Food iron absorption in man. 3. Effect of iron salt, ascorbic acid and desferrioxamine on the isotopic exchange between native food iron and an extrinsic inorganic iron tracer

Absorption of 'fortification'iron. Bioavailability in man of different samples of reduced Fe, and prediction of the effects of Fe fortification

1. The first part of this study was designed to determine the increase in the amount of iron absorbed by hypothetical groups of subjects on the border-line of Fe deficiency when they were given meals fortified with ferrous sulphate. Two levels of Fe fortification were used (1.6 and 8.9 mg/meal) and the increase in the amount of Fe absorbed by the ‘border-line’ groups was 0.13 and 0.7 mg respectively.

2. Subjects which are on the border-line of Fe deficiency may be considered the target group of an Fe-fortification programme. Therefore the experimental model used can provide valuable information on the effects on the prevalence of Fe deficiency which can be expected when such a programme is introduced.

3. In the second part of the study, the bioavailability in man of reduced Fe with different physico-chemical properties was measured. Special emphasis was given to the relationship between the values obtained in vitro and in vivo.

4. The bioavailability was expressed as absorbability relative to that of ferrous sulphate. In four samples of hydrogen-reduced Fe the bioavailability ranged from 90 to 13%. The reduced-Fe products differed considerably with respect to solubility in hydrochloric acid (8–94% dissolved after 30 min), particle size distribution (91–1% < 7 μm) and reactive surface area (< 0.1–2.7 m2/g).

5. The relationships found between physico-chemical information and bioavailability indicated that reactive surface area and dissolution rate were better predictors of the bioavailability than the particle size.