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Inorganic Phosphate Additives Highest Bioavailability — ESENeph MCQ

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ModerateChronic Kidney DiseaseInorganic Phosphate Additives Highest BioavailabilityESENeph

A 58-year-old man with diabetes and CKD G4 (eGFR 22 mL/min/1.73m2) has persistent hyperphosphataemia (phosphate 2.1 mmol/L). He takes sevelamer with meals. His dietitian has counselled on dietary phosphate restriction. Which dietary phosphate source has the HIGHEST bioavailability and should be the primary target for restriction?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Inorganic phosphate from food additives and processed foods

Inorganic phosphate from food additives (found in processed meats, soft drinks, baked goods, fast food) has >90% bioavailability compared to ~40-60% from organic animal phosphate and ~20-40% from plant-based phytate phosphate. This makes additive phosphate the highest-yield target for dietary restriction. Processed food labels should be checked for phosphate-containing additives (E338-E343, E450-E452). A shift from processed to freshly prepared whole foods can reduce phosphate intake by 400-800 mg/day without necessarily restricting protein. Plant-based protein sources have lower phosphate bioavailability than animal sources, providing a secondary dietary modification option.

Reference: Moe et al 2011 – Phosphate Bioavailability; KDIGO 2024 – CKD-MBD; UKKA 2015 – Dietary Phosphate