Relative bioavailability of iron in carbonyl iron and complex ferric orthophosphate to rat

The relative biological availability (RBV of FeSO4.7H2O = 100%) of carbonyl iron and complex ferric orthophosphate in flour and bread baked with this flour was determined in a rat hemoglobin repletion assay. Hemoglobin iron gain and iron intake during repletion were used as dose-response parameters, and the relative biological values were assessed by the slope-ratio method. The RBV of carbonyl iron in flour was not calculated because the statistical validity of the slope-ratio method was not fulfilled. The RBVs of all the tested iron sources were significantly lower than that of the ferrous sulphate standard (p less than 0.01). The RBV for complex ferric orthophosphate in flour was 45 +/- 8%, and for complex ferric orthophosphate and carbonyl iron in bread 36 +/- 7% and 35 +/- 7%, respectively. There were no differences in the bioavailability of carbonyl iron and complex ferric orthophosphate (p greater than 0.01). Baking did not effect the bioavailability of complex ferric orthophosphate (p greater than 0.01).