Hypophosphite-mediated reduction of transition metal ions in acidic medium: Kinetics, carbonate-driven precipitation, and a proposed mechanistic link to dietary-phosphate-associated thrombotic risk

We report an unexpected and reversible decolorization of aqueous CuSO ₄ and FeSO ₄ solutions upon treatment with sodium hypophosphite (NaH ₂ PO ₂ ) in hydrochloric acid medium. The chromatic suppression arises from the reduction of Cu ²⁺ to Cu ⁰ /Cu ⁺ and of Fe ³⁺ to Fe ²⁺ , both driven by the strongly reducing hypophosphite anion under acidic conditions. Upon standing in ambient air for approximately 24 h, the original colours return spontaneously, consistent with re-oxidation by atmospheric dioxygen. Addition of sodium carbonate (Na ₂ CO ₃ ) to the freshly reduced solutions precipitates CuO and Fe ₂ O ₃ , respectively. Based on these observations, we propose a biochemically plausible hypothesis – not a demonstrated pathway – by which dietary phosphate from commercial carbonated beverages or phosphate-rich fertiliser-contaminated foods may be reduced to hypophosphite in the strongly acidic gastric environment (pH 1.0–2.0) through metal-ion catalysis. The resulting hypophosphite, once absorbed along with dietary Fe ²⁺ /Cu ⁺ , reaches the bloodstream, where dissolved CO ₂ /HCO ₃ ^- acts as a carbonate source to precipitate nano-scale metal oxide particles. We hypothesise that these nanoparticles serve as heterogeneous nucleation sites for platelet aggregation and fibrin polymerisation, contributing to thrombus formation. This mechanism may have broad implications for understanding diet-related thrombotic risk.