Iron bioavailability of a casein-based iron fortificant compared with that of ferrous sulfate in whole milk: a randomized trial with a crossover design in adult women

Abstract

BackgroundA highly soluble iron–casein complex has been developed for food fortification purposes with the aim to provide high iron bioavailability.ObjectiveWe aimed to determine the iron bioavailability of the iron–casein complex relative to that of ferrous sulfate (control) when given with whole milk in healthy young women.MethodsA randomized comparator-controlled trial with a crossover design was conducted using the erythrocyte incorporation dual stable isotope (57Fe, 58Fe) technique. Iron absorption from the iron–casein complex was compared with that from ferrous sulfate in 21 healthy women aged 20–38 y with normal iron status.ResultsFractional iron absorption (geometric mean; −SD, +SD) from the iron–casein complex (3.4%; 1.4%, 5.4%) and from ferrous sulfate (3.9%; 1.7%, 6.1%) were not statistically different (P > 0.05). The relative bioavailability value of the iron–casein complex to ferrous sulfate was determined to be 0.87 (−1 SD, +1 SD: −0.90, +2.64).ConclusionsThe iron–casein complex has iron bioavailability comparable to that of ferrous sulfate in healthy young women. This trial was registered at www.anzctr.org.au as ACTRN12615000690550.

Impact of Ascorbic Acid on the In Vitro Iron Bioavailability of a Casein-Based Iron Fortificant

“…The two ICCs were also found to be digestible under simulated gastric digestion, with iron from the complexes remaining as soluble as FeSO 4 after pepsin hydrolysis. These solubility results agree with published data on the three compounds [10,47]. A good agreement between this measurement and the relative iron bioavailability in humans has also been observed several times [10,[46][47][48], especially for iron salts with good solubility in dilute acid.…”

“…These solubility results agree with published data on the three compounds [10,47]. A good agreement between this measurement and the relative iron bioavailability in humans has also been observed several times [10,[46][47][48], especially for iron salts with good solubility in dilute acid. Therefore, although similar iron absorptions from the ICC and FeSO 4 have already been demonstrated in humans [10], the greater solubility of the ICC when compared with FePP may be a first indication of its better in vivo bioavailability.…”

“…The higher iron uptake from ICC (2.9%) than from FeSO 4 would be due to the lower iron uptake from FeSO 4 than expected for the reasons provided above. The results for ICC (2.8%) in comparison with FeSO 4 agree with human data, which show no difference in iron bioavailability from the ICC and FeSO 4 [10], and a higher bioavailability from the ICC than from FeSO 4 in milk is not expected in humans in the absence of AA.…”

“…The in vitro solubility of the ICCs was compared with that of FeSO 4 heptahydrate (20.08% iron, Dr. Paul Lohmann GmbH, Emmerthal, Germany) and a micronized FePP (20.25% iron, Aksell Química, Indaiatuba, Brazil) at pH 1.7 using a protocol adapted from Lynch et al [41] and Henare et al [10]. Two aliquots of each iron compound, each containing 20 mg of iron, were weighed into 500 mL conical flasks.…”

“…The absorption of iron from this complex was assessed in young women using stable isotopes and the erythrocyte measurement method [9], and showed no statistical difference to that from FeSO 4 when added to milk [10]. This clinical trial was performed without the addition of ascorbic acid (AA), which is recognized to be the most effective enhancer of iron absorption and to counteract the effects of most iron absorption inhibitors [3,11].…”