Zinc absorption in adult humans: the effect of iron fortification

The effect of Fe fortification on the absorption of Zn was studied by radioisotopic labelling of single meals, followed by measurements of whole-body retention of 65Zn at 14 d after intake. Healthy adult volunteers participated in the study. Weaning cereal, wheat bread and infant formula, foods that are all frequently Fe-fortified, were evaluated in the study. The amounts of Fe added as FeSO4 were similar to the levels in commercial products in Europe and the USA, and were 200 or 500 mg Fe/kg (weaning cereal), 65 mg Fe/kg (white wheat flour) and 12 mg Fe/l (infant formula). For comparison, Zn absorption was measured in the same subjects, from identical test meals containing no added Fe. No statistically significant differences were found when Zn absorption from the Fe-fortified test meals was compared with that from non-Fe-fortified test meals. Fractional Zn-absorption values from Fe-fortified v. non-fortified meals were 31.1 (SD 11.9) v. 30.7 (SD 7.0)% (weaning cereal; 200 mg Fe/kg), 37.7 (SD 16.6) v. 30.2 (SD 9.9)% (weaning cereal; 500 mg Fe/kg), 36.5 (SD 14.4) v. 38.2 (SD 18.1)% (bread; 65 mg Fe/kg flour) and 41.6 (SD 8.1) v. 38.9 (SD 14.5)% (infant formula; 12 mg Fe/l). The addition of Fe to foods at the currently used fortification levels was thus not associated with impaired absorption of Zn and the consumption of these Fe-fortified foods would not be expected to have a negative effect on Zn nutrition.