Bioavailability in infants of iron from infant cereals: effect of dephytinization.

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.

Effects of the increasing consumption of dairy products upon iron absorption.

The effect of the increasing consumption of dairy products upon the iron absorption was tested in vivo on volunteers using the extrinsic tag method (with 55 Fe and 59 Fe). The total iron absorption coefficient of a typical French meal and of the same meal after addition of a glass of low-fat skimmed milk or plain yoghurt was measured. Non-heme iron absorption was 2.2% for the standard meal alone, 2.0% with the yogurt and 2.1% with the glass of milk. Total iron absorption (i.e. measured non-heme iron absorption plus estimated heme iron absorption) for the three meals was, respectively, 9.7%, 9.5% and 9.4%. These results suggest that, under real-life conditions, increasing the amount of dairy products probably has no effect upon iron absorption in meals containing appreciable amounts of dairy products.

Bioavailable iron density in French and Spanish meals.

Iron absorption from two typical French meals and three typical Spanish meals was measured, using the extrinsic tag technique (with 55Fe and 59Fe) on French and Spanish volunteers. The total iron absorption coefficient varied up to three-fold (between 3.4 and 11.4 per cent) according to the contents of haem and non-haem iron and the presence of non-haem iron absorption enhancers and inhibitors. Expressed for iron absorption of 40 per cent of the reference dose (corresponding to subjects with theoretical depleted iron stores), those coefficients varied up to four-fold (between 4.9 and 18.9 per cent). The bioavailable nutrient density ranged from 0.30 to 0.77 mg/1000 kcal in subjects with good iron stores and from 0.50 to 1.12 mg/1000 kcal for subjects with theoretical depleted iron stores. This low bioavailable iron density enabled understanding of why iron balance is especially critical in women of childbearing age in industrialized countries, where iron enrichment of food is not practised.

Vitamin status of a healthy French population: dietary intakes and biochemical markers.

The vitamin status of a representative population sample in a French district in the Paris area was assessed using a biochemical and dietary approach. Complete data were obtained for 1039 subjects 6 to 97 years old. Dietary intakes of most vitamins increased up to adolescence and then remained stable or decreased slightly in adult life. Total vitamin intakes were higher in men than in women (except for ascorbic acid), but the vitamin density of the diet was higher in females. Most subjects presented dietary intakes below the French recommended allowances for vitamin B1, B6, C, A and E. A variation in biochemical parameters according to age and sex was observed only for serum concentration of retinol, beta-carotene, vitamin E and C. Multiple regression analysis showed that dietary vitamin intakes were related to the biological status for vitamin B2, B6, C, folates, beta-carotene and vitamin E. Tobacco smoking, alcohol consumption and oral contraceptive were significantly correlated with biological status for several vitamins. While biochemical evidence of severe vitamin deficiency was not observed, a sizeable minority of the French population is not lavishly supplied with some vitamins, and this situation deserves investigation to see if any deleterious effects are associated with it.

Iron absorption from typical West African meals containing contaminating Fe.

Iron absorption from three typical West African meals was measured in fourteen subjects using the extrinsic-tag technique with 59Fe 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 39-73% 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, 70.0-160 micrograms Fe was absorbed. Expressed on an energy basis, the bioavailable nutrient density was 3.2-7.0 micrograms/100 kJ (13.4-29.5 micrograms/100 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.

Iron status of a healthy French population: factors determining biochemical markers.

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.

A double stable isotope technique for measuring iron absorption in infants.

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 6.58% 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 be conducted.

Assessment of iron status in children and adolescents with Crohn's disease: value of basic red cell ferritin.

The iron status of 22 children and adolescents with Crohn's disease (mean age: 13 years) was evaluated. Eleven patients were suffering from active disease with inflammation, identified by at least one abnormal value for serum orosomucoid, C-reactive protein or sedimentation rate (group I). Eleven patients were in clinical remission and showed no biological evidence of inflammation (group II). Hemoglobin and red cell indices, erythrocyte protoporphyrin, serum iron, transferrin, serum ferritin and basic red cell ferritin were determined in all patients. The usual indicators of iron status, particularly serum ferritin, were affected by the inflammatory processes, but basic red cell ferritin appeared to be independent of inflammation. Basic red cell ferritin can therefore be considered to be a reliable indicator of iron status in children and adolescents with Crohn's disease.

Effect of iron supplementation during pregnancy on trace element (Cu, Se, Zn) concentrations in serum and breast milk from Nigerian women.

Trace element concentrations in serum and breast milk were studied longitudinally in 197 Nigerian women from 6 months of gestation to 6 months postpartum; 99 of them received a daily iron supplement of 100 mg from 6 months of gestation to delivery. During the last 3 months of pregnancy, serum selenium declined, whereas serum zinc remained unchanged and serum copper increased. After delivery, copper concentration in maternal serum decreased, whereas serum zinc increased from delivery to 3 months postpartum and then reached a plateau. Serum selenium increased from delivery to 6 months postpartum. In breast milk, selenium and zinc decreased from 5 days to 6 months postpartum. Copper in breast milk also declined during the course of lactation but reached a plateau by 3 months postpartum. Iron concentration in breast milk remained unchanged during the study. Iron supplementation had no significant effect upon the concentrations of copper, selenium and zinc in mother serum and breast milk. In umbilical serum, iron status, copper and zinc levels were similar in the two groups, whereas, unexpectedly, selenium concentration was significantly decreased (p < 0.03) in the iron-supplemented group. Taken together, our results suggest that the beneficial effect of iron supplementation on iron deficiency was not associated with an adverse effect on copper and zinc status. On the other hand, our results suggest that Nigerian women had a marginal zinc status but an adequate selenium status.

Iron bioavailability studied in infants: the influence of phytic acid and ascorbic acid in infant formulas based on soy isolate.

The influence of phytic acid and ascorbic acid content of soy formula on iron (Fe) bioavailability was investigated in infants by analysis of the incorporation of stable isotopes of Fe into red blood cells 14 d after administration using a double stable isotope technique. Paired comparisons were made with each infant acting as his or her own control. The geometric mean fractional Fe incorporation into red blood cells increased from 5.5 to 6.8% (p < 0.05) when soy formula with the native content of phytic acid was compared with a 83% dephytinized formula. A more pronounced effect was shown with soy formula containing no phytic acid; the mean fractional Fe incorporation increased from 3.9 (native phytic acid) to 8.7% (zero phytic acid; p < 0.001). A significant (p < 0.01) effect was also demonstrated when the Fe:ascorbic acid molar ratio in the native phytate-containing formula was increased from 1:2.1 to 1:4.2; mean fractional Fe incorporation increased from 5.9 to 9.6%. These results demonstrate that the Fe bioavailability from soy-based infant formulas can be similarly increased by either removing phytic acid or increasing the ascorbic acid content.