A stable isotope technique has been developed which uses 57Fe and 58Fe as labels and which enables the simultaneous measurement of Fe absorption from two test meals in infants. The method was evaluated by measuring Fe absorption from a commercial whey-adjusted infant formula in nine healthy infants aged 13–25 weeks. Each infant was fed 210 ml formula, labelled with either 57Fe or 58Fe, on four consecutive mornings, in random order. The total Fe content in each feed was 2.5 mg Fe; either as 2.5 mg 57Fe, or 0 6 mg 58Fe plus 1.9 mg Fe with normal isotopic composition. Isotopic enrichment of Fe in erythrocytes was measured by thermal ionization mass spectrometry 14 d after the last administration, and Fe absorption was calculated based on isotope ratio shifts, total circulating Fe and intake of each isotope. Geometric mean absorption for the 57Fe and 58Fe labels was 6.72 and 658% respectively, and the absorption of the two isotopes was not significantly different (Student's paired t test). By this technique, paired comparisons of Fe absorption can be obtained and systematic studies of the influence of dietary factors on Fe absorption during infancy can he conducted.

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The iron status of a representative population sample in a district of Paris area (France) was assessed using a biochemical and dietary approach. Complete data were obtained for 1,108 subjects 6 months to 97 years old. Total iron intake increased up to adolescence and then remained stable in adult life. Iron intake was higher in men than in women. Most children and menstruating women presented a dietary iron intake below the recommended allowances. While anemia was not very common, iron deficiency (defined as the existence of at least two abnormal values in the four independent indicators of iron status: serum ferritin, erythrocyte protoporphyrin, transferrin saturation and MCV) was particularly common in infants, young children, menstruating women and elderly men. Serum ferritin, erythrocyte protoporphyrin and transferrin saturation were significantly correlated with inflammatory markers. Significant correlations were found between dietary total iron and serum ferritin (r = 0.29, p < 0.001) and hemoglobin (r = 0.44, p < 0.001). After adjustment for age, sex and inflammation, using multiple linear regression models, the relationship between both heme and nonheme iron intake and serum ferritin remained significant. Serum ferritin and hemoglobin levels were negatively correlated with calcium and phosphorus intake.

Iron bioavailability from an infant cereal made of wheat flour with a low extraction rate (70%) and cow milk was measured in infants by using a stable-isotope technique. A dephytinized infant cereal was prepared by adding commercial phytase during manufacture, resulting in degradation of 88% of the native phytic acid. Paired comparisons were made to evaluate the effect of phytic acid on iron bioavailability. Both infant cereals contained identical amounts of ascorbic acid and had a molar ratio of ascorbic acid to iron of 2:1. Iron was added as ferrous sulfate. No difference in iron bioavailability was observed in this study; the geometric mean was 8.7% (range: 3.8-16.9%) and 8.5% (range: 3.4-21.4%) from the cereal with native phytic acid (0.08% phytic acid) and the dephytinized cereal (0.01% phytic acid), respectively. Dephytinization of infant cereals containing a relatively low native phytic acid content and high amounts of ascorbic acid is thus unnecessary to ensure adequate bioavailability of iron.

Iron absorption from three typical West African meals was measured in fourteen subjects using the extrinsic-tag technique with s9Fe and 55Fe. All meals consisted of maize as the staple food. Meals were prepared in Benin under realistic conditions from locally grown foods. Of the non-haem-Fe in the meals 3 5 7 3 % did not exchange with the added inorganic radio-Fe tracer, depending on the degree of Fe contamination of meals. Non-haem-Fe absorption was low in each maize meal, but was even lower for those eaten with a vegetable sauce than for those eaten with a fish sauce. When haem-Fe absorption was included, 700-160 pg Fe was absorbed. Expressed on an energy basis, the bioavailable nutrient density was 3.2-70 pg/lOO kJ (13.4-29.5 ,ug/lOO kcal). These findings suggest that total Fe available in the typical diets of West African countries does not meet the physiological requirements of large proportions of the population.Food iron absorption : Contamination iron: African meals