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For estimating the requirements for dietary iron, it is important to know the amount of iron that is lost from the body. Inevitable losses of iron have been determined in adult humans but not in infants or children. We administered [sup.58]Fe, the least abundant stable isotope of iron, to free-living infants at 168 d of age (5.6 mo) and followed them to age 26 mo. There was no dietary restriction after isotope administration. Blood was obtained at regular intervals for determination of isotopic enrichment and indices of iron status. We estimated the quantity of circulating iron, noncirculating active iron, and storage iron at each age. The administered isotope equilibrated with total body iron by 13 mo of age. From 13 to 26 mo of age, we estimated inevitable loss and absorption of iron from the change in tracer abundance in circulating iron. The rate of decrease of tracer abundance was proportional to addition of tracee, i.e., absorption of iron. Conversely, the rate of decrease in quantity of tracer was proportional to removal of tracee, i.e., loss of iron. From 13 to 26 mo of age, iron absorption was (mean [+ or -] SD) 0.49 [+ or -] 0.13 mg/d and inevitable iron loss was 0.25 [+ or -] 0.12 mg/d. Intersubject variability of iron loss and iron absorption was high, and iron loss and absorption were highly correlated (r = 0.789, P < 0.001). Iron stores were low throughout the study and decreased significantly from 13 to 26 mo of age, suggesting that iron absorption from the diet was inadequate to maintain or increase iron nutritional status. The data suggest that, in this cohort, which may be representative, the intake of bioavailable iron from 13 to 26 mo of age was insufficient to maintain iron nutritional status. KEY WORDS: * iron absorption * iron loss * toddlers * stable isotope

Despite the general acknowledgment that breastfeeding is the most desirable means of feeding normal infants, it is evident that many infants are currently fed infant formulas and that evaluation of [...]

In growing individuals, the requirement for absorbed iron consists of iron needed for growth and iron needed to replace inevitable iron loss. We were able to estimate inevitable iron loss by adolescents because total body iron of the adolescents had been enriched with the stable isotope, [sup.58]Fe, as the result of earlier studies of iron absorption. During an interval beginning at least 1.56 y after isotope administration (a time sufficient for complete mixing of the isotope with total body iron) and extending for no less than 3.29 y, we determined the isotopic enrichment of circulating iron. On the basis of several assumptions, we calculated total body [sup.58]Fe and total body iron at the beginning and end of the interval. Because of complete mixing of the isotope with total body iron, fractional total [sup.58]Fe loss was the same as fractional loss of total iron. In males, the fractional loss of iron was 9.70%/y and the quantitative loss was 256 mg/y or 0.70 mg/d. In females, the fractional loss of iron was 14.60%/y and the quantitative loss was 306 mg/y or 0.84 mg/d. Using several assumptions, we then calculated that the iron requirement for growth during this interval was 0.76 mg/d for males and 0.31 mg/d for females. Adding the iron loss to the iron requirement for growth, the requirement for absorbed iron was estimated to be 1.46 mg/d for males and 1.15 mg/d for females. KEY WORDS: * iron loss, iron requirements, stable isotopes * adolescents

Erythrocyte incorporation of an administered iron isotope has been used as a surrogate for iron retention on the assumption (validated in normal and iron-deficient adults) that 80-100% of the retained isotope is promptly incorporated into circulating erythrocytes. This assumption has not been validated in infants or children. The purpose of our study was to determine concurrently in normal infants absorption and erythrocyte incorporation of the stable isotope, (super 58)Fe. In a preliminary study (Study 1), we demonstrated that fecal excretion of ingested isotope occurs predominantly during the first 4 d after administration but continues beyond 7 d after ingestion, that is, beyond the point at which isotope in feces can be explained either by excretion of isotope that failed to enter enterocytes or by exfoliation of isotope-enriched enterocytes. In Study 2, we administered (super 58)Fe to nine younger (age 20-69 d) and nine older (age 165-215 d) term infants and collected feces for 11 d. Geometric mean retention of (super 58)Fe by the younger infants was 31.2% of intake at 4 d and 26.9% at 11 d, and by the older infants, 35.0% at 4 d and 32.5% at 11 d. Erythrocyte incorporation of (super 58)Fe 14 d after ingestion was 5.2% of the dose by the younger infants and 12.5% by the older infants. Utilization of retained (11 d) isotope thus was 19.8% by the younger infants and 38.3% by the older infants. We conclude that far less than 80% of retained isotope is promptly incorporated into erythrocytes (utilized) by infants.

