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United States Department of Agriculture

Agricultural Research Service

Title: CACO-2 CELL FE UPTAKE FROM HUMAN MILK AND INFANT FORMULA

Authors
item Etcheverry, P - CORNELL UNIVERSITY
item Wissler, J - CORNELL UNIVERSITY
item Wortley, G - CORNELL UNIVERSITY
item Glahn, Raymond

Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 29, 2004
Publication Date: July 1, 2004
Citation: Etcheverry, P., Wissler, J., Wortley, G., Glahn, R.P. 2004. Caco-2 cell fe uptake from human milk and infant formula. Nutrition Research. 24(7):573-579.

Interpretive Summary: Iron is a critical nutrient for infants, particularly for infants over 6 months of age as they have exhausted their iron stores from the in utero period. As a result, considerable research has been conducted to optimize iron uptake from infant formula and weaning foods. In general, higher fractional (i.e. percent of ingested Fe) iron absorption from human milk has been reported when compared to cow milk or cow-milk-based infant formula. On the other hand, absolute or net iron absorption values are higher for infant formulas than from human milk. This is primarily because infant formulas in the U.S. are fortified with 10-12 mg/L iron or with less than 6.7 mg/L, which are defined, by the Food and Drug Administration (FDA), as low-iron formulas. Human milk is low in iron. It contains between 0.5 to 1.0 mg/L and 0.3 to 0.9 mg/L. Research funding and safety concerns often limit mineral absorption studies using human infant subjects. Thus, it is important to develop reliable, fast and economical in vitro methods for assessing iron bioavailability that can refine experimental objectives and address issues not possible to study in humans or animals. In our lab, we compared the effect of different commercially available infant formulas on iron absorption to that of human milk using a simulated digestion/cell culture model. The results indicate that very little Fe was absorbed from the human milk relative to the infant formulae. For example, iron uptake from Enfamil® with Iron, Enfamil® Low Iron, Carnation® Good Start® and Similac® was 265-742% greater than that of human milk. Carnation® Alsoy® was statistically higher than all other infant formulas and human milk, exhibiting an iron uptake twenty times more than that of human milk. However, when cell iron uptake was expressed on a fractional basis, human milk was considerably higher than all formulas with the exception of Alsoy®. This study demonstrates that this in vitro model is an excellent tool for comparing and developing improved infant foods.

Technical Abstract: Iron is a critical nutrient for newborn infants, and particularly for infants over 6 months of age. In general, higher fractional (i.e. percent of ingested Fe) iron absorption from human milk has been reported when compared to cow milk or cow-milk-based infant formula. On the other hand, absolute or net iron absorption values are higher for infant formulas than from human milk. It is not difficult to understand why infants over 6 months of age fed human milk might have poor iron status compared to fortified formulas. Infant formulas in the U.S. are either fortified with 10 mg/L to 12 mg/L of iron or with less than 6.7 mg/L, which are defined, by the Food and Drug Administration (FDA), as low-iron formulas. Human milk is low in iron. It contains between 0.5 to 1.0 mg/L and 0.3 to 0.9 mg/L. Research funding and safety concerns often limit mineral absorption studies using human infant subjects. Thus, it is important to develop reliable, fast and economical in vitro methods for assessing iron bioavailability that can refine experimental objectives and address issues not possible to study in humans or animals. In our lab, we compared the effect of different commercially available infant formulas on iron absorption to that of human milk using a simulated digestion/cell culture model. The results indicate that very little Fe was absorbed from the human milk relative to the infant formulae. For example, iron uptake from Enfamil® with Iron, Enfamil® Low Iron, Carnation® Good Start® and Similac® was 265-742% greater than that of human milk. Carnation® Alsoy® was statistically higher than all other infant formulas and human milk, exhibiting an iron uptake twenty times more than that of human milk. Higher levels of ascorbic acid (AA) present in the Alsoy formula compared to the other milk-based formulas might contribute to higher iron uptake by the cells. Alsoy® contains 107 mg AA/L of formula; whereas the other formulas contain between 54 mg to 80 mg AA/L. Differences in formula manufacturing procedures and ingredients (such as lower heat treatments resulting in higher ascorbic acid levels and higher contents of citrate) are likely to promote iron absorption. Alsoy® is made of soy protein isolate, which contains phytic acid, a potent inhibitor of Fe absorption. It is possible that the soy isolate has been dephytinized in an attempt to reduce the levels of phytic acid. Through this process, Fe bioavailability from soy formulas can be optimized. When Caco-2 cell ferritin levels were expressed per amount of iron in the upper chamber of the well, human milk was considerably higher than all formulas with the exception of Alsoy®.

Last Modified: 9/1/2014
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