Figure 4.

Luminal and serosal factors recognized to influence zinc absorption. Food-derived macromolecules and low molecular weight ligands positively or negatively influence the speciation of the ion as well as its luminal free and available concentration, consequently affecting its absorption by the intestinal epithelium [3]. Phytate forms stable complexes with zinc at intestinal pH, which diminishes its availability for enterocytes [153]. Conversely, the protein content of the consumed food has a positive effect on zinc absorption due to the release of amino acids and peptides upon degradation. Presumably, these increase luminal solubility of the metal, and, consequently, enhance its availability to enterocytes [154,155]. Serum albumin is an important serosal factor, acting as a basolateral zinc-acceptor and enhancing enterocytic zinc release into the blood circulation [102]. Additionally, systemic humoral factors, such as hepcidin, seem to influence ZnT-1-mediated export of zinc by intestinal cells [156], which indicates that the liver might play an important role in secreting humoral factors regulating intestinal zinc absorption.