Orthophosphate affects iron(III) bioavailability via a mechanism involving stabilization and delivery of ferric hydroxide-phosphate nanoparticles.

Haohao Wu, Tengjiao Guo, Shiyang Li, Yuanhui Zhao, Mingyong Zeng

Food chemistry 2021 Jun 15

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Orthophosphate is endogenously present in gastrointestinal fluids and increasingly ingested as additives in processed foods. However, its effect and mechanism of action on iron bioavailability remains controversial and largely unknown. Here, at initial dissolved P/Fe ratios ((P/Fe)init) ≥ 0.6, orthophosphate completely prevents hydrolytic Fe(III) precipitation at neutral pH by mediating the formation of negatively-charged (≈-29 mV ζ-potential) ferric hydroxide-phosphate nanoparticles (Fe(OH)P-NPs) consisting of ≈3.8-nm-diameter monomers. Fe(OH)P-NPs have decreased size and Fe/P ratio with increasing (P/Fe)init. Acidic pH and balanced salts in intestinal fluid counteract orthophosphate-mediated Fe(III) solubilization by weakening colloidal stability of Fe(OH)P-NPs. Protein digests from egg white, whey, casein, and fish muscle aid Fe(III) solubilization in intestinal fluid by stabilizing Fe(OH)P-NPs with casein digest displaying the highest Fe(III)-solubilizing capacity, and in calcein-fluorescence-quenching assay, deliver nanoparticulate Fe(III) to polarized Caco-2 cells via divalent-metal-transporter-1-dependent or endocytic pathways. Overall, our study provides a new paradigm for understanding orthophosphate's role in iron bioavailability. Copyright © 2021 Elsevier Ltd. All rights reserved.

Citation

Haohao Wu, Tengjiao Guo, Shiyang Li, Yuanhui Zhao, Mingyong Zeng. Orthophosphate affects iron(III) bioavailability via a mechanism involving stabilization and delivery of ferric hydroxide-phosphate nanoparticles. Food chemistry. 2021 Jun 15;347:129081