Iron absorption in breast-fed infants: effects of age, iron status, iron supplements, and complementary foods.
BACKGROUND
Iron supplements are often recommended for older breast-fed infants, but little is known about factors affecting iron absorption from human milk or supplements.


OBJECTIVE
We investigated the effects of age, iron status, and iron intake on iron absorption in healthy, term, breast-fed infants.


METHODS
Twenty-five infants were randomly assigned to receive either 1) iron supplements (1 mg x kg(-1) x d(-1)) from 4 to 9 mo of age, 2) placebo from 4 to 6 mo and iron supplements from 6 to 9 mo, or 3) placebo from 4 to 9 mo. Infants were exclusively breast-fed to 6 mo and partially breast-fed to 9 mo of age. Iron absorption was assessed by giving (58)Fe with mother's milk at 6 and 9 mo. Blood samples were obtained at 4, 6, and 9 mo, and complementary food intake was recorded at 9 mo.


RESULTS
At 6 mo, mean (+/-SD) fractional iron absorption from human milk was relatively low (16.4 +/- 11.4%), with no significant difference between iron-supplemented and unsupplemented infants. At 9 mo, iron absorption from human milk remained low in iron-supplemented infants (16.9 +/- 9.3%) but was higher (P = 0.01) in unsupplemented infants (36.7 +/- 18.9%). Unexpectedly, iron absorption at 9 mo was not correlated with iron status but was significantly correlated with intake of dietary iron, including supplemental iron.


CONCLUSIONS
Changes in the regulation of iron absorption between 6 and 9 mo enhance the infant's ability to adapt to a low-iron diet and provide a mechanism by which some, but not all, infants avoid iron deficiency despite low iron intakes in late infancy.
Domellöf
Magnus
M
Department of Clinical Sciences, Pediatrics, Umeå University, Umeå, Sweden.
Lönnerdal
Bo
B
Abrams
Steven A
SA
Hernell
Olle
O
D000042:Absorption; D019587:Dietary Supplements; D002149:Energy Intake; D005260:Female; D005293:Ferritins / Q000097:blood; D005527:Food, Fortified; D006801:Humans; D007223:Infant; D007225:Infant Food; D007501:Iron / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D007503:Iron Isotopes; D008297:Male; D009752:Nutritional Status; D013548:Sweden
D007503:Iron Isotopes; D005293:Ferritins; D007501:Iron