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Iron fortification of infant milk formula: the effect on iron status and immune function
H M Power1, H D Heese, D W Beatty
1Department of Paediatrics and Child Health, University of Cape Town, South Africa.
Insights
Increased iron fortification in infant formula is safe and improves iron status, but further research is needed on nutrient interactions and immune function. This study evaluated high-iron formula in infants from 3 months to 1 year.
Area of Science:
- Pediatric Nutrition
- Iron Metabolism
- Infant Health
Background:
- Iron deficiency is a significant concern in infants, impacting development and health.
- Standard infant formulas contain limited iron, necessitating evaluation of enhanced fortification levels.
- Cow's milk-based infant formulas are widely used, making their iron content crucial for infant populations.
Purpose of the Study:
- To assess the safety and efficacy of a cow's milk infant formula with increased iron fortification (40 mg/100g).
- To measure the impact of higher iron levels on infant iron status and immune function.
- To compare outcomes between infants receiving standard iron formula (8.3 mg/100g) and the enhanced formula.
Main Methods:
- A randomized, double-blind trial involving 149 healthy, full-term infants aged 3 months to 1 year.
- Infants were assigned to receive either standard iron formula (control group, n=74) or formula with 40 mg Fe/100g (test group, n=75).
- Iron status was assessed using hemoglobin, red cell distribution width, zinc protoporphyrin, and ferritin levels; immune function and infection incidence were also monitored.
Main Results:
- The high-iron formula was safe, with no attributable adverse effects or infections.
- Infants receiving the enhanced iron formula showed significantly improved iron status markers compared to the control group.
- Elevated iron levels led to a significant decrease in plasma zinc concentration; no differences in immune function were observed.
Conclusions:
- Increasing iron fortification in cow's milk infant formula to 40 mg/100g is safe and beneficial for iron status.
- Higher iron fortification had a less pronounced effect on iron status than anticipated.
- Further research is needed to understand iron absorption facilitators, interactions with zinc, and iron's impact on immunity.
Abstract:
We conducted a randomized double-blind trial of a cow's milk infant formula with increased iron fortification in order to confirm its safety and to measure its effects on iron status and immune function. A group of full-term, well nourished and healthy infants was followed from the age of 3 months to 1 year. A control group of 74 infants was given a commercially available infant formula containing 8.3 mg Fe/100g. The test group of 75 infants received a similar formula with 40 mg Fe/100 g. The formula with the extra iron proved to be safe and, when compared with the control group, the children in the test group had significantly improved iron status as reflected by the proportion of children classed as normal (25 of 61 cf. 44 of 65; p less than 0.003), and by the mean values of the haemoglobin concentration (11.5 cf. 11.9 g/dl; p = 0.04), red cell distribution width (15.5% cf. 14.4%; p = 0.0005), red cell zinc protoporphyrin (3.4 cf. 4.0 micrograms/g Hb; p = 0.04) and ferritin (29 cf. 17.3 micrograms/l; p = 0.004). The extra iron fortification depressed zinc concentration in plasma (90.6 cf. 83.5 micrograms/l; p = 0.05). There was no significant difference between the two groups for laboratory measures of immune function or for incidence of infection. No adverse effects such as infection could be attributed to the increased iron. We conclude that iron fortification of cow's milk infant formula may be safely increased to 40 mg/100 g (i.e. by a factor of 4.8 over the common concentration of 8.3 mg/100 g), but that this has less than the expected effect on iron status. Further studies are required to define (a) the long-term role of facilitators of iron absorption such as ascorbic acid, (b) the interaction of iron with absorption of divalent trace elements such as zinc, and (c) the effect of iron status on immune function and susceptibility to infection.