In Vitro Availability of Calcium, Iron, and Zinc from First‐Age Infant Formulae and Human Milk

Abstract

ABSTRACTBackgroundVariation in the bioavailability of calcium (Ca), iron (Fe), and zinc (Zn) occurs because of interactions of food components in the gastrointestinal microenvironment. Bioavailability is preferably determined by in vivo tests, but these are expensive, labor‐intensive, time consuming, and often unethical. As an alternative, in vitro methods can be used to predict bioavailability of nutrients from foodstuffs.MethodsA continuous‐flow dialysis model with preliminary intraluminal digestive phase, adapted to the gastrointestinal conditions of infants younger than 6 months, was used. Human milk was the reference standard. Ca, Fe, and Zn content of samples and dialysates after digestion were analyzed by atomic absorption spectrometry.ResultsCa availability is similar in human milk (13.1% ± 0.8%), whey (13.3% ± 1.2%), and soy‐based formulae (13.0% ± 1.2%;P > 0.05), and higher in casein‐predominant formula (21.2% ± 0.6%;P < 0.05). Availability of Fe is highest in human milk (8.12% ± 0.27%;P < 0.05). Fe availability in whey (1.28% ± 0.28%) and soy formulae (1.48% ± 0.28%) is similar (P > 0.05), but availability is lower in casein‐predominant formula (0.48% ± 0.22%;P < 0.05). Zn availability is also highest in human milk (13.1% ± 0.7%;P < 0.05). However, Zn availability is similar in whey (6.7% ± 0.6%) and casein formulae (8.5% ± 1.6%;P > 0.05), but lower in soy formula (2.3% ± 0.4%;P < 0.05).ConclusionsOur observations are in agreement with previous data from in vivo studies in term infants. This in vitro procedure is an inexpensive, simple, rapid, and reliable method that predicts the bioavailability of Ca, Fe, and Zn in foods.