Influence of Diet on Bioaccessibility of Iron from Dietary Supplements and Medicinal Products—Results of In Vitro Digestion Model and Analytical Determinations

BACKGROUND/OBJECTIVES: Iron is a key micronutrient for the proper growth and development of the organism. The aim of this study was to evaluate the impact of diet type, the chemical form of iron, and the formulation of the pharmaceutical preparation on its relative bioaccessibility from selected dietary supplements and medicinal products. METHODS: The research was conducted using a two-stage in vitro digestion model, simulating the physiological processes occurring in the human digestive system and ICP-OES determination of iron. The analytical model used in the study involved homogenates of whole-day dietary rations (basic, standard, and high-residue diets) with the addition of selected dietary supplements or medicinal products. It was demonstrated that iron bioaccessibility was strictly determined by dietary composition and the chemical form of the preparation. RESULTS: In the studies conducted without external supplementation, the highest iron bioaccessibility was observed in the basic diet model (7.96%), and the lowest in the standard diet (4.63%). The highest bioaccessibility value was determined for iron sulfate registered as medicine (12.58%), whereas the lowest was iron lactate (5.25%). The extended-release tablets observed the highest bioaccessibility (19.31%). CONCLUSIONS: It was proven that the developed in vitro digestion model may serve as an effective tool for the preliminary assessment of iron bioaccessibility, enabling the optimization of supplementation without ethical barriers.