Iron absorption is more closely related to iron status than to daily iron intake in 12- to 48-mo-old children

Authors: LYNCH, MARY - BAYLOR COLLEGE MED; Griffin, Ian; HAWTHORNE, K - BAYLOR COLLEGE MED; CHEN, ZHENSHENG - BAYLOR COLLEGE MED; HAMZO, MARIA - BAYLOR COLLEGE MED; Abrams, Steven

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2006
Publication Date: 1/27/2007
Citation: Lynch, M.F., Griffin, I.J., Hawthorne, K.M., Chen, Z., Hamzo, M.G., Abrams, S.A. 2007. Iron absorption is more closely related to iron status than to daily iron intake in 12- to 48-mo-old children. Journal of Nutrition. 137(1):88-92.

Interpretive Summary: Little is known about the iron requirements of young (1- to 4-y-old) children. Although these children are at high risk of iron deficiency, the current RDAs are largely based on data in adults. Iron deficiency in children is important as it can lead to long-term effects such as developmental delays that may not respond to iron treatment. In adults the amount of iron absorbed from the diet increases as dietary intake increases (although the % absorption falls), and increases as iron status worsens. We sought to see whether these relationships were true for children. We studied 28 children aged between 1 and 4 y on their normal diets. Iron absorption was measured using stable isotopes. The amount of iron absorbed from the diet was unaffected by the iron intake, but did fall as zinc intake increased. The main determinant of iron absorption was iron status. Children with poorer iron status absorbed a larger proportion of the dietary iron. Most of the children absorbed an amount of iron that would be expected to be sufficient to meet their needs for growth. We conclude that: 1. Iron intake in healthy well-nourished 1- to 4-y-old children is good, and the amount of iron absorbed from the diet is enough to avoid the risk of iron deficiency. 2. The main determinant of iron absorption in 1- to 4-y-old children is iron status. 3. Iron absorption was relatively stable across the range of intakes we studied. 4. Zinc may reduce iron absorption from the diet in 1- to 4-y-old children.

Technical Abstract: Few studies have evaluated iron absorption in small children after the first year of life. Our objective was to examine the relations among iron intake, iron absorption, and iron status in a group of healthy children. We studied 28 children, ages 12 to 48 mo, after a 7-d home adaptation to a diet representative of their usual daily mineral intake. A multi-tracer stable isotope study was performed to assess iron absorption both from a meal ((58)Fe) and from a reference iron dose ((57)Fe) given with ascorbic acid without a meal. Iron intake was 6.9 +/- 2.4 mg, approximately the 35th percentile of typical U.S. intakes. Absorption of (58)Fe was related to serum ferritin (r(2) = 0.319, P = 0.0018) and more so to reference dose iron absorption (r(2) = 0.653, P < 0.0001). Iron absorption was negatively correlated with zinc intake (r(2) = 0.090, P = 0.0049) but was not correlated with iron intake (P = 0.20). However, zinc intake was not correlated with measures of iron status, including reference dose iron absorption and serum ferritin (r(2) < 0.1, P > 0.25). Total absorbed iron was similar to needs estimated by the Institute of Medicine. We conclude that iron absorption in young children is more closely related to iron status than to iron intake. Reference dose iron absorption may be superior to serum ferritin as a surrogate measure for iron status in this age group. Although zinc intake may affect iron absorption from a meal, it does not appear to have a detectable effect on overall iron status in otherwise well-nourished children.