3228 subjects from the nutrition survey Proyecto Venezuela was studied. The sample included children from 1 to 16 y of age grouped by age and sex. Values for three indicators of iron status were compared: hemoglobin concentration, serum ferritin concentration, and percentage saturation of serum transferrin. In all groups there was a strong overlap in the hemoglobin concentration distribution curves for non-iron-deficient and iron-deficient subjects classified as such according to the other two indexes. The prevalence of iron deficiency ranged from 35% in 1-3 y olds to 10% in adolescent males, the values being almost identical in the nonanemic group compared with the total population. In the different groups, 80-97% of the subjects with abnormal values of at least one of these two indexes were not anemic. The difficulties involved in establishing a state of iron deficiency according to these indexes are discussed.

Strategies for the prevention of iron deficiency through foods in the household.

Iron deficiency can be caused not only by diets deficient in iron but by poor absorption of available dietary iron. Extrinsically tagging foods with radioiron allows the exact measurement of iron absorbed from heme and nonheme iron foods. It has furthered the study of the effect of enhancers and inhibitors of iron absorption. As a result, we have a greater understanding of why iron deficiency and iron deficiency anemia are prevalent in populations of low socioeconomic status and of which food vehicles and iron compounds are most suitable for iron fortification.

Daily physiological iron requirements in children.

Median daily iron absorption was determined in iron-replete males and females between 2 and 19 years of age from the upper and lower socioeconomic strata of the Venezuelan population. A comparison was made with iron absorption of well-nourished children, on the basis of hematological and anthropometric reference values from the U.S. The median absorption level, which was calculated from the increase in total body iron due to growth and the daily losses through exfoliation and menstruation, was also used to estimate the requirements of 95% of the population. When the requirements were expressed in terms of body weight, no significant difference in iron absorption was observed between the three Venezuelan and one U.S. groups, ranging from about 30 to 38 micrograms/kg/day in both sexes between 4 and 16 years of age. However, when the requirements were expressed without division by the weight factor, the requirements of the better nourished groups were somewhat higher than those of the Venezuelan lower socioeconomic population with, in addition, a threefold variation over the 5 to 16 year age range. These findings suggest that the total iron requirements of children at a certain age may be most adequately expressed in terms of the optimal body weight for that age.

Prevalence of anemia, iron, folic acid and vitamin B12 deficiency in two Bari Indian communities from western Venezuela.

The hematological status of 406 Bari indians from two communities was studied. One hundred and seventy nine individuals were from Campo Rosario a village located in a low arid plain south to the Perijá mountain range and 287 were from Saimadoyi, a fertile valley in the heart of the mountain. Anemia was found in 54% and 31% of the people from Campo Rosario and Saimadoyi respectively. Low serum iron was present in 28% of the population in both communities while low serum ferritin levels were encountered in 20% of the population from Campo Rosario and 5% of the people from Saimadoyi. A high prevalence of serum folate and vitamin B12 deficiency (91% and 64% respectively) was found in Campo Rosario, in contrast only 5% of the population from Saimadoyi had low folate and none were vitamin B12 deficient. While there was a positive significant correlation between hemoglobin and serum iron concentrations (r = 0.517, p < 0.001), no significative correlation was found between the other parameters studied. The high prevalence of anemia and nutrient deficiency among the Bari indians, can be attributed to inadequate diets and the varied diseases encountered in the population.

[Anemia in indigenous population of the West of Venezuela]. / Anemia en poblaciones indígenas del occidente de Venezuela.

The purpose of the study was to investigate the frequency of nutritional anemia among western venezuelan indians. Three hundred and ninety nine Yucpa indians from the communities of Aroy, Marewa and Peraya were studied. The concentrations of hemoglobin, serum iron, total iron binding capacity, serum ferritin, serum folate and serum vitamin B12 and the frequency of anemia and nutrient deficiency were determined. Anemia was found in 71.7% of people from Aroy, 52.25 from Marewa and in 74.4% from Peraya. No nutrient deficiencies were found in 48.1% of cases with anemia, while iron deficiency anemia was present in 39% of the population studied, and folate and or vitamin B12 deficiency were associated with anemia in only 12.9% of cases. The high frequency of anemia, unrelated to nutrient deficiency, among the Yucpa indians, is attributed to the prevalence of chronic infectious diseases such as hepatitis and parasitic infections, as well as skin and respiratory infectious processes.

[Iron deficiency towards the year 2000]. / Deficiencia de hierro hacia el año 2000.

This is a non-comprehensive overview of the latest 50 years about the evolution of iron metabolism and the methodology we currently have for the diagnosis of iron deficiency and its effects on human health. In the 40's iron absorption was determined by chemistry. The amount of iron absorbed was calculated as the difference between dietary iron and excreted iron. The other methods used to measure dietary iron was hemoglobin repletion. In the 70's the measurement of plasmatic ferritin was an important contribution to iron metabolism to assess iron deficiency and iron overload. In the same decade the extrinsic and intrinsic labelled methodology was an important advancement. The 70's and 80's were years where scientists aimed at finding iron absorption inhibitors, namely coffee, calcium, tea, zinc and fiber. The 80's and 90's were characterized for the emerging knowledge an iron absorption from a food, a meal and a complete diet and for the favorable effect of food iron fortification in developing countries. Also for the effect of iron excess in overall health and myocardial infarction in developed countries were studied.

The effect of change in pH on the solubility of iron bis-glycinate chelate and other iron compounds.

The effect of a pH change from 2 to 6 was tested on the solubility of ferrous sulfate, ferrous fumarate, iron bis-glycine chelate (Ferrochel) and sodium-iron ethylenediaminetetraacetic acid (NaFeEDTA). It was found that at pH 2 ferrous sulfate, Ferrochel and NaFeEDTA were completely soluble and only 75% of iron from ferrous fumarate was soluble. When pH was raised to 6, iron from amino acid chelate and NaFeEDTA remained completely soluble while solubility from ferrous sulfate and ferrous fumarate decreased 64 and 74%, respectively compared to the amount of iron initially soluble at pH 2. These results suggest that iron solubility from iron bis-glycine chelate and NaFeEDTA is not affected by pH changes within the ranges tested, probably because iron remained associated to the respective compounds.

[Dietary iron absorption. Role of vitamin A]. / Absorción del hierro de los alimentos. Papel de la vitamina A.

Iron and vitamin A are essential nutrients for human growing, development and maintenance. Deficiency of these elements is a public health problem especially in developing countries. Recently it has been reported that vitamin A has a favorable effect on iron absorption, probably due to the formation of an iron-vitamin A chelate, that keeps iron soluble and available for absorption. This vitamin establishes a competence with other iron-binding molecules (phytates and polyphenols) that are not absorbed and render insoluble iron. Food enrichment programs with both iron and vitamin A, will provide these two essential nutrients and also an enhanced iron absorption even from diets with a high content of inhibitors.