Evaluation of in vitro iron bioavailability in free form and as whey peptide-iron complexes

Finding alternatives for food fortification in a bioavailable form of iron is needed because iron deficiency leads to several diseases. Iron solubility and in vitro iron absorption were evaluated in free and complexed forms, as iron salts or peptide-iron complexes. Whey peptide-iron complexes were synthesized with various ligands (whey protein hydrolysate; its fractions > 5 kDa and < 5 kDa, obtained by ultrafiltration/diafiltration using a 5-kDa cut-off membrane; and whey protein isolate) and iron sources (FeCl2 and FeSO4). Iron bioaccessibility was assessed after in vitro gastrointestinal digestion, whereas iron uptake was measured indirectly as ferritin synthesis in a Caco-2 cell model. Although all complexes showed high bioaccessibility (> 85%), only complexes that were synthesized with low-molecular-mass peptides (< 5 kDa) and FeCl2 increased iron uptake by approximately 70% compared with FeSO4, one of the most widely used salts for fortification. Thus, this complex is an alternative for food fortification that deserves further research.