Absorption of fortification iron from milk formulas in infants.

The bioavailability of iron added to different types of cows' milk formulas was studied using mono-isotopic and double-isotopic methods in 396 infants aged 5-18 mo. All the milk formulas were fortified with ferrous sulfate in concentrations varying between 10 and 19 mg elemental iron/liter. Iron absorption from low-fat milks and full-fat milks varied from 2.9 to 5.1%. A higher range of mean absorption, 5.9 to 11.3%, was observed in the same formulas with the addition of ascorbic acid at concentrations of 100 mg/l or higher (up to 800 mg/l), demonstrating its enhancing effect on iron absorption in fortified milks. The amount of milk fat, the addition of carbohydrates, or acidification did not seem to influence iron absorption.