Erythrocyte incorporation of ingested 58Fe by 56-day-old breast-fed and formula-fed infants.
As an index of iron absorption, erythrocyte incorporation of the stable isotope, 58Fe, was determined 14 and 42 d after the administration of 58Fe-labeled ferrous sulfate to 56-d-old exclusively breast-fed infants and to infants fed a low-iron (1.8 mg/L) formula. Each infant received a dose of 0.6 to 1.0 mg of iron with ascorbic acid between feedings on each of 3 consecutive d. Fourteen d after administration of the 58Fe-labeled iron doses (age 70 d), arithmetic mean incorporation of the 58Fe label into erythrocytes by breast-fed infants was 20.0% of the dose--only slightly less than that reported for erythrocyte incorporation of iron by fasting adults fed small quantities of 59Fe-labeled human milk. Erythrocyte incorporation of iron by the formula-fed infants was 6.9% of the dose, suggesting that, even between feedings, components of infant formula exerted a major inhibitory effect on iron absorption. For reasons that are not clear, the percentage of the administered label incorporated into erythrocytes was significantly greater in breast-fed (but not in formula-fed infants) at 112 d of age than at 70 d of age.
Fomon
S J
SJ
Department of Pediatrics, College of Medicine, University of Iowa, Iowa City 52242.
Ziegler
E E
EE
Nelson
S E
SE
D000042:Absorption; D001942:Breast Feeding; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D007223:Infant; D007225:Infant Food; D007227:Infant Nutritional Physiological Phenomena; D007501:Iron / Q000097:blood*; D007503:Iron Isotopes; D008297:Male; D009751:Nutritional Requirements
D007503:Iron Isotopes; D007501:Iron