Zinc absorption from human milk, cow's milk, and infant formulas

Zinc absorption from 450 mL of human milk, cow's milk, humanized cow's milk formula, cereal-cow's milk formula, and soy formula was determined in healthy adults. The milks and formulas were extrinsically labeled with zinc chloride Zn 65 and the absorption was determined from measurement of the whole-body retention of the isotope. The zinc content of the formulas was comparable to or higher than that of human milk. Absorption of zinc was 41% +/- 9% from human milk and 28% +/- 15% from cow's milk. Absorption was 31% +/- 7% from the humanized cow's milk formula, 22% +/- 11% from the cereal-cow's milk formula, and 14% +/- 4% from the soy formula. These results indicate that, with the present levels of zinc supplementation, the amount of zinc absorbed from infant formulas is considerably lower than that absorbed from human milk.