Determination of absorption and endogenous excretion of iron in man by monitoring fecal excretion of a stable iron isotope (58Fe).

The absorption and endogenous excretion of iron in man was studied by monitoring the fecal excretion of a stable iron isotope (58Fe). The study was carried out for 12 healthy volunteers who were divided into two groups. Group I received 58Fe-labeled ferric ammonium citrate (III) (58FeAC) equivalent to 6 mg of iron as a control, and group II received a combination of 500 mg of vitamin C and 58FeAC. A new formula was used to calculate the 58Fe absorption ratio reflecting the pool of iron in the intestinal cells, and the ratio was compared with that obtained from Janghorbani's formula, which has been used as one of the common methods. As a result, the 58Fe absorption ratio in group II was statistically significantly higher than that of group I (34.4 +/- 6.1% vs. 15.0 +/- 5.5%, M +/- SD) using Janghorbani's formula. The similar absorption ratio (34.1 +/- 6.0% vs. 14.8 +/- 5.5%) was also obtained by our new formula. Our results confirmed the previous findings that the availability of iron is stimulated by the supplementation of vitamin C. Both formulae agreed in the absorption of iron, indicating that the endogenous excretion of iron (caused by the desquamated cells) in the intestine does not disguise the iron absorption.