Although feeding of formulas with iron concentration of 215 [micro]mol/L (12 mg/L) is a reliable means of preventing iron deficiency, high intakes of iron may adversely affect absorption of copper and zinc. Because data are not available to establish whether fortification at a lower level would result in equivalent iron absorption, we tested the hypothesis that iron absorption is greater by infants fed formulas with an iron concentration of 215 [micro]mol/L (12 mg/L) than by those fed formulas with an iron concentration of 143 [micro]mol/L (8 mg/L). Fifty-two normal infants entered the study at 112 [+ or -] 4 d of age, and 46 of these were successfully studied until 196 d of age. Using the stable isotope 58Fe, we determined erythrocyte incorporation of iron by infants fed Formula 8 [iron approximately 143 [micro]mol/L (8 mg/L)] and by infants fed Similac with Iron[R] [iron approximately 215 [micro]mol/L (12 mg/L)]. On each of three test days beginning at 154 d of age, a major portion of the formula was labeled with 58Fe. Geometric mean erythrocyte incorporation of iron adjusted for plasma ferritin concentration at 168 d of age was 4.82 [micro]mol/d (0.269 mg/d) by infants fed Formula 8 and 5.21 [micro]mol/d (0.291 mg/d) by infants fed Similac with Iron. Corresponding values at 196 d of age were 5.12 and 5.41 [micro]mol/d (0.286 and 0.302 mg/d). The differences in quantity of iron incorporated into erythrocytes by infants fed Formula 8 and Similac with Iron were not statistically significant (P = 0.66 at 168 d of age, P = 0.75 at 196 d of age) and were judged to be nutritionally trivial. Because we were unable to provide support for our hypothesis that iron absorption is greater by infants fed formulas providing 215 [micro]mol (12 mg) of iron per liter than by those fed formulas providing 143 [micro]mol (8 mg) of iron per liter, we conclude that, pending the results of further studies, it is reasonable to decrease the iron concentration of iron-fortified infant formulas. J. Nutr. 127: 83-88, 1997. KEY WORDS: human infants infant formulas iron absorption 58Fe

Infant formulas and foods can be supplemented with iron to prevent iron deficiency. Iron deficiency is the most common deficiency disease in infants. Experience in the US has shown that as more infants receive iron supplementation, the incidence of iron deficiency anemia in preschool children has dropped. Infant formula can be fortified with ferrous sulfate, which is very easily absorbed. Other baby foods can also be supplemented.

Fomon's February article addresses the important issue of infant diet and growth using an evolutionary approach, (1) His main concern throughout the article is the increasing use of breasffed infants [...]

Defines the body composition of male and female reference infants. Chemical analyses; Model chosen for maturation of fat-free mass; Composition at age six months.

Abstract. Estimates of calorie intake from various sources during infancy are presented in relation to age. The estimates, based on published reports and personal communications to the author, concern total calorie intake and its distribution between milk or formula and beikost (i.e., foods other than milk or formula fed to infants), relative prevalence of breast, formula- and milk-feedings, relative popularity of specific commercially prepared formulas, and percentage of calories consumed in the form of commercially prepared strained and junior foods and "table" foods. Pediatrics, 56:350-354, 1975, INFANT FEEDING, FORMULAS FOR INFANTS, CALORIC INTAKE, BEIKOST. [ABSTRACT FROM AUTHOR]

Abstract. Formulas designed for feeding of premature infants contain minerals added by the manufacturer. Although it is known that these minerals may be poorly suspended in the formula, little is known about concentrations of minerals in formula delivered to the infant under conditions prevailing in premature infant nurseries. In partially empty bottles of Similac Special Care, concentrations of calcium and phosphorus of this residual formula were found to be substantially greater than concentrations in full bottles. Presumably, concentrations of calcium and phosphorus in formula delivered to the infants was relatively low. Enfamil Premature and SMA Preemie infant formulas contain lesser quantities of added calcium and demonstrated less tendency to sedimentation. Substantial decrease in concentration of calcium was observed with all three formulas during continuous infusion, but the decrease was greatest with Similac Special Care. Little or no change in concentrations of calcium and phosphorus were observed with simulated bolus feeding by gavage. [ABSTRACT FROM AUTHOR]

Presents recommendations for proper nutritional management of normal full-term infants. Vitamin supplementation to age six months; Information on several kinds of infant formulas; Suggestions for feeding of infants after age six months.