Blood analysis
For screening, whole blood samples were analyzed for Hb using a 5-differential flow cytometer (Nihon Kohden). PF and CRP were analyzed using electrochemiluminescence (Cobas E 411; Roche Diagnostics), and turbidimetry (Vitros 4600; Ortho Clinical Diagnostics), respectively.Whole blood and plasma samples were collected from participants and shipped from Lima to the Human Nutrition Laboratory of ETH Zurich on dry ice and stored at −20°C until analysis. PF and CRP concentrations were measured in the samples using an automated immunoassay analyzer (Immulite 1000, Siemens Healthineers, Germany). Accuracy was checked by measuring control samples (CRP 3 levels, PF 2 levels) from the same manufacturer. Whole blood samples were mineralized with concentrated nitric acid in a microwave autoclave (TurboWave, MLS, Germany). The iron present in the mineralized samples was isolated by anion exchange chromatography and subsequently purified by precipitation as ferric hydroxide [