The effect of iron fortification upon trace element metabolism in healthy term infants
Iron fortification of commercial infant formulae is considered necessary to prevent iron deficiency and anaemia in infants receiving these formulae during late infancy. The current levels of iron fortification in formulae available in the U.K. may adversely affect the bioavailability of other minerals and trace elements present in the formula. The following study was designed to investigate whether the absorption of iron, zinc, copper, manganese, calcium, phosphate, magnesium or aluminium differed when infants were fed infant formula, either cows' milk based (CMF) or soy protein based (SMF), with or without iron fortification, 109molFe/1 or 10molFe/1 and 11molFe/1 or 53molFe/1 respectively. Twelve healthy infants were randomly allocated to receive either CMF (n&'61 6) or SMF (n&'61 6) from birth. After approximately four weeks they entered a double-blind cross-over study of the effects of iron fortification. This lasted a month during which each infant was allocated to receive one formula for the first two weeks then the other formula for the second two weeks. The formulae differed only in their level of iron fortification. After ten days on each formula, they participated in metabolic balance studies in which stable isotopes of iron, zinc and copper were given. Anthropometric measurements were obtained at fortnightly intervals throughout the study. Apparent absorption and maximum apparent retention of iron was significantly lower from the CMF without iron fortification than the CMF with iron fortification, as was expected, however there was no significant difference observed in fractional luminal disappearance. Maximum apparent retention and fractional luminal disappearance of zinc and copper from CMF did not appear to be related to iron fortification. Maximum apparent retention of aluminium was greater from the iron fortified CMF which also had a slightly higher aluminium concentration, 18.6mol/1 versus 16.8mol/1, which resulted in a marginally higher intake.