The 4 AAs stimulated iron absorption in iron-deprived male mice in the presence of 1.575 mM FeSO₄. 2.5 µCi of ⁵⁹Fe in the control (Ctrl) or 4 AA formulation, containing 0, 1.575, 3.15, or 6.3 mM FeSO4, was administered to each mouse by oral, intragastric gavage. Mice were sacrificed 1 hour after gavage to determine the percent of dose absorbed. Data were analyzed by Student’s t test at each iron concentration; n = 5 or 10 mice per group; *P < .05.