Extended Data Table 1.
Top, numbers of grain analysis runs for microwave digestion and ICP–MS steps for the grain surveys, including limit of detection (LOD) and certified reference material (CRM) recovery values for Ca, Fe, Se and Zn from wheat flour (SRM 1567b, NIST). Bottom, summary statistics for grain concentrations of Ca, Fe, Se and Zn in teff and wheat in Ethiopia, and maize in Malawi. The selected scale used for analysis is shown in italic.