Our objective was to determine whether meat and other dietary factors have the capacity to reduce nonheme ferric iron to the ferrous form during digestion. Beef, selected organic acids, selected purified proteins, red blood cells, whole blood, or blood plasma was mixed with FeCl3 and subjected to simulated gastrointestinal digestion. Ferrozine was used to monitor the formation of dialyzable Fe(II). Ascorbic acid, glutathione and cysteine produced large increases in Fe(II) while meat (raw and cooked), hemoglobin and red blood cells yielded smaller increases. Casein, plasma, bovine serum albumin and egg albumin did not affect Fe(II) formation. Our Results suggest dietary factors which enhance iron absorption in vivo promote Fe(III) reduction in the intestinal lumen.