Mucosal uptake, mucosal transfer and retention of iron: reproducibility of their measurement by whole-body counting and differences between Fe(II) and Fe(III).

Iron absorption was measured with a double isotope technique which enabled investigation of initial mucosal uptake, mucosal transfer and retention of iron. Radioactivity was measured with a whole-body scanner. Absorption of 1 mg Fe2+ was studied twice in 22 healthy subjects, with an interval of almost two years. No significant difference was observed in the mean values of mucosal uptake, mucosal transfer and retention of iron. In some subjects, however, values differed considerably, despite identical experimental conditions, detailed instruction and no detectable changes in the individual iron status. In another 10 subjects absorption of 1 mg Fe3+ was compared with 1 mg Fe2+. Mucosal uptake and retention of Fe2+ were twice as high as of Fe3+ while mucosal transfer did not differ significantly. It appears that investigations of groups of subjects, receiving either the same or a different iron test dose, give reliable and reproducible results. Individual and longitudinally studied values in a single subject, however, have to be interpreted with caution.