The Absorption of Hemoglobin Iron

The accepted mechanism of absorption of iron by the gastrointestinal tract involves solution and reduction to the ferrous form before its uptake by the mucosal cell (1). Food iron, much of which is bound in organic complex, has been assumed to follow the same pathway with the assistance of the digestive enzymes. Studies supporting this hypothesis have been conducted mainly with iron salts, and the extent of its applicability to absorption of iron in food remains uncertain. Measurements of absorption of radioiron biosynthetically incorporated into various foods (2-6) have shown enhancement of absorption by ascorbic acid and other reducing agents, but have not further defined the mechanism by which complex iron is absorbed. That there may be more than one pathway is suggested by the differences in level of absorption of iron in different foods, and of food iron and iron salt in comparable dosage. Hemoglobin is a form of food iron that can be prepared in standard form and that is absorbed sufficiently well for measurement of both increased and decreased absorption (7). Comparison of absorption of hemoglobin iron and iron salt reported here indicates a difference in the manner of absorption of these two forms of iron.