112.

MacPhail AP, Bothwell TH, Torrance JD, Derman DP, Bezwoda WR, Charlton RW, Mayet F. Factors affecting the absorption of iron from Fe(III)EDTA. British J Nutr. 1981; 45(2):25-227. (NA52) The modification of iron absorption from Fe(III)EDTA by agents known to promote or inhibit absorption was examined in 101 multiparous Indian women. Fe absorption from Fe(III)EDTA was compared with absorption of intrinsic Fe in a further 28 subjects. Finally the urinary excretion of radioactive Fe after 59Fe(III)EDTA by mouth was studied in 24 subjects and evidence of intraluminal exchange of Fe was examined. Fe absorption from maize porridge fortified with Fe(III)EDTA was more than twice that from porridge fortified with FeSO47H2O about 11-fold, it had no significant effect on Fe absorption from Fe(III)EDTA. Nevertheless, tea, a more potent inhibitor of Fe absorption, decreased absorption from Fe(III)EDTA to a seventh of its initial value. Fe absorption from Fe(III)EDTA given in water was increased by only 40% by adding ascorbic acid 3 mol/mol Fe but 7-fold when the proportions were increased to 6:1. This effect was blunted when the Fe(III)EDTA was given with maize porridge. In those circumstances, an ascorbate:iron value 3:1 (which doubles absorption from FeSO47H2O) produced no significant increase in Fe absorption; a value of 6:1 produced only a 2.5-fold increase. Fe absorption from Fe(III)EDTA was not changed by adding maize porridge unless ascorbic acid was present. Less than 1% of 59Fe given as 59Fe(III)EDTA was excreted in the urine and there was an inverse relation between Fe absorption and the amounts excreted. Isotope exchange between 53Fe(III)EDTA and 59FeSO47H2O was shown by finding a similar relative value for the two isotopes in urine and erythrocytes when the two labelled compounds were given together by mouth. This finding was confirmed by studies in vitro, which showed increased 59Fe solubilization from 59FeSO47H2O in maize porridge when unlabelled Fe(III)EDTA was added. Although Fe absorption from Fe(III)EDTA was marginally more it seemed to form a common pool with intrinsic food Fe in most studies. It is postulated that the mechanism whereby Fe(III)EDTA forms a common pool with intrinsic food Fe differs from that occurring with simple Fe salts. When Fe is present in the chelated form it remains in solution and is relatively well absorbed because it is protected from inhibitory ligands. Simple Fe salt, however, are not similarly protected and are absorbed as poorly as the intrinsic food Fe. It is concluded that Fe(III)EDTA may be a useful compound for food fortification of cereals because the Fe is well absorbed and utilized for Hb synthesis. The substances in cereals which inhibit absorption of simple Fe salts do not seem to inhibit absorption of Fe from Fe(III)EDTA.

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