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.

After the rapid decrease in the prevalence of iron deficiency and iron-deficiency anemia in the Venezuelan population when a national program for fortification of flours with iron and vitamins was instituted, we studied micronutrient interactions in Venezuelan diets. One hundred human adults were fed three cereal-based diets, labelled with either 59Fe or 55Fe in six studies. Each diet contained different concentrations of vitamin A (from 0.37 to 2.78 micromol/100 g cereal) or beta-carotene (from 0.58 to 2.06 micromol/100 g cereal). The presence of vitamin A increased iron absorption up to twofold for rice, 0.8-fold for wheat and 1.4-fold for corn. beta-carotene increased absorption more than threefold for rice and 1.8-fold for wheat and corn, suggesting that both compounds prevented the inhibitory effect of phytates on iron absorption. Increasing the doses of vitamin A or beta-carotene did not further significantly increase iron absorption. We measured the iron remaining in solution performing in vitro studies in which the pH of solutions was adjusted from 2 to 6 in the presence of vitamin A or beta-carotene. All of the iron from ferrous fumarate was soluble after changing the pH of the solution containing 3.4 micromol of beta-carotene to 6.0. Vitamin A was less effective. However, 78 +/- 18% of iron was soluble in the presence of 3.3 micromol of vitamin A, whereas with no vitamin addition, only 26 +/- 13% of iron was soluble (<0.05). Vitamin A and beta-carotene may form a complex with iron, keeping it soluble in the intestinal lumen and preventing the inhibitory effect of phytates and polyphenols on iron absorption.

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This study was conducted to determine the bioavailability of iron amino acid chelate (ferrochel) added to fortify breads prepared from either precooked corn flour or white wheat flour + cheese and margarine compared with the same basal breakfast enriched with either ferrous sulfate or iron-EDTA. The inhibitory effect of phytate and polyphenols on iron absorption from ferrochel was also tested. A total of 74 subjects were studied in five experiments. Iron absorption from ferrochel was about twice the absorption from ferrous sulfate (P: < 0.05). When ferrous sulfate and ferrochel were administered together or in different meals, absorption from ferrochel was about twice the absorption from ferrous sulfate (P: < 0.05). Polyphenols present in coffee and tea inhibited iron absorption in a dose-dependent manner. American-type coffee did not modify iron absorption significantly, whereas both espresso-type coffee and tea reduced iron absorption from ferrochel by 50% (P: < 0. 05). Ferrochel partially prevented the inhibitory effect of phytates. Because of its high solubility in aqueous solutions even at pH 6, its low interactions with food and high absorption, ferrochel is a suitable compound for food fortification.

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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.