Absorption of fortification iron in bread

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Abstract
A collaborative study has been made of the absorption of radioiron supplements (3 mg iron) baked into 60-g dinner rolls. The labeled iron supplements (ferrous sulfate, reduced iron, ferric orthophosphate, sodium iron pyrophosphate) were prepared under specifications agreed upon by representatives of the major manufacturers of iron sources for enrichment and fortification in the United States. Particle size for each of the supplements varied between 3 and 10 µ. Using dual radioiron tags, three to four separate absorption tests were performed in each of 75 subjects by a multiple dose administration technique. Absorption of sodium iron pyrophosphate was one-tenth and ferric orthophosphate one-third that of ferrous sulfate when baked into the same roll or into separate rolls and administered simultaneously, whereas ferrous sulfate and iron reduced by hydrogen were about equally available. In 32 fasting subjects given a 60-g roll containing 3 mg supplemental iron as tagged ferrous sulfate, absorption averaged 5.7% and was roughly one-quarter of the absorption from the same dose of ferrous sulfate administered as a solution of inorganic iron. When rolls supplemented with 3 mg iron as tagged ferrous sulfate were taken with meals or with a regular diet, absorption averaged 6.3 and 2.1% from meals with and without meat protein, respectively. Studies with an extrinsic tag demonstrated that fortification iron in the form of ferrous sulfate underwent complete exchange with the non-heme pool of dietary iron.